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Question 3641Question →

Emergency medical services arrive at the trauma bay with a 38-year-old construction worker who sustained a fall from a fourth-story scaffolding. En route, he received 1 liter of intravenous crystalloid. Upon arrival, the patient is obtunded and groaning painfully. Vital signs demonstrate a blood pressure of 78/42 mm Hg, a pulse of 138/min, and a respiratory rate of 28/min. Primary survey reveals profound pallor and diaphoresis. The trachea is midline, and jugular venous distention is absent. Auscultation of the chest demonstrates markedly absent breath sounds over the entire left hemithorax with accompanying dullness to percussion. Heart sounds are distinct and rapid. The pelvis is mechanically stable, and an extended focused assessment with sonography for trauma (eFAST) yields negative results for pericardial and intraperitoneal fluid.

A left-sided tube thoracostomy is rapidly placed, which immediately yields 1,750 mL of bright red blood. Following the administration of two units of uncrossmatched packed red blood cells, his blood pressure marginally improves to 82/48 mm Hg.

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

Computed tomography angiography of the chest

Placement of a second left-sided tube thoracostomy

Transfer to the operating room for exploratory thoracotomy

Bedside transesophageal echocardiography

Transfer to the operating room for exploratory laparotomy

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Answer: Transfer to the operating room for exploratory thoracotomy

Answer

Transfer to the operating room for exploratory thoracotomy

This patient presents with hemorrhagic shock secondary to a massive left hemothorax. The initial management for a hemothorax is a tube thoracostomy, which serves both therapeutic (lung re-expansion, hemorrhage evacuation) and diagnostic (quantifying blood loss) purposes. The absolute indications for an emergent exploratory thoracotomy in the setting of penetrating or blunt chest trauma include: 1) Initial immediate output of >1,500 mL of blood, 2) Continuous output of >200 mL/hour for 2 to 4 hours, or 3) Persistent hemodynamic instability despite adequate resuscitation. Because this patient's initial chest tube output was 1,750 mL, he requires immediate surgical exploration to identify and ligate the bleeding source (commonly intercostal arteries, internal mammary arteries, or pulmonary vessels).

Step-by-Step Solution

1

Analyze the patient's hemodynamic status and primary survey findings.

The patient is in class III/IV hemorrhagic shock (hypotensive, tachycardic, altered mental status) with clinical signs of a massive left hemothorax (absent breath sounds, dullness to percussion).

Establishing the stability of the patient and identifying the primary source of bleeding dictates the immediate trauma resuscitation pathway.

2

Evaluate the response to the initial intervention.

A tube thoracostomy was placed, yielding 1,750 mL of blood immediately, and the patient remains hemodynamically unstable despite blood product administration.

Chest tube output volume is the primary metric used to determine if a hemothorax can be managed conservatively or requires surgical exploration.

3

Apply surgical criteria for massive hemothorax management.

The immediate evacuation of >1,500 mL of blood from the pleural space is an absolute indication for emergent thoracotomy.

This high volume of acute blood loss strongly suggests injury to major intrathoracic systemic vessels (e.g., intercostal or internal mammary arteries) or pulmonary hilar structures, which will not spontaneously thrombose and require surgical hemostasis.

Key Concept

Indications for emergent exploratory thoracotomy in thoracic trauma include an immediate chest tube output of >1,500 mL of blood, or ongoing output of >200 mL/hour for 2 to 4 consecutive hours.

Question 3642Question →

A 74-year-old man with a history of hypertension and atrial fibrillation treated with apixaban is brought to the emergency department by emergency medical services. His wife reports that he experienced a sudden, severe occipital headache and intractable vomiting 45 minutes ago before collapsing. Upon arrival in the trauma bay, he is unresponsive. His eyes do not open to pain, he makes incomprehensible sounds, and he exhibits abnormal extensor posturing to painful stimuli. His blood pressure is 220/115 mmHg, heart rate is 52/min, and respiratory rate is 10/min with irregular breathing patterns.

Arrange the following clinical interventions in the most appropriate, evidence-based sequential order for the acute management of this patient.

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Answer

The correct sequence is: Endotracheal intubation, followed by a non-contrast CT of the head, followed by administration of andexanet alfa and an antihypertensive, followed by suboccipital craniectomy, and finally transfer to the neuro-ICU.

The patient presents with Cushing's triad (hypertension, bradycardia, irregular breathing) and a GCS of 5, highly suggestive of an intracranial mass lesion causing brainstem compression, such as a cerebellar hemorrhage. In any emergency, the ABCs take precedence; therefore, endotracheal intubation is the first step. Once the airway is secure, a non-contrast head CT must be obtained to confirm the diagnosis and rule out ischemic etiologies. After confirming a hemorrhage, medical stabilization must occur before surgery; because the patient is on apixaban, urgent reversal with andexanet alfa (or 4-factor PCC) and strict blood pressure control are required to prevent uncontrollable surgical bleeding. Finally, the definitive treatment for a large, symptomatic cerebellar hemorrhage is emergent suboccipital craniectomy, followed by monitoring in the neuro-ICU.

Step-by-Step Solution

1

Evaluate and secure the patient's airway, breathing, and circulation (ABCs).

Endotracheal intubation is performed.

The patient has a Glasgow Coma Scale (GCS) score of 5 (E1, V2, M2) and irregular respirations, indicating an inability to protect the airway and impending respiratory failure.

2

Diagnose the underlying central nervous system pathology.

A non-contrast head CT is obtained.

Imaging is required to differentiate between an acute ischemic stroke and an intracranial hemorrhage, which determines the entire subsequent treatment pathway.

3

Initiate medical stabilization to halt ongoing intracranial bleeding.

Andexanet alfa and an IV antihypertensive (e.g., nicardipine) are administered.

With a confirmed hemorrhage in a patient on a direct factor Xa inhibitor, reversing the coagulopathy and lowering blood pressure decreases the risk of hematoma expansion and prepares the patient for surgery.

4

Provide definitive treatment for the mass effect and brainstem compression.

An emergent suboccipital craniectomy and hematoma evacuation are performed.

A large cerebellar hemorrhage causing coma requires emergent surgical decompression to relieve intracranial pressure and prevent death from herniation.

5

Provide specialized postoperative critical care.

