A comparison of bispectral index and ARX‐derived auditory evoked potential index in measuring the clinical interaction between ketamine and propofol anaesthesia

Abstract

SummaryWe evaluated the effects of a bolus (0.4 mg.kg )1 ) and continuous infusion (1 mg.kg )1 .h )1 ) of ketamine on Bispectral Index (BIS) and A-LineÒ ARX Index (AAI) during propofol anaesthesia. We included 15 ASA I patients scheduled for general anaesthesia. Induction was performed by infusion of propofol at 100 ml.h )1 until loss of consciousness. Both BIS and AAI monitors responded appropriately at that time. The calculated effect site concentration of propofol at loss of consciousness was maintained by means of a computer controlled infusion system. A 'pseudo' steady-state effect site concentration was reached after 4 min. After 1 min of baseline measurements, ketamine was administered. BIS values increased from the 3rd to the 8th min after the administration of ketamine. The AAI showed no significant increase or decrease, but betweenpatient variability increased. As the clinical signs of the hypnotic state seem to be potentiated by ketamine, one might hypothesise a reduction in the measured BIS value or a decrease in amplitude and latency of the MLAEP curves, resulting in a lower AAI. However, several authors have described an apparently contradictory rise in BIS values when ketamine is administered as an adjuvant to anaesthesia [1,11,12]. Schwender et al. investigated the effects of ketamine induction on the MLAEP and concluded that Anaesthesia, 2003, 58, pages 957-961

Cerebral and Cardiovascular Effects of Analgesic Doses of Ketamine During a Target Controlled General Anesthesia-a Prospective Randomized Study

“…Additionally, Hirota et al [10] have previously showed that a ketamine bolus of 0.4 mg/kg significantly increases the BIS values during propofol-fentanyl anaesthesia. Vereecke et al [9] presented the same effects on the BIS values after a ketamine bolus of 0.4 mg/kg followed by a 1 mg/kg/h continuous infusion. Hans et al [13] concluded that a ketamine bolus of 0.5 mg/kg also significantly increases the BIS values, during a sevoflurane anaesthesia.…”

“…Consequently, several authors have assessed the effect of different analgesic doses of ketamine in BIS values [9][10][11][12][13][14].…”

Effects of Fentanyl and S(+)-ketamine on Cerebral Hemodynamics, Gastrointestinal Motility, and Need of Vasopressors in Patients With Intracranial Pathologies

“…As a consequence, S(+)-ketamine is suited to reach equal effects in sedation as fentanyl, which contrasts the result of other studies, where an increase of BIS was seen after administration of ketamine. 45,46 CONCLUSIONS S(+)-ketamine with BIS monitoring provides adequate and controllable sedation in neurosurgical patients.…”

Effects of Ketamine-Propofol Mixture on Intraocular Pressure and Hemodynamic in Elderly Patients: A Randomized Double-Blind Trial

“…Bispectral index (BIS) is widely used to guide the administration of hypnotic drugs. Despite a deepening level of hypnosis, several studies have reported an increase in BIS values when 0.5 mg kg -1 ketamine is administered as a rapid bolus during general anaesthesia (32,33). Therefore, we did not use BIS for assessment of the level of hypnosis during induction.…”