The effects of caudal local anesthesia blockade on the Bispectral Index during general anesthesia in children

Background: Peripheral deafferentation induced by epidural or spinal anesthesia reduces the degree of cortical arousal in adults. This study aimed at determining if caudal blockade decreases the level of arousal, as measured by Bispectral Index (BIS) in unstimulated children, and to determine if this effect differed between age groups. Methods: Hospital ethics committee approval and parental consent was obtained. Children (age between 24 months and 5 years) and infants (between 6 and 24 months of age) were recruited if they were scheduled for below umbilical surgery that would usually require caudal local anesthesia blockade. Before the procedure, subjects within each age group were randomized to either caudal group (1 ml.kg(-1) 0.25% bupivacaine), or control group (no caudal). In all groups, anesthesia was induced with sevoflurane and maintained at a constant endtidal concentration of 1.5% sevoflurane without N2O. Five minutes after induction a baseline BIS was recorded (BIS1). In the caudal groups, a caudal block was then performed while in the control groups no block was performed. Fifteen minutes later, the BIS was again recorded (BIS2). The change in BIS over this time period was the primary outcome (BIS Delta). After measurement, subjects in the control groups received a caudal block before the start of surgery. Results: Twenty-nine infants and 18 children completed the study protocol. In children, BIS Delta was significantly different between the caudal group and control (-5.7 vs -0.7, P = 0.04). In infants, no significant difference was detected in BIS Delta between caudal and control groups. Conclusions: Caudal blockade decreased the degree of arousal, as measured by BIS, in unstimulated children aged 2-5 years. No change in arousal was detected in infants.