Postop Intra-articular Infusion as an Adjunct for Pain Relief
Postoperative delivery of bupivacaine through an elastomeric pain pump decreases overall pain levels in patients undergoing total knee arthroplasty (TKA), compared with placebo, according to study by Matthew S. Austin, MD, and his colleagues at The Rothman Institute, Philadelphia, Pennsylvania.
Another important study finding was that when used with standardized regional anesthesia and a preemptive, multimodal analgesic protocol, the infusion reduced opioid consumption to what the investigators term a “remarkably small” amount.
“In and of itself, the pain ball is probably not sufficient,” Dr. Austin told ICJR, “but in the setting of a multimodal pain management regimen, this was a very nice adjunct.”
The randomized, double-blind study was honored with the 2012 Chitranjan Ranawat Award presented by The Knee Society.
“These pain balls have been used in other types of surgery, but they hadn’t really been studied well in knee replacement patients,” Dr. Austin said. “It had been used for shoulder surgeries, and incidentally they stopped using them because it was dangerous to the cartilage in the shoulder joint. But in the total knee you don’t have cartilage, so you don’t have to worry about that.”
Dr. Austin and his colleagues randomly assigned patients undergoing primary, unilateral TKA for osteoarthritis to receive 300 mL of 0.5% bupivacaine through the On-Q PainBuster pump (n = 80) or normal saline (n = 80) through an identical pump. The pump was activated immediately postoperatively and was removed on POD2 unless the patient was discharged sooner.
All patients received the same perioperative analgesia protocol, which included spinal anesthesia with 12.5 mg bupivacaine and 0.2 mg Duramorph. Altogether, 150 patients completed the study, 75 from each treatment group.
Pain scores (visual analog scale) were significantly lower in the bupivacaine group than in the control group during the first 2 postoperative days.
Specifically, on POD1, there were significant differences between groups with regard to most pain during the previous 12 hours (P = .01), least pain during the previous 12 hours (P = .01), and current pain (P = .03). On POD2, only the score for most pain was lower in the bupivacaine group (P = .04). By POD3, pain scores were similar in the 2 groups.
At the 4-week postoperative follow-up, patients were asked to recall the worst pain they had experienced while in the hospital. The average score was significantly lower in the bupivacaine group than in the control group (P = .02).
Opioid consumption was significantly reduced in the bupivacaine group compared with the control group on POD2 (P = .02) and POD3 (P = .03). In fact, on POD2, average opioid consumption in the bupivacaine group was 7 mg, 33% lower than in the control group, and on POD3 the average consumption was 4 mg, nearly 54% lower than for controls.
The investigators noted that in addition to excellent pain control and low opioid consumption, a benefit of continuous intraarticular analgesia is operating room efficiency. Placement of the catheter did not increase operating time, “a substantial practical advantage” over peripheral nerve blockade.
“Prior to this study some surgeons were using the pain ball, some were not,” Dr. Austin said. “As a result of this study, our standard of care became the pain ball.”
Goyal N, McKenzie J, Sharkey PF, Parvizi J, Hozack WJ, Austin MS. The 2012 Chitranjan Ranawat Award: Intraarticular analgesia after TKA reduces pain. Clin Orthop Relat Res. 2013;471:64-75.