Abstract
The bispectral index is affected by various factors, such as noxious stimuli and other drugs, such as muscle relaxants. The burst suppression ratio from bispectral index monitoring is correlated with electroencephalographic burst suppression, which is associated with deep anesthesia, metabolic disorders, and brain injury. We assessed patients undergoing total intravenous anesthesia and examined the effects of remifentanil on the bispectral index, burst suppression ratio, and hemodynamic changes immediately after loss of consciousness with propofol. Seventy American Society of Anesthesiologists physical status class I and II Korean female patients scheduled for general anesthesia were administered propofol with an effect-site concentration of 5 μg/mL, using a target-controlled infusion (TCI). After losing consciousness, patients received either saline or remifentanil at an effect-site concentration of 5 ng/mL for 10 min. During this period, we recorded the bispectral index values, including burst suppression ratio, blood pressure, and heart rate. With remifentanil infusion, burst suppression ratios were lower (p < 0.01) but bispectral values were not different. The burst suppression ratio was significantly different at 6, 7, 8, and 10 min after remifentanil infusion (p < 0.05). In female patients with propofol-induced unconsciousness, remifentanil alleviated the burst suppression ratio without affecting the bispectral value.
Highlights
The bispectral index (BIS) analyzes electroencephalographic waves and represents a numeric value to objectively evaluate the level of consciousness
Most studies dealing with general anesthesia have examined the effects of remifentanil on the BIS in the presence of muscle relaxants, mostly after tracheal intubation and surgical incision [2,8,9,10], some assessed propofol-sedated patients without muscle relaxants [12]
The primary objective of the current study was to examine the effects of remifentanil on the BIS in the absence of muscle relaxants and noxious stimuli in patients with propofol-induced unconsciousness
Summary
The bispectral index (BIS) analyzes electroencephalographic waves and represents a numeric value to objectively evaluate the level of consciousness. It is used widely during sedation and general anesthesia [1]. Usually consisting of propofol and remifentanil without a muscle relaxant, is the current gold standard during intraoperative neurophysiological monitoring, especially for brain or spinal surgeries [7]. In these circumstances, the BIS can be used to monitor anesthetic depth and adjust the drug dosage. Most studies dealing with general anesthesia have examined the effects of remifentanil on the BIS in the presence of muscle relaxants, mostly after tracheal intubation and surgical incision [2,8,9,10], some assessed propofol-sedated patients without muscle relaxants [12]
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