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Muscle relaxation does not alter hypnotic level during propofol anesthesia.
Robert Greif1, Scott Greenwald, Ekkehard Schweitzer
1Department of Anesthesiology and Intensive Care Medicine, Donauspital-SMZO, Vienna, Austria.
Anesthesia and Analgesia
|February 28, 2002
Summary
Neuromuscular block does not affect the Bispectral Index (BIS) during propofol anesthesia. This indicates that BIS reliably measures sedation depth in paralyzed or unparalysed patients, regardless of muscle activity.
Area of Science:
- Anesthesiology
- Neurophysiology
- Critical Care Medicine
Background:
- Electromyographic (EMG) activity can interfere with electroencephalographic (EEG) signals, potentially affecting the Bispectral Index (BIS).
- Paralysis might reduce BIS by decreasing muscle artifact or afferent input from muscle stretch receptors, which are linked to arousal.
Purpose of the Study:
- To investigate whether nondepolarizing neuromuscular block influences the Bispectral Index (BIS) during propofol-induced anesthesia.
Main Methods:
- Ten volunteers received propofol anesthesia.
- Mivacurium infusion was used to achieve varying levels of neuromuscular block (first twitch T1 at 80% to 2%).
- Bispectral Index (BIS) and frontal-temporal EMG intensity were measured at each block level.
Main Results:
- Propofol significantly decreased both BIS and EMG intensity.
- However, varying levels of neuromuscular block with mivacurium did not significantly alter BIS or EMG intensity.
- These findings suggest that neuromuscular block does not impact BIS during propofol anesthesia.
Conclusions:
- Neuromuscular block level does not affect the Bispectral Index (BIS) during propofol anesthesia.
- BIS can reliably estimate sedation depth in deeply unconscious patients, whether they are paralyzed, partially paralyzed, or unparalyzed.