Obesity is a national health issue that affects every aspect of healthcare. Comorbidities, such as diabetes, hypertension, and dyslipidemia, contribute to the complexity of care required for effective treatment of obese patients and are commonly addressed by healthcare practitioners. However, pain-related comorbidities, such as diabetic neuropathy or low back pain related to an obese body structure, appear to receive less attention. This may be related to the need to address the significant issues of disease management, such as glycemic control and BP management, in the short period of time that the primary care provider has available for seeing each patient. “Simple” pain issues may be overlooked while discussing more life-threatening health issues.
Healthcare practitioners need to provide obese patients with a venue to discuss pain management issues. Information on obesity's impact on pain and weight reduction strategies, coupled with pain management techniques, will help patients improve their health and pain relief.
Prevalence of obesity
The prevalence of obesity is a global issue that's increasing dramatically. The World Health Organization (WHO) reports that more than 1 billion people worldwide are overweight; 300 million meet the criteria for obesity.1 By 2030, if current patterns persist, 58% of the world's population is expected to be obese or overweight.2 The two main contributing factors to obesity identified at the WHO regional meetings were diet and lack of exercise. Obesity has serious consequences. In 2002, the WHO identified the burden of noncommunicable diseases, such as cardiovascular disease, diabetes, cancers, and obesity-related conditions, as accounting for 60% of global deaths and 47% of the global burden of these diseases.1
Given the serious health repercussions of obesity, it appears inevitable that obesity-related pain has taken a back seat to the more serious consequences of obesity. However, for the obese to become more active and attain a higher quality of life, pain management is a key factor. Lifestyle changes alone may not reduce the pain of osteoarthritis or low back pain complicated by obesity. Unfortunately, some healthcare providers see the obese patient as someone who has created their own problem, one that weight loss would solve. The answer isn't that simple. There are metabolic issues that need consideration when assessing the full picture of obesity-related pain.
Factors for pain assessment
One way to categorize obese patients is by using body mass index (BMI). Classifications are as follows:
- Normal weight is classified by a BMI of 18.5 to 24.9.
- Overweight is classified by a BMI of 25.0 to 29.9.
- Obese Class I is classified by a BMI of 30.0 to 34.9.
- Obese Class II is classified by a BMI of 35 to 39.9.
- Obese Class III—morbid obesity—is classified by a BMI of over 40.3
Using a BMI can help determine if the patient has an increased potential for developing a comorbid condition that will result in pain. For example, the higher the patient's weight and the longer the duration of obesity, the higher the amounts of body fat causing increased insulin resistance, which can be a part of metabolic syndrome (MetS).3 MetS is a syndrome that includes the conditions of hypertension, central adiposity, elevated fasting blood glucose, and dyslipidemia with high triglycerides and low high-density lipoprotein cholesterol.3
When insulin resistance is present alongside MetS, negative effects on the patient's health are increased. MetS can cause higher rates of diabetes and cardiovascular disease, especially in women. There's also a positive correlation between MetS and increased systemic inflammation, which is fed by adipose tissue.4 Tumor necrosis factor, interleukin-6, and C-reactive protein are all factors secreted by adipose tissue that mediate insulin resistance and create a proinflammatory state that has been associated with increased joint inflammation and osteoarthritis.4
Increases in BMI can be directly linked to a greater incidence of pain-related conditions. Obesity has been cited as a contributor to the development of low back pain (possibly a result of increased load on spinal structures). Diabetes increases with the duration and degree of obesity, which can result in diabetic neuropathy in poorly controlled diabetes. There's also research indicating that obesity is an exacerbating factor for migraine headaches.5
Women diagnosed with osteoarthritis have a BMI that's 24% higher than average.6 In a study of 677 patients who had a total knee replacement and 547 patients who had a total hip replacement with at least one MetS risk factor, findings indicated the outcome of the surgeries was negatively affected by metabolic abnormalities.4 The two major factors that affected negative outcomes were obesity and hypertension.4
Because of obesity, women may also suffer from low self-esteem that can lead to depression. Because depression may present comorbidly with chronic pain, these patients have an increased risk factor for both pain and depression.