The patient is transferred to the neuro-intensive care unit.

Continuous neuromonitoring and careful hemodynamic management are necessary to monitor for postoperative edema, recurrent hemorrhage, or hydrocephalus.

Key Concept

The management of acute cerebellar hemorrhage requires a strict sequence of airway stabilization, diagnostic imaging, medical reversal of coagulopathy, and finally definitive surgical decompression.

Question 3643Question →

Match each clinical study scenario or derived statistic to the epidemiological measure of disease frequency or association it best represents.

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Answer

12% nursing home assessment matches Point Prevalence; 5-year new asthma cases matches Cumulative Incidence; 0.6 probability ratio matches Relative Risk; H. pylori exposure odds matches Odds Ratio; Metric of 20 derived from 0.05 risk reduction matches Number Needed to Treat.

Each clinical scenario corresponds exactly to the epidemiological definition of its matched measure: existing cases (prevalence), new cases over time (incidence), ratio of probabilities (relative risk), ratio of exposure odds (odds ratio), and reciprocal of absolute risk reduction (number needed to treat).

Step-by-Step Solution

1

Analyze the first scenario regarding the nursing home assessment.

It describes existing disease at a single moment, indicating Point Prevalence.

Prevalence captures existing cases, not new cases.

2

Evaluate the second scenario involving the 5-year study of initially healthy adults.

It tracks the development of new asthma cases over time, indicating Cumulative Incidence.

Incidence requires an initially disease-free population monitored over a specified duration.

3

Assess the third scenario comparing probabilities in a clinical trial.

It describes the ratio of probabilities between two groups, indicating Relative Risk.

Relative Risk is calculated as the incidence in the exposed divided by the incidence in the unexposed.

4

Review the fourth scenario involving a retrospective comparison of gastric cancer patients and controls.

It calculates the ratio of exposure odds, indicating an Odds Ratio.

Case-control studies cannot directly measure incidence; they rely on odds ratios to estimate association.

5

Analyze the fifth scenario regarding absolute risk reduction of 0.05 yielding a value of 20.

It describes the calculation

1 / ARR

, indicating Number Needed to Treat.

Number Needed to Treat represents the number of patients required to receive the intervention to prevent one adverse outcome.

Key Concept

Epidemiological measures of disease frequency (incidence, prevalence) and association (relative risk, odds ratio, number needed to treat) each correspond to specific study designs and mathematical definitions.

Question 3644Question →

Investigators at a regional cardiovascular center analyze data from a prospective study evaluating a new oral anticoagulant compared to standard therapy for stroke prevention. The study followed patients with nonvalvular atrial fibrillation over a two-year period. Among the $1,000$ patients receiving the new anticoagulant, $20$ experienced an ischemic stroke. Among the $1,000$ patients receiving standard therapy, $70$ experienced an ischemic stroke. Based on these findings, what is the number needed to treat with the new anticoagulant to prevent one additional ischemic stroke compared to standard therapy?

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Answer: 20

Answer

The number needed to treat is 20.

The Number Needed to Treat (NNT) represents the number of patients who need to receive the experimental therapy rather than the standard therapy to prevent one additional adverse event. It is calculated as the inverse of the Absolute Risk Reduction (ARR). The ARR is the difference between the control event rate (

70/1000 = 0.07

) and the experimental event rate (

20/1000 = 0.02

). This difference is

0.05

. Therefore, the NNT is

\frac{1}{0.05}

, which equals

20

patients.

Step-by-Step Solution

1

Calculate the control event rate (CER)

\text{CER} = \frac{70}{1000} = 0.07

Establishing the baseline risk of the adverse event in the population receiving standard therapy.

2

Calculate the experimental event rate (EER)

\text{EER} = \frac{20}{1000} = 0.02

Establishing the risk of the adverse event in the population receiving the new intervention.

3

Calculate the Absolute Risk Reduction (ARR)

\text{ARR} = 0.07 - 0.02 = 0.05

Determining the absolute difference in event rates between the two groups.

4

Calculate the Number Needed to Treat (NNT)

\text{NNT} = \frac{1}{0.05} = 20

NNT is the inverse of the ARR, representing the number of patients required to receive the new treatment to prevent one additional event.

Key Concept

Number Needed to Treat (NNT) and Absolute Risk Reduction (ARR)

Question 3645Question →

Correlate the following nuanced clinical presentations of abdominal pathology with their most appropriate definitive management strategy.

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Answer

The correct pairings match post-RYGB internal hernias with immediate defect closure, advanced acute embolic ischemia with damage control resection, chronic mesenteric ischemia with elective revascularization, and watershed ischemic colitis with supportive medical management.

Each clinical scenario presents a distinct pathophysiological mechanism of impaired intestinal perfusion or obstruction that dictates a specific guideline-based intervention. Internal hernias require anatomical defect closure; infarcted bowel requires resection; chronic progressive ischemia requires elective bypass; and transient mucosal ischemia requires supportive care.

Step-by-Step Solution

1

Analyze the post-RYGB presentation.

Identified as a closed-loop obstruction from an internal hernia.

The 'whirl sign' on CT in a patient with a prior Roux-en-Y anatomy is highly specific for an internal hernia, which requires emergent surgical reduction.

2

Analyze the atrial fibrillation presentation with acidosis and pneumatosis.

Identified as acute embolic mesenteric ischemia with bowel necrosis.

Pneumatosis and portal venous gas are late signs of transmural infarction, necessitating a damage control approach with a second-look operation.

3

Analyze the chronic postprandial pain presentation with weight loss.

Identified as chronic mesenteric ischemia.

Gradual atherosclerotic occlusion of the SMA and celiac axis causes intestinal angina, best managed by elective revascularization.

4

Analyze the post-dialysis hypotensive presentation with bloody diarrhea.

Identified as non-occlusive ischemic colitis.

Transient low flow leads to mucosal ischemia at watershed zones; it typically resolves with conservative medical management.

Key Concept

Differentiating the precise pathophysiologic mechanisms and corresponding definitive managements for various manifestations of intestinal ischemia and complex obstruction.

Question 3646Question →

Vascular and cardiothoracic surgery encompasses a wide range of acute and chronic pathologies with distinct clinical presentations. Match the following classic clinical presentations with their most likely corresponding vascular diagnosis.

