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Critical care (ICU) MCQs with answers

11 single-best-answer questions on septic shock, ARDS, poisoning, AKI and electrolyte emergencies. Try each one, then open the answer to see the explanation, why the other options are wrong, and the guideline or trial behind it.

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Written by Dr. Mohammed Maree, consultant surgeon, Jerusalem. Updated 3 November 2026.

1. A patient with faecal peritonitis remains hypotensive (mean arterial pressure 55 mmHg) after 30 mL/kg of crystalloid. What is the first-line vasopressor and target?

   1. Dobutamine alone
   2. No vasopressor; give 10 more litres of fluid
   3. Adrenaline as first choice in all patients
   4. Dopamine, targeting a systolic pressure of 160
   5. Norepinephrine, targeting a mean arterial pressure of about 65 mmHg
   Show the answer and explanation

   Answer: E. Norepinephrine, targeting a mean arterial pressure of about 65 mmHg. Norepinephrine is the first-line vasopressor in septic shock. Vasopressin is added if more support is needed, and adrenaline or dobutamine are used for cardiac dysfunction. Vasopressors can be started through a peripheral line rather than waiting for central access. Source control is essential.

   Why not the others? Dopamine causes more arrhythmias than norepinephrine.

   References

   1. Evans L et al. Surviving Sepsis Campaign: international guidelines for management of sepsis and septic shock 2021. Crit Care Med 2021

2. A patient develops ARDS after severe pancreatitis and is mechanically ventilated. Which ventilation strategy reduces mortality?

   1. 100% oxygen for all patients regardless of saturation
   2. High tidal volumes of 12 mL/kg to normalise CO₂
   3. Routine high-frequency oscillation
   4. Low tidal volume ventilation (about 6 mL/kg of predicted body weight) with a plateau pressure under 30 cmH₂O, and prone positioning for severe ARDS
   5. No PEEP
   Show the answer and explanation

   Answer: D. Low tidal volume ventilation (about 6 mL/kg of predicted body weight) with a plateau pressure under 30 cmH₂O, and prone positioning for severe ARDS. Lung-protective ventilation reduces ventilator-induced lung injury and mortality. Prone positioning for at least 12–16 hours a day improves survival in moderate to severe ARDS. A higher CO₂ is accepted (permissive hypercapnia) when it is safe.

   Why not the others? Tidal volume is based on predicted (height-based) weight, not actual weight.

   References

   1. Fan E et al. An official ATS/ESICM/SCCM clinical practice guideline: mechanical ventilation in adult patients with acute respiratory distress syndrome. Am J Respir Crit Care Med 2017

3. Three days after a severe traumatic brain injury, a patient passes 400 mL of urine an hour. His sodium has risen to 156 mmol/L and urine osmolality is low. What is the likely cause and treatment?

   1. Cerebral salt wasting; hypertonic saline
   2. Diuretic overdose; stop furosemide
   3. Post-obstructive diuresis; catheter change
   4. Central (cranial) diabetes insipidus; desmopressin and replacement of free water, with frequent sodium checks
   5. SIADH; fluid restriction
   Show the answer and explanation

   Answer: D. Central (cranial) diabetes insipidus; desmopressin and replacement of free water, with frequent sodium checks. Pituitary or hypothalamic injury reduces ADH secretion, causing dilute polyuria and hypernatraemia. Desmopressin replaces ADH. Sodium must be corrected gradually to avoid cerebral oedema. SIADH, by contrast, causes hyponatraemia with concentrated urine.

   Why not the others? Fluid restriction in diabetes insipidus would worsen hypernatraemia.

   References

   1. Christ-Crain M et al. Diabetes insipidus. Nat Rev Dis Primers 2019

4. A man rescued from an enclosed house fire is confused and hypotensive, with a very high lactate (12 mmol/L) despite adequate oxygenation. What should be given urgently?

