Mortality rates in early versus late intensive care unit readmission

Background: ICU readmission is associated with poor outcomes. Few studies have directly compared the outcomes of early versus late readmissions, especially in Saudi Arabia. Objective: To compare the outcomes between early and late ICU readmissions, mainly with regards to hospital mortality. Methods: This retrospective study included unique patients who, within the same hospitalization, were admitted to the ICU, discharged to the general wards, and then readmitted to the ICU of King Saud Medical City, Riyadh, Saudi Arabia, between January 01, 2015, and June 30, 2022. Patients readmitted within 2 calendar days were grouped into the Early readmission group, while those readmitted after 2 calendar days were in the Late readmission group. Results: A total of 997 patients were included, of which 753 (75.5%) belonged to the Late group. The mortality rate in the Late group was significantly higher than that in the Early group (37.6% vs. 29.5%, respectively; 95% CI: 1%-14.8%; P = 0.03). The readmission length of stay (LOS) and severity score of both groups were similar. The odds ratio of mortality for the Early group was 0.71 (95% CI: 0.51-0.98, P = 0.04); other significant risk factors were age (OR = 1.023, 95% CI: 1.016-1.03; P < 0.001) and readmission LOS (OR = 1.017, 95% CI: 1.009-1.026; P < 0.001). The most common reason for readmission in the Early group was high Modified Early Warning Score, while in the Late group, it was respiratory failure followed by sepsis or septic shock. Conclusion: Compared with late readmission, early readmission was associated with lower mortality, but not with lower LOS or severity score.