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Answer

The correct matches are: Tearing chest pain with Aortic dissection; Cramping calf pain with exertion with Peripheral arterial disease (claudication); Sudden pain and pulselessness with Acute limb ischemia; Postprandial abdominal pain with weight loss with Chronic mesenteric ischemia.

Each clinical vignette provides pathognomonic features for a specific vascular condition. Tearing chest pain with asymmetric blood pressures is highly specific for aortic dissection. Intermittent claudication represents chronic peripheral arterial disease. The acute onset of pallor and pulselessness defines acute limb ischemia. Intestinal angina with weight loss defines chronic mesenteric ischemia.

Step-by-Step Solution

1

Analyze the presentation of sudden tearing chest pain with asymmetric blood pressures.

Identified as aortic dissection.

The description perfectly matches an intimal tear extending through the aorta, affecting branch vessels (e.g., subclavian), leading to blood pressure differentials.

2

Analyze the presentation of reproducible, exertion-induced calf pain relieved by rest.

Identified as peripheral arterial disease (claudication).

This is a chronic, supply-demand mismatch in the lower extremities due to atherosclerosis.

3

Analyze the presentation of sudden, severe lower extremity pain with the classic signs (pallor, pulselessness, paresthesias).

Identified as acute limb ischemia.

This represents sudden, complete arterial occlusion requiring emergent revascularization, distinct from chronic claudication.

4

Analyze the presentation of postprandial abdominal pain and weight loss.

Identified as chronic mesenteric ischemia.

The timing of pain (intestinal angina) correlates with increased metabolic demand of the gut after eating in the setting of chronic atherosclerotic narrowing.

Key Concept

Classic clinical presentations of major vascular and cardiothoracic surgical pathologies.

Question 3647Question →

A 74-year-old woman with a history of atrial fibrillation, noncompliant with her apixaban, presents to the emergency department with sudden-onset, severe periumbilical abdominal pain. Her vital signs show a temperature of 38.4°C (101.1°F), blood pressure of 88/54 mmHg, and heart rate of 122/min. Physical examination reveals a rigid abdomen with diffuse guarding and rebound tenderness. Laboratory studies demonstrate a leukocyte count of 24,500/mm³ and a serum lactate level of 7.2 mmol/L. Arrange the following steps in the most appropriate sequential order for the definitive management of this patient's condition.

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Answer

The correct sequence of management is: initiation of fluid resuscitation and antibiotics, followed by emergent exploratory laparotomy, then surgical embolectomy of the superior mesenteric artery, followed by resection of necrotic bowel, and finally temporary abdominal closure for a planned second-look laparotomy.

The optimal management of acute mesenteric ischemia complicated by peritonitis follows a strict physiological and surgical sequence. First, the patient must be stabilized with fluid resuscitation and broad-spectrum antibiotics due to impending or established septic shock. Second, because the patient has peritonitis (rigid abdomen, rebound tenderness) and hemodynamic instability, emergent exploratory laparotomy is indicated without delaying for preoperative imaging like computed tomography angiography. Third, upon entering the abdomen, the paramount surgical principle is to perform revascularization (e.g., superior mesenteric artery embolectomy) prior to any bowel resection. This is critical because restoring perfusion allows reversibly ischemic bowel to regain color and peristalsis, preventing unnecessary resection and minimizing the risk of short bowel syndrome. Fourth, only after blood flow is fully restored should the surgeon resect the segments of bowel that remain frankly necrotic and irreversibly damaged. Finally, because the viability of the remaining bowel can continue to evolve due to reperfusion injury, primary anastomosis is generally avoided; instead, a temporary abdominal closure is applied, and a second-look laparotomy is scheduled for 24 to 48 hours later to reassess the bowel.

Step-by-Step Solution

1

Recognize acute mesenteric ischemia with peritonitis and septic shock.

Identified the need for immediate surgical intervention and resuscitation.

The presence of a rigid abdomen, severe pain, and hemodynamic instability indicates bowel infarction and probable perforation, necessitating emergent source control.

2

Determine the initial preoperative management.

Fluid resuscitation and broad-spectrum antibiotics are initiated.

Aggressive fluid resuscitation and antimicrobial therapy are critical to stabilize the hemodynamically unstable patient before and during surgery.

3

Select the appropriate diagnostic and therapeutic pathway.

Proceed directly to exploratory laparotomy.

Advanced imaging is contraindicated in unstable patients with frank peritonitis, as it unacceptably delays life-saving surgical exploration.

4

Determine the correct intraoperative sequence of procedures.

Perform superior mesenteric artery embolectomy before bowel resection.

Reestablishing blood flow first allows marginal, reversibly ischemic bowel to recover, thereby preventing unnecessary resection of viable intestine and preserving bowel length.

5

Determine the optimal strategy for abdominal closure.

Leave the abdomen open and plan a second-look laparotomy.

Bowel viability can evolve over 24-48 hours. A planned second look ensures any delayed necrosis is addressed before definitive anastomosis is attempted.

Key Concept

In the surgical management of acute mesenteric ischemia, revascularization of the ischemic territory must precede resection of necrotic bowel to maximize preservation of viable intestinal length.

Question 3648Question →

Match each clinical presentation of a scrotal or testicular mass to its most appropriate definitive management.

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Answer

The solid intratesticular mass requires radical inguinal orchiectomy. The benign spermatocele requires observation. The varicocele is managed with varicocelectomy. The communicating hydrocele in an infant requires ligation of the patent processus vaginalis.

Each clinical presentation perfectly matches a classic urologic condition with a standardized management protocol. Solid intratesticular masses are managed oncologically with inguinal orchiectomy. Benign cysts (spermatoceles) are observed. Varicoceles that are symptomatic receive varicocelectomy. Persistent communicating hydroceles in toddlers receive surgical ligation.

Step-by-Step Solution

1

Evaluate the solid intratesticular mass in the young adult.

Identify high suspicion for testicular malignancy.

Any solid testicular mass must be treated as cancer, making radical inguinal orchiectomy the correct immediate definitive step.

2

Evaluate the transilluminating, cystic epididymal mass.

Identify a benign spermatocele.

These lesions are entirely benign and do not affect fertility or health, so observation is appropriate.

3

Evaluate the left-sided mass that decompresses when supine.

Identify a varicocele.

