Perioperative Pain Plan: Why is it Needed
More than 45 million surgical procedures are performed in the United States each year.1 Despite improved understanding of pain mechanisms, interpretation of pain signals, and development of new analgesic techniques,2 the under-treatment of postoperative pain continues.3 In fact, it has been estimated that acute postoperative pain will develop into persistent postoperative pain in 10% to 50% of individuals after common operations.4 Since chronic pain can be severe in up to 10% of these patients, persistent postoperative pain represents a major clinical problem—affecting at least 450,000 people each year. Today, many hospital systems are graded based on how well they manage postoperative pain. Therefore, effective and timely preemptive pain control not only benefits patients, it can improve hospital ranking and reduce health-care expenditures.5
Defining the Problem
Pain, as defined by the International Association for the Study of Pain (IASP), is an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage.6 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.2 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.3
Scope of Risk: Assessing Pain
Patients at the highest risk for untreated postoperative pain include the elderly and those with lower socioeconomic status. Many of the reasons for this stem from lack of patient understanding regarding acute perioperative pain, lack of appropriate patient education regarding the management of perioperative pain, and inability to afford the treatments for that perioperative pain from pharmacies and other postoperative health care providers. Approximately one-half of older patients who have unmanaged postoperative pain continue to experience that same pain chronically 1 year after discharge.7 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.8
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. There are many different validated pain-rating scales available to “objectively” quantify a patient’s pain. Table 1 lists some of assessment scales.9-13 Each of these scales, and others not listed, are validated assessments in specific patient populations. For example, a patient with advanced dementia would be most appropriately assessed for pain using the pain assessment in advanced dementia (PainAD) scale rather than a visual analog scale (VAS), as a VAS requires the patient to be able to interact with the assessor and reliably point on the scale to determine how much pain he or she is experiencing. The PainAD scale relies on mostly non-verbal assessments in order to calculate the patient’s pain. It is also important to note that not all scales have the same numerical rating of pain. The VAS rates pain from 0 to 10, while the neonatal infant pain scale (NIPS) rates pain from 0 to 12.
Using the same assessment scale throughout the perioperative period has multiple advantages. The ability to show trends during the preoperative and postoperative period allows the clinician to direct pain therapies based on efficacy as determined by the patient. If multiple assessment scales are used, it can lead to inappropriately high or low scoring of the patient’s pain because many of the validated scales do not use the same metrics to evaluate for pain. Consistencies in pain assessment scoring and following the patient score trends provides invaluable data for the clinician managing perioperative pain.
The Pain Pathway
Multimodality therapy is controversial and has had mixed results in the setting of postoperative pain.2 However, it is important to see how the concept of multimodal therapy is assembled, the different aspects of multimodal therapy, and how they each relate to a different facet of perioperative pain management. Non-pharmacological methods include physical therapy, music or art therapy, biofeedback, and a host of other modalities not covered in this review.
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).14 Transduction involves a noxious stimulus (mechanical and/or thermal in nature) causing activation of A-delta or C fibers in peripheral nerves. These nerve impulses are then transmitted though A-delta, which are larger diameter myelinated nerve fibers, and C fibers, which are smaller-diameter unmyelinated nerve fibers, from the periphery to the dorsal horn within the spinal column where they synapse with the spinal tracts and ascend into the brain.
Modulation occurs within the dorsal horn and within the brain. (Thalamus, somatosensory cortex, and periaqueductal grey matter are noteworthy landmarks within the brain that aid in localization of pain.) Modulation involves the amplification or dampening of pain signals from the periphery within the central nervous system (CNS). This is a prime target for many of the non-pharmacologic and pharmacologic treatments used in management of pain.
Perception of pain takes transduction, transmission, and modulation and combines that with the patient’s previous experiences of pain and emotional or psychological aspects of pain sensation.
Opioids are effective pain management tools that can be used during the preoperative, intraoperative, and postoperative period (Table 2). However, opioid use is also associated with postoperative nausea, vomiting, pruritus, urinary retention, and respiratory depression. For patients who are on chronic opioid therapy prior to surgery, there are certain evidence-based approaches to provide adequate analgesia in the postoperative period.15 These include: