Overestimation of Bispectral Index in sedated intensive care unit patients revealed by administration of muscle relaxant.
BACKGROUND
Electromyographic activity has previously been reported to elevate the Bispectral Index (BIS) in patients not receiving neuromuscular blockade while under sedation in the intensive care unit. This study aimed to investigate the magnitude of the decrease of BIS following administration of muscle relaxant in sedated intensive care unit patients.


METHODS
The authors prospectively investigated 45 patients who were continuously sedated with midazolam and sufentanil to achieve a Sedation-Agitation Scale value equal to 1 and who required administration of muscle relaxant. BIS (BIS version 2.10), electromyography, and acceleromyography at the adductor pollicis muscle were recorded simultaneously before and after neuromuscular blockade. Sixteen of these 45 patients were also studied simultaneously with the new BIS XP.


RESULTS
After administration of a muscle relaxant, BIS (67 +/- 19 vs. 43 +/- 10, P < 0.001) and electromyographic activity (37 +/- 9 vs. 27 +/- 3 dB, P < 0.001) significantly decreased. Multiple regression analysis showed that the decrease of BIS following administration of myorelaxant was significantly correlated to BIS and electromyographic baseline values. Using standard BIS range guidelines, the number of patients under light or deep sedation versus general anesthesia or deep hypnotic state was markedly overestimated before administration of myorelaxant (53 vs. 2%, P < 0.001).


CONCLUSIONS
The BIS in sedated intensive care unit patients may be lower with paralysis for an equivalent degree of sedation because of high muscular activity. The magnitude of BIS overestimation is significantly correlated to both BIS and electromyographic activity before neuromuscular blockade. The authors conclude that clinicians who determine the amount of sedation in intensive care unit patients only from BIS monitoring may expose them to unnecessary oversedation.
Vivien
Benoît
B
Department of Anesthesiology, Universitaire Pitié Salpêtrière, Paris, France. benoit.vivien@psl.ap-hop-paris.fr
Di Maria
Sophie
S
Ouattara
Alexandre
A
Langeron
Olivier
O
Coriat
Pierre
P
Riou
Bruno
B
D018686:Anesthetics, Intravenous; D016292:Procedural Sedation; D003422:Critical Care; D004452:Echocardiography; D004569:Electroencephalography / Q000187:drug effects*; D004576:Electromyography; D005260:Female; D006439:Hemodynamics / Q000187:drug effects; D006801:Humans; D006993:Hypnotics and Sedatives; D008297:Male; D008874:Midazolam; D008875:Middle Aged; D008991:Monitoring, Physiologic; D009125:Muscle Relaxants, Central; D009126:Muscle Relaxation / Q000187:drug effects; D018482:Muscle, Skeletal / Q000187:drug effects / Q000502:physiology; D011446:Prospective Studies; D011595:Psychomotor Agitation / Q000523:psychology; D012044:Regression Analysis; D017409:Sufentanil
D018686:Anesthetics, Intravenous; D006993:Hypnotics and Sedatives; D009125:Muscle Relaxants, Central; D017409:Sufentanil; D008874:Midazolam