Symptomatic varicoceles are managed definitively with varicocelectomy to alleviate pain or improve fertility parameters.

4

Evaluate the fluctuating scrotal swelling in a 1-year-old.

Identify a persistent communicating hydrocele.

Failure of the processus vaginalis to close by 12 months of age necessitates surgical ligation.

Key Concept

Definitive surgical management of scrotal and testicular masses

Estimated Time:1m 0s

Question 3649Question →

An 82-year-old woman is evaluated in the emergency department for a 4-day history of progressively worsening, colicky abdominal pain accompanied by nausea and feculent vomiting. Her medical history includes hypertension, osteoarthritis, and moderate dementia. She lives with her daughter, who is her legally appointed healthcare proxy. Her estranged son recently arrived at the hospital and has been demanding to direct her medical care.

Vitals:
Temperature: $37.6^\circ\text{C}$ ( $99.7^\circ\text{F}$ )
Heart rate: $105/\text{min}$
Blood pressure: $110/70 \text{ mm Hg}$

Physical examination reveals a distended and tympanitic abdomen with high-pitched bowel sounds. There is mild, diffuse tenderness to palpation but no guarding, rigidity, or rebound tenderness.

Laboratory studies:
Leukocytes: $11,500/\text{mm}^3$
Lactate: $1.6 \text{ mmol/L}$
Liver function tests: Within normal limits

A computed tomography scan of the abdomen and pelvis without contrast reveals dilated loops of small bowel up to the terminal ileum, air in the biliary tree, and a $3.5\text{-cm}$ radiopaque, calcified mass impacted in the distal ileum. The colon is decompressed.

The son demands that the medical team transition her to comfort care, stating, 'She is too frail for any surgery, and I am the oldest child, so I make the decisions.' The daughter states, 'She has excellent quality of life at home. I want whatever is medically necessary to relieve this blockage.'

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

Nasogastric tube decompression, intravenous fluids, and serial examinations

Exploratory laparotomy with enterolithotomy, cholecystectomy, and biliary fistula closure

Exploratory laparotomy and enterolithotomy alone

Intravenous antibiotics, nasogastric decompression, and transition to comfort care

Endoscopic retrograde cholangiopancreatography with stone extraction

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Answer: Exploratory laparotomy and enterolithotomy alone

Answer

The most appropriate next step is exploratory laparotomy and enterolithotomy alone, respecting the designated proxy's decision for surgical intervention while minimizing operative morbidity.

The patient presents with classic findings of gallstone ileus, characterized by the Rigler triad on imaging: small bowel obstruction, pneumobilia (air in the biliary tree), and an ectopic radiopaque gallstone. Gallstone ileus occurs when a large gallstone erodes through the inflamed gallbladder wall directly into the adjacent bowel (usually the duodenum), creating a cholecystoenteric fistula. The stone travels distally and typically impacts at the narrowest portion of the small intestine, the terminal ileum/ileocecal valve. Because this is a fixed mechanical obstruction, conservative management will fail. The surgical standard of care for gallstone ileus in elderly or frail patients is an enterolithotomy alone (surgical extraction of the stone from the bowel). A 'one-stage procedure' involving enterolithotomy, cholecystectomy, and fistula closure is associated with high mortality and should be avoided in this demographic. Ethically, the medical team must obtain consent from the legally appointed healthcare proxy (the daughter), whose decisions override those of other family members.

Step-by-Step Solution

1

Identify the primary diagnosis based on clinical and radiographic findings.

The patient has a mechanical small bowel obstruction characterized by the Rigler triad on CT scan: pneumobilia, small bowel obstruction, and an ectopic gallstone in the terminal ileum. This confirms the diagnosis of gallstone ileus.

Accurate diagnosis is required to determine the necessity of surgical versus medical management.

2

Determine the optimal surgical approach for the diagnosis in the context of the patient's demographics.

In an elderly, frail patient, the primary life-threatening issue is the bowel obstruction. The surgical priority is enterolithotomy (opening the bowel to remove the stone) alone. Performing a simultaneous cholecystectomy and fistula repair (a one-stage procedure) carries an unacceptably high mortality rate.

Damage control principles apply; the goal is to resolve the acute surgical emergency while minimizing operative time and physiological stress.

3

Resolve the ethical conflict regarding consent.

The daughter is the legally appointed healthcare proxy. Her decision for medical intervention supersedes the son's demands.

Medical teams are legally and ethically bound to follow the directives of the established healthcare proxy when the patient lacks capacity, regardless of family hierarchy or disagreements.

Key Concept

Management of gallstone ileus and healthcare proxy authority

Estimated Time:1m 30s

Question 3650Question →

Investigators are evaluating the efficacy of a newly developed long-acting monoclonal antibody for preventing severe respiratory syncytial virus (RSV) infections in high-risk premature infants. A total of $5,000$ infants are enrolled and randomized in a 1:1 ratio to receive either the monoclonal antibody or a placebo injection at the start of the RSV season. All participants are followed for $150$ days. At the end of the follow-up period, data analysis reveals that $50$ infants in the monoclonal antibody group and $150$ infants in the placebo group required hospitalization for severe RSV infection.

Based on these study results, what is the number needed to treat to prevent one RSV-related hospitalization?

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Answer: 25

Answer

25

The Number Needed to Treat (NNT) quantifies the number of patients who must receive a specific intervention to prevent one additional adverse event. It is calculated by first determining the event rates in both the control and intervention groups. Here, the event rate in the placebo (control) group is

150 / 2,500 = 0.06

. The event rate in the monoclonal antibody (intervention) group is

50 / 2,500 = 0.02

. The Absolute Risk Reduction (ARR) is the difference between these two rates (

0.06 - 0.02 = 0.04

). Finally, the NNT is the reciprocal of the ARR:

1 / 0.04 = 25

. Thus, 25 infants need to receive the monoclonal antibody to prevent one hospitalization for severe RSV.

Step-by-Step Solution

1

Determine the number of patients in each study group.

Because

5,000

infants were randomized in a 1:1 ratio, there are

2,500

infants in the monoclonal antibody group and

2,500

infants in the placebo group.

Accurate denominators are required to calculate the correct event rates for each study arm.

2

Calculate the event rate in the control group (

ER_{control}

).

