Significant progress in the management of postoperative pain has been made since the 1990s. Increased awareness of the undertreatment of postoperative pain, improved analgesic techniques, and new analgesic agents have contributed in part to improvements in its management. Despite the advances made in the management of postoperative pain, many challenges remain in improving the quality of pain control for patients.
Current Status of Postoperative Pain Management
Although a comprehensive overview of the current state of postoperative pain management is beyond the scope of this chapter, many facets are described elsewhere in this book. One of the persistent issues in the management of postoperative pain is that a relatively high percentage of patients still experience moderate to severe levels of pain, despite increased awareness by health care providers of the issue (e.g., pain as the “fifth vital sign”). Data suggest that postoperative pain continues to be undermanaged. For instance, one survey found that 80% of United States (U.S.) adult patients experienced acute pain postoperatively after outpatient surgery with approximately 85% of these patients experiencing moderate to severe pain. A similar assessment in Europe noted that 41% of adult surgical patients experienced moderate to severe pain on the day of surgery. The parents of pediatric patients undergoing tonsillectomy and adenoidectomy felt that 86% of their children experienced significant overall pain. The reasons for the continued relative undertreatment of postoperative pain is uncertain but may be related to multiple factors including heightened awareness leading to an improved identification of undertreatment of pain, the continued lack of pain assessment or documentation, underutilization of more effective analgesic techniques such as regional analgesic techniques, and the lack of adherence to available pain management guidelines.
Our current understanding of the perioperative pathophysiology basically is that a wide range of pathophysiologic responses are initiated when nociceptors are activated after tissue injury that ultimately results in a local inflammatory, behavioral, and physiologic responses. Sympathoneural and neuroendocrine activation and postoperative pain resulting from tissue injury may eventually produce potentially detrimental responses, which may be especially harmful in high-risk patients or those undergoing high-risk procedures and lead to increases in morbidity or even mortality.
Because the use of regional techniques utilizing a local anesthetic-based analgesic solution may attenuate these pathophysiologic responses to a greater extent than that seen with systemic analgesics, it is possible that use of these techniques may be associated with an improvement in some patient outcomes as well as patient satisfaction. For instance, several meta-analyses suggest that the use of regional analgesic techniques is associated with a decreased risk of postoperative pulmonary complications in patients undergoing abdominal-thoracic procedures. In addition, several systematic reviews in patients undergoing high-risk cardiothoracic-vascular procedures suggest that a decrease in pulmonary complications, cardiac dysrhythmias, and overall cardiac complications may be seen with perioperative thoracic epidural analgesia with a local anesthetic-based analgesic regimen. In patients undergoing abdominal surgery, the perioperative use of thoracic epidural analgesia with a local anesthetic-based regimen is associated with faster resolution of postoperative ileus. Finally, numerous randomized controlled trials indicate that utilizing continuous peripheral regional catheters may facilitate postoperative rehabilitation and decrease costs associated with surgery.
Different analgesic agents may have different effects when compared to one another with respect to patient-centered outcomes such as analgesia or patient satisfaction. When compared to conventional “as needed” opioid analgesia, the use of intravenous patient-controlled analgesia with opioids for postoperative pain control results in superior analgesia and greater patient satisfaction. Regional analgesic techniques utilizing a local anesthetic-based regimen provide superior postoperative analgesia versus systemic opioids. Despite the analgesic benefits of regional analgesic techniques, it is not clear whether this improved analgesia can be translated to improvements in some other patient-centered outcomes such as quality of life and quality of recovery.
To improve postoperative analgesia, utilization of multimodal analgesia, typically a combination of an opioid and nonopioid analgesic with or without a regional anesthetic block, has been encouraged to concurrently reduce opioid-related side effects. In one survey, 23% of in- and outpatients experienced side effects, mainly drowsiness, nausea, and constipation. Approximately 70% of patients would choose a nonopioid drug as they are perceived to be less addictive (49%) and have fewer adverse effects (18%). The literature on multimodal analgesia is not consistent with regard to analgesic efficacy; however, the case of academic fraud that resulted in several multimodal analgesia studies being retracted did not appear to significantly affect the overall conclusions from the literature.
