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12 Articles in Volume 12, Issue #5
A-Delta Pain Fiber Nerve Conduction Study Benefits Patients With Spinal Pain
Chronic Pain Management of the Noncompliant Patient
Clinical Applications of Radiofrequency Lesioning for Back and Neck Pain
Current Understanding and Management Of Medication-overuse Headache
Fibromyalgia: An Overview of Etiology and Non-pharmaceutical Treatment Options
June 2012 Pain Research Updates
Junk The Term Narcotics—Call Them Opioids
Managing Adverse Drug Effects in Pain: Focus on Muscle Relaxants
Music Therapy for Pain Management
Perioperative Pain Management in the Opioid-tolerant Elderly Patient: Case Challenge
Practical Tips in the Treatment Of Osteoarthritis of the Knee
Sudden, Unexpected Death in Chronic Pain Patients

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.

Physical Examination
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.

Postoperative Anesthetic Management
In the postanesthesia care unit, when the spinal anesthetic had regressed sufficiently that sensory function in the anterior thigh was present, a femoral nerve block was performed. At this point, the pain numerical rating scale was still 0 and the patient had not experienced pain or required any analgesic medication. A long-acting local anesthetic agent, 30 mL ropivacaine (0.25% with 1:400,000 epinephrine plus clonidine 100 mcg) was injected around the femoral nerve under ultrasound (US) guidance by the anesthesia acute pain service (Figures 1, 2). This nerve block is performed using a sterile technique, with the US probe placed just below the inguinal ligament. The skin is anesthetized with lidocaine, then the block needle was inserted at approximately a 45 degree angle to the skin under the US probe. The needle is kept in plane so that the tip of the needle is visualized penetrating the fascial sheath that surrounds the femoral nerve. Incremental injections are performed watching the perineural space expand with the volume of local anesthetic. The femoral nerve provides sensory innervation to the majority of the knee and this nerve block typically provides excellent pain relief for 12 to 24 hours. Special nursing and physical therapy precautions are needed because the nerve block can impair motor function temporarily, delaying ambulation.10 In addition, the patient was written a prescription for scheduled (not prn) acetaminophen 1,000 mg every 8 hours and a hydromorphone patient-controlled analgesia (PCA) pump 0.5 mg intravenously every 15 minutes. The PCA pump was discontinued on postoperative day 1 and the patient was restarted on her preoperative dose of oral hydromorphone, with additional oral doses for breakthrough pain. Her pain scores were 3 to 6 out of 10 throughout her stay, and she was discharged home on postoperative day 3.

Conclusions
This case report demonstrates several important concepts in acute perioperative pain medicine. First, preoperative multimodal medications are paramount to effective postsurgical pain control. Second, interruption of pain pathways at multiple anatomic levels is optimal. In this case, peripheral nociceptors, spinal pathways, supraspinal signaling centers, and systemic anti-inflammatories all contributed to providing analgesia for this patient. Finally, the opioid-tolerant patient requires special consideration, as her analgesic needs are increased while her opioid safety margin is diminished.

Last updated on: July 2, 2012
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