Obesity is a common comorbidity of fibromyalgia.7,8 Studies indicate that 32% to 50% of patients with fibromyalgia are obese; an additional 21% to 28% are overweight.9,10 In the general population, fibromyalgia affects about 3% to 5% of the U.S. population.7,8 It affects more women than men and is characterized by chronic widespread pain on both sides of the body with hyperalgesia in at least 11 of 18 specific points. In addition to the widespread pain, patients may also experience sleep disturbances, chronic fatigue, functional disability, mood disorder, “fibro fog” memory loss, headache, paresthesia, and irritable bowel disorder.7,8
In a study of 215 patients with fibromyalgia, 30% were overweight, with an additional 47% recognized as obese. The obese patients reported greater sensitivity to tender point palpation (especially in the lower body), decreased physical strength and lower body flexibility, and shorter sleep duration with greater restlessness while sleeping.8
Research hasn't clearly defined the cause and effect relationship between obesity and fibromyalgia. Animal studies suggest there's a link between greater levels of proinflammatory cytokines resulting in central sensitization.8 The list of mechanisms that might contribute to a link between fibromyalgia and obesity include impaired physical activity, cognitive and sleep disturbances, psychiatric comorbidity and depression, dysfunction of the thyroid gland, and impairment of the endogenous opioid system.7 The only demonstrated outcome was that obesity contributes to the continued presence of fibromyalgia and increases its severity.
Low back pain
Findings indicate that if a patient is obese at age 23, there's a risk of low back pain within 10 years. As obese patients get older, the probability of developing low back pain increases.3 There have also been associations that show a BMI of over 30 puts patients at greater risk for low back pain.11 Suspected mechanisms for the increased occurrence of low back pain in the obese patient are mechanical stress on the intervertebral disks and indirect effects of atherosclerosis on decreasing blood flow to the lumbar spine.3
Many practitioners feel that weight loss is the solution to treating low back pain in these patients. There are two important issues to consider. After low back pain is already occurring, weight loss may not reverse the effect of mechanical load bearing, and not all weight loss strategies have the same result on low back pain. In two studies of morbidly obese patients who had bariatric surgery, there was a significant decrease in low back pain after surgery.11 In a nonsurgical weight loss program, there was little evidence that demonstrated improvement in low back pain.11 Multidisciplinary programs that include exercise and weight loss, as well as dietary and behavioral modification, have a better outcome than treatment plans that aren't as comprehensive.
It's important to note that no matter which type of treatment is selected to reduce low back pain, the ability of patients to adhere to the treatment requirements should be considered to achieve the best possible outcome for the patient. In low back pain, weight loss may have a positive effect and help to relieve the pain.
Symptomatic osteoarthritis is the presence of radiographic findings of osteoarthritis in combination with symptoms attributable to osteoarthritis.12 Magnetic resonance imaging findings include cartilage lesion, osteophytes, bone marrow lesions, synovitis, effusion, and subchondral bone attrition.12 The two major risk factors for developing osteoarthritis are obesity and being female; knee injury is also a predisposition to developing knee osteoarthritis.
Even patients who were overweight but not morbidly obese had a 2.2-increased risk factor for developing knee osteoarthritis when compared with their normal weight counterparts.12 In the United Kingdom, it's estimated that 69% of knee replacement surgeries in middle-age women are attributed to obesity.13
For the morbidly obese, knee osteoarthritis presents a bigger problem. If lifestyle changes and increased exercise can't produce weight loss or favorable outcomes, total joint replacement is considered. If surgery is necessary, reconditioning after surgery can be complicated further by difficulty with mobility.
