Why anesthesiologists need to care about the way chronic pain is managed

Alexander J. Clark 0 1 Christopher C. Spanswick 0 1 0 C. C. Spanswick, MBChB Department of Anesthesia, University of Calgary , Calgary, AB, Canada 1 A. J. Clark, MD (&) Department of Anesthesia , Pain Management and Perioperative Medicine, Dalhousie University , Halifax, NS, Canada Anesthesiologists are now frequently considered specialists in perioperative medicine. This view reflects changes in practice that have evolved over the last 20 years and are currently exemplified in many departments, including those specializing in pain medicine, pain management, and perioperative medicine. Postoperatively, many patients continue to receive inadequate analgesia, and poor pain control is the leading cause of post-discharge visits to the emergency room and early re-admission to hospital after surgery.1 Patients with preoperative chronic pain, especially those receiving opioids, have a high rate of unsatisfactory perioperative pain control.2 Chronic pain in Canada affects more than one in five Canadians.3 Consequently, many patients who come under our care suffer from chronic pain. These patients are more likely to be opioid-dependent and receiving one or more medications that act on the central nervous system. Patients' complex medication profiles and their concurrent anxiety and mood disruption can have a substantial impact on the perioperative care that the anesthesiologist provides. Herein, we consider some of the special issues that anesthesiologists should understand concerning the management of patients with chronic pain in the perioperative setting. - Preoperative anxiety and catastrophizing (i.e., a construct that includes fearing the worst, rumination, and magnification of symptoms in this case pain) predict acute postoperative pain, and there is evidence that both may play a role in the development of chronic postsurgical pain.4,5 In addition, both factors have been implicated as predictors of analgesic use in the postoperative period. Catastrophizing also predicts poor quality of life after surgery.5 Preoperative anxiety and pain sensitivity have been shown to be independent predictors of propofol and sevoflurane requirements in general anesthesia as well as risk factors for poor pain control in the postoperative period.6 The most important predictor of postoperative pain in ambulatory surgery is the presence of preoperative pain. Other factors that may also impact anesthesiologists care include the anticipated degree of postoperative pain and the patients high preoperative expectations regarding postoperative analgesia.7 Patients with preoperative pain, both related and unrelated to the surgical site, are at significant risk of developing chronic pain at the site of surgery. The longer the duration and higher the severity of the preexisting pain, the more likely that chronic postsurgical pain will develop. The rates of chronic postsurgical pain vary, for example, 30-50% of patients experience chronic pain following amputation, 20-30% following breast surgery, 30-40% following thoracotomy, and 10% following inguinal hernia repair.8 Patients with chronic pain report poor mental health-related quality of life and more severe psychosomatic dysfunction before surgery and three months after surgery.9 A recent review clearly indicates that preoperative pain, anxiety, age, and type of surgery are four significant predictors of postoperative pain.10 By being aware of these factors and taking them into account, the anesthesiologist may have an impact not only on pain in the immediate postoperative period but also on the longer term recovery. The opioid-tolerant patient with chronic pain The opioid-tolerant patient requiring acute pain management in the perioperative period presents the anesthesiologist with considerable challenges. Treatment goals should be directed toward providing relief from acute postsurgical pain, preventing opioid withdrawal, and continuing appropriate preoperative opioid strategies through to discharge. The patients regular opioid medication must continue in the short term; however, to provide appropriate postoperative analgesia, there is often a need to increase the doses of opioid medication substantially and incorporate a prescription for non-opioid and adjuvant medication. In addition to managing opioid tolerance, there is always a possibility of opioid-induced hyperalgesia11 requiring additional pharmacological intervention. Discharge planning should commence before the time of hospital admission, and both the anesthesiologist and the patient should have clear expectations for a limited duration of additional opioid augmentation and a welldefined plan for a reduction in opioid medication soon after the acute phase of recovery.12 Communication with the patients primary care physician/continuing care physician is of paramount importance to ensure uninterrupted quality of care. Opioid-tolerant patients have much higher opioid requirements post-surgery. For example, patients undergoing total knee arthroplasty and taking C 30 mg of morphine equivalents po per day receive up to five to six times the usual dose of opioids while in the postanesthesia care unit (PACU) and within the first 48 hr after discharge from the PACU.2 Opioid-tolerant patients have higher pain scores than opioid-naive patients within the first 24 hr of discharge from the PACU.2 The patients usual dose of opioid medication should be administered with appropriate conversions from oral to intravenous equivalents (if necessary), and additional opioid requirements should be anticipated and provided to address the additional pain of the surgical procedure. It has been suggested that patient-controlled analgesia (PCA) with higher bolus doses of opioids and shorter lockout intervals should be used in the opioid-tolerant patient.13 Nevertheless, use of PCA can lead to very challenging situations in the patient who has previously shown loss of control over their opioid medication. In this situation, a PCA needs to be used with care. In the authors experience, a time-contingent mode of administration of opioid medication is often best, with frequent reassessment and clear communication of the expected duration of opioid dose and use. The perioperative anesthesiologist needs to understand the distinction between addiction, dependence, and tolerance as it relates to the use of opioids. It is wise to consult with an addiction specialist, especially if the patient is taking methadone or buprenorphine for addiction prior to surgery. For those individuals addicted to opioids, the perioperative period is not a time to initiate weaning.14 The ANZAC Acute Pain Management: Scientific Evidence document provides a valuable management plan (http://www. anzca.edu.au/resources/college-publications/pdfs/Acute% 20Pain%20Management/books-and-publications/acutepain. pdf; (accessed June 11th, 2013). The role of multimodal analgesia Perioperative multimodal analgesia, defined as the use of different (...truncated)