Intraoperative low-dose ketamine does not prevent a remifentanil-induced increase in morphine requirement after pediatric scoliosis surgery.
BACKGROUND
Remifentanil-based anesthesia is commonly used to facilitate neurophysiologic monitoring during pediatric scoliosis surgery. Acute opioid tolerance and/or hyperalgesia resulting from remifentanil-based anesthesia may involve activation of N-methyl-D-aspartate systems. We hypothesized that low-dose intraoperative infusion of the N-methyl-d-aspartate antagonist ketamine would suppress the development of tolerance and thereby decrease postoperative morphine consumption in children receiving remifentanil-based anesthesia for scoliosis surgery.


METHODS
Thirty-four adolescents aged 12-18 yr scheduled for scoliosis surgery were randomly assigned to receive intraoperative low-dose ketamine (bolus dose of 0.5 mg/kg followed by continuous infusion of 4 microg.kg(-1).min(-1)) or an equal volume of saline during propofol/remifentanil anesthesia. Cumulative morphine consumption was assessed using a patient-controlled analgesia device for 72 h after surgery. Postoperative morphine consumption, pain scores at rest and during cough, and sedation scores were recorded by a blinded investigator every hour for the first 4 h, every 4 hours for 20 h, and then every 12 hours for 72 h.


RESULTS
Cumulative morphine consumption at 24, 48, and 72 h after surgery did not differ significantly between groups (ketamine group: 1.57+/-0.56, 3.05+/-1.14, and 4.46+/-1.53 mg/kg; saline group: 1.60+/-0.53, 2.87+/-1.05, and 4.11+/-1.71 mg/kg, respectively). No differences in pain or sedation scores were found. The duration of anesthesia was similar in the two groups.


CONCLUSIONS
These data do not support the use of intraoperative low-dose ketamine to prevent the development of remifentanil-induced acute opioid tolerance and/or hyperalgesia during pediatric scoliosis surgery.
Engelhardt
Thomas
T
Department of Anesthesia, The Hospital for Sick Children, University of Toronto, 555 University Ave., Toronto, Ontario, Canada M5G 1X8.
Zaarour
Christian
C
Naser
Basem
B
Pehora
Carolyne
C
de Ruiter
Joost
J
Howard
Andrew
A
Crawford
Mark W
MW
D000293:Adolescent; D016058:Analgesia, Patient-Controlled; D000700:Analgesics / Q000008:administration & dosage*; D000701:Analgesics, Opioid / Q000008:administration & dosage*; D018686:Anesthetics, Intravenous / Q000008:administration & dosage*; D002648:Child; D004311:Double-Blind Method; D004361:Drug Tolerance; D005260:Female; D006801:Humans; D007430:Intraoperative Care; D007649:Ketamine / Q000008:administration & dosage*; D008297:Male; D009020:Morphine / Q000008:administration & dosage*; D010149:Postoperative Pain / Q000188:drug therapy*; D010880:Piperidines / Q000008:administration & dosage*; D000077208:Remifentanil; D012600:Scoliosis / Q000601:surgery*
D000700:Analgesics; D000701:Analgesics, Opioid; D018686:Anesthetics, Intravenous; D010880:Piperidines; D007649:Ketamine; D009020:Morphine; D000077208:Remifentanil