Acute postoperative pain can lead to persistent postoperative pain in 10%-50% of patients. Effective pain management before, during, and immediately after surgery can prevent this development.
Defining the Problem
Perioperative pain management refers to actions before, during, and after a surgical procedure that are intended to reduce or eliminate postoperative pain before the patient is discharged after the procedure. Preoperative pain management strategies involve many of the same techniques as postoperative pain management, with the one exception being the temporal relationship to the surgical procedure. Intraoperative pain techniques may involve multiple systemic pharmacologic agents and, in some cases, regional pharmacologic therapy (epidural administration and selective peripheral nerve blockade). Chronic postsurgical pain is defined as pain lasting more than 3 to 6 months after surgery. The pain differs in quality and location from pain experienced prior to surgery, and is usually associated with iatrogenic neuropathic pain caused by surgical injury to a major peripheral nerve.
Scope of Risk: Assessing Pain
Approximately one-half of older patients who have unmanaged postoperative pain continue to experience that same pain chronically 1 year after discharge. Children are also at risk for inadequately managed postoperative pain. Some of the more prominent factors for this include inability to assess pain and concerns regarding addiction.
Kids forced to endure pain for fear they’ll become addicted?
Since pain is experienced differently in all patients, it is imperative to use appropriate pain assessment scales along with a focused physical examination for defining and rating pain in patients. Age, cognitive status, language barriers, and cultural background are some of the key considerations.
The Pain Pathway
Multimodality therapy is controversial and has had mixed results in the setting of postoperative pain.
In order to adequately address the different pharmacologic options, it is important to review the pain pathways and how each of the pharmacologic options presented here can affect transduction, transmission, modulation, and perception of pain (Figure 1).
- For patients who are on chronic opioid therapy prior t o surgery, there are certain evidence-based approaches to provide adequate analgesia in the postoperative period. These include:
- Ensuring the patients receive their maintenance dose of opioid prior to surgery
- Utilizing patient-controlled analgesia (PCA)
Considering the amount of maintenance opioid the patient takes preoperatively and adjusting the postoperative doses of opioids accordingly to prevent inadequate pain management due to patient tolerance with “usual or standard” postoperative opioid doses.
One example of the need to adjust opioid dosages is the oncology patient who is currently taking 160 mg of controlled-release oxycodone every 12 hours, in addition to breakthrough doses of oxycodone on a daily basis. In this case standard doses of postoperative opioids may be insufficient to allow the patient to achieve comfort or pain relief. Higher doses of opioids are generally necessary, accounting for the patient’s physical tolerance to opioids.
The current literature is inconclusive with regards to the phenomenon of opioid-induced hyperalgesia, yet it should be part of any differential diagnosis when caring for patients who experience worsening of pain when administer ed opioids.
Anti-inflammatory agents are also excellent options for many postoperative patients. Non-steroidal anti-inflammatory agents (NSAID) are known to be opioid-sparing in the postoperative setting. NSAIDs aid in decreasing inflammation through inhibition of the cyclooxygenase (COX) enzyme system—more specifically, COX-2, which is stimulated by multiple proinflammatory cytokines, including interleukin (IL)-1alpha, IL-1beta, tumor necrosis factor alpha, and lipopolysaccharide. These cytokines induce COX-2 to produce prostaglandin E2, an inflammatory mediator that leads to progression of inflammation and pain. Inhibition of the COX-2 enzyme is how a majority of NSAIDs help t o decrease pain.
However, one prominent side effect of NSAIDs—increased risk of bleeding—is a concern for the perioperative patient, especially those undergoing procedures involving solid organs. Risk of bleeding is especially a concern with ketorolac when used for greater than 5 days, in the elderly, and at higher doses.18 There is long-standing controversy regarding the use of NSAIDs in patients undergoing orthopedic procedures (hip and knee arthroplasty, spinal fusions, etc) because of concern that NSAIDs impair bone healing. A recent review of available NSAIDs, including meloxicam, celecoxib (Celebrex), indomethacin, ibuprofen, and aspirin yielded no robust data that these agen ts are an absolute contraindication in orthopedic procedures.19 The full extent of delayed healing or the time-course of fracture development is not well defined. Other potential risks of NSAIDs include renal toxicity and thromboembolitic complications.
Local anesthetics have a large role in the intraoperative and postoperative pain management environments. Local anesthetics offer the advantage of decreased peripheral sensory input (transduction). The mechanism of action for local anesthetics is by stabilizing nerve membranes and decreasing the rate of depolarization, therefore decreasing transduction. There are data from the orthopedic literature on the use of single peripheral nerve and plexus blocks for hip and knee procedures, which allows for earlier mobilization and decreased opioid consumption postoperatively.
The use of gabapentin and pregabalin (Lyrica) in the perioperative period is relatively new compared to the use of opioids and NSAIDs, but could be beneficial in some cases. There is promising data on the use of gabapentin and pregabalin preoperati vely to decrease postoperative pain. Gabapentin and pregabalin bind to the alpha2delta calcium channels that are widely distributed in the CNS and peripheral nervous system. By reducing the hyperexcitability of the dorsal root ganglion activated by surgery, gabapentin and pregabalin may prevent the development of chronic postsurgical pain.
Preventing Chronic Pain
As noted, a growing concern among pain practitioners is that undertreated postoperative pain will lead to the development of chronic pain.
Their evidence, methods, and recommendations are available online at http://www.postoppain.org/