Frequency of Adverse Events Before, During, and After Hospital Admission.

OBJECTIVES: Adverse events (AEs) are unintended physical injuries resulting from or contributed to by medical or surgical care. We determined the frequency and type of AEs before, during, and after hospital admission.
METHODS: We conducted a cohort study of 296 adult hospital patients. We used the standardized Institute for Healthcare Improvement Global Trigger Tool for Measuring Adverse Events to review the medical records of the hospital patients for occurrence, timing relative to hospital admission, severity, and preventability of AEs. We also identified the primary physiologic system affected by the AE.
RESULTS: Among 296 patients, we identified 338 AEs. AEs occurred with similar frequency before (n = 148; 43.8%) and during hospital admission (n = 162; 47.9%). Fewer AEs occurred after discharge (n = 28; 8.3%). Half of all AEs (n = 169; 50.0%) were severe, whereas 47.9% (n = 162) were preventable.
CONCLUSIONS: AEs occur with similar frequency before and during hospitalization and may contribute more to hospital admissions than previously recognized. These findings suggest that efforts to improve patient safety should include outpatient settings in addition to the more commonly targeted acute care settings.