Characteristics and outcomes of adults with acute brain injuries admitted to intensive care units in Australia and New Zealand from 2013 to 2022

The characteristics and outcomes of patients with acute brain injuries admitted to the intensive care unit (ICU) in Australia and New Zealand (ANZ) are insufficiently described. This study aimed to describe the epidemiology of acute brain injury in ICU patients in ANZ. A binational retrospective cohort study was conducted using the ANZ Intensive Care Society Adult Patient Database. Adult unplanned admissions from 2013 to 2022 were eligible unless the presence of acute brain injury could not be determined or the admission was for end-of-life care. In cases where a patient had multiple admissions, only the first was included. The population was divided into two cohorts: acute brain injury diagnoses and other diagnoses. The primary outcome was in-hospital mortality. Secondary outcomes included 90- and 180-day mortality, ICU and hospital lengths of stay, duration of invasive ventilation, and the proportion discharged home. Acute brain injuries accounted for 92 948 of 684 981 unplanned ICU admissions (14%). Hypoxic ischaemic encephalopathy, traumatic brain injury, and seizures were the most common diagnoses. A total of 24 568 of 92 948 (26%) and 62 603 of 592 033 (10%) patients with acute brain injuries and other diagnoses, respectively, died in hospital. Among the patients with brain injury the highest hospital mortality was in hypoxic ischaemic encephalopathy (53%), intracerebral haemorrhage (36%), subarachnoid haemorrhage (22%), and ischaemic stroke (22%); the lowest mortality was in traumatic brain injury (14%), central nervous system infection (10%), and seizures (4%). Acute brain injury patients were more likely to receive invasive mechanical ventilation, had longer ICU and hospital lengths of stay, had higher 90- and 180-day mortality, and were more likely to be discharged to chronic care than other patients. Acute brain injuries accounted for a disproportionally high number of in-hospital deaths occurring in our cohort of adults who received unplanned ICU care; however, the mortality rates varied, and patients with central nervous system infections and seizures had similar or lower mortality compared to patients without brain injury.