Effects of neuromuscular block on systemic and cerebral hemodynamics and bispectral index during moderate or deep sedation in critically ill patients.

OBJECTIVE: To investigate whether neuromuscular block can affect bispectral index (BIS) or cerebral hemodynamics under moderate or deep sedation produced by propofol. DESIGN AND
SETTING: Prospective, controlled study in a university hospital affiliated intensive care unit. PATIENTS: Seventeen surgical patients undergoing elective esophagectomy.
INTERVENTIONS: After stabilization with either light or deep sedation we investigated whether the BIS, electromyographic activity (EMG), or cerebral and systemic hemodynamic parameters were affected by administration of muscle relaxant.
MEASUREMENTS AND MAIN RESULTS: Neuromuscular block reduced the BIS during moderate sedation but not during deep sedation although the EMG at both levels of sedation was significantly reduced. No positive effects of neuromuscular block on cerebral hemodynamics were obtained with monitoring of regional cerebral oxygen saturation and middle cerebral artery blood velocity; however, significant effects on systemic hemodynamic parameters were observed only at moderate propofol sedation. The values of BIS and systemic hemodynamic variables with moderate sedation were also very similar to those with deep sedation and neuromuscular block although these values differed without neuromuscular block.
CONCLUSIONS: Neuromuscular block altered the BIS score in moderately sedated patients but not in deeply sedated patients although cerebral hemodynamics was not affected by neuromuscular block during either moderate or deep sedation. Muscular relaxant also enhanced cardiovascular stability with moderate sedation. These results suggest that level of consciousness may be decreased by neuromuscular block during moderate sedation but not affected during deep sedation.