ER_{control} = \frac{150}{2500} = 0.06

(or

6\%

).

The baseline risk of the outcome without the intervention must be established.

3

Calculate the event rate in the intervention group (

ER_{intervention}

).

ER_{intervention} = \frac{50}{2500} = 0.02

(or

2\%

).

The risk of the outcome with the intervention must be established to compare against the baseline.

4

Calculate the Absolute Risk Reduction (ARR).

ARR = ER_{control} - ER_{intervention} = 0.06 - 0.02 = 0.04

.

ARR represents the absolute difference in risk between the two groups, which is required to calculate the NNT.

5

Calculate the Number Needed to Treat (NNT).

NNT = \frac{1}{ARR} = \frac{1}{0.04} = 25

.

NNT is the inverse of the ARR, representing how many patients must be treated to prevent one additional adverse outcome.

Key Concept

The Number Needed to Treat (NNT) is calculated as the reciprocal of the Absolute Risk Reduction (ARR), where ARR is the difference in event rates between the control and intervention groups (

NNT = \frac{1}{ARR}

).

Question 3651Question →

A 31-year-old man presents to the emergency department with a painful, fully rigid erection that has persisted for 18 hours. He admits to recreational cocaine use the previous evening. Physical examination reveals tense, tender corpora cavernosa with a completely flaccid glans penis and corpus spongiosum. Arrange the following diagnostic and therapeutic interventions in the correct escalating sequence for managing this condition, assuming each successive step fails to achieve permanent detumescence.

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Answer

The correct sequential algorithm for ischemic priapism is: 1) Corporal blood gas analysis, 2) Intracavernosal aspiration and irrigation, 3) Intracavernosal sympathomimetic injection, 4) Distal corporoglans shunt, 5) Proximal cavernosum-spongiosum shunt.

Ischemic priapism is a compartment syndrome of the corpora cavernosa resulting in severe hypoxia and potential necrosis of erectile tissue. The standard-of-care escalating algorithm requires diagnostic confirmation with a corporal blood gas first. Once confirmed, the least invasive therapeutic option—intracavernosal aspiration and saline irrigation—is performed. If the erection persists, an intracavernosal alpha-agonist (such as phenylephrine) is injected to stimulate venous outflow via smooth muscle contraction. If these conservative measures fail, surgical intervention is mandated to prevent permanent corporal fibrosis. A distal corporoglans shunt (e.g., Winter procedure) is performed first. Only if the distal shunt fails is a proximal cavernosum-spongiosum shunt (e.g., Quackels procedure) attempted, as proximal shunts carry a significantly higher risk of permanent erectile dysfunction.

Step-by-Step Solution

1

Differentiate ischemic from non-ischemic priapism.

Corporal blood gas analysis.

Blood gas confirms hypoxia and acidosis, differentiating the true urologic emergency of an ischemic compartment syndrome from non-ischemic (high-flow) priapism.

2

Attempt initial mechanical decompression.

Intracavernosal aspiration and irrigation.

Removing sludged, hypoxic blood directly reduces intracorporal pressure and may re-establish normal arterial inflow.

3

Attempt pharmacological smooth muscle contraction.

Intracavernosal phenylephrine injection.

Alpha-adrenergic stimulation induces cavernosal smooth muscle contraction, forcing blood into the venous outflow channels and resolving the veno-occlusive crisis.

4

Perform initial surgical decompression.

Distal corporoglans shunt.

If non-surgical management fails, a distal shunt is preferred first because it is technically simpler, can be performed under local anesthesia, and carries a lower risk profile for future erectile function.

5

Perform advanced surgical decompression.

Proximal cavernosum-spongiosum shunt.

This is reserved for cases refractory to distal shunting due to the high likelihood of permanent, severe erectile dysfunction and potential for urethral injury.

Key Concept

The algorithmic management of ischemic priapism progresses strictly from diagnosis (blood gas) to mechanical therapy (aspiration), pharmacological therapy (phenylephrine), and escalating surgical shunts (distal before proximal).

Question 3652Question →

Match each clinical presentation of an acute abdominal emergency with the most appropriate definitive next step in management.

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Answer

The correct matching aligns acute mesenteric ischemia with infarction to damage control laparotomy, closed-loop small bowel obstruction with strangulation to urgent laparotomy and resection, severe acute ascending cholangitis to emergent ERCP, and a perforated peptic ulcer to omental (Graham) patch closure.

Each clinical presentation represents a distinct, life-threatening abdominal emergency that requires a highly specific intervention. Recognizing the underlying pathophysiology—ischemic necrotic bowel, strangulated closed-loop obstruction, suppurative biliary infection, or viscus perforation—directly dictates whether the patient needs damage-control surgery, standard resection, endoscopic decompression, or an omental patch.

Step-by-Step Solution

1

Diagnose the patient with atrial fibrillation, disproportionate pain, and pneumatosis intestinalis.

Identified as acute mesenteric ischemia with late-stage bowel infarction.

Pneumatosis and portal venous gas confirm dead gut, which dictates a damage control laparotomy approach rather than just revascularization or primary anastomosis.

2

Diagnose the patient with obstipation, a 'whirl sign', and decreased bowel enhancement.

Identified as a strangulated closed-loop small bowel obstruction.

The diminished enhancement indicates ischemia, meaning non-operative management with a nasogastric tube is contraindicated; urgent exploratory laparotomy is required.

3

Diagnose the patient with fever, jaundice, RUQ pain, hypotension, and confusion.

Identified as severe acute cholangitis (Reynolds pentad).

The presence of septic shock from an infected, obstructed biliary tree mandates urgent minimally invasive decompression via ERCP to stabilize the patient.

4

Diagnose the patient on diclofenac with a rigid abdomen and subdiaphragmatic free air.

Identified as a perforated viscus, most likely a perforated peptic ulcer.

Pneumoperitoneum in this clinical context requires immediate surgical exploration and repair using an omental patch to seal the leak.

Key Concept

Triage and precise procedural selection for acute abdominal emergencies based on hemodynamics and underlying etiology.

Question 3653Question →

A resident is reviewing imaging studies and physical examination findings of patients with elevated intracranial pressure in the neurocritical care unit. Match each specific pattern of tissue displacement and associated clinical presentation with the correct brain herniation syndrome.

