USMLE Step 2 Quiz: Shock And Hemodynamic Instability

What this quiz covers

This quiz focuses on Shock And Hemodynamic Instability, giving you a quick way to practice the rules, question types, and explanations that matter most for USMLE Step 2.

How to use this quiz

Try each quiz question before looking at the correct answer. Use the explanations to review missed ideas, then come back to similar questions until the pattern feels familiar.

Question 1

1. Cardiogenic
2. Hypovolemic (correct answer)
3. Distributive
4. Obstructive

Explanation: This patient's presentation is classic for hypovolemic shock due to hemorrhage in the setting of trauma. Key features include hypotension, tachycardia, and signs of poor peripheral perfusion (cool, clammy skin; delayed capillary refill). The mechanism of injury and abdominal findings suggest intra-abdominal bleeding as the cause.

Question 2

1. Cardiogenic (correct answer)
2. Hypovolemic
3. Septic
4. Obstructive

Explanation: This patient is experiencing an acute anterior wall myocardial infarction, leading to cardiogenic shock. The diagnosis is supported by hypotension and signs of pump failure, including jugular venous distention (elevated right-sided filling pressures) and pulmonary edema (crackles), which indicate left ventricular failure.

Question 3

1. Neurogenic
2. Hypovolemic
3. Cardiogenic
4. Distributive (correct answer)

Explanation: This patient has septic shock, which is a form of distributive shock. The presentation of fever, hypotension, tachycardia, altered mental status, and a clear source of infection (urosepsis) is classic. In the early stages of septic shock, systemic vasodilation leads to warm, flushed skin (so-called 'warm shock').

Question 4

1. Hypovolemic
2. Cardiogenic
3. Septic
4. Obstructive (correct answer)

Explanation: The constellation of acute onset dyspnea, hypotension, tachycardia, and jugular venous distention with clear lungs in a patient with a major risk factor for venous thromboembolism (recent orthopedic surgery) is highly suggestive of a massive pulmonary embolism. A large PE obstructs outflow from the right ventricle, causing obstructive shock.

Question 5

1. Intravenous diphenhydramine
2. Intravenous methylprednisolone
3. Intramuscular epinephrine (correct answer)
4. Nebulized albuterol

Explanation: This patient is in anaphylactic shock, a medical emergency. The first-line and most critical treatment is intramuscular epinephrine. Epinephrine counteracts the massive histamine release by causing vasoconstriction (alpha-1 effect) to increase blood pressure and bronchodilation (beta-2 effect) to relieve airway obstruction. Antihistamines, corticosteroids, and albuterol are important adjunctive therapies but should be administered only after epinephrine.

Question 6

1. Pulmonary capillary wedge pressure (PCWP) low, Cardiac index (CI) low, Systemic vascular resistance (SVR) high (correct answer)
2. PCWP high, CI low, SVR high
3. PCWP low, CI high, SVR low
4. PCWP high, CI high, SVR high

Explanation: The patient is in hypovolemic shock from hemorrhage. This is characterized by low intravascular volume, leading to decreased preload (low PCWP). The reduced preload results in a decreased cardiac output (low CI). The body compensates by increasing systemic vascular resistance (high SVR) through vasoconstriction to maintain blood pressure.

Question 7

1. PCWP low, CI low, SVR high
2. PCWP high, CI low, SVR high
3. PCWP normal or low, CI high, SVR low (correct answer)
4. PCWP high, CI high, SVR low

Explanation: Early septic shock (or 'warm shock') is a distributive state characterized by massive peripheral vasodilation, which leads to a profoundly low systemic vascular resistance (SVR). To compensate for the low SVR and maintain blood pressure, the heart rate and contractility increase, resulting in a high cardiac index (CI). The pulmonary capillary wedge pressure (PCWP) is typically low or normal due to the vasodilation and relative hypovolemia until aggressive fluid resuscitation is provided.

Question 8

1. Administer an additional 2-liter fluid bolus
2. Begin an infusion of norepinephrine (correct answer)
3. Begin an infusion of dobutamine
4. Administer intravenous hydrocortisone

Explanation: This patient has fluid-refractory septic shock, defined by persistent hypotension despite adequate fluid resuscitation. According to the Surviving Sepsis Campaign guidelines, the next step is to initiate a vasopressor to restore mean arterial pressure (MAP) to at least 65 mmHg. Norepinephrine is the first-line vasopressor of choice due to its potent alpha-1 and modest beta-1 adrenergic effects.

Question 9

1. Atropine bolus
2. Norepinephrine infusion (correct answer)
3. Dopamine infusion
4. Placement of a transcutaneous pacemaker

Explanation: This patient has neurogenic shock, a form of distributive shock caused by the loss of sympathetic tone after a high spinal cord injury. This results in unopposed vagal activity, leading to vasodilation (hypotension) and bradycardia. After initial, cautious fluid administration, vasopressors are required. Norepinephrine is an excellent choice as its alpha-agonist effects counteract the vasodilation, and its beta-agonist effects can help support the heart rate.

Question 10

1. Intravenous hydrocortisone (correct answer)
2. Continuous insulin infusion
3. Sodium bicarbonate infusion
4. High-dose diuretic therapy

Explanation: This patient has refractory septic shock, which may be due to relative adrenal insufficiency caused by critical illness. Current guidelines recommend considering intravenous 'stress-dose' corticosteroids (e.g., hydrocortisone 200 mg/day) for adult patients with septic shock who require ongoing high doses of vasopressors to maintain hemodynamic stability. Corticosteroids can improve sensitivity to catecholamines and help reverse shock.

