Introduction: 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.
Study objectives: To determine whether monthly variations in CO poisoning occur in emergency departments.
Design: A multicenter retrospective emergency department (ED) cohort.
Study setting: 23 New Jersey and New York emergency departments.
Subjects: Consecutive patients with the ICD-9 primary diagnosis of"toxic effects CO" from January 1, 2000 to October 31, 2006.
Statistics: We tested for significant differences using chi-square and Student's t-test with alpha set at 0.5.
Results: 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).