Epidemiology of Sedation and Sedation Adequacy for Mechanically Ventilated Patients in a Medical and Surgical Intensive Care Unit

Craig R. Weinert, Andrew D. Calvin

Critical Care Med 2007, Vol. 35, No. 2

OBJECTIVE: Describe the pharmacoepidemiology of sedative medications and nurse-rated patients’ behavior and sedation adequacy.

DESIGN: Cohort study, 2001–2003.

PATIENTS: Patients ventilated for >36 hrs in a medical or surgical intensive care unit at a university-affiliated hospital. Proxies for 312 eligible subjects were approached for consent, 277 subjects enrolled, and data from 274 subjects were analyzed.

INTERVENTIONS: None.

MEASUREMENTS AND MAIN RESULTS: Distribution of Arousal and Motor Activity levels, proportion of inadequate sedation and factors associated with inadequate sedation, variation of sedative therapy intensity, and behavior over time were measured. Sedatives were administered in 85% of 18,050 four-hour intervals during mechanical ventilation. Sedation was judged as adequate in 83% of 12,414 sedation assessments; patients were judged to be undersedated in 13.9% and oversedated in 2.6% of the assessments. Patients were unarousable or minimally arousable 32% of the time and had no spontaneous motor activity (during a 10-min observation period) 21.5% of the time. There was little variation in level of consciousness or motor activity or drug dose over 24 hrs, but daytime caregivers were more likely to judge patients as oversedated (3.7%) compared with nighttime caregivers (1.6%, p < .001). Inadequate sedation was associated with sedative drug intensity and patient behavior as measured by a two-domain sedation scale. Sedative drug intensity and behavior varied during the course of respiratory failure, and survivors received 13% more sedation per 4-hr interval of mechanical ventilation than nonsurvivors (p < .001).

CONCLUSIONS: Although patients were minimally arousable or nonarousable in 32% and motionless in 21% of the sedation assessments, surprisingly, an oversedation rating occurred in <3%. This discrepancy, along with findings that time of day influences the interpretation of sedation adequacy and that patients’ behavior change over time suggests that collaborative research is needed to define adequate sedation. 

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