   1. Sodium bicarbonate only
   2. Naloxone
   3. Hydroxocobalamin for suspected cyanide poisoning, with 100% oxygen
   4. No specific treatment
   5. Furosemide
   Show the answer and explanation

   Answer: C. Hydroxocobalamin for suspected cyanide poisoning, with 100% oxygen. Burning plastics, wool and silk release hydrogen cyanide. A high lactate with altered consciousness and cardiovascular instability in smoke inhalation suggests cyanide toxicity. Hydroxocobalamin binds cyanide to form cyanocobalamin and is given empirically. Carbon monoxide poisoning is treated with 100% oxygen.

   Why not the others? Pulse oximetry is unreliable in carbon monoxide poisoning.

   References

   1. Anseeuw K et al. Cyanide poisoning by fire smoke inhalation: a European expert consensus. Eur J Emerg Med 2013

5. A family is found with headaches and confusion in a room with a faulty gas heater. Their oxygen saturations read 99%. What is the key test and treatment?

   1. Carboxyhaemoglobin on a co-oximetry blood gas; give high-flow 100% oxygen, with hyperbaric oxygen considered in severe cases
   2. Furosemide
   3. CT of the head only
   4. Antibiotics
   5. Reassure, because the saturation is normal
   Show the answer and explanation

   Answer: A. Carboxyhaemoglobin on a co-oximetry blood gas; give high-flow 100% oxygen, with hyperbaric oxygen considered in severe cases. Carbon monoxide binds haemoglobin far more avidly than oxygen. Standard pulse oximeters read carboxyhaemoglobin as oxyhaemoglobin, giving falsely normal saturation. High-flow oxygen shortens the half-life of CO. Delayed neurological effects can occur.

   Why not the others? Pregnant women and patients with loss of consciousness are at higher risk.

   References

   1. Weaver LK. Carbon monoxide poisoning. N Engl J Med 2009

6. Which ventilated ICU patient is most likely to benefit from stress ulcer prophylaxis with a PPI?

   1. A patient at high risk of bleeding, such as a ventilated patient with coagulopathy, shock or chronic liver disease
   2. No patient ever benefits
   3. All patients after any surgery
   4. A healthy patient after day-case hernia repair
   5. Every hospital ward patient
   Show the answer and explanation

   Answer: A. A patient at high risk of bleeding, such as a ventilated patient with coagulopathy, shock or chronic liver disease. Stress ulcer prophylaxis reduces clinically important GI bleeding in critically ill patients at high risk (for example mechanical ventilation with coagulopathy, shock, or liver disease). In low-risk patients, the benefit is small and may not justify the risks, including possible pneumonia and C. difficile.

   Why not the others? Prophylaxis should be reviewed and stopped when risk factors resolve.

   References

   1. Ye Z et al. Gastrointestinal bleeding prophylaxis for critically ill patients: a clinical practice guideline (BMJ Rapid Recommendations). BMJ 2020

7. What blood glucose target is recommended for most critically ill adults?

   1. No monitoring needed
   2. Under 4 mmol/L
   3. About 7.8–10 mmol/L (140–180 mg/dL), avoiding hypoglycaemia
   4. 4.4–6.1 mmol/L (tight control)
   5. Above 15 mmol/L
   Show the answer and explanation

   Answer: C. About 7.8–10 mmol/L (140–180 mg/dL), avoiding hypoglycaemia. The NICE-SUGAR trial showed that intensive glucose control (4.5–6.0 mmol/L) increased mortality, mainly through hypoglycaemia, compared with a moderate target. Glucose is monitored frequently, usually with an insulin infusion when needed.

   Why not the others? Hypoglycaemia is especially harmful in brain injury.

   References

   1. NICE-SUGAR Study Investigators. Intensive versus conventional glucose control in critically ill patients. N Engl J Med 2009

8. Several people are struck by lightning. Some are walking and talking; one is in cardiac arrest. Who should be treated first?

