Comparison of continuous lumbar plexus block with different concentrations of dexmedetomidine added to ropivacaine for postoperative analgesia in elderly patients undergoing hip replacement

Abstract

Objective To compare the efficacy of continuous lumbar plexus block(LPB)with different concentrations of dexmedetomidine added to ropivacaine for postoperative analgesia in elderly patients undergoing hip replacement. Methods Sixty elderly patients of both sexes, aged 65-85 yr, weighing 50-71 kg, of American Society of Anesthesiologists physical status Ⅱor Ⅲ, scheduled for elective total hip replacement, were divided into 2 groups(n=30 each)using a random number table: 0.5 μg/ml dexmedetomidine+ 0.1% ropivacaine group(group D1)and 1.0 μg/ml dexmedetomidine+ 0.1% ropivacaine group(group D2). Lumbar-sacral plexus block combined with general anesthesia was used.At the end of operation, LPB pump was started and set up to deliver a 4 ml bolus dose with a 30 min lockout interval and background infusion at a rate of 8 ml/h.The analgesia solution contained 0.5 μg/ml dexmedetomidine and 0.1% ropivacaine in group D1 and 1.0 μg/ml dexmedetomidine and 0.1% ropivacaine in group D2.Postoperative analgesia lasted for 48 h, and the visual analogue scale score was maintained ≤3.Patient-controlled intravenous analgesia(PCIA)pump was connected when break-through pain happened.PCIA solution contained morphine 50 mg diluted to 50 ml in 0.9% sodium chloride.PCIA pump was set up to deliver a 1 ml bolus dose with a 5 min lockout interval and no background infusion.When the visual analogue scale score >3, the patient-controlled LPB pump was used first, and 15 min later if analgesia was still ineffective, PCIA pump was applied.The number of patients in whom analgesia was effective and occurrence of adverse reactions were recorded. Results Compared with group D1, the rate of effective analgesia was significantly increased, and the incidence of nausea, vomiting and pruritus was decreased in group D2(P<0.05). No bradycardia, hypotension, over-sedation, respiratory depression, urinary retention or local skin infection was found in the two groups. Conclusion Continuous LPB with 1.0 μg/ml dexmedetomidine added to 0.1% ropivacaine provides better efficacy for postoperative analgesia in elderly patients undergoing hip replacement. Key words: Dexmedetomidine; Amides; Arthroplasty, replacement, hip; Nerve block; Lumbosacral plexus