In TKA, but superiority does not linger
A meta-analysis of local infiltration analgesia (LIA) has shed more light on its efficacy and utility in the postoperative setting. A multicenter research team concluded that although LIA reduces short-term pain compared with femoral nerve block, this effect is reversed by the first postoperative day.
“We know local infiltration analgesia is becoming more and more popular,” said Mandeep Singh, MBBS, MD, assistant professor in the Department of Anesthesiology and Pain Medicine at the University of Toronto in Ontario, Canada. “The selling point for the technique is decreased motor block and better pain control.
“However, a few years before we started using the LIA technique, the femoral nerve block was the standard of care to provide pain relief during and after surgery…. We thought we should look back at the literature and see how it compares to other techniques.”
To that end, Dr. Singh and his colleagues searched MEDLINE, Embase, CENTRAL and Cochrane Database of Systematic Reviews for articles published on LIA before April 2014. Clinical trial registries and international conference abstracts published over the last five years were also searched.
Randomized controlled studies were included if they compared LIA with no injection, placebo or regional anesthesia in adults undergoing elective, unilateral, primary total knee arthroplasty (TKA). Outcomes included pain scores at rest and with movement, cumulative morphine consumption at eight and 24 hours after surgery, hospital length of stay, functional outcomes and complications.
Femoral Nerve Block Best After Day 1
As Dr. Singh reported at the 2015 annual meeting of the Canadian Anesthesiologists’ Society (abstract 85881), 24 studies were included in the final analysis comprising 1,617 patients undergoing unilateral TKA; 753 patients were randomly assigned to the LIA group. Eight studies compared LIA with placebo, 10 with femoral nerve block and six with a neuraxial technique.
“We found that the primary components in the local infiltration were typically a local anesthetic, an NSAID [nonsteroidal anti-inflammatory drug] such as ketorolac and morphine,” he explained. “Other additives were occasionally used, such as epinephrine and tranexamic acid.”
When compared with placebo/no injection, LIA was associated with reduced pain scores at rest and at eight and 24 hours after surgery; reduced pain scores with movement at eight and 24 hours were also noted.
“If you compare LIA to femoral nerve, we found that early on, up to eight hours following surgery, the local infiltration analgesia technique was beneficial. But when looking at pain relief lasting 24 hours, the effect was reversed and femoral nerve block was found to be more beneficial.”
Cumulative oral morphine equivalent consumption was lower with LIA compared with placebo and neuraxial techniques over 24 hours, but not when compared with femoral nerve block. “Surprisingly,” Dr. Singh added, “there was no difference in length of stay or complications.”
Functional outcomes were qualitatively better with LIA. “The studies that were published early on did not document functional outcomes, such as quadriceps’ weakness or ability to ambulate,” he explained. “But the more recent studies are reporting on those parameters. Unfortunately, we were not able to perform a meta-analysis because of the heterogeneity in the types of reported outcomes.
“So we recommend that future studies have more uniform assessments, especially for functional outcomes and long-term outcomes.”
Session moderator Kwesi Kwofie, MD, said that although LIA is certainly beneficial, the issue is not cut and dried. “It’s a complicated issue because the innervation of the knee is complicated,” he said in an interview. “Trying to strike a balance b etween patient mobility, quality pain control and anticoagulation is always a challenge, no matter what technique you use. There are always trade-offs.
“For example, one of the downsides to local infiltration analgesia is its limited duration of action,” said Dr. Kwofie, who is director of regional anesthesia at Dalhousie University in Halifax, Nova Scotia, Canada. “Ultra–long-acting local anesthetics may help address this issue in the future, but have not been adequately studied. The question remains how local infiltration analgesia stacks up against other techniques.
“In the end,” Dr. Kwofie said, “I think this research is timely and adds an important piece to the puzzle. But like a lot of research, it leads us to more questions, which is not a bad thing. It means we may know better where to look for answers.”