Multimodal Pain Management With Adductor Canal Block Decreases Opioid Consumption Following Total Knee Arthroplasty
Background: Ease of access to opioids in the perioperative period is a risk factor for subsequent opioid misuse. The purpose of this study was to quantify a decrease in opioid consumption following implementation of a new analgesic protocol after total knee arthroplasty (TKA).
Methods: A retrospective cohort study was performed analyzing patients who underwent TKA at a US Department of Veterans Affairs medical center. Patients were divided into 2 groups by multimodal analgesic regimen: Analgesia with intraoperative general anesthesia, a patient-controlled analgesia pump, and oral opioids (control group) or analgesia with intraoperative spinal anesthesia, a multimodal medication regimen, and an adductor canal block (protocol group).
Results: A total of 533 TKAs were included. The mean (SD) IV morphine equivalent dose (MED) requirement was 178.2 (98.0) for the control and 12.0 (24.6) for the protocol group ( P < .001). Total mean (SD) opioid MED requirement was 241.7 (120.1) for the control group and 74.8 (42.7) for the protocol group ( P < .001). The protocol group required only 6.7% of the IV opioids and the control group 30.9%. No difference in oral opioid requirements was found ( P = .85). The control group required more opioid refills at the first postoperative visit ( P < .001).
Conclusions: The described analgesic protocol resulted in significant decreases in IV and total opioid requirement, and lower rates of opioid prescriptions at the first postoperative visit. These findings demonstrate a decrease in opioid utilization with modern perioperative analgesia protocols and reinforce multiple recommendations to decrease opioid exposure and access.
Because age and rates of COPD differed between groups, sensitivity analyses were conducted to determine whether these variables influenced postoperative opioid use. The relationship between age and group was significant for IV (P < .001) and total opioid use (P < .001). Younger patients received higher MED doses than older patients within the control group, while dosages were fairly consistent regardless of age in the protocol group (Figure 2). There was no significance in age interaction effect with regard to oral opioids (P = .83) nor opioid refills at 3-week follow-up (P = .24).
The sensitivity analysis for COPD found that a diagnosis of COPD did not significantly influence utilization of IV opioids (P = .10), or total opioids (P = .68). There was a significant interaction effect for oral opioids (Figure 3). Patients in the control group with COPD required significantly higher mean (SD) oral opioids than patients without COPD (91.5 [123.9] MED and 62.0 [36.0] MED, respectively; P = .03). In the control group, the χ2 test was significant regarding opioid prescription refills at the 3-week visit (P = .004) with 62.4% of patients with COPD requiring refills vs 44.4% without COPD (P = .004). There was no difference in refills in the protocol group (46.4% vs 48.4%).
Finally, 2-sided independent samples t test evaluated total MED use between the 2 surgeons. There was no difference in total MED per patient for the surgeons. In the control group, mean (SD) total MED for surgeon 1 was 232.9 (118.7) MED vs 252.8 (121.5) MED for surgeon 2 (P = .18). In the protocol group, the mean (SD) total MED was 72.5 (43.2) and 77.4 (42.1) for surgeon 1 and surgeon 2, respectively (P = .39).
Discussion
Coordinated efforts with major medical organizations are being made to decrease opioid prescriptions and exposure.5,6 To our knowledge, no study has quantified a decrease in opioid requirement in a VA population after implementation of a protocol that includes intraoperative spinal anesthesia and a postoperative multimodal analgesic regimen including ACB after TKA. The analgesic protocol described in this study aligns with recommendations from both the CDC and the AAOS to decrease opioid use and misuse by maximizing nonopioid medications and limiting the size and number of opioid prescriptions. However, public and medical opinion of opioids as well as prescribing practices have changed over time with a trend toward lower opioid use. The interventions, as part of the described protocol, are a result of these changes and attempt to minimize opioid use while maximizing postoperative analgesia.
Our data showed a significant decrease in total opioid use through POD 1, IV opioid use, and opioid prescriptions provided at the first postoperative visit. The protocol group used only 6.7% of the IV opioids and 30.9% of the total opioids that were used by the control group. The substantial difference in IV opioid requirement, 166.2 MED, is equivalent to 8 mg of IV hydromorphone or 55 mg of IV morphine. The difference in total opioid requirement was similar at 166.9 MED, equivalent to 111 mg of oral oxycodone.
Decreasing opioid use has the additional benefit of improving outcomes, as higher doses of opioids have been associated with increased length of stay, greater rates of DVT, and postoperative infection.23 These complications occurred in a stepwise manner, suggesting a dose-response gradient that makes the sizable decrease noted in our data of greater relevance.23 While the adverse effects (AEs) of opioids are well known, there are limited data on opioid dosing and its effect on perioperative outcomes.23
A significant decrease in the percentage of patients receiving an opioid prescription at the first postoperative visit suggests a decrease in the number of patients on prolonged opioids after TKA with implementation of modern analgesic modalities. The duration of postoperative opioid use has been found to be the strongest predictor of misuse, and each postoperative refill increases the probability of misuse by 44%.24 In addition, opioid use for > 3 months after TKA is associated with increased risk of periprosthetic infection, increased overall revision rate, and stiffness at 1 year postoperatively.9 While not entirely under the control of the surgeon, measures to decrease the number of postoperative opioid refills may lead to a decrease in opioid misuse.
