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Pain, Temperature Regulation, Sleep, and Sensory Function

Pain, Temperature Regulation, Sleep, and Sensory Function. Chapter 15. Pain. “Pain is an unpleasant sensory and emotional experience associated with actual or potential tissue damage or described in terms of such damage” —International Association for the Study of Pain

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Pain, Temperature Regulation, Sleep, and Sensory Function

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  1. Pain, Temperature Regulation, Sleep, and Sensory Function Chapter 15

  2. Pain • “Pain is an unpleasant sensory and emotional experience associated with actual or potential tissue damage or described in terms of such damage” —International Association for the Study of Pain • “Pain is whatever the experiencing person says it is, existing whenever he says it does” —McCaffrey

  3. Pain Theories • Specificity theory • Amount of pain is related to the amount of tissue injury • Accounts for many types of injuries but does not explain psychological contributions • Gate control theory • Developed to explain the complexities of the pain phenomenon

  4. Neuroanatomy of Pain • Nociception • Perception of pain • Nociceptors • Bare nerve endings in skin, muscle, joints, arteries, and the viscera that respond to chemical, mechanical, and thermal stimuli • Can detect a wide range of stimuli • Aδ fibers • Unmyelinated C polymodal fibers

  5. Pathways of Nociception

  6. Pathways of Nociception

  7. Pathways of Nociception

  8. Neuromodulation of Pain • Segmental inhibition • Diffuse noxious inhibitory controls • Integration of: • Peripheral sensory axon terminals • Spinal interneurons • Top-down control pathways • All converge on the spinal dorsal horns

  9. Neuromodulation of Pain

  10. Neuromodulation of Pain • Chemicals and neurotransmitters • Pain excitatory • Pain inhibitory • Modulators of pain • Direct excitation • Threshold depolarization from direct stimuli • Indirect excitation • Threshold depolarization from inflammatory mediators after tissue injury

  11. Endorphin Response

  12. Clinical Description of Pain • Pain threshold • Point at which a stimulus is perceived as pain • Perceptual dominance • Pain at one location may cause an increase in the threshold in another location • Pain tolerance • Duration of time or the intensity of pain that a person will endure before initiation of pain responses

  13. Pain Classifications • Nociceptive pain • Pain with a cause of normal tissue injury • Somatic • Visceral • Non-nociceptive pain • Neuropathic pain • Peripheral and central

  14. Acute Pain • Protective mechanism • Alerts an individual to a condition or experience that is immediately harmful to the body • Manifestations • Fear and anxiety • Tachycardia, hypertension, fever, diaphoresis, dilated pupils, outward pain behaviors, elevated blood sugar levels, decreased gastric acid secretion and intestinal motility, and a general decrease in blood flow

  15. Acute Pain • Acute somatic • Arises from connective tissue, muscle, bone and skin • Aδ fibers—pain is sharp and well localized • C fibers—dull, aching, and poorly localized • Acute visceral • Pain in the internal organs and abdomen • Poorly localized due to the lesser number of nociceptors

  16. Acute Pain • Referred pain • Pain that is present in an area removed or distant from its point of origin • The area of referred pain is supplied by the same spinal segment as the actual site • Myocardial infarction pain

  17. Referred Pain

  18. Chronic Pain • A situation; state of existence • May be sudden or develop insidiously • Usually defined as lasting at least 3 months • Response patterns vary • Produces significant behavior and psychological changes

  19. Common Types of Chronic Pain • Myofascial pain syndromes • Injury to the muscle and fascia • Spasm, tenderness, and stiffness • Chronic postoperative pain • Cancer pain

  20. Neuropathic Pain • Result of trauma or disease of nerves • Most often chronic • Painful diabetic neuropathy • Postherpetic neuralgia

  21. Neuropathic Pain • Deafferentation pain • Sympathetically maintained pain • Complex regional pain syndromes (CRPS) • Central pain • Phantom limb pain

  22. Pediatrics and Pain • Pathways and chemicals associated with pain are functional in preterm and newborn infants • Nociceptor system is functional by 24 weeks’ gestation • Expressions of pain • Facial expression • Crying • Body language

  23. Pediatrics and Pain

  24. Aging and Pain • Increase in pain threshold • Peripheral neuropathies • Skin thickness changes • Decrease in pain tolerance • Alteration in metabolism of drugs and metabolites

  25. Temperature Regulation • Variable • Location • Activity • Environment • Circadian rhythm • Gender

  26. Temperature Regulation • Peripheral thermoreceptors • Hypothalamic control • Heat production and conservation • Chemical reactions of metabolism • Skeletal muscle contraction • Chemical thermogenesis • Vasoconstriction • Voluntary mechanisms

  27. Heat Loss • Radiation • Conduction • Convection • Vasodilation • Decreased muscle tone • Evaporation • Increased respirations • Voluntary measures • Adaptation to warmer climates

