A patient who has been on maintenance oral methadone 80mg once a day for a history of opioid abuse is now scheduled for an open colectomy in one week. Which of the following analgesic management options is LEAST recommended:
A. Continue methadone therapy, converting methadone to IV with a 2:1 or 3:1 PO:IV ratio once a day while patient is unable to tolerate PO.
B. Offer regional anesthetic technique such as thoracic epidural for postoperative pain management with local anesthetic and hydrophilic opioid.
C. Add acetaminophen, nonsteroidal anti-inflammatory agent, and dexamethasone as multimodal analgesics.
D. Use higher doses of opioids to counteract opioid tolerance
Correct Answer: D
While patients on opioids can become tolerant within 2-3 weeks of potent opioid consumption and will require higher doses of opioids to achieve an analgesic effect, patients who undergo a bowel surgery would benefit from minimizing any further escalations of their opioids. Tolerance to the side effects of opioids (respiratory depression, bowel dysmotility) occurs much slower than tolerance to opioid’s analgesic effects. Therefore, use of higher than baseline dose of opioids will not be favorable for enhanced recovery after bowel surgery. The use of non-opioid analgesic adjuncts (acetaminophen, NSAIDs, gabapentinoids) can be considered, but good regional analgesia, whether it be in the form of a thoracic epidural, bilateral thoracic paravertebral catheters or bilateral TAP (transversus abdominis plane) catheters can be considered to reduce the need for opioid consumption. In patients who have been on high dose of opioids for maintenance therapy (such as methadone), the medication should be continued to avoid withdrawal in these patients. In a patient who is NPO, methadone can be converted to IV in order to be delivered. IV methadone has a very quick onset, and depending on the dose, a very prolonged analgesic effect. As the doses of PO methadone increase, the conversion ratio from PO:IV also escalates. Therefore, at lower doses, a 1:1 or 2:1 ratio can be used. However, with high methadone doses (>100mg/day), consider dosing ratios of 4-10:1. The literature on methadone conversion is sparse.
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