Macrotrends
Future directions for investigation in the area of postoperative pain management need to account for macrotrends that have been in place for decades and may influence not only this specific area but also health in general. Although several macrotrends are present, the ones that may affect the investigation of postoperative pain including the aging of the population, the increasing percentage of obese patients, the changing demographics of outpatient surgical patients, and the presence of a large and worsening U.S. federal deficit.
Aging
In industrial nations, the median age of the population is increasing as a result in part of an increase in average life span. For example, in the United States alone, there is an expected increase in the proportion of the population ≥ 65 years of age from 12.4% (35 million) in 2000 to 19.6% (71 million) in 2030 with the number of persons ≥ 80 years of age expected to increase from 9.3 million in 2000 to 19.5 million in 2030. Although the sex distribution with increasing age is not expected to change significantly, more significant changes are expected in the ethnic composition of persons ≥ 65 years of age. Elderly members of minority groups is expected to increase from 11.3% to 16.5% with the proportion of people of elderly Hispanic origin increasing from 5.6% to 10.9% between 2000 to 2030.
Older adults generally utilize a greater proportion of health care resources as the presence of chronic conditions affects this population disproportionately. For instance, in the United States, approximately 80% of all persons ≥ 65 years of age have at least one chronic condition with approximately 50% having at least two chronic conditions. In terms of specific diseases, almost 20% of persons ≥ 65 years carry the diagnosis of diabetes and approximately 10% have Alzheimer’s disease.
With regard to the perioperative period, one of the more significant complications for older patients is the development of postoperative delirium. Although the etiology of postoperative delirium and postoperative cognitive dysfunction is uncertain, it is clear that a major risk factor is age, with a higher incidence of postoperative delirium with increased age. Certain drugs or classes of drugs (e.g., meperidine, benzodiazepines) have been associated with an increase in postoperative delirium. A prospective study including 1359 consecutive patients of which 64 (4.7%) developed delirium found an association between preoperative benzodiazepine administration and acute postoperative delirium, in which the use of benzodiazepines before surgery nearly doubled the risk of emergence delirium. In a prospective cohort study where 91 patients developed delirium during the postoperative period, delirium was significantly associated with postoperative exposure to meperidine. In addition, an increase in the level of postoperative pain has been shown to correlate with an increased incidence of postoperative delirium. The literature on the safety and efficacy of drug therapy in delirium is lacking in terms of high-quality, well-designed randomized, double-blind, placebo-controlled trials investigating drug management of various aspects of delirium.
Obesity
The increase in the percentage of people classified as obese has significant implications for perioperative pain management and health care overall. It has been estimated that approximately one third of adults in the United States and approximately 17% of children are obese. The trend for obesity indicates that there continues to be an increase in the incidence of obese adults. An examination of the U.S. National Health and Nutrition Examination Survey revealed that the age-adjusted prevalence of obesity (defined as a body mass index of ≥ 30) was 33.8% overall (32.2% for men and 35.5% for women). This increase in obesity is associated with an increase in health care costs and utilization and overall economic impact including direct medical costs, productivity costs, transportation costs, and human capital costs. The significant economic impact highlights the importance of the obesity epidemic for future health policy and clinical research.
