ORAL CLONIDINE REDUCES POSTOPERATIVE PCA MORPHINE REQUIREMENTS

Purpose: The purpose of this study was to evaluate the effect of perio perative oral clonidine opt postoperative analgesia and PCA morphine r equirements in adult patients after major orthopaedic knee surgery. Me thods: In this prospective, double blind placebo-controlled study 44 p atients undergoing either total knee replacement or hemiarthroplasty o f the knee were randomly assigned to receive oral placebo or clonidine (5 mu g . kg(-1)) 1.5 hr before surgery, and at 12 hr; and 24 hr afte r the initial dose Five patients were subsequently withdrawn from stud y. No other preoperative drugs were given. Preoperative sedation score was recorded. A standardized general anaesthetic was administered to all patients. Postoperative blood pressure, heart rate, PCA morphine u se, visual analogue score (VAS) for pain, sedation, nausea and pruritu s were recorded for 36 hr postoperatively. Results: The cumulative PCA morphine used was 37% lower after clonidine 57.3 +/- 26.8 mg (mean +/ - SD) compared with placebo 91 +/- 31.6 mg (P = 0.031), Ther-e runs no difference in pain or sedation scores postoperatively but patients wh o received clonidine were more sedated preoperatively (P < 0.001) and had a lower mean arterial blood pressure throughout the period of stud y by 10 to 26 mmHg (P < 0.0001). Clonidine reduced the incidence of po stoperative nausea (25% vs 74%) (P < 0.01) and vomiting compared with placebo (10% vs 53%) (P < 0.01) and required less antiemetic (dimenhyd rinate 37.5 +/- 20.9 mg vs 82.1 +/- 49.4 mg) but not statistically sig nificant (P = 0,065). Conclusions: Oral clonidine is a useful componen t to postoperative balanced analgesia as it decreases PCA morphine req uirements and decreases the incidence of nausea and vomiting.