Multimodal Pain Management With Adductor Canal Block Decreases Opioid Consumption Following Total Knee Arthroplasty

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.