Post-ICU consequences of patient wakefulness and sedative exposure during mechanical ventilation.

OBJECTIVE: To determine the relationship between measures of critical illness (sedative/analgesic administration, wakefulness and organ dysfunction), intensive care unit (ICU) recall and symptoms of posttraumatic stress disorder.
DESIGN: Prospective, observational study with post-ICU follow-up.
SETTING: Medical and surgical ICUs at a teaching hospital. PATIENTS: Two hundred seventy-seven subjects requiring >36h of mechanical ventilation were enrolled; 149 completed follow-up interviews 2 months later and 80 at 6 months.
INTERVENTIONS: None.
RESULTS: ICU recall was greater for events occurring at the end of critical illness; however, 18% of subjects had amnesia for the entire ICU course. Factual ICU recall was weakly associated with increased wakefulness during mechanical ventilation (r2=0.03-0.11, p<0.05). Posttraumatic stress disorder prevalence was 17% at 2 months and 15% at 6 months. The avoidance-numbing cluster had the highest specificity (91%) for a formal diagnosis and the re-experiencing cluster had the lowest (69%). Recall of a delirious memory during critical illness was associated with more severe posttraumatic stress symptoms, but there was no association between posttraumatic stress symptoms and factual recall of ICU events. Neither ICU recall nor posttraumatic stress symptoms were associated with the intensity of sedative administration during mechanical ventilation. Posttraumatic stress symptoms were lowest in patients either the most awake during mechanical ventilation or the least awake.
CONCLUSION: Wakefulness during mechanical ventilation has a greater influence on post-ICU recall and posttraumatic stress symptoms than sedative drug exposure or severity of illness. It is difficult to predict the future psychological consequences of an individual patient's critical illness.