Pulmonary and Critical Care

303 questions

All types303 Multiple choice153 Multiple select73 Ordering77

A 54-year-old man is evaluated in the intensive care unit on hospital day 3. He was initially admitted for community-acquired pneumonia and septic shock, requiring endotracheal intubation, mechanical ventilation, and vasopressor support. His empiric antibiotic regimen was de-escalated to intravenous ceftriaxone and oral azithromycin two days ago based on sputum cultures confirming *Streptococcus pneumoniae*.

Today, his blood pressure has improved to $115/75\text{ mm Hg}$ on a minimal weaning dose of norepinephrine, and his temperature is $37.4^\circ\text{C}$ ( $99.3^\circ\text{F}$ ). He remains deeply sedated and is not initiating spontaneous breaths.

Current ventilator settings (Volume Assist-Control):
Tidal Volume: $450\text{ mL}$
Respiratory Rate: $12/\text{min}$
$\text{FiO}_2$ : $0.35$
PEEP: $5\text{ cm H}_2\text{O}$

Laboratory studies show:

Laboratory Study	Result	Reference Range
Sodium ( $\text{Na}^+$ )	$138\text{ mEq/L}$	$136 - 145\text{ mEq/L}$
Potassium ( $\text{K}^+$ )	$4.2\text{ mEq/L}$	$3.5 - 5.0\text{ mEq/L}$
Chloride ( $\text{Cl}^-$ )	$102\text{ mEq/L}$	$95 - 105\text{ mEq/L}$
Bicarbonate ( $\text{HCO}_3^-$ )	$12\text{ mEq/L}$	$22 - 28\text{ mEq/L}$
Blood urea nitrogen	$48\text{ mg/dL}$	$7 - 18\text{ mg/dL}$
Creatinine	$2.5\text{ mg/dL}$	$0.6 - 1.2\text{ mg/dL}$
Thyroid-stimulating hormone (TSH)	$0.3\text{ }\mu\text{U/mL}$	$0.5 - 5.0\text{ }\mu\text{U/mL}$
Free thyroxine ( $\text{T}_4$ )	$1.0\text{ ng/dL}$	$0.9 - 1.7\text{ ng/dL}$

Arterial blood gas analysis on current ventilator settings:

Parameter	Result	Reference Range
pH	$7.22$	$7.35 - 7.45$
$\text{PaCO}_2$	$31\text{ mm Hg}$	$35 - 45\text{ mm Hg}$
$\text{PaO}_2$	$92\text{ mm Hg}$	$80 - 100\text{ mm Hg}$

Which of the following are appropriate management steps for this patient? (Select all that apply)

Select all that apply

Increase the set respiratory rate on the mechanical ventilator

Maintain the current targeted antibiotic regimen

Administer an intravenous bolus of sodium bicarbonate

Escalate antibiotic therapy to intravenous meropenem and amikacin

Initiate intravenous levothyroxine therapy

Show answer & explanation

Answer: Increase the set respiratory rate on the mechanical ventilator; Maintain the current targeted antibiotic regimen

Answer

The appropriate steps are to increase the set respiratory rate on the mechanical ventilator and to maintain the current targeted antibiotic regimen.

The correct answer involves two key management decisions based on the patient's critical care presentation. First, the patient has a high anion gap metabolic acidosis. Using Winter's formula, the expected

\text{PaCO}_2

should be between

24

and

28\text{ mm Hg}

. The measured

\text{PaCO}_2

31\text{ mm Hg}

indicates a superimposed respiratory acidosis due to inadequate alveolar ventilation. Because the patient is sedated and not triggering breaths, increasing the ventilator's set respiratory rate is required to increase minute ventilation and lower the

\text{PaCO}_2

, helping to normalize the pH. Second, because the patient's hemodynamic status is improving on a targeted regimen directed at a known pathogen (*S. pneumoniae*), the principles of antibiotic stewardship dictate that the current regimen should be maintained without unnecessary escalation.

Step-by-Step Solution

Identify the primary acid-base disorder.

The pH is

7.22

(acidemia) and

\text{HCO}_3^-

12\text{ mEq/L}

(low), indicating a primary metabolic acidosis. The anion gap is

138 - (102 + 12) = 24

, indicating a high anion gap metabolic acidosis (likely from acute kidney injury and sepsis).

Establishing the primary disturbance is the necessary first step to determine if respiratory compensation is adequate.

Calculate the expected respiratory compensation using Winter's formula.

Expected

\text{PaCO}_2 = (1.5 \times \text{HCO}_3^-) + 8 \pm 2 = (1.5 \times 12) + 8 = 26 \pm 2\text{ mm Hg}

(Range:

24-28\text{ mm Hg}

This determines the target

\text{PaCO}_2

the patient must achieve to physiologically compensate for the metabolic acidosis.

Compare measured

\text{PaCO}_2

to the expected range and determine the necessary ventilator adjustments.

The measured

\text{PaCO}_2

31\text{ mm Hg}

is higher than the expected maximum of

28\text{ mm Hg}

, indicating a superimposed primary respiratory acidosis. The ventilator's respiratory rate must be increased to enhance

\text{CO}_2

clearance.

Because the patient is deeply sedated and mechanically ventilated, their alveolar ventilation is entirely dependent on the machine's set minute ventilation.

Evaluate the clinical trajectory and remaining laboratory data to guide pharmacological therapy.

The hemodynamics are improving on de-escalated antibiotics, so the current regimen should be maintained. The isolated low TSH with low-normal

\text{T}_4

indicates euthyroid sick syndrome, requiring no intervention.

Proper critical care management requires recognizing resolving pathology to prevent inappropriate polypharmacy and antibiotic resistance.

Key Concept

Management of a mechanically ventilated patient with metabolic acidosis requires calculating Winter's formula to ensure the set minute ventilation provides adequate respiratory compensation. Euthyroid sick syndrome is a normal physiologic response to critical illness that does not require hormone replacement.

Estimated Time:2m 0s

Question 2Question →

A 52-year-old man presents to the clinic reporting progressively worsening swelling in his lower extremities and profound daytime fatigue over the past four months. His wife, who accompanies him, notes that he frequently falls asleep during conversations and snores loudly at night. His medical history includes obesity, essential hypertension, and diet-controlled type 2 diabetes mellitus. He has no history of tobacco use.

Vital signs show a temperature of $36.8^\circ\text{C}$ ( $98.2^\circ\text{F}$ ), heart rate of $88/\text{min}$ , blood pressure of $135/85\text{ mmHg}$ , respiratory rate of $14/\text{min}$ , and oxygen saturation of $89\%$ on room air. BMI is $42\text{ kg/m}^2$ .

Physical examination reveals prominent jugular venous distention with noticeable *a* waves. Cardiac auscultation demonstrates a right ventricular heave, a loud pulmonic component of the second heart sound ( $P_2$ ), and a holosystolic murmur at the left lower sternal border that increases in intensity with inspiration. The lungs are clear to auscultation bilaterally. Bilateral $3+$ pitting edema is present up to the knees.

Laboratory studies show:
Hemoglobin: $16.8\text{ g/dL}$
Thyroid-stimulating hormone (TSH): $2.5\text{ \mu U/mL}$ (Normal: $0.4-4.0\text{ \mu U/mL}$ )
Free T4: $1.2\text{ ng/dL}$ (Normal: $0.9-1.7\text{ ng/dL}$ )

An arterial blood gas analysis obtained on room air reveals:
pH: $7.37$
$\text{PaCO}_2$ : $56\text{ mmHg}$
$\text{PaO}_2$ : $60\text{ mmHg}$
$\text{HCO}_3^-$ : $31\text{ mEq/L}$

Which of the following is the most appropriate next step in the diagnostic evaluation or management of this patient?

Initiate therapy with lisinopril and metoprolol succinate

Administer intravenous normal saline

Prescribe a course of azithromycin and oral corticosteroids

Refer for overnight polysomnography

Initiate daily levothyroxine supplementation

Show answer & explanation

Answer: Refer for overnight polysomnography

Answer

Refer for overnight polysomnography

The correct answer is to refer for overnight polysomnography. This patient's presentation of daytime somnolence, loud snoring, severe obesity, and chronic hypercapnic respiratory failure is highly characteristic of Obesity Hypoventilation Syndrome (OHS) complicated by Obstructive Sleep Apnea (OSA). The resulting chronic hypoxemia triggers hypoxic pulmonary vasoconstriction, leading to pulmonary hypertension and subsequent right-sided heart failure (Cor Pulmonale). This is evidenced by his right ventricular heave, loud

P_2

, tricuspid regurgitation murmur, and peripheral edema. Confirming the underlying sleep-disordered breathing with polysomnography is the essential next step to initiate appropriate positive airway pressure therapy.

Step-by-Step Solution

Interpret the clinical presentation and physical exam findings.

The patient exhibits signs of isolated right heart failure (Cor Pulmonale), including jugular venous distention with *a* waves, a right ventricular heave, a loud

P_2

, a tricuspid regurgitation murmur, and peripheral edema, with notably clear lungs.

Identifying the anatomic location of the heart failure (right-sided) rules out primary left-sided heart failure and points toward a pulmonary etiology.

Analyze the arterial blood gas (ABG) and laboratory results.

The ABG reveals a fully compensated chronic respiratory acidosis (pH

7.37

, elevated

\text{PaCO}_2

, elevated

\text{HCO}_3^-

) alongside hypoxemia and secondary polycythemia (elevated hemoglobin).

The combination of chronic daytime hypercapnia and severe obesity (BMI

42\text{ kg/m}^2

) meets the diagnostic criteria for Obesity Hypoventilation Syndrome (OHS).

