Monthly variations in the diagnosis of carbon monoxide exposures in the emergency department

Carbon monoxide (CO) poisoning is the leading cause of toxicological deaths worldwide. Symptoms may be subtle, contributing to its frequent delay in diagnosis. If a seasonal variation occurs, a heightened awareness during peak time may lead to improved recognition and diagnosis.

To determine whether monthly variations in CO poisoning occur in emergency departments.

A multicenter retrospective emergency department (ED) cohort.

23 New Jersey and New York emergency departments.

Consecutive patients with the ICD-9 primary diagnosis of"toxic effects CO" from January 1, 2000 to October 31, 2006.

We tested for significant differences using chi-square and Student's t-test with alpha set at 0.5.

There were 1,006 patients who were diagnosed in the ED with CO toxicity (0.024% of all ED patients). Mean age was 30 years (SD +/- 20), 54% were female, and Caucasians compromised 54% of participants. Thirty-nine percent of documented patients arrived via ambulance and 90% were subsequently discharged. Incidence of CO visits peaked in December (0.036%) and were least likely in May (0.011%). Mean monthly CO visits were statistically increased during October (p = < 0.0001), November (p = 0.008), December (< 0.0001), January (p = 0.01), and March (p = 0.04). Statistically fewer case of CO exposure were diagnosed in May (p = 0.0003), June (p = 0.005), August (p = < 0.0001), and September (p = 0.002).