Role of Local Anesthetics and Multimodal Analgesia in Total Joint Arthroplasty
Emily Baus, BS
● Orthopedic surgeons are the third-highest prescribers of opioid medications amongst all medical specialties.
● Multimodal analgesia uses a combination of different medication types and delivery routes to manage a patient’s pain.
● The use of a combination of non-opioid analgesics with distinct mechanisms of action decreases the dose of each drug needed, minimizing the risk of adverse effects.
● Local infiltration analgesia and peripheral nerve blocks are both local anesthetic techniques increasingly used to manage perioperative pain in joint arthroplasty.
● Local anesthetic techniques and practices vary widely amongst surgeons performing total joint arthroplasty. Further research is needed to determine the most efficacious options.
The origins of the Opioid Epidemic in the United States can be traced back to the 1990s and is considered to be due to a combination of factors including decreased opioid regulation, aggressive and fraudulent marketing by pharmaceutical companies, and the promotion of aggressive pain management by regulatory agencies such as the Joint Commission . Over two decades later, the crisis is still evident in the United States (US), where the US makes up only 4.6% of the world’s population but consumes 80% of the global opioid supply .
Opioid overdoses have largely resulted from either patient-related dependency or opioid prescription diversion. About half of individuals who misuse opioids reported first being exposed to an opioid from a family member or friend with a prescription . The opioid crisis has triggered a shift in perioperative pain management. As the third highest prescriber of opioids amongst medical specialties, with an estimated 7.7% of all US opioid prescriptions, orthopedic surgeons are at the forefront of developing multimodal analgesia techniques to optimize pain management while decreasing reliance on opioids [3,4]. Total hip arthroplasty and total knee arthroplasty are among the most performed procedures in orthopedics today. By 2030, the demand for primary total hip arthroplasties is estimated to grow by 174%, and the need for primary total knee arthroplasties is projected to grow by 673% . The use of multimodal analgesia is becoming common practice in orthopedics . Multimodal analgesia uses a combination of different medication types and delivery routes to manage a patient’s pain by affecting the pain pathway at various points. Adequate pain management is an essential post-operative quality measure and is physiologically necessary to reduce the surgical stress response and thus improve patient outcomes . This analysis aims to explore the use of multimodal analgesia, specifically local anesthetics, and discuss the rationale behind using an array of therapeutics to manage pain.
Multimodal Pain Management
Multimodal pain management is not a new concept. In 1993, Kehlet et al. published several papers after finding that no single technique or drug regimen completely eliminated postoperative pain . In contrast to ninety-five percent of the literature that focused on unimodal analgesia, Kehlet’s papers describe the potential benefits of multimodal pain management and its favorable outcomes on restoring function and subsequent reduction in postoperative morbidity and length of hospital stays.
Multimodal pain management involves the use of different pharmacologic agents; including non-opioid analgesics, anti-inflammatories, neuromodulators, anesthetics, and opioids to affect pain at different points in the pain pathway; including the local tissue, pain transmission across nerves, and pain perception in the brain. Figure 1 demonstrates the sites of action of various pharmacologic therapies in the pain pathway.
Figure 1: A model depicting the sites of action of various components of Multimodal Analgesia. Abbreviations: COX, cyclooxygenase; NSAIDs, nonsteroidal anti-inflammatory drugs. Reprinted from Pergolizzi J, Alegre C, Blake D, et al. Current considerations for the treatment of severe chronic pain: the potential for tapentadol. Pain Pract. 2012; 12:290–306. 129
Subsequent research has shown that the synergistic and additive effects of multimodal pain management in orthopedic surgery allow for less opioid usage and more favorable reported pain scores when compared to opioid therapy alone . In addition to decreasing the number of circulating opioids within the population, deferring opioid-centric pain management also reduces opioid-induced side effects such as sedation, constipation, nausea and vomiting, and pruritus . Despite the overall shift away from unimodal opioid analgesia, there is no consensus over the optimal multimodal analgesic regimen for patients following total joint arthroplasty .
Local Infiltration Analgesia
One component of multimodal analgesia is local anesthetics. These local anesthetics act at the cell membrane by blocking voltage-gated sodium channels, thereby inhibiting the generation of action potentials and transmission of pain sensation from the nerve endings. . Local infiltration analgesia (LIA) is a technique that involves the infiltration of a large volume dilute solution of a long-acting local anesthetic agent, often with adjuvants, throughout the surgical site at the time of surgery . By addressing pain receptors directly at the source, LIA greatly reduces the potential for affecting muscle function post-operatively and decreases the risk of dysesthesia or iatrogenic nerve injury . This technique gained popularity after it was brought to attention by Kerr and Kohan in 2008 , and current data have exemplified this widespread use. According to a survey of 622 orthopedic surgeons who perform total joint arthroplasties, local infiltration anesthesia (LIA) is routinely used by 80.3% of respondents for both total knee arthroplasty (TKA) and total hip arthroplasty (THA) . However, the contents and dosing of medications in LIA cocktails have varied significantly in the published literature. Moucha et al. published a meta-analysis of medications typically included in local infiltration cocktails. These medications routinely included a long-acting anesthetic such as ropivacaine or bupivacaine, NSAIDs, and epinephrine . Less commonly, corticosteroids, antibiotics, and alpha-2 antagonists have also been included .
In addition to its utility as a component of multimodal analgesia, LIA has been shown to decrease the risk of falls in patients when compared to peripheral nerve blocks . This is due to the epinephrine in LIA cocktails causing vasoconstriction at the wound site, preventing the systemic spread and subsequent effects of the anesthetic. Considering the importance of early mobility in total joint arthroplasties, this effect is highly favorable for physiotherapy and rehabilitation.
Peripheral Nerve Blocks
Peripheral nerve block (PNB) is a technique describing the injection or continuous infusion of analgesic medications into peripheral neural sites. In contrast to LIA’s local effects on the tissue surrounding a surgical wound, PNB interrupts nociceptive signals of the affected nerve, thus attenuating pain from regions innervated by the given nerve or nerve plexus . Many types of peripheral nerve blocks and their accompanying anesthetics have been described within the literature. The most common PNBs for total joint arthroplasty include nerve blocks affecting the lumbar plexus, as well as the femoral nerve and sciatic nerve with their associated branches . PNBs can be administered via a single injection or a continuous infusion of an anesthetic by placing an indwelling catheter. In a survey study following orthopedic surgeons who perform total joint and knee arthroplasty, 68.7% report using peripheral nerve blocks in patients undergoing total knee arthroscopy . Blocks can also be used in total hip arthroplasty, although less frequently . Clinical trials comparing the use of peripheral nerve blocks versus local infiltration analgesia suggest a synergistic effect may be possible . PNBs provide sufficient analgesia but have been shown in some cases to limit the ability of a patient to ambulate in the immediate postoperative period, which is essential as it relates to the patient’s recovery .
As a component of multimodal analgesia, local anesthetics are widely used and highly effective. The utilization of drugs that act by mechanisms in the pain pathway can minimize the use of opioids to manage perioperative pain. Despite their common use in total joint arthroplasty by orthopedic surgeons, there is still wide variation in the types of local infiltrative anesthetics and peripheral nerve blocks used. The decision of which local anesthetic method to utilize depends on the planned surgical procedure and evaluation of the risk and benefits unique to each modality. There is currently no consensus or gold standard on the most effective method to use for specific procedures. Further research is needed to determine the best composition and delivery route for local anesthetics in total joint arthroplasty.
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