Case-control study to investigate variables associated with incidents and adverse events in the emergency department

To detect and analyse incidents (Is) and adverse events (AEs) in the ED. We hypothesised that I/AE are associated with patient load.

We undertook a case-control study in a tertiary level hospital ED (from 1 April 2012 to 31 March 2013). Three percent of patients were randomly selected and screened for I/AEs. I/AEs were adjudicated by consensus of four FACEMs. Controls were matched to cases 2:1. Logistic regression was used to analyse the data.

We sampled 2167 patients. After exclusions, 217 I/AEs were detected and analysed. The I and AE rates were 6.0 and 4.1%, respectively. The serious AE rate was 0.8% and 30 day mortality was 0.1%. Diagnostic error occurred in 3.7% of all patients and adverse drug reactions in 2.5%. Seventy-seven percent of the I/AEs were judged preventable. ED occupancy of <35 patients was the reference group. Compared with this group, if 36-40 or 41-45 patients were in the ED, I/AEs were more likely to occur (odds ratio [OR] 2.37 [95% confidence interval (CI) 1.40-4.01, P < 0.0] and 1.8 [95% CI 1.03-3.15, P = 0.04], respectively) but not when there were >46 patients (OR 1.7, 95% CI 1.0-3.1). Higher hospital occupancy (90-99%) was a protective factor for sustaining an I/AE (OR 0.57, 95% CI 0.35-0.92, P = 0.02).

I/AEs are common in the ED and a large proportion is preventable. Strategies for prevention are required. The relationship with patient load needs further clarification, since our data suggests increased I/AE rates with higher occupancy but not highest occupancy.