It is recognized that perioperative patients who are obese are potentially at higher risk for postoperative complications. Obesity is one of the major risk factors for obstructive sleep apnea. The prevalence of sleep-related breathing disorders may be increasing due in part to the increasing prevalence of obesity. The presence of obesity and obesity-related issues may influence postoperative pain management as there are guidelines for management of postoperative pain for patients who have obstructive sleep apnea. Opioid-induced ventilatory impairment (OIVI) is a more complete term encompassing opioid-induced central respiratory depression (decreased respiratory drive), decreased level of consciousness (sedation), and upper airway obstruction, all of which, alone or in combination, may result in decreased alveolar ventilation and increased arterial carbon dioxide levels. Concerns about OIVI are warranted, as deaths related to opioid administration in the acute pain setting continue to be reported. Risks are often said to be higher in patients with obstructive sleep apnea. Unfortunately, many surgical patients who have obstructive sleep apnea have not been formally diagnosed (e.g., sleep study).
Government Debt
Possibly the most significant factor affecting the delivery of U.S. health care is the increasing federal debt level. As the government currently pays for approximately 50% of all health care costs in the United States with the proportion of health care constituting a greater percentage of the gross domestic product (GDP) over time, federal debt and U.S. health care policy are in essence intertwined, which may have implications for the future reimbursement for postoperative pain management. Although U.S. health care spending grew at a historically low 4% in 2009, the proportion of the GDP spent on health care increased to approximately 18% with the growth rate of health care continuing to outpace the growth in the overall economy. If current trends are extrapolated into the future, the United States will be spending approximately 40% of its GDP on health care by 2075. Because of the unsustainable increase in health care spending, there has been much political pressure to control health care spending, presumably in part through the inevitable implementation of clinical programs that allow for the delivery of high-quality clinical care in an environment of slower spending growth. Despite the lack of solid evidence, there have been many general proposals to “bend the curve” in an attempt to decrease the rise of health care costs including reducing consumer demand for health care services, decreasing payments to health care providers, reorganizing the payment for and delivery of care (e.g., accountable care organizations), and implementing cost-effectiveness standards for delivery of clinical care.
Patient-Centered Assessments
The evaluation of postoperative pain management involves the assessment of its efficacy and determination of side effects. Clinically, these are typically assessed by asking the patients to rate their pain on a scale 0 (no pain) to 10 (most severe pain) during rest and movement, and the presence of side effects such as nausea, vomiting, pruritus, and sedation. The research measurement tools include the use of visual analog scores (VAS), verbal rating scores (VRS: none, mild, moderate, severe), or time to first analgesic request and observation of side effects. Unfortunately, these tools are not sophisticated enough and do not reflect the multidimensionality of pain perception; patient satisfaction and functional and emotional components are not assessed.
The Initiative on Methods, Measurement, and Pain Assessment in Clinical Trials (IMMPACT) group recommended outcome measures for pediatric postoperative pain research but not for adults. Some measurement tools are available to measure the other domains of pain perception and have been utilized in previous studies. These include the Opioid-Related Symptoms Distress Scale to assess symptoms related to opioid intake including difficulty passing urine, headache, feelings of lightheadedness, fatigue, or weakness. The Mini-Mental Status examination measures sedation as well as the cognitive ability of the patient. Physical/functional conditioning is measured by the Short Form (SF)-36 46 and its variations SF-12 and SF-8, measurement of activities of daily living, the 6-minute walking test, and evaluation of the functions of the arm, shoulder, and hand. Emotional functioning can be assessed with a simple VAS and Likert scales as well as sophisticated scales for anxiety such as the Profile of Mood States (POMS) or the Yale Preoperative Anxiety scale. The POMS, a measurement tool recommended by the IMMPACT Group, assesses the six aspects of mood including depression, fatigue, anxiety, hostility, vigor, and confusion. Patient satisfaction as assessed by the patient or the parents, in terms of overall global efficacy and patient global assessment, can be measured by simple VAS or Likert scales. The IMMPACT group recommended the Patient Global Impression of Change in studies on chronic pain. The Patient Global Assessment of Response to Therapy (PGART) is a categorical scale that combines pain relief and side effects. Some of the recommended measurement tools are noted in Box 82.1 .
