Acetaminophen Toxicity Medical Slides

Present the nomogram with critical caveats: plot serum acetaminophen level against time since ingestion (valid only for single acute ingestions with known time, levels drawn ≥4 hours post-ingestion). Treatment line at 150 mcg/mL at 4 hours (US uses this line; original Rumack line at 200 was lowered for safety margin). Limitations: invalid for repeated supratherapeutic ingestion, extended-release formulations, unknown ingestion time, or coingestants that delay absorption. When the nomogram cannot be applied, treat empirically with NAC if any concern for significant ingestion.

Present both protocols: IV (21-hour Prescott protocol): 150 mg/kg in 200 mL D5W over 1 hour → 50 mg/kg in 500 mL over 4 hours → 100 mg/kg in 1000 mL over 16 hours. Oral (72-hour Smilkstein protocol): 140 mg/kg loading → 70 mg/kg every 4 hours × 17 additional doses. Both are equally effective when started within 8 hours. IV preferred for: vomiting, hepatic failure, pregnancy. Anaphylactoid reactions to IV NAC occur in ~10-20% (dose-rate dependent, more common in asthmatics) — slow infusion rate, treat with antihistamines, do not discontinue NAC.

Present the acetaminophen-specific Kings College Criteria: pH <7.3 after resuscitation OR all three of: (1) grade III/IV encephalopathy, (2) INR >6.5 (PT >100 seconds), (3) creatinine >3.4 mg/dL. These carry ~95% PPV for death without transplant. Additional poor prognostic indicators: lactate >3.5 at 4 hours or >3.0 at 12 hours post-resuscitation, MELD >33, factor V <10%. Emphasize early transplant center referral — do not wait for all criteria to be met. Spontaneous survival with NAC and supportive care is possible even with severe hepatotoxicity (peak ALT >10,000 does not predict mortality).