Determine the underlying etiology and the appropriate next diagnostic step.

The patient's OHS and highly probable coexisting Obstructive Sleep Apnea (OSA) have induced hypoxic pulmonary vasoconstriction, leading to pulmonary hypertension and Cor Pulmonale. Polysomnography is indicated.

Confirming the diagnosis of OSA is essential to initiate targeted positive airway pressure therapy, which is the definitive treatment to reverse the hypoxic vasoconstriction.

Key Concept

Patients with Obesity Hypoventilation Syndrome (OHS) and Obstructive Sleep Apnea (OSA) develop chronic hypercapnia and hypoxemia, which leads to hypoxic pulmonary vasoconstriction, pulmonary hypertension, and eventually right-sided heart failure (Cor Pulmonale).

Question 3Question →

A 71-year-old man is transported to the emergency department from a local nursing facility due to the sudden onset of severe breathlessness and orthopnea that started 3 hours ago. He has a past medical history of severe chronic obstructive pulmonary disease (COPD) and ischemic cardiomyopathy with a left ventricular ejection fraction of $30\%$ .

Upon arrival, he is visibly agitated and using accessory muscles of respiration. Vital signs are:
- Temperature: $37.1^\circ\text{C}$ ( $98.8^\circ\text{F}$ )
- Blood pressure: $172/100\text{ mm Hg}$
- Heart rate: $118\text{/min}$ and regular
- Respiratory rate: $29\text{/min}$
- Oxygen saturation: $82\%$ on ambient air

Physical examination reveals jugular venous distention when sitting upright at 45 degrees. Chest auscultation demonstrates widespread expiratory wheezing mixed with fine bibasilar crackles. Cardiac auscultation reveals tachycardia and a prominent third heart sound (S3). There is 2+ bilateral pitting edema up to the knees.

Arterial blood gas analysis on ambient air shows:
- pH: 7.22
- $PaCO_2$ : $75\text{ mm Hg}$
- $PaO_2$ : $48\text{ mm Hg}$
- $HCO_3^-$ : $31\text{ mEq/L}$

Which of the following are the most appropriate initial steps in the management of this patient? (Select exactly two)

Select all that apply

Apply noninvasive positive-pressure ventilation

Administer a rapid-acting intravenous loop diuretic

Commence empiric broad-spectrum antibiotics and systemic corticosteroids

Infuse intravenous sodium bicarbonate to correct the acidemia

Administer high-dose nebulized bronchodilators as the primary therapy

Show answer & explanation

Answer: Apply noninvasive positive-pressure ventilation; Administer a rapid-acting intravenous loop diuretic

Answer

The most appropriate initial steps are applying noninvasive positive-pressure ventilation (NPPV) and administering a rapid-acting intravenous loop diuretic.

The correct interventions directly address the pathophysiology of acute decompensated heart failure (ADHF). Noninvasive positive-pressure ventilation (NPPV) provides positive intrathoracic pressure, which decreases venous return (preload) and reduces left ventricular transmural pressure (afterload), thereby improving cardiac output. It also recruits fluid-filled alveoli, improving gas exchange and reducing the work of breathing. Intravenous loop diuretics (e.g., furosemide) are indicated to rapidly reduce intravascular volume and alleviate venous congestion.

Step-by-Step Solution

Analyze the clinical presentation and physical examination findings.

The patient presents with severe respiratory distress, hypertension, JVD, an S3 gallop, bibasilar crackles, and peripheral edema.

These are classic signs of acute decompensated heart failure (ADHF) with volume overload. The wheezing represents 'cardiac asthma' secondary to peribronchial edema, not necessarily a primary COPD exacerbation.

Interpret the arterial blood gas (ABG) results.

The ABG shows acidemia (pH 7.22), severe hypercapnia (

PaCO_2

75\text{ mm Hg}

), hypoxemia (

PaO_2

48\text{ mm Hg}

), and an elevated bicarbonate (

HCO_3^-

31\text{ mEq/L}

This indicates an acute-on-chronic respiratory acidosis. The elevated bicarbonate reflects baseline chronic

CO_2

retention from severe COPD, while the acute drop in pH is driven by the sudden rise in

PaCO_2

due to alveolar flooding from cardiogenic pulmonary edema.

Determine the optimal immediate interventions based on the diagnosis.

The patient requires immediate support for oxygenation and ventilation, along with aggressive volume removal.

NPPV effectively supports ventilation, reduces the work of breathing, and provides favorable hemodynamic effects (decreased preload and afterload). Intravenous loop diuretics are required to rapidly treat the volume overload.

Key Concept

The initial management of acute decompensated heart failure (ADHF) complicated by acute hypercapnic respiratory failure prioritizes noninvasive positive-pressure ventilation (NPPV) and intravenous loop diuretics, while differentiating 'cardiac asthma' from a primary COPD exacerbation.

Question 4Question →

A 72-year-old man with a history of chronic obstructive pulmonary disease (COPD) and hypertension is brought to the emergency department for severe, worsening shortness of breath over the past 24 hours. He reports that his breathing is especially difficult when he lies down to sleep, forcing him to sleep in a recliner chair. He denies fever, chills, or any change in the volume or color of his sputum. Blood pressure is 155/92 mm Hg, pulse is 108/min, and respirations are 26/min. Pulse oximetry shows 88% on room air. Physical examination reveals distended jugular veins, bilateral crackles at the lung bases, and an S3 gallop. There is 2+ bilateral lower extremity pitting edema.

Arterial blood gas analysis on room air shows:

Parameter	Value
pH	7.28
PaCO2	60 mm Hg
HCO3-	27 mEq/L

Which of the following is the most appropriate next step in the management of this patient?

Intravenous furosemide

Inhaled albuterol and systemic glucocorticoids

Intravenous piperacillin-tazobactam

Intravenous sodium bicarbonate

Empiric oral azithromycin

Show answer & explanation

Answer: Intravenous furosemide

Answer

Intravenous furosemide is the most appropriate next step in management.

The correct answer is intravenous furosemide because the patient's presentation is classic for acute decompensated heart failure (ADHF). Despite his history of COPD, findings such as orthopnea (sleeping in a recliner), an S3 gallop, jugular venous distention, and pitting edema indicate severe volume overload and left ventricular dysfunction. Intravenous loop diuretics like furosemide rapidly decrease intravascular volume, relieving pulmonary congestion and improving respiratory mechanics. The respiratory acidosis seen on his blood gas will improve once the underlying pulmonary edema is resolved.

Step-by-Step Solution

Analyze the patient's symptoms and vital signs.

The patient has severe dyspnea, orthopnea, hypoxemia, and significant hypertension.

To identify the acuity and exact nature of the respiratory distress.

Evaluate the physical examination findings.

Findings include jugular venous distention, bibasilar crackles, an S3 gallop, and bilateral lower extremity pitting edema.

These specific signs help differentiate between possible causes of dyspnea in a patient with multiple comorbidities.

Synthesize findings to form a definitive diagnosis.

The combination of orthopnea, JVD, an S3 gallop, and edema strongly points to acute decompensated heart failure (ADHF) leading to cardiogenic pulmonary edema, despite the history of COPD.

Accurate diagnosis is required before initiating targeted therapy.

Determine the appropriate initial management.

Intravenous loop diuretics (such as furosemide) should be administered to rapidly reduce volume overload and relieve pulmonary congestion.

This is the standard, high-yield first-line treatment for ADHF.

Key Concept

Patients with a history of COPD can present with dyspnea due to acute decompensated heart failure (ADHF). Key differentiating features pointing to ADHF include orthopnea, jugular venous distention (JVD), an S3 gallop, and peripheral edema, which should be managed primarily with intravenous loop diuretics.

Estimated Time:1m 0s

Question 5Question →

A $64$ -year-old woman is evaluated in the emergency department for severe shortness of breath and increasing leg swelling over the past week. She has a history of severe chronic obstructive pulmonary disease (COPD) requiring home oxygen therapy. Her temperature is $37.0^\circ\text{C}$ ( $98.6^\circ\text{F}$ ), blood pressure is $105/68\text{ mm Hg}$ , pulse is $118\text{ /min}$ , and respirations are $28\text{ /min}$ . Jugular venous pulsation is visible at $15\text{ cm H}_2\text{O}$ . Cardiac examination reveals a prominent parasternal heave and a loud $P_2$ . Lung auscultation shows significantly prolonged expiration and diffuse wheezing, with no crackles. The liver edge is palpable $4\text{ cm}$ below the right costal margin and is tender. Moderate pitting edema is present in the lower extremities. Arterial blood gas on $2\text{ L/min}$ supplemental oxygen shows:

pH: $7.31$
$PaCO_2$ : $62\text{ mm Hg}$
$PaO_2$ : $54\text{ mm Hg}$
$HCO_3^-$ : $31\text{ mEq/L}$

A trial of non-invasive positive pressure ventilation (NIPPV) is initiated for acute-on-chronic hypercapnic respiratory failure. Ten minutes later, the patient becomes lethargic and her blood pressure drops precipitously to $70/40\text{ mm Hg}$ . Which of the following is the most appropriate immediate next step in management?

