The influence of timing of systemic ketamine administration on postoperative morphine consumption.
OBJECTIVE
To determine the influence of timing of systemic ketamine administration on postoperative morphine consumption.


METHODS
Prospective randomized study.


METHODS
Operating rooms, postanesthesia care unit, and gynecology service of a university hospital.


METHODS
Forty-five patients undergoing laparotomy for benign gynecologic pathologies were randomized into 3 groups.


METHODS
In Group 1, before surgical incision, patients received 0.5 mg/kg ketamine IV, followed by normal saline infusion and normal saline IV at wound closure in group 1 (n = 15). In group 2 (n = 15), patients received 0.5 mg/kg ketamine IV before surgery, followed by ketamine infusion 600 mug . kg(-1) . h(-1), until wound closure and normal saline IV at that time. In the other group (group 3, n = 15), patients received normal saline IV before surgery, followed by saline infusion and then 0.5 mg/kg ketamine IV at wound closure. In the postoperative period, patient-controlled analgesia IV morphine was used for postoperative pain relief. First requested analgesic medication time was recorded. Postoperative pain was assessed by measuring morphine consumption at 0 to 2, 0 to 4, and 0 to 24 hours and visual analog scale (VAS) pain scores in response to cough at 2nd, 4th, and 24th hours and during rest at 0 to 2, 0 to 4, and 0 to 24 hours after surgery.


RESULTS
First requested analgesia was shorter in group 1 than the others (P < .01). Mean VAS pain scores in response to cough at 24th hour in groups 2 and 3 were significantly lower than in group 1 (P < .001 and P < .01, respectively). Mean VAS pain scores during rest at 0 to 24 hours in groups 2 and 3 were significantly lower than in group 1 (P < .01 and P < .05, respectively). Morphine consumption was lower in groups 2 and 3 at 0 to 2 hours (P < .001 and P < .01). Moreover, morphine consumption at 0 to 4 hours in group 2 was significantly lower (P < .01).


CONCLUSIONS
Lower pain scores and morphine consumption in groups 2 and 3 may be related to higher plasma ketamine concentrations caused by the higher doses and later administration. Our findings suggest that a single preoperative dose of ketamine provided less analgesia compared with other dosing regimens that included intraoperative infusions or postoperative administration.
Bilgin
Hülya
H
Department of Anesthesiology, Faculty of Medicine, Uludağ University, Bursa 16059, Turkey. hbilgin@uludag.edu.tr
Ozcan
Berin
B
Bilgin
Tufan
T
Kerimoğlu
Beklen
B
Uçkunkaya
Nesimi
N
Toker
Abit
A
Alev
Tijen
T
Osma
Selcan
S
D000328:Adult; D016058:Analgesia, Patient-Controlled / Q000379:methods; D000700:Analgesics / Q000008:administration & dosage* / Q000494:pharmacology; D000701:Analgesics, Opioid / Q000008:administration & dosage*; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D005260:Female; D013509:Gynecologic Surgical Procedures / Q000379:methods; D006801:Humans; D007649:Ketamine / Q000008:administration & dosage* / Q000494:pharmacology; D008875:Middle Aged; D009020:Morphine / Q000008:administration & dosage*; D010147:Pain Measurement; D010149:Postoperative Pain / Q000517:prevention & control*; D011446:Prospective Studies; D012965:Sodium Chloride / Q000008:administration & dosage; D013997:Time Factors
D000700:Analgesics; D000701:Analgesics, Opioid; D012965:Sodium Chloride; D007649:Ketamine; D009020:Morphine