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Answer

The presentations map directly to the respective anatomical boundaries breached: temporal lobe over tentorium is Uncal, cingulate beneath falx is Subfalcine, bilateral downward shift is Central, and upward cerebellar shift is Upward cerebellar herniation.

Correctly identifying herniation syndromes relies on mapping specific clinical deficits (like CN III palsy or ACA territory ischemia) to corresponding structural shifts within the rigid cranial vault. Each herniation pathway produces a highly stereotypic syndrome.

Step-by-Step Solution

1

Analyze the anatomical shift and cranial nerve/motor findings for the first description.

Temporal lobe shift with CN III palsy strongly indicates uncal herniation.

The uncus is the medial temporal lobe structure closest to the tentorial edge and the oculomotor nerve.

2

Evaluate the second description focusing on horizontal displacement beneath the falx.

Horizontal shift of the cingulate gyrus indicates subfalcine herniation, putting the ACA at risk.

The falx cerebri separates the cerebral hemispheres, and the cingulate gyrus is the most medial structure to herniate underneath it.

3

Assess the third description detailing bilateral, symmetric downward progression.

Symmetric diencephalon/midbrain downward shift points to central transtentorial herniation.

Unlike uncal herniation, central herniation lacks early focal lateralizing signs and presents with global rostrocaudal deterioration.

4

Examine the fourth description involving superior displacement and hydrocephalus.

Superior movement through the tentorial notch defines upward cerebellar herniation.

Mass effect in the posterior fossa pushes structures upwards against the tentorium, obstructing CSF flow at the aqueduct.

Key Concept

Brain herniation syndromes: anatomical pathways and distinct clinical manifestations.

Question 3654Question →

Match each clinical and diagnostic presentation with the most likely thyroid pathology.

Click a left item, then click its matching right item

Show answer & explanation

Answer

The correct matches are: Patient 1 with Papillary thyroid carcinoma, Patient 2 with Medullary thyroid carcinoma, Patient 3 with Anaplastic thyroid carcinoma, and Patient 4 with Toxic thyroid adenoma.

Each clinical vignette provides classic, pathognomonic features of different thyroid pathologies. Recognizing these patterns—such as specific cytological markers, tumor markers like calcitonin, rapid aggressive clinical growth, or functional status on a radionuclide scan—is essential for determining the appropriate endocrine surgery approach.

Step-by-Step Solution

1

Analyze the cytology findings for the first patient.

The presence of 'Orphan Annie eye' nuclei and psammoma bodies is pathognomonic for papillary thyroid carcinoma.

Identifying specific cellular features on cytology dictates the definitive diagnosis for well-differentiated thyroid cancers.

2

Assess the laboratory and historical findings for the second patient.

Elevated calcitonin and a family history suggestive of pheochromocytoma point to Multiple Endocrine Neoplasia type 2 (MEN 2), which is associated with medullary thyroid carcinoma.

Calcitonin is a specific tumor marker for parafollicular C cell neoplasms.

3

Evaluate the clinical progression and histology for the third patient.

A rapidly growing, compressive mass in an elderly patient with undifferentiated pleomorphic cells is highly characteristic of anaplastic thyroid carcinoma.

Advanced age, rapid growth rate, and lack of cellular differentiation are hallmarks of this highly aggressive malignancy.

4

Interpret the laboratory and imaging results for the fourth patient.

Suppressed TSH with a 'hot' nodule on a radionuclide scan indicates a hyperfunctioning, likely benign mass, diagnosing a toxic thyroid adenoma.

Autonomously functioning thyroid nodules suppress pituitary TSH and strongly concentrate iodine radiotracers.

Key Concept

Diagnosis and management of thyroid nodules and malignancies based on cytology, laboratory markers, and imaging.

Estimated Time:1m 30s

Question 3655Question →

A 74-year-old woman is evaluated in the clinic for a 6-month history of a slow, broad-based, shuffling gait, new-onset urinary incontinence, and mild cognitive decline. The physician suspects normal pressure hydrocephalus (NPH). Arrange the following diagnostic and therapeutic steps in the standard evidence-based sequence for managing this condition, from first to last.

Drag items to arrange them in the correct order

Show answer & explanation

Answer

The correct sequence for managing suspected normal pressure hydrocephalus is: 1) Perform neuroimaging (CT or MRI) of the head, 2) Conduct a large-volume lumbar puncture, 3) Reassess for transient clinical improvement, and 4) Place a ventriculoperitoneal (VP) shunt if the tap test is positive.

The standard management of normal pressure hydrocephalus (NPH) follows a strict logical sequence to balance diagnostic accuracy with patient safety. First, non-invasive neuroimaging (CT or MRI) is required to confirm ventriculomegaly and ensure there are no contraindications to a lumbar puncture, such as an intracranial mass. Second, because imaging findings of NPH can overlap with simple brain atrophy (hydrocephalus ex vacuo), a large-volume lumbar puncture (Miller Fisher tap test) must be performed. Third, the patient's gait and cognition are reassessed; temporary improvement confirms that the symptoms are driven by CSF dynamics rather than irreversible neurodegeneration. Finally, only patients who demonstrate a positive clinical response to the tap test are referred for neurosurgical placement of a ventriculoperitoneal (VP) shunt, which offers definitive, long-term CSF diversion.

Step-by-Step Solution

1

Order non-contrast neuroimaging (CT or MRI).

Confirmation of enlarged ventricles without significant sulcal enlargement.

Rules out mass lesions, strokes, or obstructive hydrocephalus, establishing the structural criteria for NPH before any invasive testing is performed.

2

Perform a large-volume lumbar puncture.

Removal of 30-50 mL of cerebrospinal fluid.

Simulates the therapeutic effect of a surgical ventricular shunt to test if the patient's neurological symptoms are reversible.

3

Conduct a clinical reassessment.

Measurement of the patient's response to CSF drainage.

Identifies if the patient is a strong candidate for permanent surgical intervention; gait improvement is the most reliable predictor of surgical success.

4

Perform surgical shunting.

Placement of a ventriculoperitoneal (VP) shunt.

Provides definitive, continuous diversion of CSF to treat the underlying pathophysiology and maintain symptom relief.