| Domain | Measurement Tool |
|---|---|
| Pain | VAS, VRS |
| Physical/functional | SF-36, SF-12, SF-8 |
| Conditioning | Roland-Morris, Oswestry Disability Index (low back pain) |
| Constant Morley Score (shoulder function) | |
| Six-minute walking test | |
| Emotional functioning | Profile of Mood States (POMS) |
| Yale Preoperative Anxiety Scale | |
| Side effects | Opioid-Related Symptoms Distress Scale |
| Pain relief and side effects | Patient Global Assessment of Response to Therapy (PGART) |
| Patient satisfaction | Patient Global Impression of Change (PGIC) |
Sophisticated tools are available to evaluate most of the domains involved in pain perception. These include the McGill Pain Questionnaire (MPQ), SF-36, SF-12 47 and SF-8, modified Brief Pain Inventory (BPI), Quality of Recovery (QoR) scoring system, American Pain Society Quality Improvement Patient Outcome Questionnaire, and the Health Outcomes Recovery Survey. None of the sophisticated measurement tools measures all five domains, and emotional functioning and physical conditioning were superficially studied in some of the questionnaires. Only the Quality of Recovery (QoR)-40 and the Health Outcomes Recovery Survey evaluate side effects, and only the Quality Improvement Patient Outcome Questionnaire measures patient satisfaction. The QoR-40 assesses all the domains of pain perception except patient satisfaction. Patient satisfaction can therefore be evaluated together with the QoR-40. The inability of the sophisticated measurement tools to assess all the domains of pain perception calls for a multidimensional tool that measures all such domains.
Assessment of Postoperative Pain in Children
For pediatric pain, measurement tools include the Beyer’s Oucher Scoring System, the Children’s Hospital of Eastern Ontario Pain Scale (CHEOPS), the Children and Infants Postoperative Pain Scale (CHIPPS), and the Crying Requires oxygen for saturation < 95%, Increased vital signs, Expression, Sleepless Score (CRIES) Scale. Some of the tests observe the emotional and vital signs to assess the patient’s degree of pain. These involve several characteristics of the child, including alertness, crying, facial expression, restlessness, body movement, posturing of the trunks and legs, and vital signs. For children with cognitive impairment, the revised Face, Legs, Activity, Cry, and Consolability (r-FLACC) tool and the Nursing Assessment of Pain Intensity (NAPI) may have higher utility than the Non-Communicating Children’s Pain Checklist-Postop Version (NCCPC-PV).
The IMMPACT group recommended the following self-report measures for acute pain intensity: (1) poker chip tool for patients 3 to 4 years of age, (2) Faces Pain Scale Revised for patients 4 to 12 years of age, and (3) visual analog scale for patients 8 years of age or older. For observational pain scales, the IMMPACT group recommended the FLACC, CHEOPS, Parents Postoperative Pain Measure (PPPM), and the COMFORT Scale for patients 1 year and older and the Toddler-Preschooler Postoperative Pain Scale for patients 1 to 5 years. For the cognitively impaired children, the Non-Communicating Children’s Pain Checklist–Postop Version (NCCPC-PV) may be useful. The COMFORTneo Scale appears to be a promising tool for the assessment of pain in neonates.
For emotional assessment in pediatric patients, the IMMPACT group recommended the Adolescent Pediatric Pain Tool for use in children 8 years of age or older and the Facial Affective Scale as the single-item scale of the affective component of pain. For observational measures of the assessment of behavioral distress during procedures, the Procedure Behavior Checklist (PBCL) and Procedure Behavioral Rating Scale Revised (PBRS-R) was recommended. Both measurement tools can be used for patients 1 year of age or older. The VAS Anxiety Scale in children aged 7 to 16 years compares favorably with other measures of preoperative anxiety in children.
Macrotrends
Future directions for investigation in the area of postoperative pain management need to account for macrotrends that have been in place for decades and may influence not only this specific area but also health in general. Although several macrotrends are present, the ones that may affect the investigation of postoperative pain including the aging of the population, the increasing percentage of obese patients, the changing demographics of outpatient surgical patients, and the presence of a large and worsening U.S. federal deficit.
