MRCP Part 2

Sample

1. A 24-year-old woman presents 6 hours after ingesting 30 tablets of paracetamol 500 mg at a single known time. She is asymptomatic with normal observations. What is the most appropriate next step?

For a single ingestion at a known time presenting after 4 hours, a plasma paracetamol level plotted on the treatment nomogram guides whether N-acetylcysteine is needed. Activated charcoal is only useful within about 1 hour of ingestion. Treatment is not required if the level is below the treatment line and the patient is well.

Sample

2. A 40-year-old man reports taking "a lot" of paracetamol tablets over the preceding 8 hours during an argument. He cannot specify the exact timing or total dose. How should he be managed?

In a staggered overdose or when the time of ingestion is uncertain, the treatment nomogram cannot be applied reliably. N-acetylcysteine should be started empirically while further assessment and paracetamol, INR, creatinine and liver function tests are obtained.

Sample

3. Thirty minutes into a N-acetylcysteine infusion, a patient develops facial flushing, urticaria and mild wheeze. What is the most appropriate action?

These are anaphylactoid (non-IgE, dose-related histaminergic) reactions to N-acetylcysteine rather than true anaphylaxis. Management is to pause or slow the infusion, treat with an antihistamine and, if needed, nebulised bronchodilator, then restart at a reduced rate. Permanent discontinuation is rarely necessary.

Sample

4. A patient with paracetamol-induced acute liver failure is being assessed for transfer to a transplant centre. Which finding is one of the King's College criteria for consideration of liver transplantation?

The King's College criteria for paracetamol-induced liver failure include an arterial pH below 7.3 after resuscitation, or the combination of grade III/IV encephalopathy with INR greater than 6.5 and creatinine above 300 micromol/L. A raised ALT alone or the paracetamol level does not predict outcome once liver failure is established.

Sample

5. A malnourished 55-year-old man with chronic alcohol excess takes a paracetamol overdose. Which factor increases his risk of hepatotoxicity?

Chronic alcohol excess, malnutrition, eating disorders and enzyme-inducing drugs deplete hepatic glutathione and induce CYP2E1, increasing conversion of paracetamol to the toxic metabolite NAPQI. Such patients are at greater risk of hepatotoxicity at a given plasma level.

Sample

6. A 30-year-old man presents after a large aspirin overdose. Arterial blood gas shows a mixed respiratory alkalosis and metabolic acidosis, and the salicylate level is rising. What is the most appropriate treatment for moderate toxicity?

Urinary alkalinisation with intravenous sodium bicarbonate enhances renal elimination of salicylate by trapping the ionised drug in alkaline urine. Potassium must be corrected because hypokalaemia impairs alkalinisation. Acetazolamide worsens the acidosis and is contraindicated.

Sample

7. A patient with salicylate poisoning is deteriorating. Which feature is an indication for haemodialysis?

Haemodialysis is indicated in severe salicylate poisoning: very high levels (typically above 700 mg/L), refractory acidosis, renal failure, pulmonary oedema, seizures or coma. Salicylate is small, water-soluble and poorly protein-bound at toxic levels, making it well cleared by dialysis.

Sample

8. A 45-year-old woman presents shortly after an aspirin overdose. Which acid-base disturbance is characteristically seen early in adults?

Salicylate directly stimulates the respiratory centre, causing an early respiratory alkalosis in adults. As toxicity progresses, uncoupling of oxidative phosphorylation and accumulation of organic acids produces a high anion gap metabolic acidosis, giving a characteristic mixed disturbance.

Sample

9. A 22-year-old man is found with a respiratory rate of 6, pinpoint pupils and a reduced conscious level after suspected heroin use. What is the most appropriate immediate management?

Opioid toxicity causes respiratory depression, pinpoint pupils and coma. Titrated naloxone reverses respiratory depression; small incremental doses avoid precipitating acute withdrawal while maintaining ventilation. Airway support and oxygen are given concurrently.

Sample

10. A patient given naloxone for a methadone overdose initially improves but the effect is short-lived. What is the key management consideration?

Naloxone has a short duration of action compared with long-acting opioids such as methadone. Respiratory depression can recur once naloxone wears off, so patients require prolonged observation and may need a continuous naloxone infusion titrated to respiratory rate.