Efficacy and respiratory effects of low-dose spinal morphine for postoperative analgesia following knee arthroplasty.
A randomized, double-blind study of 38 patients undergoing total knee replacement was undertaken to compare the efficacy and respiratory effects of low-dose spinal morphine and patient-controlled i.v. morphine against patient-controlled i.v. morphine alone. Patients received either morphine 0.3 mg or saline 0.3 ml with 0.5% heavy spinal bupivacaine 2-2.5 ml. Respiratory effects were measured continuously for 14 h postoperatively with an Edentec 3711 respiratory monitor. There was an improvement in pain relief in the intrathecal morphine group, with significantly lower median VAS pain scores on movement at 4 h (0 (median 0-1.5) vs 5 (1.25-7.75) P < 0.01), 12 h (2 (1-5) vs 6 (3-8) P < 0.01) and 24 h (3 (1-5) vs 5 (3-7) P < 0.05) postoperatively, despite using significantly less patient-controlled morphine (20 mg (10.25-26.25) vs 38.5 mg (27-51) P < 0.01) in the first 24 h. There was a small but statistically significant reduction in the median oxygen saturation (SpO2) in the intrathecal morphine group 97 (95-99)% compared with the placebo group 99 (97-99)% (P < 0.05). Although marked disturbances in respiratory pattern were observed in both groups, none of the patients in the study had severe hypoxaemia (SpO2 < 85% > 6 min h-1) and there was no significant difference in the incidence of mild (SpO2 < 94% > 12 min h-1) or moderate (SpO2 < 90% > 12 min h-1) hypoxaemia or in the incidence of episodes of apnoea or hypopnoea in the two groups.
Cole
P J
PJ
Acute Pain Management Unit, York District Hospital, UK.
Craske
D A
DA
Wheatley
R G
RG
D000368:Aged; D016058:Analgesia, Patient-Controlled; D000701:Analgesics, Opioid / Q000008:administration & dosage*; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000627:therapeutic use; D019645:Arthroplasty, Replacement, Knee; D004008:Diclofenac / Q000627:therapeutic use; D004311:Double-Blind Method; D004359:Drug Therapy, Combination; D006801:Humans; D007278:Injections, Spinal; D009020:Morphine / Q000008:administration & dosage*; D010147:Pain Measurement; D010149:Postoperative Pain / Q000188:drug therapy*; D012119:Respiration / Q000187:drug effects*; D016896:Treatment Outcome
D000701:Analgesics, Opioid; D000894:Anti-Inflammatory Agents, Non-Steroidal; D004008:Diclofenac; D009020:Morphine