Perioperative Pain Management in the Opioid-tolerant Elderly Patient: Case Challenge
History: A 76-year-old woman is scheduled for total knee arthroplasty on her right knee. The patient has a history of severe osteoarthritis of her right knee that is limiting her ability to exercise. Her exercise limitations have impaired her ability to socialize with her peer group. She experiences significant knee pain when climbing stairs or walking more than 50 yards. The patient has trouble sleeping on days when her knee pain is worse. In addition, she has experienced mild depression at times, which she feels is at least partially attributable to her pain symptoms. She has acquaintances that have undergone knee arthroplasty, and now have improved function. The patient hopes the surgery will allow her to have a more active lifestyle and possibly improve her depression.
The patient is a nonsmoker, with a history of hypertension, mild renal insufficiency, and fibromyalgia. The patient’s fibromyalgia has been managed with gabapentin 300 mg by mouth twice daily and, in addition, her primary care provider has placed her on low-dose hydromorphone 2 mg by mouth twice daily to help manage her fibromyalgia symptoms. In general, opioids are not considered helpful in the treatment of fibromyalgia, but are used as a treatment of last resort. Because of her renal insufficiency, non-steroidal anti-inflammatory drugs are contraindicated.
The patient is a mildly obese woman who appears her stated age. She walks with a limp secondary to her knee pain. Using a numerical rating scale (0, no pain; 10, worst pain) the patient describes her knee pain as 4 out of 10 on average, and 8 out of 10 on bad days. The patient’s heart, lung, and airway examinations are within normal limits. Her blood pressure in the preoperative holding area is slightly elevated compared to her baseline blood pressure. Her American Society of Anesthesiologists (ASA) class is designated a II, which means she has mild, compensated systemic disease (hypertension, renal insufficiency).
Preoperative Anesthetic Management
After a preoperative evaluation, the patient was given an option of either a general or spinal anesthetic. Although there are no studies that have shown a mortality difference between these options, there are some advantages to the spinal anesthetic, including lower intraoperative blood lost and a lower incidence of postoperative deep venous thrombosis.1 Other major advantages of spinal anesthesia compared to general anesthesia are more stable blood pressure and heart rate, and better early postsurgical pain control. This latter aspect is due to the slow dissipation of the spinal anesthetic over several hours, allowing a gradual transition to the postoperative analgesics.
Patients undergoing major orthopedic surgery also receive several preoperative medications integral to a pain management protocol. These medications commonly include a 1,000 mg oral dose of acetaminophen, which has been shown to lower postoperative opioid requirements2-4; 200 mg oral dose of celecoxib (Celebrex), a selective cyclooxygenase-2 inhibitor that decreases inflammation without affecting platelet or gastric mucosal protection5; and dexamethasone 5 mg intravenous, which will decrease wound inflammation, postsurgical pain, and nausea.6 In addition, as part of the pain protocol, the patient is given an oral dose of gabapentin 900-1,200 mg, which has been shown to reduce the postoperative opioid requirement by up to 35% and reduce opioid-related side effects.7
There were two other important topics that were discussed with this patient concerning her current opioid regimen. Clinically, a patient who has been on a low-dose opioid will need a large increase (200%-400%) in the usual requirement for postoperative pain care.5 In addition, the therapeutic window of opioids is narrowed, meaning that the opioid dose needed to provide analgesia is very close to the dose that causes significant respiratory depression. Our patient was counseled that her postoperative opioid requirement would be higher for 2 to 3 weeks and that it was likely she might have periods of significant pain postoperatively. We also recommended that the patient have a femoral nerve block performed by our department’s acute pain service. The patient chose to have a spinal anesthetic, a modified pain protocol regimen was given because of the patient’s renal insufficiency (celecoxib was withheld), and she consented to have a postoperative femoral nerve block.
Intraoperative Anesthetic Management
In the operating room, the patient received a spinal anesthetic using isobaric bupivacaine 0.5%, a long-acting local anesthetic that provides prolonged pain relief after the surgical procedure. Included in the spinal anesthetic was a synthetic opioid, fentanyl, which binds to opioid receptors in the spinal cord and gives additional long-lasting pain relief beyond the effect of the local anesthetic. As part of a pain treatment protocol for joint replacement, the patient received IV ketamine—an N-Methyl-D-aspartate (NMDA) receptor antagonist—an agent which can improve long-term pain control, particularly in opioid-tolerant patients.8 As is our usual practice, the patient was sedated with the benzodiazepine midazolam (Versed) and propofol (Diprivan), a major sedative hypnotic, for the duration of the procedure. She also received a small dose of the anti-inflammatory drug dexamethasone. At the end of the procedure, the wound was infiltrated with long-acting local anesthetic. In addition, after the wound was closed, the surgeon performed a periarticular injection of 30 mL of ropivacaine (Naropin, 0.5%). High volumes of local anesthetic around the wound have been shown to have an anti-inflammatory effect.9 If this patient did not have renal insufficiency, the surgeon might also include 15 mg toradol (Ketorolac) added to the local anesthetic to further reduce periarticular inflammation.