Pain

• Pain is defined as "an unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or potential tissue damage" by the International Association for the Study of Pain
• 1 in 5 people in Canada live with chronic pain, approximately 7.6 million people
• Chronic pain is more common in people assigned female at birth (AFAB)
• Indigenous Peoples have the highest prevalence of chronic pain in Canada
• Chronic pain affects 41% of Canada’s veterans
• Nociceptive pain arises from damage to body tissue and is described as sharp, aching, or throbbing pain
• Neuropathic pain arises from direct damage to the nervous system itself and is usually described as burning or shooting/radiating pain
• Nociplastic pain arises from a change in the way sensory neurons function, rather than from direct damage to the nervous system
• Acute pain lasts less than 3 months, is commonly caused by something organic, and pain reduction is the treatment goal
• Chronic pain lasts more than 3-6 months, may not have an organic cause, and functionality is the treatment goal
• Nociceptive pain types include:

  • somatic pain: sharp, hot, stinging + localized
  • visceral pain: dull, cramping, aching + not localized
• Transduction is stimulation by noxious stimuli which leads to the release of NTs (bradykinins, nerve growth factor, prostaglandins) that stimulate nociceptors to transmit APs
• Pain perception occurs in higher cortical structures and can be modified by cognitive and behavioral functions
• Brain and spinal cord modulate pain via various ways, including the release of glutamate, substance P, and endogenous opioids
• Neuropathic pain can result from peripheral or central nervous system injury
• Nociplastic pain should be viewed as an overarching terminology that can be applied to a diverse range of clinical conditions that share common neurophysiological mechanisms
• Acute pain typically lasts less than 3-6 months and is due to tissue damage signaling harm or potential for harm
• Acute pain serves a useful purpose (adaptive) and is often due to an identifiable cause such as surgery, acute illness, trauma, labour, or medical procedures
• Acute pain may be nociceptive or neuropathic and can have negative effects if poorly treated, increasing the risk of chronic pain syndromes, including nociplastic pain (maladaptive)
• Acute pain presentation may include symptoms like sharp, dull, shock-like, tingling, shooting, radiating, fluctuating in intensity, and varying in location
• Acute pain signs may include hypertension, tachycardia, diaphoresis, mydriasis, and pallor, but there may be no obvious signs
• Acute pain is always subjective, and there is no specific lab test for pain
• Important to identify and treat acute pain effectively for effective pain management
• Pain management is most effective when validated and accurate pain assessments are carried out
• Pain scales for assessment include visual analogue scale (VAS) for adults and Faces scale for children
• PQRSTU assessment for pain includes questions related to Provocative, Palliative, Quality, Quantity, Region, Radiation, Severity, Timing, Treatment, and Understanding
• Primary goal of therapy for acute pain is to achieve a level of pain relief that allows the patient to attain certain functional goals and improve quality of life
• Non-pharmacologic therapies are important in the treatment of acute + chronic pain
• Pharmacotherapy for acute pain includes medications like Acetaminophen, NSAIDs, and Opioids
• Acetaminophen inhibits CNS prostaglandins and peripherally blocks pain impulse generations
• NSAIDs inhibit COX-1 and 2 enzymes to reduce the formation of prostaglandin precursors
• Opioids bind to opioid receptors, suppress neuronal firing, and alter the perception and response to pain
• Acetaminophen dosing between 325 and 1000 mg q4-6h. Max is 4 g/d in acute and 3.2 g/d in chronic use.

  children: 10-15 mg/kg/dose q4-6h (max. 75 mg/kg/d or 4 g/24h)
• Acetylsalicylic Acid (ASA) irreversibly inhibits COX-1 and COX-2 enzymes via acetylation to decrease the formation of prostaglandin precursors
• Non-Selective NSAIDs dosing depends on the specific drug being used
• Chronic Non-cancer Pain lasts more than 3 months
• Chronic pain can lead to a chronic pain syndrome with symptoms like fatigue, decreased activity, and deconditioning
• Chronic pain can lead to depressed mood, substance use, and suicidal thoughts or actions
• Chronic pain can lead to social and financial stress, affecting relationships, work, and treatment costs
• Chronic pain often has mixed causes and the exact cause may not be identified