MRCEM Single Best Answer Course: Modules, Lessons and Questions

A 41-year-old woman presents to the ED with a two-hour history of a painful, pale, demarcated area of skin on her left cheek following a winter fell run in wet conditions. The area is soft, blanches with pressure, and sensation is intact. What is the most appropriate immediate management?

A Rub the area vigorously with a warm towel to restore circulation
B Apply a dry dressing and arrange outpatient dermatology review
C Rapid rewarming in water at 37-39°C for 15-30 minutes
D IV iloprost infusion and urgent vascular surgery referral
E Apply ice packs to reduce inflammation and prevent further tissue injury

Overall explanation

This presentation describes superficial frostbite (first-degree or superficial second-degree): soft, blanching tissue with preserved sensation, indicating no deep tissue freezing. Immediate management is rapid rewarming in warm water at 37-39°C for 15-30 minutes, which is the evidence-based first-line treatment. Rubbing the affected area causes mechanical trauma to fragile tissue and must be avoided. Surgical debridement and thrombolytics are reserved for deep frostbite with established demarcation. (BMJ Best Practice: Frostbite; Wilderness Medical Society Practice Guidelines for Frostbite, referenced in RCEM Learning Environmental Emergencies.)

A 38-year-old man presents with severe bronchospasm, widespread urticaria, and hypotension following IV cefuroxime. Despite 500 micrograms IM adrenaline and 1 litre IV crystalloid, wheeze persists and SpO2 is 89% on 15 L/min oxygen. What is the most appropriate next step?

A Repeat IM adrenaline 500 micrograms
B Nebulised salbutamol 5 mg
C IV magnesium sulphate 2 g over 20 minutes
D IV hydrocortisone 200 mg
E IV aminophylline 250 mg over 20 minutes

Overall explanation

Persistent bronchospasm in anaphylaxis after adrenaline should be treated with nebulised salbutamol, as in acute severe asthma. Adrenaline predominantly addresses the systemic vasodilation and mast-cell mediator release, but bronchospasm may remain refractory. Nebulised salbutamol 5 mg is an evidence-based adjunct recommended by Resuscitation Council UK 2025 for this scenario.

A 25-year-old woman is successfully treated for anaphylaxis to latex intraoperatively. She is asymptomatic and haemodynamically stable after one IM adrenaline dose and IV fluids. She asks whether she can go home. What is the minimum recommended ED observation period?

A 4 hours, provided she remains asymptomatic
B 2 hours, with adrenaline auto-injector issued before discharge
C 24 hours, in all cases of anaphylaxis regardless of severity
D 6 to 12 hours from the time of reaction
E 1 hour, if vital signs have normalised

Overall explanation

Biphasic anaphylaxis -- a recurrence of symptoms without re-exposure to the trigger -- occurs in up to 20% of cases and can present up to 72 hours later. Resuscitation Council UK 2025 recommends a minimum 6-12 hour observation period in hospital following an anaphylactic reaction requiring adrenaline, with extended observation for severe or refractory reactions. Safe discharge requires adrenaline auto-injector prescription and written allergy action plan.

A 72-year-old woman on long-term beta-blocker therapy for atrial fibrillation develops anaphylaxis after contrast administration. She receives two doses of 500 micrograms IM adrenaline without haemodynamic improvement. BP remains 70/40 mmHg. What is the most appropriate next pharmacological intervention?

A IV hydrocortisone 200 mg
B IV chlorphenamine 10 mg
C Repeat IM adrenaline 500 micrograms for a third time
D IV glucagon 1-2 mg bolus
E IV metaraminol 500 micrograms bolus

Overall explanation

Beta-blocker therapy blunts the chronotropic and vasopressor response to adrenaline by antagonising beta-1 and beta-2 receptors. In refractory anaphylaxis in patients on beta-blockers, IV glucagon (1-2 mg) bypasses the beta-receptor blockade by raising intracellular cAMP via glucagon receptors, producing positive inotropic and chronotropic effects. Resuscitation Council UK 2025 guidance identifies beta-blocker use as a risk factor for treatment-resistant anaphylaxis.

A 6-year-old boy (22 kg) develops stridor, periorbital oedema, and urticaria within minutes of eating a birthday cake containing peanuts. HR 142 bpm, BP 78/44 mmHg, SpO2 91% on air. What is the correct initial adrenaline dose and route?

A 100 micrograms IV adrenaline (1:10000)
B 300 micrograms IM adrenaline (1:1000)
C 150 micrograms IM adrenaline (1:1000)
D 500 micrograms SC adrenaline (1:1000)
E 500 micrograms IM adrenaline (1:1000)

Overall explanation

Children aged 6-12 years receive 300 micrograms IM adrenaline (0.3 mL of 1:1000) as the first-line intervention in anaphylaxis. IM injection into the anterolateral thigh is the correct route. IV adrenaline is reserved for refractory anaphylaxis in critical care under continuous monitoring. Resuscitation Council UK 2025 Anaphylaxis Algorithm specifies age-banded IM adrenaline doses.

A 4-year-old girl is brought to the Emergency Department with a 24-hour history of fever and irritability. Her parents report she has not passed urine for 12 hours. Temp 38.7°C, HR 148 bpm, RR 32, SpO2 98% on air. She is alert but pale and mottled. There is no rash. Urine dipstick shows leucocytes and nitrites. Which investigation result would most alter immediate management in this child?

