Anesthesia for Patients with Chronic Pain or Opioid Tolerance

Introduction:

Severe chronic pain is often catastrophic for the affected individuals, causing substantial suffering, health impairment, and low quality of life. Managing chronic pain patients demands careful evaluation and planning to achieve appropriate pain management. A wider adoption of the best perioperative and intraoperative pain management practices is required.

What Is Chronic Pain?

Chronic pain is pain that lasts longer than six months and longer characterized by specific patterns and locations.

What Are Opioids?

Opioids, also called narcotics, are medications used to treat persistent, chronic, or severe pain. Opioids are prescribed to treat chronic body aches, relieve postoperative pain and cancer pain, and alleviate pain associated with automobile injuries, accidents, and traumatic injuries encountered in sports and other activities.

Are Opioids Safe in Relieving Chronic Pain?

Although opioids are part of an effective pain management regimen, they should always be taken under the physician’s supervision to avoid side effects and risk of addiction. Some of the most commonly used opioids are Codeine, Fentanyl, Morphine, etc. The most commonly encountered adverse effects of opioids are:

• Addiction.

• Sleepiness.

• Constipation.

• Nausea.

• Shallow breathing.

• Slowed heart rate.

• Loss of consciousness.

What Is Opioid Tolerance?

Opioid tolerance is characterized by reduced responsiveness to an opioid drug such as Morphine and usually ends up in increasing the doses to achieve the desired effect.

What Are the Perioperative Implications of Chronic Opioid Use?

1. Treating chronic pain with opioids carries risks of side effects and possible drug interactions that need to be monitored in the perioperative settings.

2. Chronic pain patients are more sensitive to painful conditions, making it more challenging to treat them postoperatively. Patients taking opioid medication are more sensitive to pain, and the opioid-induced vulnerability may persist for a longer time after opioid withdrawal.

3. Chronic opioid use leads to the following:

• Central sensitization.

• Increased nociception.

• Opioid-induced hyperalgesia (increased sensitivity towards pain).

1. Preoperative opioid dependency is also a risk factor for uncontrolled and problematic pain after surgery, requiring multiple follow-ups by acute pain services in an academic hospital.

2. Tapering the opioid dose before surgery results in better postoperative outcomes.

3. Reducing the presurgical opioid dosage minimizes the intra- and postoperative opioid dosage and improves postoperative pain management, making the preoperative assessment of patients under chronic opioid use beneficial.

What Are the Measures Taken to Manage Patients with Chronic Pain or Patients with Opioid Tolerance?

1. Preoperative Assessment:

• Complications like opioid-induced hyperalgesia (OIH) and opioid tolerance develop due to the inadvertent use of opioids in the management of non-malignant pain.

• The paradoxical worsening of pain sensitivity without a new injury or exacerbation of an old injury is called opioid-induced hyperalgesia (OIH).

• The OIH and opioid tolerance both result in decreased efficacy of opioid analgesic effects.

• Opioid tolerance may be suspected in all patients treated with opioids for a long time.

• Opioid tolerance may be assumed to be present with a daily intake per oral opioid equivalent of over 72 mg for one month or Morphine intravenously 1 mg/h for one week.

• Patients on long-term opioid therapy should take their usual opioid dose in the morning, on the day of surgery, or as a premedication before surgery.

• For chronic opioid users, at least 30 to 100 percent more opioids than the preoperative daily dose may be required.

• Intraoperatively, opioid-tolerant patients may have much higher-than-expected additional intraoperative opioid requirements and are at an increased risk of awareness.

• Special care should be taken when administering Methadone as it is associated with higher mortality rates due to prolonged QT time, arrhythmias, and interaction with different drugs.

• Special attention should be given to

1. Older patients (>70 years of age).

2. Patients with sleep apnea.

3. Patients under medication that influences Methadone metabolism.

4. Patients with significant underlying diseases (pulmonary, cardiac).

• Methadone should not be increased preoperatively.

• ECG (electrocardiogram) and, if possible, methadone blood concentration should be checked preoperatively.

• If the patients cannot take Methadone orally, half of their daily dose should be administered intravenously.

• Buprenorphine has a relatively longer half-life (25 to 45 hours), slow elimination from the body (two to three days), and slow dissociation rate (166 minutes), which directs gradual decreasing dosage of Buprenorphine four weeks priorly to the surgery, so that Buprenorphine is cleared completely from the body well before surgery.

• The use of a Buprenorphine patch (up to 70 μg h−1) and Buprenorphine sublingually in lower doses than 10 mg (divided into 2 to 3 equal doses) is unlikely to interfere with the use of full opioid agonists for acute pain management and should also be continued in the perioperative period with additional opioids as required.

2. Opioid Sparing Techniques:

• To reduce the physiological consequences of chronic opioid usage like hyperalgesia and tolerance, the concept of “multimodal” or “balanced” analgesia has been developed (a combination of analgesic medication and techniques with different sites or mechanisms of actions in order to improve analgesia while reducing the requirements for opioids and thereby lessening adverse effects).

• Opioid-sparing techniques will be of great importance in patients taking strong opioids.

• The most important components of multimodal analgesia are regional and local anesthetic pain relief, which can be applied wherever possible to reduce opioid needs.

• Acetaminophen is an important non-opioid analgesic in postoperative analgesia for preventing nausea and vomiting when used preoperatively.

• Perioperative Ketamine decreases postoperative pain scores, reduces postoperative opioid requirements, and reduces postoperative nausea and/or vomiting. It also reduces the risk of chronic pain in the first three to six months after the surgery.

• Gabapentinoids like Pregabalin have a role in opioid-tolerant patients as an opioid-sparing adjunct.

• Lidocaine has been demonstrated to decrease pain scores and opioid analgesic consumption in patients with poorly controlled pain, previous substance abuse, or when an epidural is contraindicated or failed, as in laparoscopic surgery or trauma.

3. Organization of Acute Pain Services (APS) And Transitional Pain Services:

• The effective relief of pain is of the utmost importance in treating patients. The treatment of complicated pain patients with chronic pain is not possible without the contribution of acute pain services (APS).

• The pain treatment instituted by the acute pain services induces a reduction in pain intensity in both medical and surgical patients.

• The problem of chronic pain after major surgery will be addressed through multidisciplinary, integrated care beginning preoperatively, extending postoperatively, and continuing after hospital discharge. This is called transitional pain service.

• The transitional pain service aims to offer effective treatment for patients at a high risk of developing chronic postsurgical pain after undergoing a variety of surgical procedures.

Conclusion

Patients with chronic pain deserve special attention and require long-term hospitalization and multiple appointments with healthcare providers after discharge from the hospital. Such patients require a close follow-up in relation to anesthesia, pre-intra, and postoperative care. Assessing the preoperative risk and taking prudent steps in minimizing opioid usage with appropriate measures will fetch better results.