Acute and critical care medicine for MRCPI Part 2

A 34-year-old woman presents 6 hours after taking an unknown quantity of paracetamol as a staggered overdose over 12 hours. She is asymptomatic. Paracetamol level is 42 mg/L, ALT 38 U/L, INR 1.0. What is the most appropriate management?

1. Start N-acetylcysteine regardless of the level, because the overdose was staggered correct Correct. The treatment nomogram applies only to a single acute ingestion at a known time. For a staggered overdose or an uncertain time of ingestion, the level cannot be interpreted against the line and N-acetylcysteine is given to everyone who has taken a potentially toxic dose.
2. Discharge with psychiatric follow-up, since she is asymptomatic with normal liver tests Wrong. Paracetamol toxicity is silent early, normal transaminases at six hours tell you nothing about what will happen at 72.
3. Plot the level on the treatment nomogram and treat only if above the line Wrong. The nomogram is invalid for staggered ingestion, and applying it here would falsely reassure.
4. Administer activated charcoal alone Wrong at this stage. Charcoal is considered within about an hour of ingestion, and this ingestion began 12 hours ago.
5. Repeat the paracetamol level in 4 hours and decide then Wrong. Serial levels do not rescue an uninterpretable nomogram, and the delay wastes the window in which N-acetylcysteine is most effective.

The point: The paracetamol nomogram is only valid for a single ingestion at a known time between 4 and 15 hours. Staggered, unknown timing, or a presentation beyond 15 hours all mean treat. Know the King's College criteria for transplant referral: pH below 7.3, or the triad of INR above 6.5, creatinine above 300 and grade 3 or 4 encephalopathy.

Source: TOXBASE / MHRA guidance on the treatment of paracetamol overdose TOXBASE (National Poisons Information Service) · tier 3, national formulary