Observation for Potentially Poisoned Patients: How Long Is Long Enough?
Abstract & commentary
Source: Hollander JE, et al. Emergency department observation of poisoned patients: How long is necessary? Acad Emerg Med 1999;6:887-894.
Patients intentionally exposed to drugs and toxins frequently present to emergency departments requiring both medical and psychiatric evaluations. When signs and symptoms of poisoning are severe, the decision to admit these patients for definitive medical care is easy. In the absence of significant signs and symptoms, however, the decision to discharge these patients or refer them to psychiatry if indicated is more difficult because of concerns over the delayed onset of toxicity for an unknown ingestion. As a result, patients are traditionally observed for 4-6 hours following their presentation. Unfortunately, although this generic observation period is widely utilized, little data exist to support its use.
Hollander and associates challenge this dogmatic approach in an interesting study. Two hundred sixty patients with intentional oral poisoning were enrolled, 28 of whom were immediately admitted and 17 of whom were immediately cleared. Although the remaining 215 patients were all observed for six hours, the clinicians caring for them were asked at two and four hours whether they thought the patients could be cleared. All of the patients felt to be medically cleared at two hours were discharged from the medical ED at six hours. At four hours, 61 of the remaining 109 patients were felt to be medically cleared. Once again, all of these patients were discharged from the ED at six hours. Of the remaining 48 patients, 26 more were cleared at six hours.
Comment by Robert Hoffman, MD
This study demonstrates several important aspects of poisoning. Only 50 of the initial cohort of 260 patients with intentional oral exposure ultimately required admission for medical reasons. Almost half, 122 patients, could be medically cleared by two hours. Thus, for the majority of patients, a generic 4-6 hour observation period was unnecessary.
I would suggest that the following criteria be considered for early discharge. Patients should be free of symptoms and have normal vital signs and normal physical examinations. Some form of gastrointestinal decontamination should be accomplished. The ECG should be normal, and a serum acetaminophen level (required in every intentional overdose) should be nontoxic. If the history suggests exposure to a toxin where a drug level might influence therapy, such as lithium, digoxin, or theophylline, that drug level should be nontoxic. On the other hand, patients who intentionally ingest toxins with known delayed presentations (such as oral hypoglycemic agents, MAO inhibitors, and methanol) and those who ingest sustained- or delayed-release preparations (such as some aspirin, lithium, theophylline, calcium channel, and beta adrenergic antagonist preparations) must be observed for longer periods of time. In these instances, initial asymptomatic presentations and low drug levels can reliably be expected to progress to life-threatening clinical symptoms and higher drug levels even well beyond the traditional six-hour observation period.
ED observation after intentional oral poisoning:
a. should last 4-6 hours for all patients, based on the current literature.
b. may not require a 4-6 hour period in all patients.
c. is necessary only in patients manifesting signs and symptoms of poisoning in the first two hours.
d. is necessary only in patients manifesting signs and symptoms of poisoning in the first four hours.
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