Delirium and Weakness Acquired in the Intensive Care Unit: Individual and Combined Effects on 90-Day Mortality in Survivors of Critical Illness

AimsTo compare the individual and combined effects on 90-day mortality among four critically ill survivor groups: normal (without ICU-acquired delirium or ICU-acquired weakness), delirium-only (with ICU-acquired delirium only), weakness-only (with ICU-acquired weakness only) and delirium-weakness (combined ICU-acquired delirium and weakness).MethodsA prospective cohort study consecutively recruited delirium-free critically ill patients admitted to six medical ICUs at a university hospital. Delirium was assessed once daily for 14 days (or until death or ICU discharge) using the Confusion Assessment Method for the ICU. Participants who were discharged from the ICUs were assessed for weakness using the Medical Research Council scale. A summed score below 48 defines ICU-acquired weakness. These survivors were evaluated again for 90-day mortality. The study is reported using the STROBE checklist.ResultsDelirium developed in 107 (43.2%) participants during their first 14 days of ICU stay; 55 (22.2%) met criteria for weakness by ICU discharge. Participants with delirium were at increased risk for also developing ICU-acquired weakness, and the 90-day mortality was 18.2%. Independent of age and Acute Physiology and Chronic Health Evaluation II score at ICU admission, delirium-only and weakness-only were not associated with higher 90-day mortality, while participants in the delirium-weakness group had a 3.69-fold higher risk of death, compared to those who were normal during the ICU stay. A non-significant interaction was found, suggesting the joint effect of delirium and weakness on mortality is not higher than the sum of both effects individually.ConclusionsMortality is substantially high among critically ill survivors who experience both delirium and weakness, although no additive effect on mortality was observed when these conditions occur together. Our findings highlight the urgent need to optimise ICU care by prioritising the prevention, early identification and management of these two common ICU-acquired conditions.Patient ContributionStudy participation and completion of all assessments.Trial Registration identifier: NCT04206306