Remove the non-invasive positive pressure ventilation mask

Perform emergent endotracheal intubation

Administer an intravenous bolus of furosemide

Initiate an intravenous infusion of sodium bicarbonate

Administer intravenous piperacillin-tazobactam and vancomycin

Show answer & explanation

Answer: Remove the non-invasive positive pressure ventilation mask

Answer

Remove the non-invasive positive pressure ventilation mask

The correct answer identifies that the sudden onset of profound hypotension following the initiation of non-invasive positive pressure ventilation (NIPPV) is due to a precipitous drop in venous return. The patient's physical exam (JVD, hepatomegaly, edema, clear lungs) reveals severe right ventricular failure (cor pulmonale) secondary to COPD. The failing right ventricle requires high filling pressures (preload) to maintain adequate stroke volume. When NIPPV is applied, the positive pressure is transmitted to the intrathoracic cavity, compressing the intrathoracic veins and sharply reducing venous return. This sudden loss of preload drastically drops right ventricular output, leading to reduced left ventricular filling and systemic shock. The immediate, life-saving intervention is to remove the NIPPV mask to restore venous return.

Step-by-Step Solution

Analyze the patient's baseline clinical presentation.

The patient has signs of isolated right ventricular failure (JVD, parasternal heave, hepatomegaly, peripheral edema, clear lungs) secondary to chronic lung disease. This confirms a diagnosis of cor pulmonale.

Establishing the baseline hemodynamic state is required to predict how the patient will respond to cardiopulmonary interventions.

Evaluate the arterial blood gas results.

The ABG shows a pH of 7.31, PaCO2 of 62, and HCO3- of 31, indicating acute-on-chronic respiratory acidosis. NIPPV is a standard appropriate initial therapy for this gas exchange derangement.

Understanding the indication for NIPPV clarifies why it was started, setting up the subsequent complication.

Identify the mechanism of the sudden hemodynamic collapse after NIPPV initiation.

NIPPV delivers positive pressure to the airways, which transmits to the intrathoracic cavity. Increased intrathoracic pressure compresses the vena cava, reducing venous return (preload) to the right atrium.

Connecting the intervention to its physiological consequence is necessary to identify the cause of the shock.

Determine the effect of reduced preload on a failing right ventricle.

A failing right ventricle (cor pulmonale) is highly dependent on elevated filling pressures to maintain stroke volume. The sudden reduction in preload leads to a precipitous drop in right ventricular output, subsequent loss of left ventricular filling, and profound systemic hypotension.

This explains why the blood pressure dropped to 70/40 mm Hg and why the patient became lethargic.

Select the appropriate immediate intervention.

The inciting cause of the shock must be immediately reversed by removing the NIPPV mask to restore negative intrathoracic pressure and venous return.

Reversing the mechanical obstruction to venous return is the only way to immediately restore cardiac output in this scenario.

Key Concept

Patients with right ventricular failure (cor pulmonale) are highly dependent on adequate preload; initiating positive pressure ventilation increases intrathoracic pressure, which can precipitously reduce venous return and cause profound hypotensive shock.

Estimated Time:2m 0s

Question 6Question →

A $72$ -year-old woman is brought to the emergency department for sudden-onset severe shortness of breath, lightheadedness, and right-sided chest pain. She recently returned from a $12$ -hour international flight two days ago. Her medical history includes moderate chronic obstructive pulmonary disease (COPD) and hypertension.

On arrival, she is somnolent but arousable. Temperature is $37.0^\circ\text{C}$ ( $98.6^\circ\text{F}$ ), blood pressure is $82/50\text{ mm Hg}$ , pulse is $118/\text{min}$ , and respirations are $28/\text{min}$ . Oxygen saturation is $85\%$ on room air.

Physical examination reveals elevated jugular venous pressure. Lung auscultation is clear bilaterally.

Bedside transthoracic echocardiography demonstrates a severely enlarged right ventricle with hypokinesis of the free wall and normal apical contraction. The left ventricle is small and hyperdynamic.

An arterial blood gas on room air shows:
pH: $7.29$
$\text{PaCO}_2$ : $26\text{ mm Hg}$
$\text{PaO}_2$ : $54\text{ mm Hg}$
$\text{HCO}_3^-$ : $12\text{ mEq/L}$

Which of the following is the most appropriate next step in the management of this patient?

Administration of systemic alteplase

Transport for computed tomography pulmonary angiography

Intravenous administration of furosemide

Intravenous administration of piperacillin-tazobactam

Endotracheal intubation and mechanical ventilation

Show answer & explanation

Answer: Administration of systemic alteplase

Answer

Administration of systemic alteplase

The correct answer is the administration of systemic alteplase. This patient presents with classic signs of a massive (high-risk) pulmonary embolism (PE): sudden-onset dyspnea, hypoxia, and hemodynamic instability (hypotension) following a major risk factor (prolonged travel). In patients with suspected massive PE who are too unstable to safely undergo definitive imaging (CT pulmonary angiography), bedside transthoracic echocardiography is the diagnostic test of choice. The presence of right ventricular dilation and free wall hypokinesis with apical sparing (McConnell's sign) provides sufficient evidence of acute right heart strain to justify immediate intervention. The treatment of choice for massive PE in the absence of absolute contraindications is systemic thrombolysis (e.g., alteplase). Thrombolytics rapidly lyse the clot, reducing pulmonary vascular resistance, alleviating right ventricular strain, and improving cardiac output.

Step-by-Step Solution

Identify the primary clinical syndrome.

The patient presents with sudden-onset dyspnea, hypoxia, right-sided chest pain, and profound hypotension (

82/50

mm Hg) following a period of prolonged immobilization.

Establishing the severity and likely etiology (massive pulmonary embolism causing cardiogenic shock).

Interpret the diagnostic data.

Bedside echocardiography shows right ventricular dilation and hypokinesis with apical sparing (McConnell's sign), confirming acute right heart strain. The ABG shows a primary metabolic acidosis (lactic acidosis from shock) with appropriate respiratory compensation.

To confirm the diagnosis of massive PE and safely rule out other causes of shock or acute respiratory failure.

Determine the most appropriate next step in management.

In a hemodynamically unstable patient with high clinical suspicion for PE and bedside echo evidence of RV strain, systemic thrombolysis (alteplase) is indicated immediately without waiting for definitive CT imaging.

To rapidly dissolve the thrombus, reduce right ventricular afterload, and restore cardiac output.

Key Concept

Massive (high-risk) pulmonary embolism is defined by hemodynamic instability (systolic BP

< 90

mm Hg) and should be managed with systemic thrombolytics if bedside echocardiography shows right heart strain, as these patients are often too unstable for CT pulmonary angiography.

Alternative Method

In advanced centers, catheter-directed thrombolysis or surgical pulmonary embolectomy may be considered as alternative emergent treatments for massive PE, particularly if systemic thrombolysis has failed or is absolutely contraindicated.

Estimated Time:1m 30s

Question 7Question →

A 55-year-old man is brought to the emergency department by his wife due to progressively worsening shortness of breath and lethargy over the past week. His wife reports he recently had a mild viral upper respiratory tract infection and has been falling asleep mid-conversation for the past two days. His medical history is significant for morbid obesity, hypertension, and type 2 diabetes mellitus. He has a 5-pack-year smoking history but quit 15 years ago.

Vital signs are:
Temperature: $37.1^\circ\text{C}$ ( $98.8^\circ\text{F}$ )
Pulse: $98\text{/min}$
Blood pressure: $145/90\text{ mmHg}$
Respiratory rate: $22\text{/min}$
$SpO_2$ : $84\%$ on room air
BMI: $46\text{ kg/m}^2$

Physical examination shows a somnolent but easily arousable obese man. Jugular venous pulsation is visible $9\text{ cm}$ above the sternal angle. Chest auscultation reveals shallow, distant breath sounds bilaterally with no crackles or wheezes. Cardiac examination shows a regular rhythm with a prominently split second heart sound and a loud pulmonic component ( $P_2$ ). The abdomen is protuberant. There is 3+ pitting edema of the bilateral lower extremities extending to the knees.

Laboratory results reveal a leukocyte count of $8,500/\mu\text{L}$ and a B-type natriuretic peptide (BNP) level of $110\text{ pg/mL}$ (normal: $<100\text{ pg/mL}$ ). Chest radiography shows an enlarged main pulmonary artery but clear lung fields without infiltrates, effusions, or cardiomegaly.

Arterial blood gas analysis on room air reveals:
pH: $7.31$
$PaCO_2$ : $62\text{ mmHg}$
$PaO_2$ : $55\text{ mmHg}$
$HCO_3^-$ : $31\text{ mEq/L}$

Which of the following is the most appropriate initial step in the management of this patient?

Initiation of noninvasive positive pressure ventilation

Administration of intravenous furosemide and nitroglycerin

Administration of intravenous sodium bicarbonate

Administration of intravenous piperacillin-tazobactam

Endotracheal intubation and mechanical ventilation

Show answer & explanation

Answer: Initiation of noninvasive positive pressure ventilation

Answer

Initiation of noninvasive positive pressure ventilation

The correct option addresses the primary pathophysiological issue: acute-on-chronic hypercapnic respiratory failure due to Obesity Hypoventilation Syndrome (OHS). OHS is characterized by severe obesity (BMI

\geq 30 \text{ kg/m}^2

) and chronic daytime hypercapnia (

PaCO_2 \geq 45 \text{ mmHg}

). Chronic hypoxia and hypercapnia lead to hypoxic pulmonary vasoconstriction, ultimately causing pulmonary hypertension and right-sided heart failure (cor pulmonale), evidenced in this patient by the elevated JVP, loud

P_2

, and pitting edema. In the setting of an acute exacerbation (often triggered by mild infections), the most appropriate initial intervention for a hemodynamically stable patient who is easily arousable is noninvasive positive pressure ventilation (NPPV). NPPV provides ventilatory support, improves gas exchange, and decreases the work of breathing, significantly reducing the need for invasive mechanical ventilation.

Step-by-Step Solution

Analyze the patient's clinical presentation and physical exam findings.

The patient is morbidly obese with daytime somnolence, elevated JVP, loud P2, and severe lower extremity edema, but has clear lung fields and a normal BNP.