Question 11

1. Renal failure
2. Tachyarrhythmias (correct answer)
3. Peripheral ischemia
4. Hyperglycemia

Explanation: Large randomized controlled trials have demonstrated that norepinephrine is superior to dopamine as the first-line vasopressor in septic shock. The primary reason for this is that dopamine has more pronounced beta-1 agonist effects, leading to a significantly higher incidence of tachyarrhythmias, including atrial fibrillation and ventricular tachycardia, which can further compromise hemodynamic stability. Norepinephrine is associated with a lower mortality rate in septic shock.

Question 12

1. Addition of a vasopressin infusion
2. Placement of an intra-aortic balloon pump (correct answer)
3. Aggressive intravenous diuretic therapy
4. Urgent coronary artery bypass grafting

Explanation: This patient is in refractory cardiogenic shock, failing maximal medical therapy. The next step is to provide mechanical circulatory support to unload the failing ventricle and improve systemic perfusion. An intra-aortic balloon pump (IABP) is a commonly used temporizing device that decreases afterload and increases coronary perfusion, thereby improving cardiac output. More advanced options like LVADs or ECMO may also be considered. Diuretics would be harmful, and CABG is not an immediate hemodynamic support measure.

Question 13

1. Aortic dissection
2. Myocardial infarction
3. Brainstem herniation (correct answer)
4. Pulmonary embolism

Explanation: This patient's presentation is consistent with a Cushing reflex (hypertension, bradycardia) evolving into brainstem herniation. The initial severe hypertension is a response to increased intracranial pressure (ICP). The subsequent precipitous drop in blood pressure and worsening bradycardia (the 'terminal' phase of the Cushing reflex) signifies brainstem compression and failure of autonomic centers, leading to a profound distributive shock state (neurogenic shock).

Question 14

1. The patient has developed cardiogenic shock.
2. The patient requires vasopressor therapy.
3. The patient is still fluid responsive. (correct answer)
4. The CVP measurement is inaccurate.

Explanation: The passive leg raise (PLR) is a dynamic test to assess fluid responsiveness. It provides a reversible 'auto-bolus' of fluid from the legs to the central circulation. A significant increase (>10-15%) in stroke volume or cardiac output after a PLR indicates that the patient is on the steep portion of their Frank-Starling curve and will likely benefit from additional intravenous fluids. Static measures like CVP are poor predictors of fluid responsiveness.

Question 15

1. Resuscitation is failing and a second vasopressor is needed.
2. The patient is developing acute kidney injury.
3. She is demonstrating an appropriate response to management. (correct answer)
4. A second, unidentified source of infection is likely present.

Explanation: The patient is showing signs of improvement following the two most critical interventions for septic shock: resuscitation (fluids and vasopressors) and source control (surgery). The decreasing lactate level is a key indicator that tissue perfusion is improving. A stable mean arterial pressure on vasopressors and adequate urine output (>0.5 mL/kg/hr) further support a positive response to therapy. This demonstrates successful initial shock management.

Question 16

1. Massive hemorrhage into the pleural space
2. Impaired ventricular filling (correct answer)
3. Systemic vasodilation from spinal injury
4. Primary myocardial pump failure

Explanation: This patient presents with Beck's triad (hypotension, jugular venous distention, and muffled heart sounds), which is classic for cardiac tamponade. Cardiac tamponade causes obstructive shock by impairing diastolic filling of the ventricles due to pressure from the pericardial effusion, leading to decreased stroke volume and cardiac output.

Question 17

1. 0.9% Saline
2. Lactated Ringer's
3. 5% Albumin
4. O-negative packed red blood cells (correct answer)

Explanation: This patient is in Class IV hemorrhagic shock. The primary problem is the loss of oxygen-carrying capacity and clotting factors, not just volume. While crystalloids are used initially, the immediate priority in a patient with profound hypotension from hemorrhage is to restore oxygen delivery by transfusing blood products. O-negative packed red blood cells are the universal donor type and should be given emergently while crossmatched blood is prepared.

Question 18

1. Decrease in heart rate from 130/min to 110/min
2. Normalization of skin temperature
3. Increase in urine output to >0.5 mL/kg/hr (correct answer)
4. Resolution of anxiety and confusion

Explanation: While improvements in heart rate, skin temperature, and mental status are all positive signs, urine output is a direct and quantifiable measure of renal perfusion, which serves as an excellent surrogate for overall adequacy of end-organ perfusion. Achieving a target urine output of >0.5 mL/kg/hr is a key goal of fluid resuscitation in shock.

Question 19

1. The patient is developing acute liver failure.
2. Fluid overload is causing hemodilution.
3. There is persistent tissue hypoperfusion. (correct answer)
4. The norepinephrine infusion is causing metabolic acidosis.

Explanation: Lactate is a marker of anaerobic metabolism, which occurs when tissues are inadequately perfused with oxygen. A rising lactate level, even with an acceptable blood pressure, is a critical sign of worsening shock and persistent tissue hypoperfusion at the microcirculatory level. It indicates that resuscitation efforts are failing and is associated with a poor prognosis.

Question 20

1. Intravenous fluid bolus
2. Dobutamine infusion (correct answer)
3. Phenylephrine infusion
4. Blood transfusion

Explanation: The patient's hemodynamic profile (low cardiac index, high PCWP, high SVR) is classic for cardiogenic shock. The primary problem is impaired myocardial contractility. Dobutamine is an inotrope (beta-1 agonist) that increases contractility and cardiac output. An IV fluid bolus would worsen the already high filling pressures (PCWP). Phenylephrine would further increase the high SVR, worsening afterload. A blood transfusion is not indicated without evidence of bleeding or severe anemia.