Paracetamol poisoning

Manage now— do this, in order

• Decide on the clock and on milligrams per kilogram, never on how the patient looks — paracetamol poisoning in its treatable phase has no clinical features at all, and a well patient with normal bloods is the typical patient.
• Acetylcysteine is time-critical: highly efficacious within 8 hours of ingestion, effective within 8–10 hours, declining steeply thereafter — so never delay it for a laboratory result in any patient presenting after 8 hours from ingestion. Starting the antidote unnecessarily is trivially reversible; starting it late is not — and lateness is a reason to hurry, never to withhold, since acetylcysteine reliably prevents toxicity within 12 hours, may still be beneficial up to 72 hours after ingestion, and improves outcome in established paracetamol-induced liver failure.
• Intravenous acetylcysteine, adult and paediatric mg/kg identical: 150 mg/kg over 60 minutes, then 50 mg/kg over 4 hours, then 100 mg/kg over 16 hours — a total of 300 mg/kg over 21 hours (chart). Diluents for an adult: 200 mL of 5% glucose for the loading dose, 500 mL for the second bag and 1000 mL for the third; 0.9% sodium chloride is an accepted alternative diluent. For a 70 kg adult the doses are 10.5 g, then 3.5 g, then 7 g. Never give a rapid 15-minute loading infusion when 60 minutes is available — anaphylactoid reactions are dose-rate related.Doctor / NurseNot available at your setup — Infusion pump.
• In children the mg/kg doses are unchanged but diluent volumes must be reduced in proportion to weight using a weight-banded dilution chart — adult volumes given to a small child risk fluid overload and dilutional hyponatraemia with seizures; most protocols cap the dosing weight, commonly at 110 kg.Doctor / Nurse
• 0–8 hours since ingestion: wait until 4 hours post-ingestion, then take blood for the paracetamol concentration, creatinine and electrolytes, bicarbonate, liver function and INR, and treat if the concentration lies above the treatment line — but if the result will not be available before 8 hours post-ingestion and more than 150 mg/kg has been ingested, start acetylcysteine immediately and stop it later if the level proves below the line. 8–24 hours since ingestion: send blood urgently but commence acetylcysteine immediately if the ingested dose exceeds 150 mg/kg — do not wait for the concentration; if less is reported and the history is reliable, await the result and use the nomogram, treating any borderline level beyond 12 hours.
• More than 24 hours since ingestion: start acetylcysteine at once if the patient is jaundiced or has hepatic tenderness, and treat if the ALT is above the upper limit of normal, the INR is above 1.3 in the absence of another cause, or paracetamol is detectable; if the concentration is undetectable with normal ALT and INR in an asymptomatic patient, no antidote is indicated and any infusion already started may be stopped. Staggered ingestion, repeated therapeutic excess or unknown history: the nomogram does not apply — treat if more than 75 mg/kg has been ingested in 24 hours, or if the ALT or INR is abnormal; in an unconscious patient of unknown history a detectable concentration, a raised ALT or an INR above 1.3 each mandates treatment.Not available at your setup — Liver function tests, Coagulation (PT/INR).
• Where intravenous acetylcysteine is unavailable or not tolerated, give the oral regimen: 140 mg/kg loading, then 70 mg/kg every 4 hours, diluted to about 5% with water or juice — conventionally for 72 hours (the loading dose plus 17 further doses), although 20–48 hour regimens have shown equivalent success. Where no acetylcysteine exists at all, methionine 2.5 g orally every 4 hours for four doses is the alternative, but is probably less effective after delayed presentation. Activated charcoal 50–100 g orally or by gastric tube in adults, or 1 g/kg (maximum 50 g) in children, within 1–2 hours of ingestion — although charcoal adsorbs oral acetylcysteine, the interaction is not clinically significant, and charcoal must never delay acetylcysteine; never give it to a comatose or convulsing patient unless the airway is protected by a cuffed endotracheal tube.
• For an anaphylactoid reaction (up to 15% of patients): stop the infusion; give chlorphenamine 10–20 mg intravenously in an adult for more severe cases; treat bronchospasm with oxygen-driven nebulised salbutamol 5 mg (2.5 mg under 5 years) and hypotension with 0.9% sodium chloride 500 mL in an adult or 10 mL/kg in a child; then restart at a slower rate once symptoms settle, usually within 30–60 minutes, and complete the full 300 mg/kg — a half-delivered course is an untreated overdose. Distinguish true anaphylaxis — stridor, tongue or lip angio-oedema with airway compromise, or profound refractory hypotension — which requires intramuscular adrenaline 0.5 mg (0.5 mL of 1 in 1000) into the anterolateral thigh, repeated after 5 minutes if necessary.Doctor / Nurse
• Nausea and vomiting are common and are not a reason to stop: ondansetron 4–8 mg intravenously 8-hourly in adults, or 0.1–0.15 mg/kg (maximum 4 mg per dose) in children (metoclopramide 10 mg IV is an alternative but is best avoided in children, adolescents and young adults because of acute dystonic reactions). At the end of the 21-hour course, repeat creatinine and electrolytes, bicarbonate, liver function and INR — and if these are abnormal, particularly if the ALT or INR is still rising, continue the 16-hour infusion (100 mg/kg over 16 hours) back-to-back until recovery. Correct hypoglycaemia immediately (10% glucose 2 mL/kg intravenously in a child) and run a continuous glucose infusion where endogenous production fails; measure glucose 2-hourly in the acute phase and prothrombin time at least twice daily. Never give fresh frozen plasma except in major bleeding or before an unavoidable invasive procedure, because it abolishes the prothrombin time as a prognostic instrument.Doctor / NurseNot available at your setup — Coagulation (PT/INR), Liver function tests.