These findings are highly specific for isolated right-sided heart failure (cor pulmonale) secondary to hypoxic pulmonary vasoconstriction, rather than left-sided heart failure.

Interpret the arterial blood gas (ABG) values.

pH is 7.31 (acidemia), PaCO2 is 62 mmHg (respiratory acidosis), and HCO3- is 31 mEq/L (metabolic compensation).

This confirms a primary respiratory acidosis. The elevated baseline bicarbonate indicates a chronic component (chronic CO2 retention), with an acute exacerbation dropping the pH.

Synthesize the data to establish the diagnosis.

The combination of severe obesity, chronic hypercapnia, and right heart failure confirms Obesity Hypoventilation Syndrome (OHS), currently presenting with acute-on-chronic hypercapnic respiratory failure triggered by a viral URI.

OHS is defined by obesity (BMI > 30) and awake alveolar hypoventilation (PaCO2 > 45) that cannot be attributed to other conditions.

Determine the most appropriate initial management.

Noninvasive positive pressure ventilation (NPPV) should be initiated.

In hemodynamically stable, arousable patients with acute hypercapnic respiratory failure (such as in OHS or COPD exacerbations), an initial trial of NPPV improves ventilation, reduces the work of breathing, and often prevents the need for intubation.

Key Concept

Obesity Hypoventilation Syndrome and Cor Pulmonale Management

Estimated Time:1m 30s

Question 8Question →

Emergency medical services bring a 67-year-old man to the hospital due to profound lethargy and reduced urine output over the last 24 hours. His medical history includes severe chronic obstructive pulmonary disease (COPD) and ischemic cardiomyopathy. A legally binding advance directive in his electronic medical record designates his wife as his healthcare proxy; she has previously consented to all life-saving interventions. Currently, his son is at the bedside and explicitly demands that no breathing tubes be placed. Vital signs reveal a temperature of 38.9°C (102.0°F), blood pressure of 82/45 mm Hg, pulse of 126/min, and respirations of 32/min. Physical examination shows a somnolent patient who only localizes to painful stimuli. Jugular venous pressure is 5 cm H₂O. Lung auscultation demonstrates diminished breath sounds bilaterally with shallow inspiratory efforts. The patient receives 3 liters of intravenous crystalloids, broad-spectrum antibiotics, and a norepinephrine infusion. A brief accidental disconnection of his oxygen tubing by a staff member is noted and immediately corrected. Arterial blood gas analysis on room air shows:

pH: $7.23$
PaCO₂: $35 \text{ mm Hg}$
PaO₂: $72 \text{ mm Hg}$
HCO₃⁻: $14 \text{ mEq/L}$

Based on these findings, which of the following is the most appropriate next step in management?

Proceed with invasive mechanical ventilation

Maintain current management as the arterial blood gas demonstrates appropriate compensation

Administer an intravenous loop diuretic to treat acute pulmonary edema

Withhold advanced airway management in compliance with the son's directives

Recommend immediate disciplinary action for the staff member involved in the oxygen disconnection

Show answer & explanation

Answer: Proceed with invasive mechanical ventilation

Answer

Proceed with invasive mechanical ventilation

The correct action is to proceed with invasive mechanical ventilation. This patient presents with septic shock, evidenced by fever, hypotension, and primary metabolic acidosis. In primary metabolic acidosis, the appropriate respiratory compensation is calculated using Winter's formula (

PaCO_2 = 1.5 \times [HCO_3^-] + 8 \pm 2

). For this patient, the expected

PaCO_2

29 \pm 2 \text{ mm Hg}

. The measured

PaCO_2

35 \text{ mm Hg}

, which is inappropriately elevated and points to a superimposed acute respiratory acidosis. Clinically, his somnolence, tachypnea with shallow efforts, and inability to achieve target ventilation signify respiratory muscle fatigue and impending complete respiratory failure, making prompt intubation mandatory.

Step-by-Step Solution

Analyze the primary acid-base disorder.

The patient has a primary metabolic acidosis.

The arterial blood gas shows acidemia (pH = 7.23) driven by a low bicarbonate level (HCO₃⁻ = 14 mEq/L), consistent with lactic acidosis from septic shock.

Calculate the expected respiratory compensation using Winter's formula.

The expected PaCO₂ range is 27 to 31 mm Hg.

Using the formula: Expected PaCO₂ = 1.5 × [HCO₃⁻] + 8 ± 2. Calculation: 1.5 × 14 + 8 = 21 + 8 = 29 ± 2 mm Hg.

Compare the expected PaCO₂ to the measured PaCO₂.

The measured PaCO₂ (35 mm Hg) is higher than the expected maximum compensation (31 mm Hg).

This indicates a concomitant acute respiratory acidosis, meaning the patient is failing to mount the necessary respiratory drive to compensate for the metabolic acidosis.

Synthesize the clinical presentation to determine the immediate intervention.

The next best step is to secure the airway with invasive mechanical ventilation.

The combination of severe sepsis, somnolence, shallow inspiratory efforts, and a superimposed respiratory acidosis confirms impending respiratory failure. The son's demands do not legally override the established proxy's prior consent.

Key Concept

Patients with severe metabolic acidosis require profound hyperventilation for respiratory compensation; a PaCO₂ higher than predicted by Winter's formula indicates impending respiratory failure requiring mechanical ventilation.

Estimated Time:2m 0s

Question 9Question →

A 65-year-old man is brought to the emergency department by his family due to a 2-day history of worsening shortness of breath and an increase in the volume and purulence of his sputum. His medical history includes chronic obstructive pulmonary disease and mild heart failure with preserved ejection fraction. Vital signs show a temperature of 37.4°C (99.3°F), blood pressure of 138/86 mm Hg, heart rate of 108/min, respiratory rate of 24/min, and oxygen saturation of 89% on room air. Physical examination reveals a prolonged expiratory phase with diffuse expiratory wheezing bilaterally. There is no jugular venous distention, and no lower extremity edema is appreciated. A chest radiograph demonstrates hyperinflated lung fields and flattened diaphragms without focal consolidations or pleural effusions. An arterial blood gas analysis on room air shows a pH of 7.32, PaCO2 of 54 mm Hg, and PaO2 of 58 mm Hg. Which of the following are appropriate initial management steps for this patient? (Select all that apply)

Select all that apply

Administration of nebulized short-acting bronchodilators

Administration of a systemic corticosteroid

Administration of intravenous furosemide

Administration of broad-spectrum intravenous antibiotics such as vancomycin and cefepime

Intravenous infusion of sodium bicarbonate

Show answer & explanation

Answer: Administration of nebulized short-acting bronchodilators; Administration of a systemic corticosteroid

Answer

The correct interventions are the administration of nebulized short-acting bronchodilators and the administration of a systemic corticosteroid.

The patient is experiencing an acute exacerbation of chronic obstructive pulmonary disease (AECOPD), characterized by the cardinal symptoms of increased dyspnea, increased sputum volume, and increased sputum purulence. The initial medical management of an AECOPD requires aggressive bronchodilation to relieve airflow obstruction and systemic glucocorticoids to reduce airway inflammation. Short-acting bronchodilators (e.g., albuterol, ipratropium) provide rapid relief of bronchospasm. Systemic corticosteroids (e.g., oral prednisone or intravenous methylprednisolone) have been shown to shorten recovery time, improve lung function, and decrease the risk of early relapse. Because the patient has increased sputum purulence, antibiotics are also indicated, but they should be targeted (e.g., azithromycin or doxycycline) rather than broad-spectrum.

Step-by-Step Solution

Identify the primary clinical problem.

Acute exacerbation of chronic obstructive pulmonary disease (AECOPD).

The patient has a history of COPD and presents with the cardinal symptoms of increased dyspnea, increased sputum volume, and increased sputum purulence, alongside physical exam findings of bronchospasm without signs of fluid overload.

Evaluate the acid-base status.

Acute-on-chronic respiratory acidosis.

The arterial blood gas shows acidemia (pH 7.32) driven by hypercapnia (PaCO2 54 mm Hg) with partial metabolic compensation, typical for an acute decompensation in COPD.

Select appropriate evidence-based therapies.

Short-acting bronchodilators and systemic corticosteroids.

These are the foundational, first-line medical treatments for AECOPD to reduce airway inflammation, relieve bronchospasm, and improve airflow.

Key Concept

The initial management of an acute exacerbation of COPD requires short-acting bronchodilators, systemic corticosteroids, and targeted (not unnecessarily broad-spectrum) antibiotics if cardinal symptoms are present.

Estimated Time:1m 15s

Question 10Question →

During morning multidisciplinary rounds in the intensive care unit, the team evaluates a 73-year-old male who has been mechanically ventilated for the past $48$ hours. His initial presentation involved profound hypoxemia due to community-acquired pneumonia. The patient's medical history includes ischemic cardiomyopathy (left ventricular ejection fraction of $25\%$ ) and severe emphysema.

He was empirically started on intravenous vancomycin and piperacillin-tazobactam. The microbiology laboratory has just finalized the results of blood and bronchoalveolar lavage fluid cultures obtained at admission; both demonstrate heavy growth of *Streptococcus pneumoniae*. The susceptibility report confirms the isolate is sensitive to all tested antibiotics, including ceftriaxone and penicillin.

Vital signs reveal a heart rate of $112$ /min and a blood pressure of $118/72$ mm Hg. He is afebrile. Physical examination shows engorged neck veins when the head of the bed is elevated. Cardiac auscultation identifies a third heart sound (S3). Lung examination yields diffuse bilateral crepitations that extend to the mid-apices, accompanied by prolonged expiratory wheezing.

