Prevalence of autonomic signs and symptoms in antimuscarinic drug poisonings.

Classically described antimuscarinic poisoning signs and symptoms include mydriasis, decreased secretions, ileus, urinary retention, hyperthermia, tachycardia, and altered mental status. These features may be used clinically to assist in the diagnosis of patients with unknown poisonings. We sought to analyze the prevalence of antimuscarinic physical examination findings in evaluating patients presenting with acute poisoning from antimuscarinic agents. We conducted a retrospective, medical record review at two urban tertiary care teaching hospitals. The study population consisted of patients presenting to the Emergency Department with a diagnosis of acute poisoning secondary to medications with known antimuscarinic side effects during a 78-month period between January 1994 and July 2001. Cases were excluded for incomplete medical records or unreliable histories of ingestion, and when concomitant ethanol intoxication was present on laboratory analysis. Clinical information obtained from each patient included vital signs, pupillary size, electrocardiogram abnormalities, the presence of mucous membrane and axillary secretions, initial urine output after bladder catheterization, quality of bowel sounds, mental status changes, the occurrence of seizures and coma, need for orotracheal intubation, and time required for clinical resolution. Diagnostic and therapeutic information including laboratory tests, administration of sodium bicarbonate, and usage of physostigmine was also collected. We identified a total of 345 cases, 213 of which met inclusion criteria. Of these cases, the most common documented findings included decreased secretions in 75.1%, tachycardia in 68.1%, confusion in 49.3%, drowsiness in 48.2%, and hypoactive or absent bowel sounds in 44.6%. Combining signs and symptoms to predict this toxic syndrome was not very reliable. Tachycardia, decreased oral or axillary secretions, and mydriasis proved to be the most predictive trio of clinical signs, but were found in only 28.2% of cases. At least one of these three signs was documented in 94% of our patients. The combination of tachycardia and decreased secretions was the most common pair of findings, recorded in 55.4% of cases. We conclude that the clinical presentation of antimuscarinic syndrome is variable.