The association between nighttime transfer from the intensive care unit and patient outcome*

OBJECTIVE: To determine the impact of nighttime transfer of patients from the intensive care unit (ICU) on clinical outcome. DESIGN: Retrospective, observational. SETTING: Three intensive care units of a tertiary care medical center. PATIENTS: We used prospectively collected information from the Acute Physiology and Chronic Health Evaluation III database of 11,659 patients transferred from the ICU to the regular ward. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Based on the time of transfer, patients who were transferred from the ICU to the regular ward were categorized into daytime (7:00 am-6:59 pm) and nighttime (7:00 pm-6:59 am) transfers. Patients who were transferred to other ICUs or other facilities, died in the ICU, were discharged home, or did not authorize their medical records to be reviewed for research were excluded. Only the first ICU admission of each patient was considered for outcome analysis. Of the 11,659 study patients, 418 (3.6%) were transferred at night. The first ICU day predicted mortality rate and the last ICU day Acute Physiology Score and Acute Physiology and Chronic Health Evaluation III scores in the nighttime transfer group were higher compared with the daytime transfers. The hospital mortality rate of the nighttime transfers was 5.3% compared with 4.5% of the daytime transfers (p = 0.478). There was no statistically significant difference between the two groups in severity adjusted hospital mortality rate. The ICU readmission rate of the nighttime transfers was higher (12.2% compared with 9.0%, p = 0.027) and the median (interquartile range) hospital length of stay longer (8 5-15 vs. 7 4-13 days, p = 0.013) compared with the daytime transfer group. CONCLUSIONS: Our study did not find an association between nighttime ICU discharge and hospital mortality. However, the ICU readmission rate was higher and the hospital length of stay longer in the nighttime transfer group.