IMPACT OF PAIN
Based on a 2016 study, an estimated 50 million American adults, or 20.4% of the adult population, report that they suffer from chronic pain (Dahlhamer J, et al. 2018). Of that number, 19.6 million people (8.6% of the population) are described as having “high-impact” chronic pain, or pain that frequently limits life or work activities. Pain has significant economic and personal impacts. Even acute pain that is self-limiting and from which the sufferer completely recovers can affect income and interpersonal relationships. Chronic pain has widespread economic consequences. The annual healthcare costs associated with pain in the United States are estimated at $500-635 billion dollars, more than what is spent annually on heart disease ($309 billion), cancer ($243 billion), or diabetes ($188 billion). The estimated value of lost productivity due to pain was between $299-335 billion (Gaskin & Richard, 2012). Moreover, pain can impact an individual’s professional life. People may miss work because of the severity of pain. Since earning a living is of critical importance, fears about losing jobs or failing to meet employers’ expectations can be a source of significant stress for individuals with chronic pain. Pain may also interfere with interpersonal relationships. The stress and discomfort of living with chronic pain may lead to problems with family and friends. Families of patients who have chronic pain also live through pain with their loved ones. Ineffective pain management affects not only patients, but also families and friends. Another potential consequence of chronic pain is prescription drug misuse or abuse. Drug misuse is described as using a medication for a reason other than its prescribed use, or more frequently and/or at a higher dosage than prescribed.
The most common pharmacological intervention for pain relief is analgesics, which are often prescription medications. Prescription analgesics are not only abused by those who suffer from pain, but are also a source of drug abuse by those without a prescription. The 2018 National Study on Drug Use and Health data showed that prescription pain medication was the second most common form of illicit drug use in 2018, and an estimated 9.9 million Americans aged 12 years and older misused prescription pain relievers in 2018 (Substance Abuse and Mental Health Services Administration, 2019). Of that number, 1.7 million were categorized as having a substance use disorder, which is when the person experiences clinically significant impairments in life activities and health as a result of drug use. This survey also revealed that: The most common reason people misused pain medication was to relieve physical pain (63.6%). Other reasons were to relax or get high, relieve stress/tension, aid sleep, help with emotions, or because they were “hooked.” Most people who misused prescription pain medication obtained them from a friend or relative (51.3%), followed by obtaining a prescription or stealing from a medical provider (37.6%), and buying them from a drug dealer or stranger (6.5%). Other statistics related to prescription drug misuse/abuse are: ● The U.S. makes up five percent of the world’s population and consumes about 80% of the world’s prescription opioid drugs. ● In 2017, prescription opioid drugs contributed to 35% of all U.S. opioid overdose deaths (Scholl et al., 2019). ● In 2017, 17,029 people died from overdoses involving prescription opioids (Scholl et al, 2019). 2. Transmission : Action potentials move via neurons from peripheral receptors to the spinal cord and then to the brain. 3. Perception : The brain receives the information from the action potentials and perceives them as painful. 4. Modulation : The process by which the transmission of pain is altered (Copstead & Banasik, 2013). Nociceptors can be stimulated by direct injury to the nerve endings themselves or they can be stimulated from the release of chemicals as a result of the injury and the inflammatory response. These chemicals include potassium, hydrogen, lactate, prostaglandins, serotonin, and bradykinin, and affect the membrane potential of the pain receptor and depolarize, causing an action potential that makes its way to the brain and is processed by the brain as pain. signals travel to the brain via the spinothalamic tract (Copstead & Banasik, 2013). The A- delta pain fibers are mostly transmitted via a spinothalamic tract known as the neospinothalamic tract and secrete an instantaneously acting neurotransmitter known as glutamate (Guyton & Hall, 2006). The neospinothalamic tract has fewer synapses than the paleospinothalamic tract that the slower C fibers travel, and the information they carry is quickly transmitted to the thalamus and the primary somatosensory cortex (Copstead & Banasik, 2013). As a result of this quick transmission, pain is easily pinpointed. The slower C pain fibers take the paleospinothalamic pathway. It is believed that type C pain fibers secrete both glutamate and a slower acting neurotransmitter known as substance P, which is associated with the transmission of slow and chronic pain (Guyton & Hall, 2006). This pathway contains more synapses
THE PHYSIOLOGY OF PAIN
How does someone “sense” pain? The experience of pain is not easily explained and depends on not only physical factors, but also on cultural and emotional factors (Copstead & Banasik, 2013). The following is a brief overview of the physical sensation(s) of pain. Nociception is a four-stage process that the body utilizes to process painful stimuli: 1. Transduction : Painful stimuli are converted to neuronal action potentials at the sensory receptor. Transduction Painful stimuli are first encountered by nociceptors, which are nerve endings. Nociceptors convert painful stimuli into neuronal action potentials that travel through the spinal cord and finally, to the brain. Nociceptors are located throughout the body in the skin, muscle, connective tissue, the circulatory system, and the viscera of the abdomen, pelvis, and thoracic cavity (Copstead & Banasik, 2013). Transmission A-delta fibers and C fibers are primary afferent neurons that transmit action potentials (also known as nerve impulses) to the central nervous system. A-delta fibers are larger and myelinated and quickly carry impulses that result in sharp and stinging pain; C fibers are smaller and unmyelinated, taking longer to transmit impulses and result in a dull, aching pain sensation (Copstead & Banasik, 2013; Guyton & Hall, 2006). A-delta fibers are responsible for the initial sharp pain sensation a person feels, which causes the person to swiftly remove the affected body part from the cause of injury (Guyton & Hall, 2006). C fibers relay a slower pain that grows greater over time and causes suffering (Guyton & Hall, 2006). Nociceptive impulses travel through A- delta and C fibers and enter the spinal cord from the dorsal roots and then to synapse relay neurons at the dorsal horn (Guyton & Hall, 2006). The pain
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