Altered lower brainstem neurophysiological response is associated with mortality in deeply sedated critically ill patients.

BACKGROUND AND OBJECTIVES

Absent cough reflex is associated with mortality in intensive care unit (ICU) patients requiring deep sedation, suggesting that lower brainstem dysfunction contributes to adverse outcomes. We conducted a multicenter observational cohort study to confirm this hypothesis by assessing the peak latency (PL) of the lower brainstem-generated P14 evoked potential (EP), which is slightly increased by sedatives. We aimed to demonstrate that a P14-PL > 16 ms is independently associated with day-28 mortality.

PATIENTS AND METHODS

Mechanically ventilated adult patients, comatose or deeply sedated, brain injured or not, were included. At day 3, EPs were performed in patients remaining unconscious. The Simplified Acute Physiological Score (SAPSII), initial Glasgow Coma Scale (GCS), sedation depth, and brainstem reflexes were collected. The primary outcome was day-28 mortality. The secondary outcomes were delayed awakening and delirium after sedation discontinuation.

RESULTS

Between 2015 and 2019, 322 patients were included. EPs were performed in 264 (82%) patients, including 140 (53%) brain-injured and 251 (95%) deeply sedated patients. The median age, SAPSII and initial GCS were 62 [50; 71], 49 [40; 62] and 11 years [6; 15], respectively. A P14-PL > 16 ms was found in 76 (29%) patients and was associated with day-28 mortality (adjusted hazard ratio, 3.0; 95% confidence interval, [1.7-5.2]). Absent cough and pupillary light reflexes were associated with death. Only absent oculocephalogyric reflex was associated with delayed awakening (adjusted odds ratio, 2.1, 95%CI, [1.1-3.7]).

INTERPRETATION

Impaired neurological and neurophysiological lower brainstem responses are associated with mortality in deeply sedated patients. Funded by the French Ministry of Health; PRORETRO; no. P120915; ClinicalTrials.gov registry: NCT02395861; date: 24 March 2015.