Objective: In some studies, it has been shown that the concept of office hours (OH) and out-of-office hours (OFH) at intensive care unit (ICU) admission has an effect on ICU mortality. In this study, we aimed to examine the effect of this concept on ICU mortality in a medical ICU (MICU).

Material and Method: After retrospectively examining the general characteristics of the patients hospitalized in Gazi University Hospital MICU between January 1, 2017 and December 31, 2018, patients were divided into two groups as admitted ICU in OH (Monday-Friday; 08.00 am to 04.59 pm) or in OFH (Monday-Friday; 05.00 pm to 07.59 am, weekends, and all public holidays). These two groups were then compared in terms of patient characteristics and ICU mortality.

Results: Five hundred and twenty seven patients were included in the study. 238 of these patients were admitted to MICU in OH and 289 of them in OFH. The median age of the patients was 70 (57-79) years, 52% of them were male. There was no difference between the patients admitted ICU in OH and OFH in terms of age, gender, acute illness severity scores, reasons for hospitalization, length of ICU stay, interventions and treatments in the ICU. Patients admitted to ICU in OFH had higher organ failure scores (SOFA score) (p =0.026). In terms of comorbidities, there was a difference between those admitted to ICU in OH and those admitted to ICU in OFH. More acute kidney injury (AKI) developed during their ICU stay in patients admitted to ICU in OFH. A total of 212 patients (40.23%) died during ICU hospitalization. Of these, 131 (61.79%) were admitted to ICU in OFH, 81 (38.21%) were admitted to ICU in OH and this difference was statistically significant (p =0.008).

Conclusion: In this study, admission to ICU in OFH increased the ICU mortality. Having higher organ failure scores and different comorbidities in patients admitted to ICU in OFH were found to be the factors explaining this mortality difference. New studies with broad participation are needed to verify this result and explain its reasons.