Key Concept

The diagnostic and therapeutic algorithm for normal pressure hydrocephalus requires demonstrating structural ventriculomegaly on imaging followed by confirmed physiological responsiveness to CSF drainage prior to definitive neurosurgical shunting.

Question 3656Question →

A 68-year-old man comes to the physician because of a 3-month history of progressively worsening shortness of breath, a persistent "brassy" cough, and mild difficulty swallowing solid foods. He has a history of long-standing, poorly controlled hypertension and has smoked a pack of cigarettes daily for 40 years. His temperature is 37.0°C (98.6°F), blood pressure is 165/95 mm Hg, heart rate is 82/min, and respiratory rate is 18/min. Physical examination shows normal jugular venous pressure and no lower extremity edema. The lungs are clear to auscultation except for a faint, high-pitched expiratory sound heard predominantly over the central chest. Chest radiography reveals a significantly widened superior mediastinum and a prominent aortic silhouette. Which of the following is the most likely underlying cause of this patient's symptoms?

Mechanical compression of adjacent structures by a dilated vessel

Progressive inflammatory airflow limitation affecting the small airways

Fluid transudation into the alveoli secondary to ventricular dysfunction

Reversible bronchospasm triggered by chronic respiratory irritation

Inappropriate relaxation of the lower esophageal sphincter with microaspiration

Show answer & explanation

Answer: Mechanical compression of adjacent structures by a dilated vessel

Answer

The most likely cause of this patient's symptoms is mechanical compression of adjacent structures by a dilated vessel (thoracic aortic aneurysm).

The correct answer is mechanical compression of adjacent structures by a dilated vessel. This patient's presentation is classic for a thoracic aortic aneurysm (TAA). Aneurysms of the aortic arch and descending thoracic aorta can compress adjacent mediastinal structures as they expand. Compression of the tracheobronchial tree leads to dyspnea, wheezing or stridor (often misdiagnosed initially as asthma or COPD), and a characteristic dry, "brassy" cough. Compression of the esophagus leads to dysphagia. The diagnosis is strongly supported by the chest radiograph finding of a widened mediastinum and prominent aortic silhouette in a patient with significant risk factors (smoking, hypertension).

Step-by-Step Solution

1

Analyze the patient's presenting symptoms.

The patient has a brassy cough, dyspnea, central chest wheezing (stridor), and dysphagia.

Identifying the cluster of symptoms helps localize the pathology. These specific symptoms point toward mechanical compression in the mediastinum (trachea and esophagus).

2

Evaluate the patient's risk factors and vital signs.

The patient is an older male with a heavy smoking history and poorly controlled hypertension.

These are the classic, primary risk factors for atherosclerosis and the development of aortic aneurysms.

3

Interpret the radiographic findings in the context of the clinical presentation.

Chest radiography shows a widened superior mediastinum and enlarged aortic silhouette.

A widened mediastinum combined with compressive symptoms in a high-risk patient confirms the diagnosis of a thoracic aortic aneurysm.

Key Concept

Thoracic aortic aneurysms often present asymptomatically but can cause distinct compressive symptoms as they enlarge, including a "brassy" cough and dyspnea (tracheal/bronchial compression), dysphagia (esophageal compression), and hoarseness (recurrent laryngeal nerve compression).

Question 3657Question →

A local health department investigates an outbreak of a novel skin rash in an agricultural community. Officials enroll a cohort of $2,000$ residents and follow them over a $3$ -month period. Among the $500$ residents who work directly with a newly introduced pesticide, $100$ develop the rash. Among the $1,500$ residents who do not work with the pesticide, $150$ develop the rash. Which of the following is the relative risk of developing the rash associated with pesticide exposure?

0.1

0.5

2.0

2.25

10.0

Show answer & explanation

Answer: $2.0$

Answer

The relative risk is

2.0

.

The relative risk (RR) is calculated by dividing the incidence of the disease in the exposed group by the incidence in the unexposed group. The incidence in the exposed group is

100 / 500 = 0.20

. The incidence in the unexposed group is

150 / 1,500 = 0.10

. Therefore, the relative risk is

0.20 / 0.10 = 2.0

. This indicates that individuals exposed to the pesticide are twice as likely to develop the rash compared to those unexposed.

Step-by-Step Solution

1

Calculate the incidence of the rash in the exposed group.

100 / 500 = 0.20

Incidence is the number of new cases divided by the population at risk in that specific group.

2

Calculate the incidence of the rash in the unexposed group.

150 / 1,500 = 0.10

This establishes the baseline risk for those without the pesticide exposure.

3

Calculate the relative risk by dividing the incidence in the exposed by the incidence in the unexposed.

0.20 / 0.10 = 2.0

Relative risk compares the likelihood of disease between two groups in a cohort study.

Key Concept

Relative risk (RR) is the measure of association used in cohort studies, calculated as the incidence of disease in the exposed group divided by the incidence in the unexposed group.

Estimated Time:1m 0s

Question 3658Question →

A 62-year-old woman is evaluated in the neurosurgical intensive care unit on postoperative day 5 following a right temporal craniotomy for glioblastoma resection. Over the past 12 hours, she has become progressively lethargic. She now only opens her eyes to painful stimuli and mutters incomprehensibly. Her temperature is 38.9°C (102.0°F), blood pressure is 145/88 mmHg, heart rate is 105/min, and respiratory rate is 16/min. Physical examination reveals pronounced nuchal rigidity. The surgical incision is well-approximated, clean, and has no fluctuance or drainage. An indwelling urinary catheter, placed prior to surgery, remains in situ. Which of the following is the most appropriate next step in management?

Perform a non-contrast CT scan of the head

Perform an immediate lumbar puncture

Remove the indwelling urinary catheter and send a urine sample for culture

Initiate broad-spectrum intravenous antibiotics and observe clinically

Administer intravenous haloperidol and obtain a psychiatric consultation

Show answer & explanation

Answer: Perform a non-contrast CT scan of the head

Answer

The most appropriate next step is to perform a non-contrast CT scan of the head.

