Severity of Illness and Mortality According to Time of Admission to Intensive Care

Staffing at hospital wards is at its lowest during nighttime, which may endanger prompt recognition of the need for intensive care. High severity of illness of patients admitted to the intensive care unit (ICU) in the morning may reflect delayed referral for intensive care during the night. We investigated whether severity of illness at ICU admission is dependent on admission time.

We analysed data from 25 Finnish ICUs between 2005 and 2022, utilising the national ICU registry. We excluded readmissions, children, non-emergency admissions, cardiac surgery patients and patients admitted for the purpose of organ donation. We explored the severity of illness, as quantified with the Simplified Acute Physiology Score (SAPS) II score, and in-hospital mortality according to admission hours. We also conducted linear and logistic regression analyses adjusting for age, sex, admission type, source of admission, diagnosis category and severity of illness.

The study population comprised 131,175 ICU patients. The mean (± SD) SAPS II score at admission was 37.9 ± 17.4, and overall in-hospital mortality was 14.7%. The mean SAPS II score was 39.0 ± 17.9 for morning admissions (6-12 a.m.) and 37.6 ± 17.2 during other times (p < 0.001). The corresponding in-hospital mortalities were 17.5% and 13.9%, respectively (p < 0.001). After adjusting for differences in patient characteristics, morning admissions remained independently associated with higher SAPS II score (mean difference 0.87 points, 95% CI, 0.65-1.09) and in-hospital mortality (OR 1.17, 95% CI, 1.13-1.21).

Patients admitted to intensive care during morning hours experienced higher severity of illness and higher in-hospital mortality.

This analysis, from the national ICU database in Finland, shows that cases with morning admission to the ICU appear to have more severe illness compared to those admitted at other times of day. The authors consider if there might be some nighttime delay for recognition of ICU need which could contribute to this observation.