Low-dose intravenous ketamine potentiates epidural analgesia after thoracotomy.
BACKGROUND
Ketamine potentiates intravenous or epidural morphine analgesia. The authors hypothesized that very-low-dose ketamine infusion reduces acute and long-term postthoracotomy pain.


METHODS
Forty-nine patients scheduled to undergo open thoracotomy were randomly assigned to receive one of two anesthesia regimens: continuous epidural infusion of ropivacaine and morphine, along with intravenous infusion of ketamine (0.05 mg . kg(-1) . h(-1) [approximately 3 mg/h], ketamine group, n = 24) or placebo (saline, control group, n = 25). Epidural analgesia was continued for 2 days after surgery, and infusion of ketamine or placebo was continued for 3 days. Pain was assessed at 6, 12, 24, and 48 h after surgery. Patients were asked about their pain, abnormal sensation on the wound, and inconvenience in daily life at 7 days and 1, 3, and 6 months after surgery.


RESULTS
The visual analog scale scores for pain at rest and on coughing 24 and 48 h after thoracotomy were lower in the ketamine group than in the control group (pain at rest, 9 +/- 11 vs. 25 +/- 20 and 9 +/- 11 vs. 18 +/- 13; pain on coughing, 26 +/- 16 vs. 50 +/- 17 and 30 +/- 18 vs. 43 +/- 18, mean +/- SD; P = 0.002 and P = 0.01, P < 0.0001 and P = 0.02, respectively). The numerical rating scale scores for baseline pain 1 and 3 months after thoracotomy were significantly lower in the ketamine group (0.5 [0-4] vs. 2 [0-5] and 0 [0-5] vs. 1.5 [0-6], median [range], respectively; P = 0.02). Three months after surgery, a higher number of control patients were taking pain medication (2 vs. 9; P = 0.03).


CONCLUSIONS
Very-low-dose ketamine (0.05 mg . kg(-1) . h(-1)) potentiated morphine-ropivacaine analgesia and reduced postthoracotomy pain.
Suzuki
Manzo
M
Department of Anesthesiology, Second Hospital Nippon Medical School, Kanagawa, Japan. manzo@nms.ac.jp
Haraguti
Syuji
S
Sugimoto
Kikuzo
K
Kikutani
Takehiko
T
Shimada
Yoichi
Y
Sakamoto
Atsuhiro
A
D000368:Aged; D000369:Aged, 80 and over; D015360:Analgesia, Epidural / Q000379:methods*; D000700:Analgesics / Q000008:administration & dosage; D004311:Double-Blind Method; D004357:Drug Synergism; D005260:Female; D006801:Humans; D007649:Ketamine / Q000008:administration & dosage*; D008297:Male; D008875:Middle Aged; D010147:Pain Measurement / Q000187:drug effects / Q000379:methods; D010149:Postoperative Pain / Q000188:drug therapy* / Q000453:epidemiology / Q000473:pathology; D013908:Thoracotomy / Q000009:adverse effects
D000700:Analgesics; D007649:Ketamine