Purpose of the Review
The present review is intended to give an overview of fibromyalgia for the anesthesiologist. While the basics of the treatment of fibromyalgia are included, the intent is to provide context to discuss the potential implications in perioperative management
After years of skepticism and questioning, fibromyalgia is now a widely accepted medical disorder with many years of research identifying the augmented pain and sensory processing and distinct clinical phenotype. As there is no definitive test, biomarker or physical exam to ensure the presence of fibromyalgia, the diagnosis is given to a patient with widespread pain and co-morbid symptomatology.
Diagnostic Criteria for Fibromyalgia
The diagnosis of fibromyalgia has been a source of confusion and frustration for clinicians for many years.
Traditional teaching required assessment of “tender points” with a diagnosis of fibromyalgia being made when the patient reported 11 or more of the 18 discrete points during physical examination.(10) Although most patients with fibromyalgia satisfy the tender point criteria, it is common that patients describe other areas of pain and tenderness, along with other comorbid symptoms and diagnoses. As such, the American College of Rheumatology (ACR) has created new diagnostic criteria for fibromyalgia that replace the tender point evaluation with a self-report measure of widespread body pain and comorbid symptomatology (fatigue, trouble thinking, waking up tired, depression, abdominal pain/cramps, and headache).
Altered Sensory Perception and Central Neurotransmission
Pain is the most common complaint of fibromyalgia patients. Patients with fibromyalgia demonstrate altered thresholds for virtually every type of sensory testing, including nociception, proprioception, and even auditory perception.(16, 17) Many experts describe the sensory differences as altered volume control—essentially, the volume or gain on sensory processing is turned up in these patients
Psychological diagnoses, especially depression and anxiety, are common in the fibromyalgia population, as they are in any chronic pain condition. Although some have suggested that psychopathology is the “cause” of fibromyalgia, at any given time a minority of individuals with fibromyalgia will display an active Axis I or II psychiatric disorder, and psychological variables do not fully explain the widespread body pain and symptoms seen in this population. It is likely that some of the same neurotransmitter abnormalities that contribute to pain amplification (e.g., high Substance P and glutamate, low serotonin, norepinephrine and GABA) also contribute to the fatigue, sleep, memory, and mood symptoms experienced by individuals with fibromyalgia or fibromyalgia-ness.
Supporting the notion that there is a strong familial contribution to fibromyalgia, as well as more broadly chronic pain and tenderness, several genes have been identified that occur more commonly in fibromyalgia patients than controls
Opioid and NSAID Therapy
Although NSAIDs and opioids are very effective analgesics for acute pain, and amongst the first line agents selected for many patients with long-standing pain, there is no evidence that either of these treatments is effective in fibromyalgia.
Could this be an instance of the 6 Worst Words in Evidence-Based Medicine There is certainly NO evidence that these treatments do NOT work either.
These are among the many lines of evidence that suggest that chronic pain is not simply acute pain that has lasted too long, and it cannot be effectively treated as such. Despite the recommendation against the use of opioids in fibromyalgia, as well as the (largely anecdotal) concern that these patients may preferentially be at risk for opioid-induced hyperalgesia that would actually lead to worsening of their pain with these agents, their use in the condition is still widespread.
Although many clinicians assume that our treatments for fibromyalgia are less effective than those we use for other chronic pain conditions, data suggest otherwise, and overall efficacy of our current drugs for fibromyalgia is comparable to pharmacological therapy for other chronic pain states. [which essentially means very low efficacy -ed.]
actualizing this type of personalized analgesia is the detection of patients with altered central pain processing. The anesthesia community is beginning to embrace the multiple domains that need to be included in pain research beyond a 0-10 number, such as physical function and psychological measures. The use of well-constructed self-report questionnaires allows us to get a phenotype. Additional research is needed to understand the sensitivity and potential applications of self-report questionnaires. The use of point-of-care genotypic analyses as a portion of the preoperative assessment for pain sensitivity is also an area of a great deal of research. Hopefully, through a combination of genotype and phenotype, pain prone patients can be identified and anesthesia can be tailored to the individual.
Pain is the most common complaint of fibromyalgia patients. Patients with fibromyalgia demonstrate altered thresholds for virtually every type of sensory testing, including nociception, proprioception, and even auditory perception.
Endogenous opioid levels (and PET derived mu-opioid receptor occupancy) tend to be paradoxically elevated with decreased opioid receptor availability, perhaps explaining why individuals with fibromyalgia and other “central” pain states do not seem to respond to opioids.
As was previously noted, patients tend to respond better to medications targeting the altered central neurotransmitters, including serotonin and norepinephrine.
The only recommended fibromyalgia medications used with any regularity in the perioperative period are gabapentin and pregabalin; however, these medications have been widely applied in the acute pain setting without regard to a particular responder profile
lack of a definitive clinical biomarker or test for fibromyalgia, these findings have largely validated the complaints and symptoms of fibromyalgia patients, altered the treatment recommendations (See “Treatment of Fibromyalgia” section below), and led to an explosion in new pain research.
It is clear that there is a subset of the population that has altered pain and other sensory thresholds due to central nervous system factors. The fibromyalgia population seems like a logical starting point for the implementation of “personalized analgesia.”