In the first 48 hours after total knee arthroplasty, a continuous adductor canal block reduced opioid consumption compared with placebo, according to study results.
“When we set out to do this study, there were some early articles on nerve block and knee surgery, but they hadn’t quite characterized the nerve block and efficacy that well,” study author David Auyong, MD,an anesthesiologist at the Virginia Mason Medical Center in Seattle, told Orthopedics Today. “Nobody had really put in a continuous nerve block, so that was probably the biggest angle that we were going to characterize: how well a continuous nerve block worked over 48 hours.”
Auyong, along with co-author Neil Hanson, MD, randomly assigned 80 patients presenting for primary unilateral total knee arthroplasty (TKA) to receive either a continuous ultrasound-guided adductor canal block with 0.2% ropivacaine or placebo; all patients received a preoperative single-injection femoral nerve block with spinal anesthesia.
The researchers evaluated cumulative intravenous morphine consumption 48 hours after surgery, with analysis of covariance adjusted for baseline characteristics. Resting pain scores, peak pain scores during physical therapy on postoperative days 1 and 2, quadriceps maximum voluntary isometric contraction, distance ambulated during physical therapy, postoperative nausea and vomiting, and satisfaction with analgesia were included as secondary outcomes.
Study results showed a least-square mean difference in cumulative morphine consumption of –16.68 mg over 48 hours and a least-square mean of total morphine use of –11.17 mg between 24 and 48 hours.
Auyong and Hanson found similarities between intention-to-treat analysis and per-protocol results. Patients who received adductor canal blocks had better quadriceps strength and further distance ambulated on postoperative day 2, according to functional outcomes.
“This study showed the nerve block had significant improvements in lowering opioid consumption. At the same time, patients were more comfortable both at rest and during physical therapy. [Patients also] had stronger legs and were able to participate in physical therapy better,” Auyong said. “It pretty much hit an amazing trifecta that improved pain with less opioids and improved leg strength and physical therapy.” — by Casey Tingle
Disclosure: Auyong reported no relevant financial disclosures.