Population-based incidence and outcome of acetaminophen poisoning by type of ingestion.

OBJECTIVES: 1) To determine, in a population-based sample, the observed frequency of acetaminophen overdose-related ED evaluation and hospitalization. 2) To examine the relative frequency of hospitalization by pattern of ingestion, the outcome of each group, and the presence or absence of postulated risk factors.
METHODS: This study was a 46-month, retrospective chart review of all acetaminophen-related visits, by patients at least 10 years of age, to either of the two hospitals that serve a four-county region of central Virginia.
RESULTS: Of 636 charts identified for review, only 137 involved acute or chronic acetaminophen overdose. One hundred twenty-six patients presented after an acute ingestion; 122 of these patients gave a history of a single, supratherapeutic ingestion of acetaminophen. Twenty-five patients were hospitalized for treatment. Eighteen of these were treated with N-acetylcysteine (NAC) based on the Rumack-Matthew nomogram; one suffered significant hepatic injury. The other seven presented at least 18 hours after ingestion, with no measurable serum acetaminophen. Two of these suffered significant hepatic injury. Four additional patients presented after multiple ingestions within 24 hours. Three were hospitalized, but none experienced significant injury. Only 11 patients were evaluated for chronic acetaminophen overmedication for pain (more than 6 g/day over a period of more than 24 hours). Four were admitted for treatment; three suffered significant hepatic injury. Thus, the observed incidence of acute acetaminophen ingestion in this region was 21.4/100,000/yr (95% CI = 17.7 to 25.2). The observed incidence of hospitalization for acute acetaminophen toxicity was 4.8/100,000/yr (95% CI = 3.0 to 6.5). The observed incidence of hospitalization for all acetaminophen poisoning was 5.5/100,000/yr (95% CI = 4.1 to 7.0). High ethanol consumption was present more frequently in those who suffered hepatic injury.
CONCLUSIONS: Most patients evaluated for acetaminophen ingestion present early following acute single overdose. Relatively few of these patients require hospitalization and, for those hospitalized, the outcome is good. More significantly, acetaminophen overdose patients whose risk cannot be estimated using the Rumack-Matthew nomogram represented 44% of those hospitalized and 83% of those who suffered significant hepatic injury. Emergency physicians need to determine how they can impact the outcome of these patients. Efforts should be directed at further characterizing historical, physical, and biochemical markers of risk and at determining in which circumstances hospitalization for NAC or other therapies is justified.