An arterial blood gas analysis on current ventilator settings reveals:
- pH: $7.18$
- pCO $_2$ : $56$ mm Hg
- pO $_2$ : $82$ mm Hg
- HCO $_3^-$ : $20$ mEq/L

Which of the following interventions are appropriate for this patient at this time? (Select all that apply)

Select all that apply

Initiate intravenous loop diuretic therapy

Raise the set respiratory rate or tidal volume on the ventilator

Maintain the existing empiric antimicrobial coverage with vancomycin and piperacillin-tazobactam

Administer systemic glucocorticoids and scheduled short-acting bronchodilators

Infuse intravenous sodium bicarbonate to correct the acidemia

Show answer & explanation

Answer: Initiate intravenous loop diuretic therapy; Raise the set respiratory rate or tidal volume on the ventilator

Answer

The appropriate next steps are to initiate intravenous loop diuretic therapy and to raise the set respiratory rate or tidal volume on the ventilator.

The correct interventions address the patient's two most acute, life-threatening derangements. First, the patient presents with volume overload resulting in cardiogenic pulmonary edema, characterized by an S3 gallop, elevated jugular venous pressure, and widespread crackles with wheezing (so-called 'cardiac asthma'). Diuresis with an intravenous loop diuretic is the cornerstone of therapy for acute decompensated heart failure. Second, the arterial blood gas reveals a mixed acid-base disorder. With a bicarbonate of

20

mEq/L, the expected pCO

_2

calculated by Winter's formula is

38 \pm 2

mm Hg. The patient's actual pCO

_2

56

mm Hg, indicating a significant superimposed respiratory acidosis. Because the patient is mechanically ventilated, the primary treatment for this respiratory acidosis is to increase the minute ventilation by raising either the respiratory rate or the tidal volume.

Step-by-Step Solution

Evaluate the patient's current physical examination and vital signs.

The patient has elevated jugular venous pressure, an S3 gallop, and diffuse crackles with wheezing.

These are classic signs of volume overload and acute decompensated heart failure, which can present with wheezing (cardiac asthma), necessitating diuresis.

Review the microbiology results and current medications.

Cultures grew pan-sensitive Streptococcus pneumoniae, but the patient is still on vancomycin and piperacillin-tazobactam.

Antimicrobial stewardship requires de-escalating from broad-spectrum to targeted therapy (e.g., ceftriaxone) once susceptibilities are known.

Interpret the arterial blood gas using Winter's formula.

Expected pCO2 = 1.5 × 20 + 8 ± 2 = 38 ± 2 mm Hg. The actual pCO2 (56 mm Hg) is much higher than expected.

This confirms a superimposed respiratory acidosis compounding the mild metabolic acidosis, requiring an increase in minute ventilation (via rate or tidal volume) to correct.

Key Concept

Management of acute decompensated heart failure ('cardiac asthma') and mixed acid-base disorders in the ICU requires diuresis, targeted ventilation adjustments, and adherence to antimicrobial stewardship.

Question 11Question →

A 22-year-old woman with a history of type 1 diabetes mellitus is admitted to the intensive care unit with a two-day history of high fever, productive cough, and progressive lethargy. She has been unable to tolerate oral intake and missed her last four doses of insulin. On arrival, her temperature is $38.9^\circ\text{C}$ ( $102^\circ\text{F}$ ), pulse is $132\text{/min}$ , respiratory rate is $36\text{/min}$ , and blood pressure is $88/54\text{ mm Hg}$ . Oxygen saturation is $89\%$ on ambient air. Physical examination reveals deep, rapid breathing and bronchial breath sounds with crackles in the right lower lung field. Laboratory studies show a serum glucose of $510\text{ mg/dL}$ , sodium of $134\text{ mEq/L}$ , potassium of $4.9\text{ mEq/L}$ , chloride of $98\text{ mEq/L}$ , and bicarbonate of $10\text{ mEq/L}$ . A chest radiograph confirms a right lower lobe consolidation. The patient is resuscitated with intravenous normal saline, started on a continuous insulin infusion, and administered intravenous ceftriaxone and azithromycin. Two hours later, her respiratory effort wanes and she becomes severely hypoxemic, necessitating endotracheal intubation. She is placed on volume assist-control mechanical ventilation with a tidal volume of $400\text{ mL}$ , a respiratory rate of $14\text{/min}$ , $FiO_2$ of $0.70$ , and positive end-expiratory pressure (PEEP) of $5\text{ cm }H_2O$ . Thirty minutes later, arterial blood gas analysis reveals:

$pH$ : $7.15$
$PaCO_2$ : $38\text{ mm Hg}$
$PaO_2$ : $72\text{ mm Hg}$
$HCO_3^-$ : $10\text{ mEq/L}$

Which of the following is the most appropriate next step in the management of this patient?

Administer an intravenous bolus of sodium bicarbonate

Decrease the tidal volume to

300\text{ mL}

Increase the ventilator respiratory rate

Administer intravenous furosemide

Escalate antimicrobial therapy to intravenous vancomycin and meropenem

Show answer & explanation

Answer: Increase the ventilator respiratory rate

Answer

Increase the ventilator respiratory rate

The correct answer is to increase the ventilator respiratory rate. This patient has a severe primary metabolic acidosis secondary to diabetic ketoacidosis. In a spontaneously breathing patient, this profound metabolic acidosis triggers compensatory hyperventilation (Kussmaul respirations) to blow off

CO_2

and mitigate the drop in serum

pH

. According to Winter's formula, her expected

PaCO_2

should be

23 \pm 2\text{ mm Hg}

based on her bicarbonate level of

10\text{ mEq/L}

. However, after intubation, sedation, and paralysis, she is completely dependent on the mechanical ventilator for her minute ventilation. The current ventilator settings (tidal volume of

400\text{ mL}

and a physiological rate of

14\text{/min}

) are providing a 'normal' minute ventilation that is entirely inadequate for her massive compensatory needs. This has resulted in a

PaCO_2

38\text{ mm Hg}

, representing a superimposed, iatrogenic acute respiratory acidosis that has driven her

pH

down to

7.15

. To correct this life-threatening acidemia, her minute ventilation must be substantially increased by raising the ventilator's respiratory rate.

Step-by-Step Solution

Identify the primary acid-base disorder.

The patient has a primary metabolic acidosis with a

HCO_3^-

10\text{ mEq/L}

and a

pH

7.15

She presents with diabetic ketoacidosis, which causes a high anion gap metabolic acidosis.

Calculate the expected respiratory compensation.

Using Winter's formula, the expected

PaCO_2 = (1.5 \times 10) + 8 = 23 \pm 2\text{ mm Hg}

Calculating the expected

PaCO_2

is essential to determine if the respiratory system is adequately compensating for the metabolic derangement.

Compare expected and actual

PaCO_2

values.

The actual

PaCO_2

38\text{ mm Hg}

is significantly higher than the expected range of

21\text{-}25\text{ mm Hg}

This discrepancy indicates a superimposed acute respiratory acidosis because the patient is retaining too much

CO_2

relative to her profound metabolic needs.

Determine the cause of the failure and correct it.

The mechanical ventilator's set respiratory rate (

14\text{/min}

) is much lower than her native compensatory rate (

36\text{/min}

), depriving her of the necessary minute ventilation. The rate must be increased.

Failing to match the required minute ventilation in a patient with severe metabolic acidosis causes rapid, life-threatening acidemia.

Key Concept

Ventilator management and minute ventilation requirements in severe metabolic acidosis

Estimated Time:2m 0s

Question 12Question →

A 34-year-old woman with no significant past medical history is evaluated in the clinic for a 6-month history of progressively worsening exertional dyspnea and fatigue. She has no cough, wheezing, orthopnea, or leg swelling. She does not smoke. Vital signs are within normal limits. Physical examination reveals a prominent right ventricular heave, a loud pulmonic component of the second heart sound (P2), and a faint holosystolic murmur at the left lower sternal border that increases in intensity with inspiration. The lungs are clear to auscultation bilaterally. Electrocardiogram shows right axis deviation and right ventricular hypertrophy. Suspecting a primary pulmonary vascular disorder, the physician plans a comprehensive diagnostic workup.

Arrange the following diagnostic and management steps in the correct chronological sequence according to consensus guidelines for unexplained pulmonary hypertension, moving from initial screening to definitive management:

Drag items to arrange them in the correct order

Show answer & explanation

Answer

The correct sequence is: Echocardiography, followed by a V/Q scan, then right heart catheterization, followed by acute vasoreactivity testing during the catheterization, and finally initiation of targeted pulmonary vasodilator therapy.

The correct sequence for evaluating unexplained pulmonary hypertension begins with non-invasive screening using transthoracic echocardiography to estimate pulmonary pressures. Once PH is suspected, a V/Q scan must be performed to evaluate for chronic thromboembolic pulmonary hypertension (CTEPH), as it is highly sensitive for chronic clots. If the V/Q scan is normal or low probability, right heart catheterization is strictly required to definitively confirm precapillary hemodynamics (mean pulmonary artery pressure ≥ 20 mmHg, PCWP ≤ 15 mmHg, PVR ≥ 3 Wood units). During the catheterization for idiopathic PAH, acute vasoreactivity testing with a short-acting vasodilator (like inhaled nitric oxide) is performed. Finally, based on the hemodynamic and vasoreactivity results, targeted PAH therapy (such as a calcium channel blocker for vasoreactive patients, or an endothelin receptor antagonist for non-reactive patients) is initiated.

Step-by-Step Solution

Identify the most likely diagnosis and the best initial screening test.

The patient's presentation strongly suggests idiopathic pulmonary arterial hypertension. Transthoracic echocardiography is selected as the first step.

