Postoperative analgesia after intrathecal co-administration of clonidine hydrochloride (75 micrograms) and morphine sulfate (0.5 mg) was compared with analgesia produced after either intrathecal morphine (0.5 mg) or 0.9% sodium chloride in 90 patients undergoing total hip replacement under bupivacaine spinal anesthesia. Patient-controlled morphine requirements were significantly reduced (P < 0.001) postoperation by both clonidine/morphine (median 5 mg/24 h) and morphine (median 7 mg/24 h) compared with control (saline) (median 28 mg/24 h). However, no significant additional reduction in postoperative analgesic requirements was shown with the clonidine/morphine combination compared with morphine alone. Visual analog pain scores, although good in all groups at all times, were significantly poorer in the control group at 2 h (P < 0.04) and 4 h (P < 0.001) after operation compared with both treatment groups, and significantly poorer than the clonidine/morphine group at 6 h (P < 0.002) and 24 h (P < 0.009) postoperation. Mean arterial blood pressure was significantly lower in the clonidine/morphine group than in the two other groups (P < 0.001) between 2 and 5 h after operation. The incidence of emesis was similar in the clonidine/morphine and morphine groups and was significantly more than in the control group.

Postoperative analgesia was assessed after intrathecal administration of morphine-6-glucuronide (M6G) 100 micrograms and 125 micrograms in 75 patients undergoing total hip replacement. Analgesia was excellent and was similar to that obtained after intrathecal administration of morphine sulfate 500 micrograms. Visual analog pain scores recorded postoperatively were low (median = 0) and were similar in all three groups. However, at 6 and 10 h after operation significantly more patients in the M6G 125 group recorded pain as 0 compared with patients in the morphine group (P < 0.04, P < 0.01) and significantly more patients in the M6G 100 group recorded pain as 0 at 24 h after operation compared with patients in the morphine group (P < 0.04). Postoperative meperidine consumption using a patient-controlled system was also similar in each of the three treatment groups. Nausea and emesis occurred frequently in all groups; morphine (nausea 88%, vomiting 76%), M6G 100 micrograms (nausea 76%, vomiting 64%), and M6G 125 micrograms (nausea 88%, vomiting 60%). Respiratory depression occurred in two and three patients, respectively, in the M6G 100-microgram and 125-microgram groups but did not occur in any patient who received morphine sulfate. The lack of statistical significance in the difference in incidence of respiratory depression between the groups may represent a type II error. However, the risk of late respiratory depression developing after administration of any intrathecal opioid necessitates careful postoperative observation of patients. As M6G is a potent intrathecal analgesic further investigation of this drug using small doses may be useful.

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SummaryAnaesthesia, postoperative analgesia and the incidence of adverse effects after intrathecal pethidine hydrochloride 0.50 mg.kg -I and 0.75mg.kg-were assessed and compared with a conventional technique using isobaric bupivacaine 13.75mg Pethidine, a phenylpiperidine-derived opioid, possesses local anaesthetic activity [I, 21. It has been used successfully to provide intrathecal anaesthesia for a variety of surgical procedures [3-1 I] and prolonged postoperative analgesia has been reported. These studies differed in the dosages employed, duration of sensory and motor blockade obtained and incidence of side effects and these in turn reflected differences in methodology and the nature of the surgery. The possibility of providing intra-operative anaesthesia and prolonged postoperative analgesia following a single intrathecal injection makes this technique an attractive proposition. We compared the quality of anaesthesia and the incidence of adverse events occurring with two intrathecal doses of pethidine (0.50 mg.kg -I and 0.75 mg.kg -I ) in patients scheduled for transurethral resection of the prostate gland. The technique was compared with a conventional intrathecal technique using isobaric bupivacaine. MethodsUniversity Research Ethics Committee approval and informed written consent were obtained from 60 ASA 1 and 2 patients admitted for inpatient transurethral resection of the prostate gland (TURP). Approval for administering pethidine intrathecally was obtained from the Medicines Control Agency (UK).Before operation patients were randomly allocated to receive either: isobaric bupivacaine 13.75 mg (2.75 ml, 0.5%) (group B), pethidine hydrochloride 0.50 mg.kg -' (group P50) or pethidine hydrochloride 0.75 mg.kg-' (group P75). Drugs were diluted to a standard injectate volume of 4ml with 0.9% sodium chloride and were prepared by a consultant anaesthetist who took no further part in patient management or assessment. Patients in whom there was a contraindication to regional anaesthesia, a history of hepatic, renal or coagulative dysfunction, patients

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