Nature, Occurrence and Consequences of Medication-Related Adverse Events During Hospitalization

Background: Medication-related adverse events (MRAEs) form a large proportion of all adverse events in hospitalized patients and are associated with considerable preventable harm. Detailed information on harm related to drugs administered during hospitalization is scarce. Knowledge of the nature and preventability of MRAEs is needed to prioritize and improve medication-related patient safety.

Objective: To provide information on the nature, consequences and preventability of MRAEs occurring during hospitalization in the Netherlands.

Study Design: Analysis of MRAEs identified in a retrospective chart review of patients hospitalized during 2004.

Methods: The records of 7889 patients admitted to 21 hospitals in 2004 were reviewed by trained nurses and physicians using a three-stage process. For each hospital, patient records of 200 discharged and 200 deceased patients were randomly selected and reviewed. For each patient record, characteristics of the patient and the admission were collected. After identification of an MRAE the physician reviewers determined the type, severity, preventability, drug category and excess length of stay associated with the MRAE. Data on additional interventions or procedures related to MRAEs were obtained by linking our data to the national hospital registration database. The excess length of stay and the additional medical procedures were multiplied by unit costs to estimate the total excess direct medical costs associated with the MRAE.

Results: In total, 148 MRAEs occurred in 140 hospital admissions. The incidence of MRAEs was 0.9% (95% CI 0.7, 1.2) and the incidence of preventable MRAEs was 0.2% (95% CI 0.1, 0.4) per hospital admission. The majority of non-preventable MRAEs were adverse drug reactions caused by cancer chemotherapy. Preventable MRAEs were most often found in relation to anticoagulant treatment administered in combination with NSAIDs. Both non-preventable and preventable MRAEs resulted in considerable excess length of hospital stay and costs. On average, MRAEs resulted in an excess length of stay of 6.2 days (95% CI 3.6, 8.8) and average additional costs of €2507 (95% CI 1520, 3773).

Conclusions: This study was the first to provide detailed information on MRAEs during hospital admissions in the Netherlands, which were associated with both considerable patient harm and additional medical costs. To increase patient safety, interventions need to be developed that reduce the burden of MRAEs. These interventions should target the areas with the highest risk of MRAEs, notably antibacterials, cancer treatment, anticoagulant treatment and drug therapy in elderly patients.