Echocardiography is the universal non-invasive standard to estimate right ventricular systolic pressure and evaluate for left-sided heart disease.

Determine the appropriate non-invasive test to rule out Group 4 pulmonary hypertension.

A ventilation/perfusion (V/Q) scan is ordered next.

Guidelines mandate V/Q scanning to screen for chronic thromboembolic pulmonary hypertension (CTEPH) before invasive testing, as it is significantly more sensitive than CT pulmonary angiography for chronic microvascular clots.

Select the definitive diagnostic test to confirm precapillary hemodynamics.

Right heart catheterization (RHC) is performed.

RHC is the gold standard required to definitively differentiate pre-capillary PAH from post-capillary venous hypertension and to formally establish the diagnosis.

Determine the appropriate procedural test to guide specific medical therapy.

Acute vasoreactivity testing with inhaled nitric oxide is conducted.

During RHC, vasoreactivity must be assessed in idiopathic PAH to identify the small subset of patients who will respond favorably to high-dose calcium channel blockers.

Choose the final management step based on the comprehensive diagnostic workup.

Targeted pulmonary vasodilator therapy is initiated.

Once formal hemodynamics and vasoreactivity status are established, appropriate evidence-based therapy can be safely prescribed without risk of exacerbating unconfirmed underlying conditions.

Key Concept

The diagnostic algorithm for pulmonary hypertension requires sequential non-invasive screening (Echocardiography, then V/Q scan) followed by invasive confirmation (Right heart catheterization with vasoreactivity testing) before initiating targeted PAH therapy.

Estimated Time:2m 30s

Question 13Question →

A $64$ -year-old male construction worker presents to the emergency department for escalating breathlessness and a productive cough over the past three days. He notes that his baseline morning cough has worsened, and he is now producing thick, yellow-green sputum. His past medical history is significant for severe chronic obstructive pulmonary disease (COPD) and essential hypertension. He is currently compliant with a daily tiotropium inhaler. Vital signs demonstrate a temperature of $37.5^\circ\text{C}$ ( $99.5^\circ\text{F}$ ), blood pressure of $132/84$ mmHg, heart rate of $94$ /min, and respiratory rate of $24$ /min. Pulse oximetry shows an oxygen saturation of $91\%$ on room air. Chest auscultation reveals prominent bilateral expiratory wheezing with a prolonged expiratory phase. There are no crackles. The jugular venous pressure is normal, and there is no lower extremity edema. Which of the following is the most appropriate pharmacological management for this patient?

Inhaled albuterol, oral prednisone, and oral azithromycin

Inhaled albuterol, oral prednisone, and intravenous piperacillin-tazobactam

Intravenous furosemide and noninvasive positive-pressure ventilation

Intravenous bumetanide and oral levofloxacin

Inhaled albuterol, oral prednisone, and intravenous vancomycin

Show answer & explanation

Answer: Inhaled albuterol, oral prednisone, and oral azithromycin

Answer

Inhaled albuterol, oral prednisone, and oral azithromycin

The correct answer provides the standard optimal therapy for an acute exacerbation of chronic obstructive pulmonary disease (COPD) in the emergency department. This patient presents with all three cardinal symptoms: increased dyspnea, increased sputum volume, and increased sputum purulence. Management requires inhaled short-acting bronchodilators (e.g., albuterol) to relieve bronchospasm, systemic corticosteroids (e.g., oral prednisone) to reduce airway inflammation, and an antibiotic to treat potential bacterial triggers. A targeted agent such as a macrolide (e.g., azithromycin) is preferred to cover typical respiratory pathogens while respecting antibiotic stewardship.

Step-by-Step Solution

Identify the primary clinical syndrome based on the patient's presentation.

The patient has increased dyspnea, increased sputum volume, and increased sputum purulence, which are the three cardinal signs of an acute exacerbation of chronic obstructive pulmonary disease (COPD).

Recognizing the cardinal symptoms determines the need for specific therapeutic interventions, particularly antibiotics.

Evaluate the patient for signs of alternative diagnoses, such as acute decompensated heart failure.

The physical examination shows no crackles, no jugular venous distention, and no lower extremity edema.

Differentiating between a primary pulmonary process and a cardiac process prevents the administration of harmful or ineffective treatments like loop diuretics.

Select the appropriate evidence-based interventions for an uncomplicated COPD exacerbation.

The correct regimen includes short-acting bronchodilators, systemic corticosteroids, and a targeted, narrow-spectrum antibiotic (like azithromycin).

This combination addresses bronchoconstriction, airway inflammation, and bacterial infection while adhering to antibiotic stewardship guidelines.

Key Concept

The management of an acute COPD exacerbation with three cardinal symptoms includes short-acting bronchodilators, systemic corticosteroids, and targeted antibiotics (e.g., macrolides or tetracyclines). Broad-spectrum antibiotics should be avoided unless specific risk factors are present.

Question 14Question →

A 26-year-old man is evaluated in the emergency department for severe shortness of breath that has progressively worsened over the past 48 hours. He has a lifelong history of asthma and uses a short-acting bronchodilator as needed. Yesterday, he moved into an apartment with a roommate who owns a cat. On arrival, the patient is fully alert but speaks in short, two-word sentences. Initial vital signs include a temperature of 37.1°C ( $98.8$ °F), blood pressure of 135/82 mmHg, pulse of 122/min, and respiratory rate of 30/min. Pulse oximetry shows an oxygen saturation of 93% on room air. Physical examination demonstrates prominent accessory muscle use and loud, diffuse expiratory wheezing.

He is immediately treated with continuous nebulized albuterol, ipratropium, and intravenous methylprednisolone. Two hours later, the nurse urgently alerts the physician because the patient has become drowsy and is difficult to rouse. Repeat vital signs show a blood pressure of 108/65 mmHg, pulse of 138/min, and a respiratory rate of 12/min. Oxygen saturation is 87% on 4 L/min via nasal cannula. Repeat chest auscultation reveals markedly diminished breath sounds bilaterally with absent wheezing.

An arterial blood gas analysis on the current oxygen setting shows:

Laboratory	Result
$pH$	$7.24$
$PaCO_2$	$60$ mmHg
$PaO_2$	$56$ mmHg
$HCO_3^-$	$25$ mEq/L

Which of the following is the most appropriate next step in the management of this patient?

Perform endotracheal intubation

Administer intravenous sodium bicarbonate

Administer intravenous furosemide

Begin continuous intravenous piperacillin-tazobactam

Initiate bilevel positive airway pressure therapy

Show answer & explanation

Answer: Perform endotracheal intubation

Answer

Perform endotracheal intubation

The correct intervention is endotracheal intubation. This patient is experiencing severe status asthmaticus complicated by impending respiratory failure. Initially, acute asthma exacerbations typically present with hyperventilation and a respiratory alkalosis (low

PaCO_2

). However, as the respiratory muscles fatigue against severe airway resistance, minute ventilation drops, leading to carbon dioxide retention (hypercapnia) and acute respiratory acidosis. The triad of altered mental status (drowsiness), a decreasing respiratory rate (from 30/min to 12/min), and a 'silent chest' (markedly diminished breath sounds due to critical airflow limitation) are hallmark signs that the patient can no longer maintain independent respiration. Immediate definitive airway protection via endotracheal intubation and mechanical ventilation is necessary to ensure adequate gas exchange and prevent anoxic brain injury or cardiac arrest.

Step-by-Step Solution

Analyze the clinical progression and physical examination findings.

The patient transitioned from being alert with loud wheezing and tachypnea to being lethargic with a 'silent chest' and bradypnea.

Tracking these changes identifies the transition from an acute asthma attack to severe respiratory muscle fatigue.

Interpret the arterial blood gas (ABG) values.

The ABG demonstrates a low pH (

7.24

) and a significantly elevated

PaCO_2

(

60

mmHg).

This confirms acute, uncompensated respiratory acidosis, verifying that alveolar hypoventilation has occurred.

Select the appropriate intervention for impending respiratory failure.

Endotracheal intubation and mechanical ventilation are required.

Lethargy, hypercapnia, and hypoventilation in the setting of status asthmaticus necessitate immediate definitive airway protection and ventilatory support to prevent cardiac arrest.

Key Concept

Impending respiratory failure in severe asthma exacerbations is clinically characterized by a normalizing or elevated

PaCO_2

, altered mental status, and a 'silent chest', requiring immediate endotracheal intubation and mechanical ventilation.

Question 15Question →

A 32-year-old woman presents to the outpatient clinic with a 1-day history of right-sided pleuritic chest pain and mild dyspnea. Her vital signs show a temperature of 37.1°C (98.8°F), pulse of 92/min, respiratory rate of 16/min, and blood pressure of 118/76 mm Hg. Oxygen saturation is 99% on room air. She has no history of venous thromboembolism, recent surgery, or immobilization. Her physical examination is unremarkable. Arrange the following diagnostic steps in the most appropriate sequential order for the evaluation of this patient.

Drag items to arrange them in the correct order

Show answer & explanation

Answer

The correct sequence is to first assess the pretest clinical probability, followed by measuring D-dimer levels, and finally performing a computed tomography pulmonary angiography if indicated.

The correct sequence reflects the standard evidence-based algorithm for evaluating suspected pulmonary embolism in a hemodynamically stable patient. The first priority is always to establish the pretest probability using a scoring system like the Wells criteria. Because this patient is young, has no significant risk factors, and has stable vital signs, her pretest probability is low. For low-risk patients, a high-sensitivity D-dimer test is the most appropriate next step because a negative result non-invasively rules out a pulmonary embolism. Computed tomography pulmonary angiography (CTPA) should only be performed subsequently if the D-dimer test is positive.

