Aim: This study investigates the impact of admission timing on intensive care unit (ICU) outcomes for patients transferred from internal medicine wards to the ICU at a tertiary university hospital.

Study Design: A retrospective cohort study was conducted in a nine-bed medical ICU at Gazi University Hospital from January 2020 to November 2022. Patients aged 18 years and older admitted from internal medicine wards were included. Statistical analyses compared outcomes based on admission timing and ICU mortality.

Results: Of 316 patients, 59% were admitted during off-hours, with an overall ICU mortality of 56%. No difference in mortality was found between office-hour and off-hour admissions (52% vs. 59%, p=0.17). There were no differences in the length of ICU stay (5 [3-11] days vs. 5 [3-12] days, p=0.72), requirements for invasive (60% vs. 61%, p=0.47) or non-invasive mechanical ventilation (17% vs. 16%, p=0.44), intermittent (30% vs. 30%, p=0.54) or continuous renal replacement therapy (22% vs. 26%, p=0.24) requirement, and nosocomial infection rate (49% vs. 52%, p=0.35) based on admission timing. Independent mortality risk factors included the requirement for invasive mechanical ventilation (odds ratio (OR): 3.33 [95% confidence interval (CI): 1.49-7.29], p<0.01), the presence of circulatory shock (OR: 2.02 [95% CI: 1.29-2.89], p<0.01) solid cancer (OR: 1.98 [95% CI: 1.22-3.19], p<0.01), and the Acute Physiology and Chronic Health Evaluation II (APACHE II) score (OR: 1.08 [95% CI: 1.01-1.16], p=0.04).
Conclusions: Unlike some previous studies, we found no difference in ICU mortality between office-hour and off-hour admissions in patients admitted from internal medicine wards. This finding suggests that equal staffing distribution throughout the day may prevent adverse effects of out-of-hours admissions, and support better organization in specialized ICUs.