Does the addition of fentanyl to bupivacaine in caudal epidural block havean effect on the plasma level of catecholamines in children?

We evaluated the effect of adding fentanyl to bupivacaine, compared with bu pivacaine alone, on the stress response. The effect was evaluated by determ ining blood levels of epinephrine (E) and norepinephrine (NE) in pediatric patients receiving caudal epidural blocks. Sixty children, 1-8 yr of age, s cheduled for elective herniorrhaphy, were randomly allocated to two groups of 30 patients each. Group A received inhaled anesthesia and caudal epidura l block with bupivacaine 0.25% alone, 1.0 mL/kg. Group B received identical anesthesia; however, fentanyl 1 mu g/kg was added to the bupivacaine in th e caudal block. Blood samples for E and NE plasma levels were drawn at indu ction time (H-0), at the end of surgery (H-1), and in the postanesthesia ca re unit (H-2). In both groups, there was a significant decrease in the E an d NE plasma levels, when comparing H-1 and H-2 with H-0 within the same gro up (P < 0.001). There were no significant differences in the E and NE plasm a levels between the two groups at H-0, H-1, and H-2 (P = 0.5, P = 0.12, P = 0.5, respectively). Pain scores (modified Children's Hospital of Eastern Ontario Pain Score) were also similar in both groups (P = 0.19). This study suggests that adding fentanyl 1 mu g/kg to bupivacaine in the caudal epidu ral block in children does not influence plasma levels of E and NE, nor doe s it improve the analgesic intensity of the caudal block.