Perioperative Management of the Opioid-Tolerant Patient
Suppose you have a new patient who presents with long-standing knee pain from osteoarthritis; she has finally decided she wants a total knee arthroplasty.
She is currently taking 480 mg of oxycodone daily, prescribed by her primary care provider for the knee pain. Should you to wean her from the opioid preoperatively? What about the possibility of withdrawal symptoms and/or excruciating pain?
And are you sure she’s even taking that much oxycodone daily?
Defining Opioid Tolerance
Asokumar Buvanendran, MD, Professor, Department of Anesthesiology, Rush University Medical Center, Chicago, Illinois, posed those questions to attendees at the recent ICJR South/RLO Course, where he discussed options for managing the opioid-tolerant patient who is scheduled for joint replacement therapy.
Dr. Buvanendran said opioid tolerance is a predictable pharmacologic adaptation to the drug. The degree of tolerance depends on duration of exposure, daily dose requirement, and receptor associated/disassociated kinetics (how much of the drug binds to the opiate receptors).
In general, opioid tolerance can develop as early as 2 weeks after the start of therapy. The morphine equivalent of 1 mg intravenously (IV) or 3 mg orally per hour for 1 month is considered to be high-grade opioid tolerance.
So we know the patient in the above scenario falls into that category – her oxycodone dose converts to 960 mg/day of morphine equivalents, or 40 mg/hour. What should you do preoperatively?
The severe preoperative pain this patient is experiencing is likely to lead to unbearable acute postoperative pain if she is weaned from her current oxycodone dose. That would put her at increased risk for chronic persistent pain after surgery.
So weaning an opioid-tolerant patient from the drug preoperatively is not the answer. Dr. Buvanedran said the real answer is to continue the preoperative opioid regimen and then add adjuvant medications in an effort to reduce the preoperative pain to 3 or less (on a scale of 1 to 10, with 10 being the worse pain).
Before doing anything, though, confirm that the patient is taking the amount of oxycodone she says she is taking. This can be done with a simple urine test. A study published in the Journal of Addiction Medicine in 2010 found that 5% of patients who were supposedly taking prescription opioids were found to be negative for the drug.
The urine test can also tell you if she is taking any illicit drugs. According to a 2007 study in Pain Management, 20% of patients taking opioids for chronic pain are also self-medicating with illicit drugs.
When you take this patient to the operating room, maintain her baseline opioids while also adding opioid-independent pain medication, such as ketamine or dexmedetomine and local infiltration of the surgical site with an anesthetic, to help manage postoperative pain.
Research has shown, Dr. Buvanendran said, that a small dose of ketamine given IV can decrease postoperative opioid use, as well as the time to the first request for postoperative analgesia.
The patient’s oral opioid dose should be converted to an intravenous morphine dose, Dr. Buvanendran said, generally at a 3:1 ratio (3 mg oral to 1 mg IV). He recommends giving 50% of the dose during the surgical procedure and dividing the remaining 50% by 24 and giving that amount hourly over the next 24 hours.
Continue the baseline opioid dose postoperatively, but be prepared: An opioid-tolerant patient may need 2.5 to 3 times the normal amount of opioids in the postoperative period to control pain, Dr. Buvanendran said.
He also recommends a multimodal approach to analgesia that includes IV PCA with hydromorphone, fentanyl, or sufentanil, as well as IV ketamine at 2-10 mg/kg/minute, titrated for analgesia.
Also, be alert for opioid withdrawal symptoms, including:
- Nausea, vomiting, diarrhea
- Papillary dilation, piloerection or sweating
- Muscle aches
Opioid-tolerant patients present challenges for the orthopaedic surgeon. There is no evidence that discontinuing opioids before surgery is beneficial to the patient or the surgeon. The strategies suggested by Dr. Buvanedran will help make the perioperative period more comfortable for the opioid-tolerant patient.
Dr. Buvanendran’s presentation is available on ICJR.net.
All presentations from ICJR South/RLO Courses are available here.