Predictors of intensive care unit readmission within 48 hours after discharge

Introduction

Readmission to the ICU during the same hospitalization is associated with significant morbidity and mortality and results in a longer length of stay and higher costs. There is therefore growing interest to identify reliable predictors for readmission. The aim of our study was to assess the incidence of ICU readmissions, identify predictors of ICU readmission, and determine patient outcome.

Methods

We performed a retrospective case–control study. The study population consisted of all patients who were discharged alive from our 28-bed surgical, thoracic–surgical and medical ICU in a university teaching hospital in a 1-year period. A case was defined as a patient readmitted to the ICU within 48 hours after discharge. For each case, three control patients were randomly selected from the study population. The following information was collected: demographic parameters and APACHE II score, parameters of hemodynamic, respiratory and renal function, length of ICU stay, duration of invasive ventilatory support (ventilator time), and time between extubation and discharge. To determine a predictive model, covariate selection was done by the two-sample t test, Mann–Whitney test and univariate logistic regression. From significant (P < 0.10), plausible and clinically relevant variables, a predictive model was generated using multivariate logistic regression.

Results

During a 1-year period 1,635 patients were admitted to our ICU. Of 1,393 patients at risk for readmission, 25 (1.8%) readmissions occurred in 23 patients. Nine of the 23 (39%) readmitted patients died during their hospitalization, while the overall ICU mortality was 10.6%. The most important reason for readmission (68% of the cases) was respiratory deterioration. In the univariate analysis, age, ventilator time during first admission and time between extubation and ICU discharge were significant predictors of readmission. In the multivariate analysis, age (OR 1.1; 95% CI 1.00–1.13; P = 0.03) and ventilator time during first admission (OR 1.1; 95% CI 1.00–1.10; P = 0.03) were significant predictors, corrected for patient characteristics. Furthermore, patients who were readmitted had a significant longer duration of total (first and second admission) ventilator time (188 vs 106 hours, P = 0.012), and total ICU stay (400 vs 127 hours, P = 0.009).

Conclusion

Patients readmitted to the ICU have significant longer overall ventilator time, ICU stay, and a higher ICU mortality. The ventilator time during first admission (especially beyond 300 hours) is an important predictor of readmission. The time it takes to get patients ready for discharge after extubation also differed significantly. The data suggest that elderly patients who have been ventilated for a long period are at particular risk for readmission and should receive additional care before discharge from the ICU.