A White cell count above 20 x10⁹/L
B CRP above 100 mg/L
C Urine microscopy showing more than 50 white cells per high-power field
D Blood culture positive for Gram-negative bacilli
E Serum lactate above 2 mmol/L

Overall explanation

In a febrile child with clinical signs of organ dysfunction (tachycardia, mottling, reduced urine output) and a positive dipstick, the priority is to determine whether sepsis-mediated haemodynamic compromise is present. A blood lactate above 2 mmol/L identifies tissue hypoperfusion and triggers the high-risk sepsis pathway with immediate IV antibiotics and fluid resuscitation. The NICE Sepsis guidance (NG51, 2016, updated 2024) mandates lactate measurement as part of the initial sepsis work-up in any child with suspected sepsis and risk factors for deterioration. RCPCH and NICE fever in under-5s guidance (NG143) also directs escalation when mottling is present.

A 19-year-old woman presents with sudden palpitations and mild dyspnoea. HR 192 bpm, BP 118/76 mmHg, SpO2 99% on air. The ECG shows a regular narrow-complex tachycardia. Vagal manoeuvres have failed. Adenosine 6 mg IV is given without effect.

What is the most appropriate next dose of adenosine?

A 6 mg intravenous adenosine
B 12 mg intravenous adenosine
C 18 mg intravenous adenosine
D 3 mg intravenous adenosine
E Intravenous verapamil 5 mg

Overall explanation

Per the Resuscitation Council UK 2025 Adult Tachyarrhythmia Algorithm, if the initial 6 mg adenosine bolus fails to terminate a regular narrow-complex tachycardia, a second dose of 12 mg IV should be given. If this also fails, a further 12 mg may be given. Adenosine must be administered as a rapid bolus into a large proximal vein, followed by a rapid saline flush.

A 31-year-old man presents with acute onset lip and tongue swelling, no urticaria, and no wheeze. BP 122/76 mmHg, HR 82 bpm, SpO2 98% on air. He started lisinopril four days ago. Tryptase is requested. What diagnosis best explains this presentation?

A Allergic contact urticaria progressing to angioedema
B Carcinoid syndrome presenting with facial flushing and swelling
C ACE inhibitor-induced angioedema
D Hereditary angioedema type I
E Anaphylaxis triggered by a concurrent food allergen

Overall explanation

ACE inhibitor-induced angioedema is caused by bradykinin accumulation, not IgE-mediated mast cell degranulation. It typically occurs within the first week of starting an ACE inhibitor, presents with isolated angioedema without urticaria, and does not respond to adrenaline, antihistamines, or corticosteroids. Serum tryptase will be normal, distinguishing it from anaphylaxis. Immediate management is airway assessment; lisinopril must be stopped and ACE inhibitors avoided permanently.

A 45-year-old man with no cardiac history presents with 2 hours of central chest pain. HR 76, BP 130/82, SpO2 98%, ECG normal. His 0-hour hs-cTnI is 6 ng/L (laboratory 99th percentile 16 ng/L). Using the ESC 0/1-hour pathway, the 1-hour hs-cTnI is 9 ng/L. What is the most appropriate disposition?

A Admit under cardiology for stress testing within 72 hours
B Discharge with safety-netting and arrange outpatient cardiology or rapid-access chest pain clinic review
C Extend troponin monitoring to 3 hours and then reassess for discharge
D Repeat ECG at 1 hour and discharge only if no new changes, without cardiology follow-up
E Activate the cardiac catheterisation laboratory for urgent coronary angiography

Overall explanation

The ESC 0/1-hour high-sensitivity troponin pathway stratifies patients with an absolute troponin below the 99th percentile at both timepoints and a delta change below the assay-specific threshold into a low-risk 'rule-out' group. This patient can be safely discharged with appropriate safety-netting and outpatient follow-up rather than admission. (NICE NG185, 2020, updated 2023; ESC 2020 NSTE-ACS guidelines.)

A 78-year-old woman with known heart failure presents with increasing leg swelling and breathlessness. She takes furosemide 80 mg daily and digoxin 125 mcg daily. Vitals: HR 96, BP 118/74, RR 22, SpO2 93%. Blood results: Na+ 138 mmol/L, K+ 2.8 mmol/L, Mg2+ 0.52 mmol/L, creatinine 104 µmol/L. The ECG has been handed to you by the nurse for interpretation.
Which intervention is the most important immediate priority before further diuresis?

A Give IV potassium chloride 40 mmol at 20 mmol/hour via peripheral cannula
B Withhold digoxin and arrange outpatient cardiology review
C Commence oral potassium chloride supplementation and recheck levels in four hours
D Administer IV furosemide 80 mg to relieve pulmonary oedema
E Give IV magnesium sulphate 10 mmol (2.5 g) over 15-20 minutes

Overall explanation

Hypokalaemia and hypomagnesaemia frequently coexist in patients on loop diuretics. Magnesium depletion causes renal potassium wasting, making hypokalaemia refractory to potassium replacement alone until magnesium is corrected. Both electrolyte disturbances increase the risk of digoxin toxicity and predispose to ventricular arrhythmias. IV magnesium replacement must be given first; potassium replacement should follow. Further furosemide will worsen both deficiencies and is hazardous without correction. (NICE CKS: Hypokalaemia; BNF electrolyte replacement guidance.)

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