Continuous intra-articular infusion of bupivacaine for postoperative pain following total knee arthroplasty.

This study assessed the efficacy of local, continuous infusion of bupivacaine for pain control following total knee arthroplasty. Eleven men and 19 women with an average age of 65 years (range: 43-83 years) randomly received either 0.25% bupivacaine or normal saline by local infusion pump. Standard wound drainage also was implemented. Pain was assessed with a visual analog scale along with patient-controlled analgesia demand, narcotic delivery, and nonsteroidal anti-inflammatory administration. Drug lost to drainage also was assessed. Mean preoperative visual analog scores were similar between the saline and bupivacaine groups (6.5 +/- 1.4 and 6.1 +/- 2.0, respectively; P = .535). By the end of the second postoperative day, scores decreased to 3.4 +/- 3.2 for the saline group and 2.5 +/- 1.6 for the bupivacaine group. Although postoperative reductions were statistically significant (P = .007), the main treatment effect was not (P = .404). Mean narcotic demand and usage were 87 +/- 114.1 requests with usage of 11.8 +/- 12.3 mg for the saline group and 96 +/- 104.8 requests with usage of 7.5 +/- 3.8 mg for the bupivacaine group (P = .505). Cumulative ketorolac administration was 47 +/- 52.2 mg for the saline group and 83.6 +/- 64.9 mg for the bupivacaine group (P=.100). Hydrocodone-acetaminophen usage also was similar between the saline and bupivacaine groups (88 +/- 43.9 mg and 64.6 +/- 35 mg, respectively) (P = .112). Drug lost to drainage was estimated to be 27%. These findings suggest continuous local analgesic infusion after total knee arthroplasty does not offer significant improvements in either pain relief or medication use. Drug loss from drainage may exceed 25% and may compromise analgesic effectiveness.