Step-by-Step Solution

Determine pretest probability

Low clinical probability identified

Establishing the clinical risk score guides whether to use a biomarker test or proceed directly to imaging.

Measure D-dimer levels

Diagnostic threshold evaluated

Effectively rules out pulmonary embolism in low-risk patients, preventing unnecessary radiation exposure.

Perform CTPA

Definitive imaging diagnosis

Required to confirm the diagnosis only if the initial D-dimer screening test is positive.

Key Concept

Diagnostic algorithm for hemodynamically stable suspected pulmonary embolism based on clinical pretest probability

Question 16Question →

A 59-year-old woman is evaluated on hospital day 3 for new-onset respiratory distress. She was initially admitted for pyelonephritis complicated by septic shock and received 4 liters of intravenous crystalloid fluids over the first 24 hours. Blood cultures drawn on admission grew *Escherichia coli* that is susceptible to ceftriaxone, ciprofloxacin, and ampicillin. She has a history of type 2 diabetes mellitus and hypertension. Current medications include intravenous piperacillin-tazobactam.

Temperature is 37.2°C (99.0°F), blood pressure is 142/86 mmHg, heart rate is 112/min, and respiratory rate is 28/min. Pulse oximetry is 88% on room air. Physical examination reveals jugular venous distention to 11 cm H2O. Lung auscultation demonstrates bilateral crackles extending to the mid-scapulae and diffuse expiratory wheezes.

Arterial blood gas analysis on room air reveals:
pH: 7.25
PaCO2: 42 mmHg
PaO2: 56 mmHg
HCO3-: 18 mEq/L

Which of the following is the most appropriate next step in the management of this patient?

Intravenous furosemide and noninvasive positive pressure ventilation

Inhaled albuterol and intravenous methylprednisolone

Escalation of antimicrobial therapy to intravenous meropenem

Intravenous sodium bicarbonate infusion

Intravenous normal saline bolus and transition to ceftriaxone

Show answer & explanation

Answer: Intravenous furosemide and noninvasive positive pressure ventilation

Answer

Intravenous furosemide and noninvasive positive pressure ventilation

The correct answer combines intravenous furosemide and noninvasive positive pressure ventilation (NPPV). This patient developed acute decompensated heart failure (ADHF) secondary to aggressive fluid resuscitation for sepsis. Clinical signs include elevated jugular venous pressure, bibasilar crackles, and hypoxemia. The wheezing represents 'cardiac asthma' resulting from peribronchial edema. The ABG demonstrates a primary metabolic acidosis (

HCO_3^-

18\ mEq/L

). According to Winter's formula (

Expected\ PaCO_2 = 1.5 \times 18 + 8 = 35 \pm 2\ mmHg

), the

PaCO_2

should be between

33

and

37\ mmHg

. Her actual

PaCO_2

42\ mmHg

, which indicates a superimposed respiratory acidosis due to respiratory muscle fatigue from the severe pulmonary edema. Immediate treatment requires diuresis to reduce volume status and NPPV to offload the work of breathing and improve gas exchange.

Step-by-Step Solution

Analyze the physical examination findings and clinical history.

The patient has elevated jugular venous distention, bilateral crackles, and wheezing following large-volume fluid resuscitation, indicating volume overload and acute pulmonary edema.

Differentiating iatrogenic volume overload from progression of sepsis or primary pulmonary disease is the first step in diagnosing her acute deterioration.

Interpret the arterial blood gas (ABG) using Winter's formula.

The patient has a primary metabolic acidosis (

HCO_3^-

= 18 mEq/L). Using Winter's formula (

1.5 \times 18 + 8 = 35 \pm 2

), the expected

PaCO_2

is 33-37 mmHg. The actual

PaCO_2

is 42 mmHg.

Calculating expected respiratory compensation reveals a superimposed, uncompensated respiratory acidosis, indicating the patient is developing respiratory muscle fatigue.

Determine the most appropriate management.

The combination of diuresis (furosemide) and noninvasive positive pressure ventilation (NPPV) is selected.

Furosemide reduces total body volume, while NPPV decreases the work of breathing, improves oxygenation, and decreases cardiac preload, addressing both the fluid overload and the impending respiratory failure.

Key Concept

Recognition of iatrogenic volume overload causing acute decompensated heart failure and a mixed acid-base disorder, requiring diuresis and ventilatory support.

Estimated Time:1m 30s

Question 17Question →

A 68-year-old male retired teacher comes to the urgent care clinic complaining of a three-day history of increased shortness of breath and a persistent cough. He states his normally clear sputum has become thick and yellow. His medical history includes hypertension and a 45-pack-year smoking habit. He currently takes amlodipine. His temperature is 37.2°C (99.0°F), blood pressure is 134/82 mmHg, heart rate is 94/min, and respiratory rate is 24/min. Pulse oximetry reveals an oxygen saturation of 90% on room air. On auscultation, there is a prolonged expiratory phase with diffuse bilateral wheezing. Jugular venous distention is absent, and there is no dependent edema. A bedside arterial blood gas analysis on room air shows:

Laboratory Test	Result
pH	7.31
pCO2	52 mmHg
HCO3-	26 mEq/L
pO2	60 mmHg

Which of the following is the most appropriate next step in the management of this patient?

Administer inhaled short-acting bronchodilators, oral glucocorticoids, and an oral macrolide antibiotic

Administer intravenous furosemide and initiate noninvasive positive pressure ventilation

Administer intravenous piperacillin-tazobactam and vancomycin

Calculate the expected respiratory compensation using Winter's formula to guide therapy

Obtain an urgent echocardiogram and administer a brain natriuretic peptide (BNP) antagonist

Show answer & explanation

Answer: Administer inhaled short-acting bronchodilators, oral glucocorticoids, and an oral macrolide antibiotic

Answer

Administer inhaled short-acting bronchodilators, oral glucocorticoids, and an oral macrolide antibiotic

The correct approach is to administer inhaled short-acting bronchodilators, oral glucocorticoids, and an oral macrolide antibiotic. This patient's presentation of worsened dyspnea, increased cough, and purulent sputum in the setting of a significant smoking history is classic for an acute exacerbation of COPD. The standard pharmacological management for an exacerbation with purulent sputum includes short-acting bronchodilators (to relieve bronchospasm), systemic corticosteroids (to reduce airway inflammation), and antibiotics (to treat common bacterial triggers).

Step-by-Step Solution

Analyze the patient's symptoms and history.

The patient has a heavy smoking history, increased shortness of breath, and a change to thick, yellow sputum.

Identifying the three cardinal symptoms (increased dyspnea, increased sputum volume, increased sputum purulence) is required to diagnose an acute COPD exacerbation.

Evaluate the physical exam findings.

Diffuse bilateral wheezing and a prolonged expiratory phase are present, with no signs of fluid overload.

This confirms obstructive lung disease and helps rule out acute decompensated heart failure.

Determine the appropriate management bundle.

The standard treatment bundle includes bronchodilators, systemic corticosteroids, and antibiotics.

Antibiotics are specifically indicated because the patient has increased sputum purulence along with other cardinal symptoms.

Key Concept

Diagnosis and management of an acute exacerbation of chronic obstructive pulmonary disease (COPD)

Estimated Time:1m 0s

Question 18Question →

A 74-year-old male farmer is brought to the emergency department by his wife due to a 3-day history of progressively worsening shortness of breath, increased cough frequency, and a change in his sputum from clear to thick yellowish-green. He has a 45-pack-year smoking history and uses an albuterol inhaler as needed. Upon arrival, his temperature is $37.7^\circ\text{C}$ ( $99.9^\circ\text{F}$ ), blood pressure is $145/88\text{ mmHg}$ , pulse is $114/\text{min}$ , and respiratory rate is $26/\text{min}$ . Pulse oximetry shows an oxygen saturation of $85\%$ on room air. Physical examination reveals an anxious, mildly somnolent patient who is easily arousable and follows commands. He is using accessory muscles of respiration. Auscultation demonstrates globally diminished breath sounds with a prolonged expiratory phase and diffuse expiratory wheezing. Jugular venous pressure is normal, and there is no lower extremity edema. An arterial blood gas drawn on room air reveals:

Measurement	Value
pH	$7.28$
PaO $_2$	$54\text{ mmHg}$
PaCO $_2$	$66\text{ mmHg}$
HCO $_3^-$	$30\text{ mEq/L}$

Which of the following are appropriate initial management steps for this patient? (Select all that apply)

Select all that apply

Initiate noninvasive positive pressure ventilation

Administer oral azithromycin

Administer intravenous furosemide

Administer intravenous piperacillin-tazobactam and vancomycin

Administer intravenous sodium bicarbonate

Show answer & explanation

Answer: Initiate noninvasive positive pressure ventilation; Administer oral azithromycin

Answer

The correct steps are to initiate noninvasive positive pressure ventilation and administer oral azithromycin.

The correct initial management steps include noninvasive positive pressure ventilation (NPPV) and targeted antibiotic therapy. The patient is experiencing an acute exacerbation of COPD (AECOPD) complicated by acute respiratory failure. The ABG demonstrates an acute-on-chronic respiratory acidosis (pH 7.28, PaCO2 66 mmHg). NPPV is the preferred initial ventilatory support for AECOPD patients with a pH < 7.35 and PaCO2 > 45 mmHg, as it decreases the work of breathing, improves gas exchange, and reduces the need for endotracheal intubation. Additionally, because the patient exhibits the cardinal symptoms of an AECOPD (increased dyspnea, increased sputum volume, and increased sputum purulence), empiric antibiotic therapy targeting common respiratory pathogens (e.g., with a macrolide like azithromycin) is indicated.

