A New Acetaminophen Nomogram With a Different Purpose

Development and Implementation of An Emergency Department Observation Unit Protocol for Deliberate Drug Ingestion in Adults – Preliminary Results

BACKGROUND

Patients presenting after reported overdose are typically precluded from admission to emergency department observation units (EDOU). The purpose of this study was to describe the initial experience with an EDOU overdose protocol.

METHODS

Retrospective chart review of all individuals presenting to a tertiary care hospital with a chief complaint of overdose or intoxication for the period 7/1/2004 through 12/24/2004. Inclusion criteria for EDOU placement included asymptomatic patients aged >or= 15 years presenting after known or suspected potentially toxic exposure. Exclusion criteria included isolated ethanol intoxication, presence of persistent self-injurious or violent behaviors, chronic intoxication, ingestion of sustained release preparation, and presence of previously defined high-risk criteria.

RESULTS

Retrospective chart review demonstrated that 163 patients presented to the ED after ingestion during this time period, of which 15 were excluded secondary to age. Six patients were admitted to the EDOU. No patient eloped or attempted further self-harm while in the EDOU. No clinical decompensation occurred. Another 27 patients were retrospectively identified as EDOU candidates, eight of whom were admitted to the MICU.

CONCLUSION

Although initial numbers are too small for meaningful analysis, the results suggest that prolonged observation of this problematic patient subset within an EDOU is feasible.

Estimated risk of hepatotoxicity after an acute acetaminophen overdose in alcoholics

A published logistic regression model based on the Canadian Acetaminophen Overdose Study registry was used to calculate the risk of hepatotoxicity after an acute acetaminophen overdose and to estimate a treatment threshold line for alcoholic patients who did not co-ingest alcohol (i.e., abstinent alcoholics) on the Rumack-Matthew nomogram. The risk of hepatotoxicity in nonalcoholic and abstinent alcoholic patients was calculated at the acetaminophen concentration of 150 microg/ml at 4h (37.5 microg/ml at 12h) treatment threshold line. This corresponds to the "possible risk" line on the Rumack-Matthew nomogram and represents a 1.6% risk of hepatotoxicity for nonalcoholic patients at or below this line. At or below this same 150 microg/ml at 4-h line, abstinent alcoholic patients have a hepatotoxicity risk of 10.7%. The risk of hepatotoxicity in abstinent alcoholics' equivalent to that of nonalcoholics (i.e., 1.6%) occurs at a lower acetaminophen concentrations treatment threshold line, that is, 104 microg/ml at 4h (26 microg/ml at 12h). Because of difficulties plotting this new line on the familiar Rumack-Matthew semilogarithmic scale, a line connecting 100 microg/ml at 4h (25 microg/ml at 12h) is proposed. This line equates to a 1.1% risk of hepatotoxicity in abstinent alcoholic patients. The analysis supports the observation that based on the published model abstinent alcoholics might have a greater risk of hepatotoxicity after an acute acetaminophen overdose. This proposed new risk line can be used in hypothesis generation for future clinical studies in this alcohol related problem.