The onus for the identification of opioid-dependent patients rests with the surgical team, preoperative evaluation staff, and anesthesia team (Table 56-15: Surgical Guidelines for Perioperative Pain Management of Opioid-Tolerant Patients).
- Preoperative management involves determining the patient's “baseline” opioid requirement and instruction to the patient to take his or her normal opioid dose on the day of surgery.
- Patients maintained on methadone should continue their “baseline” dose throughout the perioperative period. Patients receiving >200 mg/day of methadone may develop a prolonged QT interval, which places them at risk for torsades de pointes. (A baseline electrocardiogram should be obtained.)
- Full antagonists (naloxone, naltrexone) and the partial agonists–antagonists (nalbuphine, pentazocine, butorphanol) should be avoided because they precipitate withdrawal symptoms in opioid-dependent patients.
- Intraoperative management of opioid-dependent patients requires the prudent use of fentanyl, morphine, or hydromorphone to provide effective intraoperative anesthesia and postoperative analgesia and to prevent opioid withdrawal. This requires the administration of the patient's “baseline” opioid requirement plus his or her intraoperative requirements secondary to surgical stimulation.
- Because of chronic opioid administration, opioid doses may need to be increased 30% to 100% vis-à-vis the opioid-naive patient.
- The optimal intraoperative dose of opioid varies considerably from patient to patient; therefore, monitoring intraoperative vital signs such as heart rate, pupil size, and respiratory rate can be useful and allows the clinician to avoid the negative consequences of overdosing or underdosing the patient with opioid.
- Titrating fentanyl, morphine, or hydromorphone to a respiratory rate of 12 to 14 breaths/min and a moderately miotic pupil is recommended.
- It is also recommend that patients who are receiving chronic methadone therapy may receive an additional intraoperative dose of 0.1 mg/kg IV, which can be titrated to hemodynamic effect and pupillary response.
- Postoperative Management
- Upon arrival to the recovery room, IV opioids may be administered on an “as needed” basis; however, initiation of an IV PCA opioid with both a basal and incremental (bolus) dose minimizes the risk of breakthrough pain.
- Nonopioid coanalgesics (low-dose ketamine) are opioid sparing and should be part of any multimodal perioperative pain management regimen in opioid-dependent patients.
- Regional anesthesia (peripheral nerve blockade, epidural analgesia) is highly recommended in this patient population.
- Careful monitoring of the patient for excessive sedation and respiratory depression is mandatory, and caregivers in the recovery room and on the postsurgical units should be alerted to the potential risk for respiratory depression when parenteral and neuraxial opioids are combined.