Intrathecal administration of either 17.5 mg plain ropivacaine or 17.5 mg plain bupivacaine was well tolerated and an adequate block for total hip arthroplasty was achieved in all patients. A more rapid postoperative recovery of sensory and motor function was seen in Group R compared with Group B.

This study was designed to evaluate the efficacy and safety of two concentrations of intrathecal ropivacaine, 7.5 and 10 mg ml(-1), in patients undergoing total hip arthroplasty. One hundred and four patients, ASA I-III, were randomized to receive an intrathecal injection of one of two concentrations of isobaric ropivacaine. Group 1 (n=51) received 2.5 ml of 7.5 mg ml(-1) ropivacaine (18.75 mg). Group 2 (n=53) received 2.5 ml of 10 mg ml(-1) ropivacaine (25 mg). The onset and offset of sensory block at dermatome level T10, maximum upper and lower spread of sensory block and the onset, intensity and duration of motor block were recorded, as were safety data. Onset of motor and sensory block was rapid with no significant differences between the two groups. The median time of onset of sensory block at the T10 dermatome was 2 min (range 1-25 min) in Group 1 and 2 min (range 1-21 min) in Group 2. The median duration of sensory block at the T10 dermatome was 3.0 h (range 0.5-4.2 h) in Group 1 and 3.4 h (1.1-5.9 h) in Group 2 (P=0.002). The median duration of complete motor block was significantly prolonged (P<0.05) in Group 2 compared with Group 1 (1.9 vs 1.2 h, respectively). Anaesthetic conditions were excellent in all but one patient. Intrathecal ropivacaine, in doses of 18.75 and 25 mg, was well tolerated and provided effective anaesthesia for total hip arthroplasty.

We have studied the anaesthetic and analgesic properties of intrathecal clonidine and intrathecal morphine in patients undergoing total hip replacement under spinal anaesthesia. After routine spinal anaesthesia with 0.5% plain bupivacaine 2.75 ml, patients were allocated randomly to receive intrathecal clonidine, morphine or saline (control) as adjuvant to the bupivacaine. Postoperative analgesic effects were measured by consumption of morphine via patient-controlled analgesia and visual analogue pain scores. Both intrathecal clonidine and intrathecal morphine prolonged the time to first analgesia compared with saline (mean 278 (SD 93.2) min, 498 (282.4) min and 54 (61.9) min, respectively) (P < 0.001). Total morphine consumption on the first night after operation was significantly less in the intrathecal morphine group. There were no differences between the clonidine and the control group. Intrathecal clonidine prolonged the duration of spinal analgesia, but was markedly inferior to the intrathecal morphine in providing subsequent postoperative analgesia.

The efficacy of ropivacaine 100 mg (5 mg ml(-1)), 150 mg (7.5 mg ml(-1)) and 200 mg (10 mg ml(-1)) and bupivacaine 100 mg (5 mg ml(-1)) given by intra-articular injection into the knee after the end of surgery was studied in 72 ASA I-II patients scheduled for elective knee arthroscopy under general anaesthesia in a randomized, double-blind study. Kapake (paracetamol 1 g and codeine 60 mg) was given as a supplementary analgesic. Pain scores were assessed 1-4 h after surgery and a verbal rating scale of overall pain severity was assessed on second postoperative day. Ropivacaine or bupivacaine concentrations were determined in peripheral venous plasma up to 3 h after injection in eight patients in each group. Verbal rating pain scores were lower with ropivacaine 150 mg compared with bupivacaine 100 mg (P<0.05). There was a tendency for lower analgesic consumption and pain scores with all doses of ropivacaine (not significant). The mean (SD) maximum total plasma concentrations of ropivacaine were 0.64 (0.25), 0.78 (0.43), and 1.29 (0.46) mg litre(-1) after 100, 150 and 200 mg. The corresponding unbound concentrations were 0.018 (0.009), 0.024 (0.020) and 0.047 (0.022) mg litre(-1). Both were proportional to the dose. The maximum total concentration after bupivacaine 100 mg was 0.57 (0.36) mg litre(-1). The time to reach maximum plasma concentration was similar for all doses and varied between 20 and 180 min. All concentrations were well below the threshold for systemic toxicity.

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