Aging
In industrial nations, the median age of the population is increasing as a result in part of an increase in average life span. For example, in the United States alone, there is an expected increase in the proportion of the population ≥ 65 years of age from 12.4% (35 million) in 2000 to 19.6% (71 million) in 2030 with the number of persons ≥ 80 years of age expected to increase from 9.3 million in 2000 to 19.5 million in 2030. Although the sex distribution with increasing age is not expected to change significantly, more significant changes are expected in the ethnic composition of persons ≥ 65 years of age. Elderly members of minority groups is expected to increase from 11.3% to 16.5% with the proportion of people of elderly Hispanic origin increasing from 5.6% to 10.9% between 2000 to 2030.
Older adults generally utilize a greater proportion of health care resources as the presence of chronic conditions affects this population disproportionately. For instance, in the United States, approximately 80% of all persons ≥ 65 years of age have at least one chronic condition with approximately 50% having at least two chronic conditions. In terms of specific diseases, almost 20% of persons ≥ 65 years carry the diagnosis of diabetes and approximately 10% have Alzheimer’s disease.
With regard to the perioperative period, one of the more significant complications for older patients is the development of postoperative delirium. Although the etiology of postoperative delirium and postoperative cognitive dysfunction is uncertain, it is clear that a major risk factor is age, with a higher incidence of postoperative delirium with increased age. Certain drugs or classes of drugs (e.g., meperidine, benzodiazepines) have been associated with an increase in postoperative delirium. A prospective study including 1359 consecutive patients of which 64 (4.7%) developed delirium found an association between preoperative benzodiazepine administration and acute postoperative delirium, in which the use of benzodiazepines before surgery nearly doubled the risk of emergence delirium. In a prospective cohort study where 91 patients developed delirium during the postoperative period, delirium was significantly associated with postoperative exposure to meperidine. In addition, an increase in the level of postoperative pain has been shown to correlate with an increased incidence of postoperative delirium. The literature on the safety and efficacy of drug therapy in delirium is lacking in terms of high-quality, well-designed randomized, double-blind, placebo-controlled trials investigating drug management of various aspects of delirium.
Obesity
The increase in the percentage of people classified as obese has significant implications for perioperative pain management and health care overall. It has been estimated that approximately one third of adults in the United States and approximately 17% of children are obese. The trend for obesity indicates that there continues to be an increase in the incidence of obese adults. An examination of the U.S. National Health and Nutrition Examination Survey revealed that the age-adjusted prevalence of obesity (defined as a body mass index of ≥ 30) was 33.8% overall (32.2% for men and 35.5% for women). This increase in obesity is associated with an increase in health care costs and utilization and overall economic impact including direct medical costs, productivity costs, transportation costs, and human capital costs. The significant economic impact highlights the importance of the obesity epidemic for future health policy and clinical research.
It is recognized that perioperative patients who are obese are potentially at higher risk for postoperative complications. Obesity is one of the major risk factors for obstructive sleep apnea. The prevalence of sleep-related breathing disorders may be increasing due in part to the increasing prevalence of obesity. The presence of obesity and obesity-related issues may influence postoperative pain management as there are guidelines for management of postoperative pain for patients who have obstructive sleep apnea. Opioid-induced ventilatory impairment (OIVI) is a more complete term encompassing opioid-induced central respiratory depression (decreased respiratory drive), decreased level of consciousness (sedation), and upper airway obstruction, all of which, alone or in combination, may result in decreased alveolar ventilation and increased arterial carbon dioxide levels. Concerns about OIVI are warranted, as deaths related to opioid administration in the acute pain setting continue to be reported. Risks are often said to be higher in patients with obstructive sleep apnea. Unfortunately, many surgical patients who have obstructive sleep apnea have not been formally diagnosed (e.g., sleep study).
