Postoperative Pain as a Spectrum: Treatment Strategies
Among the generally recognized risk factors for persistent post-surgical pain are anxiety, catastrophizing, preoperative pain, acute postoperative pain, pre-existing opioid use, and depressive symptom
In a talk titled “Preventing persistent post-surgical pain and promoting opioid cessation after discharge,” given at the annual meeting of the American Academy of Pain Medicine, March 15-19, 2017, in Orlando, Florida, Jennifer Hah, MD, MS, an anesthesiologist and pain specialist at the Pain Management Center at Stanford Health Care, California, provided an overview of postoperative care, its shortcomings, and current research in the field.1
“When we think of pain after surgery, we often think of acute vs chronic pain, but perhaps there is more of a continuum with no clear delineation,“ stated Dr Hah. A number of shortcomings are associated with systematic reviews and meta-analyses on postoperative care. These include highly variable dosing protocols in studies investigating the effects of gabapentin and pregabalin, as well as treatment duration and drug bioavailability (which was shown to range from 3% to 90% for gabapentin), all of which can influence treatment outcomes. In addition, evidence is scarce regarding the efficacy of nonsteroidal anti-inflammatory agents (NSAIDs), ketamine infusions, or local anesthetics on postoperative pain.
What treatments have shown efficacy in relieving post-surgical pain? Results from an evidence-based review indicate that thoracic epidural infusions and paravertebral nerve blocks provide a reduction in persistent pain related to breast cancer surgery for a period lasting from 2.5 to 12 months after surgery.2 In addition, these treatments were found to provide an opioid-sparing effect, thus decreasing the incidence of opioid-related adverse events. Another review that looked at the efficacy of epidural anesthesia on post-thoracotomy pain showed that the number to treat in order to prevent chronic pain was 4.3
“What else can we add to the picture [as these treatments all belong to the local analgesic realm]?” asked Dr Hah. A 3-month cognitive behavioral-based physical therapy regimen initiated 6 weeks after surgery led to reductions in pain and pain-related disability in patients undergoing lumbar spine surgery for chronic pain.4
“Is pain resolution more than pain intensity? I would hope so,” said Dr Hah. The high variability of postoperative pain is thought to partly underlie the discrepancies in results across studies. To palliate this issue, Dr Hah and her colleagues sought to ameliorate the way in which patients are classified, using data mining algorithms. This approach led to the identification of 2 patient clusters: patients with low- and high-pain.5 The investigators examined postoperative pain trajectories for a period of 10 days following surgery in 106 patients.5 Upon stratification by surgery type, clusters were found to separate patients in a 50:50 ratio. This categorization, achieved with a data mining algorithm, was shown to predict both pain- and opioid cessation with a highly significant threshold. The researchers hope to develop additional biomarkers to identify patients at risk for prolonged pain and opioid use after surgery.
Among the generally recognized risk factors for persistent post-surgical pain are anxiety, catastrophizing, preoperative pain, acute postoperative pain, pre-existing opioid use, and depressive symptoms. Patients taking illicit opioids pre-operatively were found to be at higher risk for prolonged pain.5 Extensive literature reflects this trend: in a study focusing on veterans, non-medical prescription opioid use was associated with pain interference.6 Another study in primary care clinics indicated an association between self-reported opioid use and chronic pain,7 and in the US adult population as a whole, non-medical prescription analgesic use is significantly associated with pain.8
Anxiety sensitivity, in which patients feel that unusual body sensations may harm them, is usually perceived as negative. However, anxiety sensitivity was found to predict short duration of pain.9 This counterintuitive finding may be due to the fact that patients are so focused that they are more compliant than other patients with following rehabilitation directions, and taking their medications as directed.
A number of strategies have been proposed to address postoperative pain, including “transitional pain service,” which is instituted by identifying patients prior to surgery who are at risk for prolonged pain and opioid use following surgery.10 In those patients, enhanced communication and close monitoring may prevent a transition from acute to chronic postoperative pain.