Postoperative morphine use and hyperalgesia are reduced by preoperative but not intraoperative epidural analgesia: implications for preemptive analgesia and the prevention of central sensitization.
BACKGROUND
The aim of this study was to evaluate the postoperative morphine-sparing effects and reduction in pain and secondary mechanical hyperalgesia after preincisional or postincisional epidural administration of a local anesthetic and an opioid compared with a sham epidural control.


METHODS
Patients undergoing major gynecologic surgery by laparotomy were randomly assigned to three groups and studied in a double-blinded manner. Group 1 received epidural lidocaine and fentanyl before incision and epidural saline 40 min after incision. Group 2 received epidural saline before incision and epidural lidocaine and fentanyl 40 min after incision. Group 3 received a sham epidural control (with saline injected into a catheter taped to the back) before and 40 min after incision. All patients underwent surgery with general anesthesia.


RESULTS
One hundred forty-one patients completed the study (group 1, n = 45; group 2, n = 49; group 3, n = 47). Cumulative patient-controlled analgesia morphine consumption at 48 h was significantly lower (P = 0.04) in group 1 (89.8 +/- 43.3 mg) than group 3 (112.5 +/- 71.5 mg) but not group 2 (95.4 +/- 60.2 mg), although the hourly rate of morphine consumption between 24 and 48 h after surgery was significantly lower (P < 0.0009) in group 1 (1.25 +/- 0.02 mg/h) than group 2 (1.41 +/- 0.02 mg/h). Twenty-four hours after surgery, the visual analog scale pain score on movement was significantly less intense (P = 0.005) in group 1 (4.9 +/- 2.2 cm) than group 3 (6.0 +/- 2.6 cm) but not group 2 (5.3 +/- 2.5 cm), and the von Frey pain threshold near the wound was significantly higher (P = 0.03) in group 1 (6.4 +/- 0.6 log mg) than in group 3 (6.1 +/- 0.8 log mg) but not group 2 (6.2 +/- 0.7 log mg).


CONCLUSIONS
Preincisional administration of epidural lidocaine and fentanyl was associated with a significantly lower rate of morphine use, lower cumulative morphine consumption, and reduced hyperalgesia compared with a sham epidural condition. These results highlight the importance of including a standard treatment control group to avoid the problems of interpretation that arise when two-group studies of preemptive analgesia (preincisional vs. postsurgery) fail to find the anticipated effects.
Katz
Joel
J
Department of Psychology and School of Kinesiology and Health Science, York University, Toronto, Ontario, Canada. jkatz@uhnres.utoronto.ca
Cohen
Lorenzo
L
Schmid
Roger
R
Chan
Vincent W S
VW
Wowk
Adarose
A
D000223:Adaptation, Psychological; D000328:Adult; D000339:Affect / Q000187:drug effects; D015360:Analgesia, Epidural; D016058:Analgesia, Patient-Controlled; D000701:Analgesics, Opioid / Q000009:adverse effects* / Q000627:therapeutic use*; D000779:Anesthetics, Local; D004311:Double-Blind Method; D005260:Female; D005283:Fentanyl; D013509:Gynecologic Surgical Procedures; D006801:Humans; D006930:Hyperalgesia / Q000188:drug therapy / Q000517:prevention & control* / Q000523:psychology; D007432:Intraoperative Period; D008012:Lidocaine; D008603:Mental Health; D008875:Middle Aged; D009020:Morphine / Q000009:adverse effects* / Q000627:therapeutic use*; D010147:Pain Measurement; D017288:Pain Threshold / Q000187:drug effects; D010149:Postoperative Pain / Q000188:drug therapy / Q000517:prevention & control* / Q000523:psychology; D011300:Preoperative Care; D012944:Social Support; D011795:Surveys and Questionnaires
D000701:Analgesics, Opioid; D000779:Anesthetics, Local; D009020:Morphine; D008012:Lidocaine; D005283:Fentanyl