Treatment options for the obese patient with pain include medications and nonpharmacologic modalities, such as acupuncture or yoga. When discussing options for controlling pain, it's important to inform patients that a combination of treatments is more likely to produce optimum pain reduction.
Medications can be affected by the ratio of adipose tissue to lean body tissue. In the obese patient, there's a higher ratio of adipose tissue when compared with lean body tissue, which is thought to interfere with the protein binding of drugs, allowing an increased concentration into the free plasma concentration. Although obesity increases the total volume of both lean and adipose tissue when compared with nonobese patients of the same age, height, and sex, this difference requires individualized prescriptions for obese patients to ensure that medications are dosed appropriately.14
For most obese patients in pain, opioids will be considered for pain management. Some aren't candidates for nonsteroidal anti-inflammatory drugs due to impaired organ function, such as renal dysfunction, or comorbidities, such as diabetes or the potential for gastric bleeding.
Additional options for pain management in the obese patient can include not only medication management but also the use of regional analgesia such as blocks and physical therapy programs geared to patients who need a less strenuous approach. Referrals to pain clinics, physical therapy programs designed for the obese patient, and physiatrists can help reduce pain and increase functionality. If the obese patient needs a surgical intervention, additional concerns will need to be addressed.
Sedation and the maintenance of a patent airway are always concerns when opioids are used for obese patients, especially in the postoperative time period when anesthetic agents have been used. However, reviews indicate that two factors, site of surgery (especially bariatric surgery) and coexisting sleep apnea, have been cited as contributory to an increased risk of pulmonary complications in obese patients.15 Most obese patients can tolerate opioids in the usual doses, although they require close monitoring, especially for sedation and respiratory depression.
General recommendations for pain management after surgery for obese individuals include:15
- the use of multimodal analgesia using regional and opioid sparing techniques
- avoidance of sedatives, especially when combined with opioids
- noninvasive ventilation with supplemental oxygen
- early mobilization and ambulation
- elevating the head of the bed to 30 degrees
- a low threshold for pulse oximetry, which should be continuous and combined with end-tidal carbon dioxide monitoring for added safety
- arterial BP management
- placement in a nursing specialty area, such as an ICU or step-down unit, with continuous, postoperative monitoring until oxygen saturation is greater than 90% while asleep without supplemental oxygen.
When obese patients use patient-controlled analgesia, the use of continuous infusion is contraindicated. Opioid requirements aren't related to body surface, age, gender, or anesthetic regimen.15 Adding a nonopioid medication can decrease pain and provide an opioid-sparing effect.15,16 Other medications such as clonidine, ketamine, and dexmedetomidine could be useful adjuvants for postoperative pain relief, but have significant contraindications and less research to support use at this time.16
The use of regional blocks with local anesthetic for adjunct pain relief is recommended, as well as epidural pain management for surgical pain. These techniques can reduce the need for opioids and can have a positive effect on the risk of respiratory depression. Obese patients will need less local anesthetic when administered as an epidural as compared with nonobese patients. This can be correlated with the decreased cerebrospinal fluid volumes in obese individuals.14
Less-invasive adjuvant pain relief modalities can also be considered. In one study, aromatherapy with lavender was shown to decrease morphine dosage needed for pain management in the postanesthesia unit, although more research is needed.15 Relaxation techniques such as music or relaxation tapes can provide a way to avoid medications through distraction. Reiki or therapeutic touch can also provide relaxation. In the outpatient setting, patients can participate in pool exercise therapy to lessen the burden on joints.
Rising to the challenge
It can be a challenge to provide effective pain management for obese patients; however, a multimodal pain management regimen that combines medications and complementary techniques can help increase pain relief. Recognizing that the patient may need to be in an area with continuous monitoring will help lessen the potential for adverse events in postoperative patients. Always remember that most obese patients are very familiar with the healthcare system and may have had less than positive experiences. Recognizing the patient's pain and working with the patient to help minimize the effects of the pain can lead to a more positive outcome.
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