Effect of adverse drug reactions on length of stay in intensive care units

The objective of the present study was to determine the frequency of adverse drug reactions (ADRs) in intensive care units (ICUs) and to evaluate their effect on the length of stay. We performed a prospective study to detect ADRs in 420 patients hospitalised in 10 predetermined beds in the ICU of our hospital between the months of March and December 1996. While the patients were staying in the ICU, data was gathered regarding suspected ADRs and on different variables related to the length of stay. 96 different ADRs were detected in 85 of the 420 patients seen [20.2%, 95% confidence intervals (95% CI) 16.5 to 24.4]. The ADRs were most frequently caused by the following drugs: nitrates (n = 25), opiates (n = 21) and ultrashort-acting benzodiazepines (n = 10). Eight ADRs were severe, the suspected medication had to be discontinued in 51 cases and new drugs were necessary to manage the ADRs in 73 cases. The crude estimation of the effect of the number of ADRs performed with a bivariant regression model indicated that each ADR was related to a 2.38-day increase (95% CI 1.31 to 3.45) in the length of stay. Although this estimation was reduced to 1.76 days (95% CI 0.72 to 2.79), when other confounding variables associated with the length of stay were considered, it was still important. In conclusion, the ADRs were a significant clinical problem in the ICUs and were responsible for a significant increase in the length of stay.