title: Epidural morphine delays the onset of tourniquet pain during epidural lidocaine anesthesia.
abstract: We conducted a randomized, double-blinded study to examine the onset time of tourniquet pain during epidural lidocaine anesthesia either with or without morphine in the epidural solution. Forty-five patients undergoing knee surgery with a thigh tourniquet were randomly allocated into 3 groups of 15 patients each: epidural morphine (EM; epidural administration of 17 mL of 2% lidocaine plus 2 mg of morphine, followed by IV injection of 0.2 mL of normal saline), IV morphine (IVM; 17 mL of 2% lidocaine plus 0.2 mL of normal saline, followed by IVM 2 mg IV), and control (17 mL of 2% lidocaine plus 0.2 mL of normal saline, followed by 0.2 mL of normal saline IV). The onset time of tourniquet pain was recorded. The level of sensory block was determined by the pinprick method at the occurrence of tourniquet pain. Hemodynamic changes and side effects of EM were also recorded. The onset time of tourniquet pain from both the epidural injection and the tourniquet inflation were significantly longer in the EM group (103 +/- 15 min and 80 +/- 15 min, respectively) compared with the IVM group (74 +/- 12 min and 50 +/- 12 min, respectively; P < 0.05) and the Control group (67 +/- 9 min and 45 +/- 9 min, respectively; P < 0.05). The level of sensory block at the onset of tourniquet pain and hemodynamic changes were not different among the three groups. Only two and three patients in the EM group complained of nausea/vomiting and pruritus, respectively. Respiratory depression was not observed in any patient. We conclude that epidural injection of the mixture of 2 mg of morphine and 2% lidocaine solution delayed the onset of tourniquet pain during epidural lidocaine anesthesia without significant morphine-related side effects.
  
  
  CONCLUSIONS
  We examined the effect of epidural morphine on the onset of tourniquet pain during epidural lidocaine anesthesia. We found that the addition of 2 mg of morphine to epidural 2% lidocaine significantly delayed the onset of tourniquet pain without increasing morphine-related side effects.
authors.affiliation: Department of Anesthesiology, Tri-Service General Hospital, National Defense Medical Center, No. 13 Lane 61, Wan-Shou Road, Mu-Ja, 116, Taipei, Taiwan. cherng1018@sinamail.com
authors.forename: Chen-Hwan
authors.initials: CH
authors.lastname: Cherng
authors.forename: Chih-Shung
authors.initials: CS
authors.lastname: Wong
authors.forename: Fang-Lin
authors.initials: FL
authors.lastname: Chang
authors.forename: Shung-Tai
authors.initials: ST
authors.lastname: Ho
authors.forename: Chian-Her
authors.initials: CH
authors.lastname: Lee
mesh_terms: D000701:Analgesics, Opioid; D000767:Anesthesia, Epidural; D000779:Anesthetics, Local; D004311:Double-Blind Method; D006801:Humans; D006993:Hypnotics and Sedatives; D007717:Knee / Q000601:surgery; D008012:Lidocaine; D008874:Midazolam; D009020:Morphine; D019637:Orthopedic Procedures; D010147:Pain Measurement / Q000187:drug effects; D011446:Prospective Studies
chemical_list: D000701:Analgesics, Opioid; D000779:Anesthetics, Local; D006993:Hypnotics and Sedatives; D009020:Morphine; D008012:Lidocaine; D008874:Midazolam