Excess mortality caused by medical injury

We wanted to estimate excess risk of in-hospital mortality associated with medical injuries identified using an injury surveillance system, after controlling for risk of death resulting from comorbidities.

The Wisconsin Medical Injuries Prevention Program (WMIPP) screening criteria were used to identify medical injuries, defined as "any untoward harm associated with a therapeutic or diagnostic healthcare intervention," among discharge diagnoses for all 562,317 patients discharged from 134 acute care hospitals in Wisconsin in 2002. We then derived estimates for crude and adjusted relative risk of in-hospital mortality associated with the presence of a medical injury diagnosis. Logistic regression adjusted for baseline risk of mortality using a comorbidity index, age, sex, Diagnosis Related Groups, hospital characteristics, and clustering within hospital.

There were 77,666 discharges that met WMIPP criteria for at least 1 medical injury (13.8%). Crude risk ratios for death ranged from 1.27 to 2.4 for those with medical injuries within 1 of 4 categories: drugs/biologics; devices, implants, and grafts; procedures; and radiation. After adjustment, estimates of excess mortality decreased, and significance persisted only for injuries related to procedures (39%; 95% confidence interval [CI], 28%-52%) and devices, implants, and grafts (16%; 95% CI, 3%-30%).

Estimates of excess mortality that do not account for baseline mortality risk may be exaggerated. Findings have implications for the care family physicians provide in the hospital and for the advice they give their patients who are concerned about the risks of hospitalization.