Improving Pain and Outcomes in the Perioperative Setting

The Growth of Unidimensional Pain Assessment Tools

A subjective and personal experience, pain remains difficult to quantify within the confines of empirically based medical tradition. Regardless of this challenge, however, management still necessitates accurate and timely assessment, particularly in the perioperative patient. The promotion of pain as a fifth vital sign in the 1990s has been criticized for its potential unintended consequences, however, this initiative also highlighted the limitations of our assessment tools and encouraged the development of improved methods to evaluate pain and its modifying factors.

As the Numeric Rating Scale (NRS) and Visual Analog Scale (VAS) became common standards for the regular interval assessment of patients in the perioperative setting, it was evident that these self-reporting tools were superior to health professional estimates and minimized the impact of cultural and racial bias. Multiple studies comparing the NRS and VAS scales consistently demonstrated similar sensitivities and superiority to the Verbal Rating Scales (VRS) in their ability to detect differences in both acute and cancer pain. Temporally-based assessments and measurement of pain trajectory have also become increasingly commonplace.

However, it has become increasingly evident that single-dimension pain tools lack the sophistication needed to guide effective therapies. In fact, a large retrospective review of medical records before and after the implementation of the “Pain as the 5th Vital Sign” initiative did not find any improvement in quality of pain care, especially with individuals with severe pain documented on NRS. Clinicians and investigators increasingly appreciated the impact of anxiety, depression, addiction, and the psychosocial context of the experience. For example, in the primary care setting, the NRS was found to have only modest accuracy for identifying patients with clinically important pain, defined as pain that interferes with function or intense enough to require a physician visit. Single dimension pain tools were inherently subjective and also not generalizable. Despite qualifying descriptions, patient A’s pain score of 4 may equate to patient B’s pain score of 6. These limitations in the unidimensional assessment of perioperative pain necessitated a new approach.

The Importance of Multidimensional Assessment

In response to these shortcomings, a focus on multidimensional assessment models has grown to evaluate properly the complexity, the modifying factors, and the associated disability of pain. Traditionally used in the chronic pain setting, tools such as the McGill Pain Questionnaire and Brief Pain Inventory (BPI) have been further validated in the postoperative setting. The McGill Pain Questionnaire provides a description of not only the intensity, but also quality of pain a patient is experiencing and can be used to monitor the efficacy of interventions and pain trajectory (ideal for the perioperative setting). The BPI accurately assesses pain severity and self-perceived functional limitations. Similar to the McGill Pain Questionnaire, BPI can monitor responsiveness to both behavioral and pharmacologic interventions. Another tool, the Multidimensional Affect and Pain Survey (MAPS) was designed to assess three main clusters: somatosensory pain, emotional pain, and well-being. The preoperative use of MAPS has shown to predict postoperative opioid usage. An additional instrument, the Pain Catastrophizing Scale (PCS) is an important predictor of functionality and disability. PCS scores measure catastrophic thinking related to pain and have been shown to correlate significantly with postoperative pain scores, particularly during activity following various types of surgeries. Lastly, it is well known that concomitant psychological factors such as anxiety and depression modulate the experience and perception of pain in the perioperative period and the chronification of acute pain. Consistently, preoperative anxiety as measured by the Hospital Anxiety and Depression Scale (HADS) and State-Trait Anxiety Inventory have also been shown to correlate with the severity of postoperative pain.

An Increased Focus on Perioperative Functional Outcomes

The most valuable assessments in the perioperative period may be those that measure function along with pain. The evaluation of functional limitation during required postoperative physical activities is noted as critical to the recovery trajectory. For example, measuring whether pain limits a patient’s ability to take deep breaths, cough after thoracic surgery, or ambulate after orthopedic surgery may be more important to overall outcomes than simply measuring pain during rest. With a growing focus on function and recovery along with the psychological comorbidities associated with pain, the use of these multidimensional tools has assumed a prominent role in guiding the prediction of pain in the perioperative period.

Table 41.1 is a summary and comparison of common multidimensional pain outcome tools that we recommend to assess and predict pain more fully in perioperative period.

Table 41.2 provides appropriate clinical settings and populations for commonly used psychological assessment tools.

As shown, there are a variety of useful and predictive tools that can be used in the perioperative period with the opportunity to tailor choices to the particular needs of both patient population and health system. We recommend the use of these multidimensional pain assessments in conjunction with functional activity outcomes to assess complicated patients properly in the perioperative setting.