Recognition of nonhepatic coma in the setting of acetaminophen overdose

Prognostic factors of acetaminophen exposure in the United States: An analysis of 39,000 patients

Acetaminophen is a frequently used over-the-counter or prescribed medication in the United States. Exposure to acetaminophen can lead to acute liver cytolysis, acute liver failure, acute kidney injury, encephalopathy, and coagulopathy. This retrospective cohort study (1/1/2012 to 12/31/2017) investigated the clinical outcomes of intentional and unintentional acetaminophen exposure using the National Poison Data System data. The frequency of outcomes, chronicity, gender, route of exposure, the reasons for exposure, and treatments as described. Binary logistic regression was used to estimate the prognostic factors and odds ratios (OR) with 95% confidence intervals (CI) for outcomes. This study included 39,022 patients with acetaminophen exposure. Our study demonstrated that the likelihood of developing severe outcomes increased by aging (OR = 1.12, 95% CI: 1.08-1.015) and was lower in females (OR = 0.88, 95% CI: 0.78-0.99). Drowsiness/lethargy (OR = 1.48, 95% CI: 1.22-1.82), agitation (OR = 1.66, 95% CI: 1.11-2.50), coma (OR = 23.95, 95% CI: 17.05-33.64), bradycardia (OR = 2.29, 95% CI: 1.22-4.32), rhabdomyolysis (OR = 8.84, 95% CI: 3.71-21.03), hypothermia (OR = 4.1, 95% CI: 1.77-9.51), and hyperthermia 2.10 (OR = 2.10, 95% CI: 1.04-4.22) were likely associated with major outcomes or death. Treatments included intravenous N-acetylcysteine (61%), oral N-acetylcysteine (10%), vasopressor (1%), hemodialysis (0.7%), fomepizole (0.1%), hemoperfusion (0.03%), and liver transplant (0.1%). In conclusion, it is important to consider clinical presentations of patients with acetaminophen toxicity that result in major outcomes and mortality to treat them effectively.

Antidote removal during haemodialysis for massive acetaminophen overdose

CONTEXT

Haemodialysis is sometimes used for patients with massive acetaminophen overdose when signs of "mitochondrial paralysis" (lactic acidosis, altered mental status, hypothermia and hyperglycaemia) are present. The role of haemodialysis is debated, in part because the evidence base is weak and the endogenous clearance of acetaminophen is high. There is also concern because the antidote acetylcysteine is also dialyzable. We prospectively measured serum acetylcysteine concentrations during haemodialysis in three such cases.

CASE DETAILS

Three adults each presented comatose and acidemic 10 to ~18 h after ingesting > 1000mg/kg of acetaminophen. Two were hypothermic and hyperglycaemic. Serum lactate concentrations ranged from 7 mM to 12.5 mM. All three were intubated, and initial acetaminophen concentrations were as high as 5980 μM (900 μg/mL). An intravenous loading dose of 150 mg/kg acetylcysteine was initiated between 10.8 and ~18 h post ingestion, and additional doses were empirically administered during haemodialysis to compensate for possible antidote removal. A single run of 3-4 h of haemodialysis removed 10-20 g of acetaminophen (48-80% of remaining body burden), reduced serum acetaminophen concentrations by 56-84% (total clearance 3.4-7.8 mL/kg/min), accelerated native acetaminophen clearance (mean elimination half-life 580 min pre-dialysis, 120 min during and 340 min post-dialysis) and corrected acidemia. Extraction ratios of acetylcysteine across the dialysis circuit ranged from 73% to 87% (dialysance 3.0 to 5.3 mL/kg/min). All three patients recovered fully, and none developed coagulopathy or other signs of liver failure.

DISCUSSION

When massive acetaminophen ingestion is accompanied by coma and lactic acidosis, emergency haemodialysis can result in rapid biochemical improvement. As expected, haemodialysis more than doubles the clearance of both acetaminophen and acetylcysteine. Because acetylcysteine dosing is largely empirical, we recommend doubling the dose during haemodialysis, with an additional half-load when dialysis exceeds 6 h.

Understanding lactic acidosis in paracetamol (acetaminophen) poisoning

Paracetamol (acetaminophen) is one of the most commonly taken drugs in overdose in many areas of the world, and the most common cause of acute liver failure in both the UK and USA. Paracetamol poisoning can result in lactic acidosis in two different scenarios. First, early in the course of poisoning and before the onset of hepatotoxicity in patients with massive ingestion; a lactic acidosis is usually associated with coma. Experimental evidence from studies in whole animals, perfused liver slices and cell cultures has shown that the toxic metabolite of paracetamol, N-acetyl-p-benzo-quinone imine, inhibits electron transfer in the mitochondrial respiratory chain and thus inhibits aerobic respiration. This occurs only at very high concentrations of paracetamol, and precedes cellular injury by several hours. The second scenario in which lactic acidosis can occur is later in the course of paracetamol poisoning as a consequence of established liver failure. In these patients lactate is elevated primarily because of reduced hepatic clearance, but in shocked patients there may also be a contribution of peripheral anaerobic respiration because of tissue hypoperfusion. In patients admitted to a liver unit with paracetamol hepatotoxicity, the post-resuscitation arterial lactate concentration has been shown to be a strong predictor of mortality, and is included in the modified King's College criteria for consideration of liver transplantation. We would therefore recommend that post-resuscitation lactate is measured in all patients with a severe paracetamol overdose resulting in either reduced conscious level or hepatic failure.