Step-by-Step Solution

Diagnose the primary condition based on the clinical presentation.

The patient has an acute exacerbation of chronic obstructive pulmonary disease (AECOPD) characterized by the three cardinal symptoms: increased dyspnea, increased sputum volume, and increased sputum purulence.

Identifying the cardinal symptoms directs the specific pharmacological management, particularly the need for antibiotics.

Interpret the arterial blood gas (ABG) results.

The ABG shows an acidemia (pH 7.28) driven by hypercapnia (PaCO2 66 mmHg), with an elevated bicarbonate (HCO3- 30 mEq/L) indicating chronic metabolic compensation. This is an acute-on-chronic respiratory acidosis.

Understanding the acid-base status is required to determine the need for ventilatory support.

Select evidence-based interventions for the identified condition and severity.

Initiate noninvasive positive pressure ventilation (NPPV) due to the respiratory acidosis (pH < 7.35) and prescribe targeted antibiotics (azithromycin) due to the presence of purulent sputum.

NPPV reduces mortality and need for intubation in AECOPD with respiratory acidosis. Antibiotics reduce the risk of treatment failure in purulent exacerbations.

Key Concept

Management of acute exacerbations of COPD with respiratory acidosis

Question 19Question →

A 78-year-old man with end-stage idiopathic pulmonary fibrosis is admitted to the intensive care unit and intubated for acute respiratory failure. He is currently deeply sedated and unresponsive. His arterial blood gas reveals a pH of $7.21$ , $PaCO_2$ of $68$ mmHg, and $HCO_3^-$ of $26$ mEq/L. The medical team determines his fibrotic lung disease is irreversible and he cannot be successfully weaned from mechanical ventilation.

The patient's medical record contains a valid advance directive clearly appointing his daughter as his sole healthcare proxy. The directive states he does not wish to be kept on life support if his condition is irreversible. However, the patient's son has just arrived at the hospital, disagrees with the daughter, and demands the team perform a tracheostomy and immediately start empirical intravenous meropenem and vancomycin to 'prevent any potential infections.' The patient has no fever, normal white blood cell count, and clear tracheal secretions.

Which of the following actions by the critical care physician are appropriate? (Select all that apply)

Select all that apply

Acknowledge the daughter as the primary surrogate decision-maker regarding the continuation of mechanical ventilation.

Decline the request to initiate empirical intravenous meropenem and vancomycin.

Defer decision-making authority to the son to avoid legal conflict during the family dispute.

Initiate the broad-spectrum antibiotics to provide prophylactic coverage against nosocomial infections.

Apply Winter's formula to the provided arterial blood gas values to assess for an appropriate compensatory response.

Show answer & explanation

Answer: Acknowledge the daughter as the primary surrogate decision-maker regarding the continuation of mechanical ventilation.; Decline the request to initiate empirical intravenous meropenem and vancomycin.

Answer

The correct actions are to acknowledge the legally appointed healthcare proxy (the daughter) as the sole decision-maker and to decline the medically inappropriate request for prophylactic broad-spectrum antibiotics.

The daughter is the legally appointed healthcare proxy according to the patient's advance directive. In critical care ethics, a designated proxy legally and ethically supersedes other family members. Their decisions must be honored as long as they align with the patient's previously expressed wishes. Furthermore, the critical care physician has a professional duty to provide only medically indicated care. Initiating potent broad-spectrum antibiotics (such as meropenem and vancomycin) without objective evidence of an active infection directly violates antibiotic stewardship principles and inappropriately exposes the patient to the risk of multidrug-resistant organisms and medication toxicity. Therefore, the physician must politely but firmly decline the son's medical demand while maintaining the daughter's authority.

Step-by-Step Solution

Evaluate the legal hierarchy of decision-makers in the intensive care unit.

The daughter is identified as the designated healthcare proxy in a valid, documented advance directive.

A legally appointed proxy supersedes the wishes of other family members, including first-degree relatives who may disagree.

Assess the clinical indication for the son's requested medical interventions.

There is no clinical evidence of infection (no fever, normal WBC, clear secretions), making antibiotics medically inappropriate.

Physicians have a duty to practice sound antibiotic stewardship and must not prescribe non-indicated, broad-spectrum agents simply to appease family members.

Key Concept

In the critical care setting, physicians must honor established advance directives and legally appointed surrogate decision-makers, while concurrently practicing appropriate antibiotic stewardship by refusing medically non-indicated treatments demanded by family.

Question 20Question →

A $68$ -year-old male is evaluated in the intensive care unit for altered mental status. He was admitted $4$ days ago for an acute exacerbation of chronic obstructive pulmonary disease (COPD) and acute decompensated heart failure. His initial treatment included noninvasive positive pressure ventilation, intravenous furosemide, and a $5$ -day course of azithromycin and ceftriaxone, which he completed yesterday. He has a history of severe COPD, heart failure with preserved ejection fraction, and hypertension.

Over the past $24$ hours, he has become increasingly lethargic and is currently difficult to arouse. He is receiving oxygen at $2 \text{ L/min}$ via nasal cannula. Temperature is $37.0^\circ\text{C}$ ( $98.6^\circ\text{F}$ ), blood pressure is $105/60 \text{ mm Hg}$ , pulse is $108/\text{min}$ , and respirations are $9/\text{min}$ . Physical examination shows flat jugular veins when supine. Mucous membranes are dry. Cardiopulmonary examination reveals distant heart sounds and decreased breath sounds bilaterally without wheezing or crackles. There is no lower extremity edema.

Laboratory results are as follows:

Parameter	Result
Serum sodium	$135 \text{ mEq/L}$
Serum potassium	$2.6 \text{ mEq/L}$
Serum chloride	$82 \text{ mEq/L}$
Serum bicarbonate	$44 \text{ mEq/L}$
Blood urea nitrogen	$52 \text{ mg/dL}$
Serum creatinine	$1.1 \text{ mg/dL}$
Urine chloride	$8 \text{ mEq/L}$

Arterial blood gas analysis on $2 \text{ L/min}$ nasal cannula:

Parameter	Result
pH	$7.55$
PaCO $_2$	$54 \text{ mm Hg}$
PaO $_2$	$62 \text{ mm Hg}$

Which of the following is the most appropriate next step in the management of this patient?

Intravenous infusion of

0.9\%

sodium chloride and potassium chloride

Initiation of noninvasive positive pressure ventilation

Intravenous administration of acetazolamide

Intravenous administration of furosemide

Initiation of empiric piperacillin-tazobactam and vancomycin

Show answer & explanation

Answer: Intravenous infusion of $0.9\%$ sodium chloride and potassium chloride

Answer

Intravenous infusion of 0.9% sodium chloride and potassium chloride

The correct option is intravenous infusion of 0.9% sodium chloride and potassium chloride. This patient's lethargy and altered mental status are driven by a severe metabolic alkalosis (pH 7.55) and the resulting compensatory hypoventilation (RR 9/min, PaCO2 54 mm Hg). The primary disorder is established by the profound alkalemia and markedly elevated serum bicarbonate (44 mEq/L). The expected respiratory compensation for metabolic alkalosis is a 0.7 mm Hg increase in PaCO2 for every 1 mEq/L increase in HCO3-. Here, the expected PaCO2 is 40 + [0.7 × (44 - 24)] = 54 mm Hg, which perfectly matches the measured PaCO2. This rules out a superimposed primary respiratory disorder. The etiology is saline-responsive (contraction) metabolic alkalosis secondary to aggressive loop diuretic use, confirmed by physical signs of hypovolemia (flat jugular veins, dry mucous membranes), pre-renal azotemia (BUN/creatinine ratio of 47), hypokalemia, and importantly, a urine chloride of less than 20 mEq/L (8 mEq/L). The definitive treatment for saline-responsive metabolic alkalosis is volume expansion with isotonic saline and potassium repletion. This restores renal perfusion, enabling the excretion of excess bicarbonate, which will subsequently correct the pH and resolve the compensatory hypoventilation.

Step-by-Step Solution

Analyze the arterial blood gas to determine the primary acid-base disorder.

The pH is 7.55 (alkalemia). The elevated HCO3- (44 mEq/L) identifies the primary disorder as a metabolic alkalosis.

Establishing the primary acid-base derangement is the first step in diagnosing altered mental status in a patient with mixed pulmonary and renal issues.

Calculate the expected respiratory compensation for the metabolic alkalosis.

Expected PaCO2 = 40 + [0.7 × (44 - 24)] = 40 + 14 = 54 mm Hg. The measured PaCO2 is exactly 54 mm Hg.

This confirms a pure metabolic alkalosis with appropriate respiratory compensation. The hypercapnia is not a primary respiratory acidosis.

Assess the etiology of the metabolic alkalosis using volume status and urine chloride.

Flat neck veins, BUN/Cr ratio > 40, dry mucous membranes, and urine chloride < 20 mEq/L point to severe volume depletion (contraction alkalosis).

Aggressive loop diuretic therapy for decompensated heart failure caused profound hypovolemia, hypokalemia, and hypochloremia.

Select the appropriate targeted intervention.

Administer 0.9% sodium chloride and potassium chloride to restore intravascular volume and correct electrolyte deficits.

Correcting the volume and chloride deficit allows the kidneys to excrete bicarbonate, resolving the alkalemia and the compensatory hypoventilation.

Key Concept

Patients with severe metabolic alkalosis develop compensatory hypoventilation to retain CO2. If the metabolic alkalosis is saline-responsive (urine Cl < 20 mEq/L), the treatment is volume expansion with normal saline and potassium replacement, avoiding interventions that inappropriately increase ventilation.

Estimated Time:2m 0s

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