Association between prior ICU admission for drug overdose and ICU readmission: A retrospective registry-based study

We aimed to investigate patients discharged alive from hospital following an ICU admission for drug overdose and whether exposure of prior overdose-related ICU admission was associated with a future ICU readmission.

This multicentre registry-based study included data from 167 ICUs across Australia that reported to the Australia New Zealand Intensive Care Society Adult Patient Database. We included all adult patients (≥16 years) discharged alive from the hospital after an ICU admission for an overdose between 1st July 2018 and 31st December 2023. The exposure of interest was an overdose-related ICU admission in the six months prior to the index ICU admission.

The primary outcome was all-cause ICU readmission within the following six months. The secondary outcome was ICU readmission due to an overdose within six months. We used mixed-effects multivariable logistic regression to adjust for confounders and identify risk factors for ICU readmission.

Of 30,125 index episodes of ICU overdose admissions (25,604 individuals), 2555 (8.5%) had an overdose-related ICU admission in the prior six months. They had higher rates of all-cause ICU readmission compared to those without a prior overdose-related ICU admission (40.9% vs. 8.9%; p < 0.001). After accounting for other factors including younger age, female sex, Indigenous status, higher SOFA scores, chronic respiratory disease, cirrhosis, dialysis dependence and frailty, an overdose in the six months prior to the index ICU admission was associated with ICU readmission in the following six months (OR = 1.93; 95%CI: 1.59-2.34; p < 0.001).

This large Australian registry-based study found that in patients discharged alive from hospital following an ICU admission for overdose, patients with a history of prior ICU admission for overdose had almost double the risk for ICU readmission. These findings have implications for risk stratification, clinical decision-making and resource planning.