Opioid use disorder

Opioid use disorder

Anesthetic relevance	High
Anesthetic management	Use non-opioid pain adjuncts (regional, GABA agonists, NSAIDs) and higher dosing of full mu receptor agonist opioid analgesics (e.g. fentanyl, hydromorphone)
Specialty	Pain
Signs and symptoms	N/A
Diagnosis	N/A
Treatment	N/A
Article quality
Editor rating	In development
User likes	2

This article focuses primarily on management considerations for patients on methadone or Suboxone therapy.

Epidemiology

According to the 2019 Substance Abuse and Mental Health Administration National Survey on Drug Use and Health, 5.7 million people (2.1 percent of people aged 12 or older) in the US were estimated to have used heroin at some point in their lives while 431,000 (0.2 percent) reported use in the last month. Illicit fentanyl and prescription drug misuse have also contributed to rising rates of opioid overdose deaths from approximately 3,000 in 2010 to over 15,000 in 2016

Anesthetic implications

Patients with opioid use disorder on maintenance therapy with methadone or Suboxone (buprenorphine-naloxone) are at high risk of inadequately controlled pain post-procedure due to low dosing or slow titration. Additionally, patients with poorly managed pain are at risk of prolonged hospital stays, increased cravings, and potential relapse.

Pathophysiology

Buprenorphine is a partial mu-opioid receptor agonist and kappa-opioid receptor. It is unique in that its action at the mu-opioid receptor can block binding of other opioids.

Methadone is a synthetic long-acting mu-opioid agonist that similarly binds and occupies receptor. It is multifaceted in that it is an NMDA antagonist (a pathway implicated in the development of opioid tolerance). This explains the perioperative benefits of methadone and ketamine as opioid sensitizers. Methadone also acts as a serotonin and norepinephrine reuptake inhibitor which improves mood in patients (albeit while increasing the risk of serotonin syndrome).

Anesthetic management

Preoperative optimization

Patients can continue to receive adequate pain control peri-operatively while continuing on their home opioid agonist therapy. The dose of buprenorphine has implications for the risk of opioid tolerance and increased post-operative pain. According to UCSF guidelines for perioperative management of buprenorphine, for example, patients on a high dose of buprenorphine (>8 mg/day) should consider gradual dose reduction prior to elective surgery to prevent decreased efficacy of full mu-opioid agonists during the treatment of acute pain. At doses lower than 8 mg/day of buprenorphine, patients can continue their normal Suboxone dose through procedure day and day of discharge.

Similarly, it is recommended that patients continue their dose of home methadone[1]. One approach is to split a patient's total daily dose into three divided doses. This takes into account methadone's biphasic pharmacokinetics (having both alpha and beta elimination). Alpha elimination corresponds to methadone's analgesic duration which approximates to 8 hours. This is in contrast to its beta elimination (preventing withdrawal in patient's on opioid maintenance therapy) which lasts 30-60 hours.

Non-opioid agents include medications such as Tylenol and the gabapentinoids, gabapentin/pregabalin. A shared neuro-inflammatory and central sensitization process akin to that of neuropathic pain may explain the cross-benefit of gabapentin in patients with opioid-induced hyperalgesia.

Intraoperative management

Regional anesthesia techniques (including continuous epidural and peripheral nerve catheters) should be strongly considered in a non-opioid driven anesthetic. Providers should consider Toradol and redosing of Tylenol in longer procedures. Ketamine is a useful adjunct due to its useful effect of increasing opioid sensitivity when run at low dose rates (0.2-0.3 mg/kg/hr). It's use may be limited in elderly patients who are at increased risk of experiencing dysphoria/delirium post-operatively or are more sensitive to adverse effects from polypharmacy.

Similarly, methadone given as a single dose of 0.1-0.3 mg/kg (based on ideal body weight) has been reported to significantly reduce post-operative opioid requirements and has been studied extensively in patient's receiving spinal fusion procedures. This has not been studied well however amongst patient's already on methadone/with history of substance use disorder. It may be worth considering

Otherwise, the use of full mu-opioid receptor agonists (fentanyl, hydromorphone) remain important to the management of intraoperative pain. Providers should consider scheduled dosing throughout the procedure balancing the risk of hypotension and respiratory depression seen older patients, those with OSA, and patients with end-organ failure.

Postoperative management

Consider continuing methadone and buprenorphine as part of the post-operative pain management plan. Buprenorphine is unlikely to cause respiratory depression and causes less drug euphoria. Naloxone should not be co-administered due to the risk of causing acute withdrawal.

Providers should continue typical regimens for mild-severe pain post-op (oxycodone, fentanyl, hydromorphone), however higher than normal starting doses of opioids may be required. The typical calculation of milligram morphine equivalents (MME) do not give an accurate sense of equivalent dosing.

Consider post-operative stay in the ICU for pain management and consultation of in-house pain service.