Reduced morphine consumption and pain severity with transdermal fentanyl patches following total knee arthroplasty

To determine the effects of transdermal fentanyl patches (TFPs) for postoperative analgesia in patients undergoing total knee arthroplasty (TKA) surgery. A randomized, double-blind, controlled trial study of 40 ASA I-III patients undergoing TKA surgery was performed under general anaesthesia. Patients were randomly divided into two groups. Group I (n = 20) received two 25 mu g TFPs placed on the laterals of chest wall approximately 12 h before induction of general anaesthesia. Group II, the control group (n = 20), received placebo patches of identical size. Postoperative pain at rest was assessed with visual analogue scale (VAS) at 0, 30 min and 2, 4, 6, 12, 24, 48 and 72 h. Total rescue consumption of morphine was estimated with patient control analgesia during the first 72 h after operation. The degree of active knee flexion and incidence of side effects were also evaluated. The VAS scores at 2, 4, 6, 12, 24, 48 and 72 h were significantly less in the group I compared to the group II (p < 0.05). Total morphine consumption was significantly less in group I than in group II (p < 0.05). No significant differences were found between the groups in the postoperative active knee flexion (n.s.). Side effects were similar between the groups. Transdermal fentanyl patches provide effective pain relief and decrease total rescue morphine consumption during the first 72 h after operation without additive side effects in patients undergoing TKA surgery. I.