The correct answer is to perform a non-contrast CT scan of the head. This patient is presenting with fever, altered mental status, and nuchal rigidity on postoperative day 5 following a craniotomy, which is highly suspicious for postoperative bacterial meningitis or an intracranial space-occupying infection (such as a subdural empyema or brain abscess). In any patient with suspected meningitis who has 'red flag' features—such as severe altered mental status, focal neurologic deficits, papilledema, immunocompromise, or a history of recent central nervous system surgery—a CT scan of the head must be performed prior to a lumbar puncture. This is crucial to rule out increased intracranial pressure, hydrocephalus, or a mass lesion, as performing a lumbar puncture in these settings can precipitate a pressure gradient shift and subsequent fatal cerebral herniation. If neuroimaging is significantly delayed, blood cultures should be drawn and empiric antibiotics administered immediately, but imaging remains the definitive next procedural step.

Step-by-Step Solution

1

Analyze the patient's clinical presentation and timeline.

The patient presents with high fever, nuchal rigidity, and severely altered mental status on postoperative day 5 following a craniotomy.

To establish the most likely differential diagnosis, which in this case is a postoperative central nervous system infection (e.g., bacterial meningitis, subdural empyema, or brain abscess).

2

Evaluate the criteria for obtaining neuroimaging prior to a lumbar puncture.

The patient has critical 'red flag' criteria: a history of recent central nervous system surgery and a severely abnormal level of consciousness.

To determine the safest diagnostic workflow. A lumbar puncture in the setting of increased intracranial pressure or an undiagnosed mass lesion can cause fatal brain herniation.

3

Determine the most appropriate next procedural step.

A non-contrast CT scan of the head must be ordered before attempting cerebrospinal fluid analysis.

Neuroimaging is required to evaluate for midline shift, mass effect, or hydrocephalus to ensure structural stability of the brain before proceeding with invasive testing.

Key Concept

In patients with suspected bacterial meningitis who have high-risk features (e.g., recent neurosurgery, severe altered mental status, focal neurologic deficits, or papilledema), a CT scan of the head must be performed prior to a lumbar puncture to prevent cerebral herniation.

Estimated Time:1m 30s

Question 3659Question →

Match each clinical presentation with its most likely underlying vascular pathology or pathophysiologic mechanism.

Click a left item, then click its matching right item

Show answer & explanation

Answer

Patient 1 matches with Acute macroembolic occlusion of the SMA. Patient 2 matches with Atherosclerotic critical stenosis of splanchnic arteries. Patient 3 matches with Arterial macroembolization from an LV thrombus. Patient 4 matches with Arterial microembolization from a peripheral aneurysm.

Each clinical vignette provides specific clues pointing to distinct pathophysiologic mechanisms of vascular disease. Atrial fibrillation suggests a cardiac embolic source to the gut (SMA). Postprandial pain implies a chronic demand-supply mismatch (chronic mesenteric ischemia). A recent anterior MI suggests a ventricular mural thrombus embolizing to a major limb artery. A popliteal aneurysm with blue toes and palpable pulses points to distal microembolization of mural debris.

Step-by-Step Solution

1

Analyze the patient with atrial fibrillation and pain out of proportion to exam.

Identified as acute mesenteric ischemia.

The heart is a common source of emboli in atrial fibrillation, which frequently lodge in the superior mesenteric artery.

2

Analyze the patient with postprandial pain, weight loss, and severe PAD.

Identified as chronic mesenteric ischemia.

Chronic atherosclerosis leads to a mismatch between splanchnic blood supply and intestinal metabolic demand during digestion.

3

Analyze the patient with acute limb ischemia following a recent anterior MI.

Identified as macroembolization to the lower extremity.

Anterior MIs often lead to apical akinesis and mural thrombus formation, which can dislodge and acutely occlude major peripheral arteries.

4

Analyze the patient with blue toe syndrome, intact distal pulses, and a popliteal aneurysm.

Identified as microembolization.

Intact pulses rule out a large occlusion. Mural thrombus within the aneurysm sheds small debris into the distal microcirculation.

Key Concept

Clinical presentations of major vascular occlusive diseases (macroembolic versus microembolic, acute versus chronic).

Question 3660Question →

A 59-year-old male with untreated hypertension arrives at the emergency department reporting the abrupt onset of a severe, tearing pain in his anterior chest that radiates straight to his interscapular region. His blood pressure is 210/115 mmHg, and his heart rate is 112/min. A portable chest radiograph demonstrates a widened mediastinum. Acute aortic dissection is highly suspected. Arrange the following clinical steps in the most appropriate chronological sequence for the evaluation and management of this patient.

Drag items to arrange them in the correct order

Show answer & explanation

Answer

The correct chronological sequence is: 1) Administer an intravenous beta-blocker, 2) Administer an intravenous vasodilator, 3) Obtain a computed tomography angiography (CTA), and 4) Consult cardiothoracic surgery.

The initial management of a suspected acute aortic dissection focuses on 'anti-impulse' therapy to halt the progression of the intimal tear. This requires a strict sequence: first, administer a negative inotropic and chronotropic agent (like an intravenous beta-blocker) to decrease the rate of rise of ventricular pressure (dP/dt) and heart rate. Second, administer a vasodilator to lower the overall blood pressure to a target systolic of 100-120 mmHg. Once the patient's hemodynamics are stabilized, definitive imaging (such as a CTA) is obtained to confirm the diagnosis and classify the dissection anatomically. Finally, if a Type A dissection is confirmed, emergent cardiothoracic surgery consultation is required for operative repair.

Step-by-Step Solution

1

Administer an intravenous beta-blocker

Decreased heart rate and reduced shearing forces on the aortic wall

Negative inotropic and chronotropic agents must be given first to decrease left ventricular dP/dt and prevent dissection propagation.

2

Administer an intravenous vasodilator

Lowered systolic blood pressure to the target range of 100-120 mmHg

Decreases hydrostatic pressure on the dissection flap. Must be given only after heart rate is controlled to avoid reflex sympathetic activation.

3

Obtain a CTA of the chest and abdomen

Visualization of the intimal flap and exact anatomical extent of the dissection

Definitive imaging is necessary to distinguish between Stanford Type A (ascending) and Type B (descending) dissections to guide ultimate therapy.

4

Consult cardiothoracic surgery

Operative planning and intervention

Stanford Type A dissections have a critically high mortality rate without prompt surgical repair.

Key Concept

The chronological protocol for suspected acute aortic dissection requires heart rate control (beta-blockers) prior to blood pressure control (vasodilators), followed by definitive imaging and surgical consultation.

Estimated Time:1m 0s

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