Emergency medical services bring a 73-year-old woman to the resuscitation bay after she wa… — USMLE Step 2 CK

Emergency medical services bring a $73$ -year-old woman to the resuscitation bay after she was found lethargic and struggling to breathe at home. According to her daughter, the patient has a history of type II bipolar disorder, primary hypothyroidism, and tobacco use disorder ( $35$ pack-years). For the past three days, she has been sleeping in a recliner due to worsening orthopnea.

On arrival, her temperature is $36.2^\circ \text{C}$ ( $97.2^\circ \text{F}$ ), blood pressure is $76/48 \text{ mm Hg}$ , pulse is $124/\text{min}$ , and respiratory rate is $28/\text{min}$ . Oxygen saturation is $85\%$ on room air.

Physical examination reveals a somnolent, mottled patient with cool extremities. The external jugular veins are engorged up to the angle of the jaw while the patient is positioned at a $45^\circ$ angle. Auscultation of the chest demonstrates diffuse, prolonged expiratory wheezing and coarse crackles at both lung bases. Cardiac auscultation reveals a rapid, regular rhythm with a prominent $S_3$ gallop. There is $2+$ pitting edema in the lower extremities.

Laboratory studies reveal:
Leukocyte count: $11,200/\text{mm}^3$
Lactate: $4.5 \text{ mmol/L}$
Thyroid-stimulating hormone (TSH): $2.4 \text{ mU/L}$ (normal: $0.5-5.0 \text{ mU/L}$ )
Free thyroxine (T4): $0.7 \text{ ng/dL}$ (normal: $0.9-1.7 \text{ ng/dL}$ )
Troponin I: $0.05 \text{ ng/mL}$ (normal $< 0.03 \text{ ng/mL}$ )

Arterial blood gas analysis on room air shows:
pH: $7.25$
$\text{PaCO}_2$ : $30 \text{ mm Hg}$
$\text{PaO}_2$ : $55 \text{ mm Hg}$
$\text{HCO}_3^-$ : $13 \text{ mEq/L}$

An electrocardiogram shows sinus tachycardia with low QRS voltage in the limb leads and non-specific ST-segment changes.

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

Initiation of a norepinephrine infusion and focused cardiac ultrasonographyAnswer
B
Administration of continuous nebulized albuterol and intravenous methylprednisolone
C
Immediate transfer to the radiology department for a contrast-enhanced chest scan
D
Intravenous bolus of levothyroxine and hydrocortisone administration
E
Infusion of an alkalinizing agent to correct an isolated metabolic acidosis

Answer

The correct management is the initiation of a norepinephrine infusion and focused cardiac ultrasonography.

The correct answer identifies the need for immediate vasopressor support and bedside diagnostic imaging. This patient is in cardiogenic shock, characterized by profound hypotension, evidence of poor end-organ perfusion (altered mental status, cool/mottled extremities, lactic acidosis), and volume overload (elevated JVP, pulmonary edema,

S_3

gallop). Norepinephrine is the initial vasopressor of choice for undifferentiated shock and cardiogenic shock with severe hypotension. Focused cardiac ultrasonography (point-of-care ultrasound) is the gold standard next step to rapidly determine the etiology (e.g., severe ischemic left ventricular dysfunction, acute valvular regurgitation, or pericardial tamponade) without moving the unstable patient.

Step-by-Step Solution

Evaluate the patient's hemodynamic status and physical exam findings.

The patient exhibits frank shock (blood pressure

76/48 \text{ mm Hg}

, cool and mottled extremities, lethargy) coupled with classic signs of left and right heart failure (pulmonary crackles,

S_3

gallop, jugular venous distention).

Identifying the phenotype of shock is critical. The combination of pump failure signs and poor perfusion definitively points to cardiogenic shock.

Differentiate confounding pulmonary and endocrine presentations.

The wheezing is identified as cardiac asthma rather than a COPD exacerbation. The low T4 with normal TSH is identified as euthyroid sick syndrome, ruling out myxedema coma.

Multisystem organ dysfunction in shock frequently causes secondary laboratory and physical abnormalities that can mimic primary diseases.

Calculate the expected respiratory compensation for the metabolic acidosis.

Using Winter's formula (

1.5 \times 13 + 8 = 27.5 \pm 2

), the expected

\text{PaCO}_2

25.5-29.5 \text{ mm Hg}

. The actual

\text{PaCO}_2

30 \text{ mm Hg}

, indicating a concurrent respiratory acidosis.

Determining the presence of respiratory failure dictates whether airway intervention might be imminently required, confirming the severity of the pulmonary edema.

Determine the immediate intervention.

Stabilize the mean arterial pressure using a first-line vasopressor (norepinephrine) while simultaneously performing a bedside echocardiogram.

Hemodynamic stabilization takes precedence, and point-of-care ultrasound safely identifies the precise cardiac pathology without risking the patient's life in the radiology suite.

Key Concept

Cardiogenic shock diagnosis and immediate management

Question

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Topics

More questions from this topic