Government Debt
Possibly the most significant factor affecting the delivery of U.S. health care is the increasing federal debt level. As the government currently pays for approximately 50% of all health care costs in the United States with the proportion of health care constituting a greater percentage of the gross domestic product (GDP) over time, federal debt and U.S. health care policy are in essence intertwined, which may have implications for the future reimbursement for postoperative pain management. Although U.S. health care spending grew at a historically low 4% in 2009, the proportion of the GDP spent on health care increased to approximately 18% with the growth rate of health care continuing to outpace the growth in the overall economy. If current trends are extrapolated into the future, the United States will be spending approximately 40% of its GDP on health care by 2075. Because of the unsustainable increase in health care spending, there has been much political pressure to control health care spending, presumably in part through the inevitable implementation of clinical programs that allow for the delivery of high-quality clinical care in an environment of slower spending growth. Despite the lack of solid evidence, there have been many general proposals to “bend the curve” in an attempt to decrease the rise of health care costs including reducing consumer demand for health care services, decreasing payments to health care providers, reorganizing the payment for and delivery of care (e.g., accountable care organizations), and implementing cost-effectiveness standards for delivery of clinical care.
Patient-Centered Assessments
The evaluation of postoperative pain management involves the assessment of its efficacy and determination of side effects. Clinically, these are typically assessed by asking the patients to rate their pain on a scale 0 (no pain) to 10 (most severe pain) during rest and movement, and the presence of side effects such as nausea, vomiting, pruritus, and sedation. The research measurement tools include the use of visual analog scores (VAS), verbal rating scores (VRS: none, mild, moderate, severe), or time to first analgesic request and observation of side effects. Unfortunately, these tools are not sophisticated enough and do not reflect the multidimensionality of pain perception; patient satisfaction and functional and emotional components are not assessed.
The Initiative on Methods, Measurement, and Pain Assessment in Clinical Trials (IMMPACT) group recommended outcome measures for pediatric postoperative pain research but not for adults. Some measurement tools are available to measure the other domains of pain perception and have been utilized in previous studies. These include the Opioid-Related Symptoms Distress Scale to assess symptoms related to opioid intake including difficulty passing urine, headache, feelings of lightheadedness, fatigue, or weakness. The Mini-Mental Status examination measures sedation as well as the cognitive ability of the patient. Physical/functional conditioning is measured by the Short Form (SF)-36 46 and its variations SF-12 and SF-8, measurement of activities of daily living, the 6-minute walking test, and evaluation of the functions of the arm, shoulder, and hand. Emotional functioning can be assessed with a simple VAS and Likert scales as well as sophisticated scales for anxiety such as the Profile of Mood States (POMS) or the Yale Preoperative Anxiety scale. The POMS, a measurement tool recommended by the IMMPACT Group, assesses the six aspects of mood including depression, fatigue, anxiety, hostility, vigor, and confusion. Patient satisfaction as assessed by the patient or the parents, in terms of overall global efficacy and patient global assessment, can be measured by simple VAS or Likert scales. The IMMPACT group recommended the Patient Global Impression of Change in studies on chronic pain. The Patient Global Assessment of Response to Therapy (PGART) is a categorical scale that combines pain relief and side effects. Some of the recommended measurement tools are noted in Box 82.1 .
| Domain | Measurement Tool |
|---|---|
| Pain | VAS, VRS |
| Physical/functional | SF-36, SF-12, SF-8 |
| Conditioning | Roland-Morris, Oswestry Disability Index (low back pain) |
| Constant Morley Score (shoulder function) | |
| Six-minute walking test | |
| Emotional functioning | Profile of Mood States (POMS) |
| Yale Preoperative Anxiety Scale | |
| Side effects | Opioid-Related Symptoms Distress Scale |
| Pain relief and side effects | Patient Global Assessment of Response to Therapy (PGART) |
| Patient satisfaction | Patient Global Impression of Change (PGIC) |
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