   1. The person with burns first
   2. Only those with visible injuries
   3. The walking wounded first
   4. Nobody, because lightning arrests are not survivable
   5. The patient in cardiac arrest (“reverse triage”), because lightning victims in arrest often respond to prompt CPR and ventilation
   Show the answer and explanation

   Answer: E. The patient in cardiac arrest (“reverse triage”), because lightning victims in arrest often respond to prompt CPR and ventilation. Lightning causes a direct current shock that can stop the heart and breathing. The heart often restarts spontaneously, but respiratory arrest persists, causing secondary hypoxic arrest. Prompt CPR and ventilation save many lives, so those who appear dead are treated first, unlike conventional triage.

   Why not the others? Fern-like (Lichtenberg) skin marks are characteristic of lightning.

   References

   1. Davis C et al. Wilderness Medical Society practice guidelines for the prevention and treatment of lightning injuries: 2014 update. Wilderness Environ Med 2014

9. A septic patient has acute kidney injury with a creatinine of 350 µmol/L, a potassium of 5.5 and adequate urine output. There is no fluid overload or severe acidosis. Should dialysis be started now?

   1. Never; dialysis is harmful
   2. No; start renal replacement therapy for specific indications (refractory hyperkalaemia, severe acidosis, fluid overload, uraemic complications) rather than by creatinine alone
   3. Yes; when creatinine is above 200
   4. Yes; every AKI needs immediate dialysis
   5. Only if potassium is normal
   Show the answer and explanation

   Answer: B. No; start renal replacement therapy for specific indications (refractory hyperkalaemia, severe acidosis, fluid overload, uraemic complications) rather than by creatinine alone. The STARRT-AKI trial found no survival benefit from starting renal replacement therapy early compared with a standard approach, and more patients remained dependent on dialysis with the early approach. Many patients recover without dialysis.

   Why not the others? Indications include potassium above about 6.5 despite treatment, severe metabolic acidosis, pulmonary oedema and uraemic encephalopathy or pericarditis.

   References

   1. STARRT-AKI Investigators. Timing of initiation of renal-replacement therapy in acute kidney injury. N Engl J Med 2020

10. Two days after bilateral femoral shaft fractures, a young man becomes confused and hypoxic, with petechiae over the chest and axillae. What is the most likely diagnosis?

    1. Pneumothorax
    2. Fat embolism syndrome; supportive care with oxygen or ventilation; early fracture fixation reduces the risk
    3. Meningitis; lumbar puncture
    4. Alcohol withdrawal
    5. Pulmonary embolism only; thrombolysis
    Show the answer and explanation

    Answer: B. Fat embolism syndrome; supportive care with oxygen or ventilation; early fracture fixation reduces the risk. Fat embolism syndrome follows long bone and pelvic fractures, typically 24–72 hours after injury, with the triad of respiratory distress, neurological changes and petechial rash. Treatment is supportive. Early stabilisation of fractures reduces its incidence.

    Why not the others? Petechiae in the axillae and conjunctivae are a characteristic clue.

    References

    1. Kosova E, Bergmark B, Piazza G. Fat embolism syndrome. Circulation 2015

11. During massive transfusion for trauma, a patient develops perioral tingling, hypotension and prolonged QT. Which electrolyte should be checked and replaced?

    1. Sodium
    2. Magnesium only
    3. Phosphate
    4. Potassium only by restriction
    5. Ionised calcium, because citrate in blood products binds calcium
    Show the answer and explanation

    Answer: E. Ionised calcium, because citrate in blood products binds calcium. Citrate anticoagulant in stored blood binds calcium, causing hypocalcaemia that worsens coagulopathy and cardiac contractility. Ionised calcium is monitored during massive transfusion and kept in the normal range. Hyperkalaemia, hypothermia and acidosis are other complications.

    Why not the others? Hypocalcaemia is part of a “lethal diamond” with hypothermia, acidosis and coagulopathy.

    References

    1. Rossaint R et al. The European guideline on management of major bleeding and coagulopathy following trauma: sixth edition. Crit Care 2023

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