According to this study:

* Minimizing sedation in mechanically ventilated patients is beneficial, but neither the adequacy of sedation over an entire episode of respiratory failure nor the effect of caregivers' assessments of adequacy has been studied.

* Day nurses are significantly more likely to judge patients as oversedated than are night nurses.

Commonly, mechanically ventilated patients are sedated to reduce the physiologic and psychological stress associated with respiratory failure and to enable them to better tolerate invasive life support measures. However, studies show that using protocols that minimize sedation and keep the patient more responsive improves outcomes. Balancing those needs and defining adequate sedation are problematic. The authors of this study investigated the adequacy of sedation during a period of mechanical ventilation and the factors that influence how adequacy is assessed by different caregivers.

The authors evaluated the adequacy of sedation in 274 adult patients who were mechanically ventilated continuously for three to 21 days in a medical or surgical ICU. ICU nurses used the Minnesota Sedation Assessment Tool (MSAT), which quantifies unstimulated motor activity and arousal, to assess the level and adequacy of sedation in patients every four hours. An MSAT score was available for 12,414 four-hour intervals of intubation with sedation.

Patients were judged to be minimally arousable or unarousable 32% of the time and had no spontaneous muscle movement 21.5% of the time. Somewhat less than one-third of the time, their eyes were open and tracking. Nonetheless, nurses considered patients oversedated only 2.6% of the time and undersedated 13.9% of the time. Sedation was deemed adequate 83% of the time. In addition, day nurses were more likely to consider patients oversedated (3.7%) than were night nurses (1.6%), despite there being little difference in the sedative dosages given at night and during the day or the levels of consciousness and motor activity. The authors state that the influence of a caregiver's work cycle on her or his interpretation of the patient's level of sedation should be further studied.

The authors also found an unexpected association between survival and the course of sedative administration. Although both survivors and nonsurvivors initially received comparable amounts of sedation, those who died had a "notable increase" in sedative administration in the second half of the course of mechanical ventilation. The authors suggest, though, that the difference might be attributable to impaired drug excretion and altered dose-response relationships in the critically ill.

The study's limitations included the absence of protocols that specified the sedatives to be used and numerical sedation goals. In addition, daily interruption of sedation was required only for propofol, the most commonly used sedative. The study's observational design also made it difficult to establish dosage equivalency for the eight sedatives that were evaluated, and many patients were receiving more than one.

The authors conclude that "multiple factors [horizontal ellipsis] influence nurses' judgment of sedation adequacy, including time of day and two behavioral domains (level of consciousness and spontaneous motor activity)." Therefore, they contend, a scale like the MSAT, which has multiple domains and few levels, more accurately measures the adequacy of sedation than a scale with only one domain and many levels.

C. Cutugno