  28. Temperature Regulation • Pediatrics • Produce sufficient body heat but are unable to conserve heat produced • Small body size and high body surface to weight ratio • Thin subcutaneous layer • Aging • Slow blood circulation, vasoconstrictive response, and metabolic rate • Decreased sweating and perception of heat and cold

  29. Fever • Resetting of the hypothalamic thermostat • Activate heat production and conservation measures to a new “set point” • Exogenous pyrogens • Endogenous pyrogens • Endogenous cryogens

  30. Fever

  31. Benefits of Fever • Kills many organisms • Decreases serum levels of iron, zinc, and copper • Deprives bacteria of food • Promotes lysosomal breakdown and autodestruction of cells • Increases lymphocytic transformation and phagocyte motility

  32. Hyperthermia • Not mediated by pyrogens • No resetting of the hypothalamic set point • 41o C (105.8o F): nerve damage produces convulsions • 43o C (109.4o F): death results • Forms • Heat cramps, heat exhaustion, heat stroke

  33. Heat Cramps • Severe spasmodic cramps in the abdomen and extremities • Following prolonged sweating and associated sodium loss • Common in individuals not accustomed to heat or those performing strenuous work in warm climates • Fever, rapid pulse, and increased blood pressure often accompany the cramps

  34. Heat Exhaustion • Collapse due to prolonged high core or environmental temperatures • Prolonged vasodilation and profuse sweating • Dehydration, depressed plasma volumes, hypotension, decreased cardiac output, tachycardia • Manifestations • Dizziness, weakness, nausea, and syncope

  35. Heatstroke • Potentially lethal result of a breakdown in an overstressed thermoregulatory center • Brain cannot tolerate temperatures >40.5o C (104.9o F) • Temperature maintained by blood flow through the veins in the head and face • Cardiovascular and thermoregulatory centers may cease functioning with higher temperatures

  36. Heatstroke • Manifestations • Cerebral edema, degeneration of the CNS, swollen dendrites, and renal tubular necrosis • Rapid peripheral cooling will cause peripheral vasoconstriction and limit core cooling • Children are more susceptible • Produce more metabolic heat when exercising • Greater surface area to mass ratio • Sweating capacity is less than adults

  37. Malignant Hyperthermia • Complication of inherited muscular disorder • Precipitated by the administration of volatile anesthetics and neuromuscular blocking agents • Increased calcium release or decreased calcium uptake with muscle contraction • Causes sustained muscle contractions • Increased oxygen consumption and lactic acid production

  38. Hypothermia • Body temperature less than 35° C • Produces: • Vasoconstriction, alterations in the microcirculation, coagulation, and ischemic tissue damage • Ice crystals, which form inside the cells, causing them to rupture and die • Tissue hypothermia slows the rate of chemical reactions; increases blood viscosity and slows blood through the microcirculation; facilitates blood coagulation and stimulates vasoconstriction

  39. Hypothermia • Accidental hypothermia • Commonly the result of sudden immersion in cold water or prolonged exposure to cold • Therapeutic hypothermia • Used to slow metabolism and preserve ischemic tissue during surgery or limb reimplantation • May lead to ventricular fibrillation and cardiac arrest

  40. Trauma-Induced Temperature Change • CNS trauma • Accidental injuries • Hemorrhagic shock • Major surgery • Thermal burns

  41. Sleep • Active, multiphase process • Hypothalamus is the major sleep center • Hypocreatins (ovexins) • Promote wakefulness and rapid eye movement (REM) sleep • Two phases • Rapid eye movement (REM) sleep • Non–rapid eye movement (NREM) sleep

  42. EEG Stages of Wakefulness and Sleep

  43. NREM Sleep • 75% to 80% of sleep time • Four stages evaluated by EEG • Stage I • Stage II • Stage III • Stage IV

  44. REM Sleep • 20% to 25% of sleep time • Also known as paradoxic sleep • Occurs every 90 minutes beginning after 1 to 2 hours of sleep

  45. Normal Sleep Cycles

  46. Pediatrics and Sleep • Newborns sleep 16 to 17 hours per day • 53% of that time is spent in active (REM) sleep • The infant sleep cycle is about 50 to 60 minutes • Infants enter REM sleep immediately upon falling asleep

  47. Aging and Sleep • Total sleep time is decreased • Elderly take longer to fall asleep, and awaken more frequently during the night • Amount of time in stage IV sleep decreases • Potential causes • Physical ailments, lack of daily routine, circadian rhythm changes, and medications

  48. Sleep Disorders • Four classifications • Disorders initiating sleep • Insomnia • Sleep-disordered breathing • Upper airway resistance syndrome • Obstructive sleep apnea • Obesity hypoventilation syndrome

  49. Sleep Disorders • Four classifications (cont’d) • Disorders of sleep/wake cycle • Parasomnias • Somnambulism • Night terrors • Enuresis • Dysfunctions of sleep, sleep stages, or partial arousals

  50. Sleep and Disease • Secondary sleep disorders • Alterations in the quality and/or quantity of sleep due to primary diseases • Depression, pain, sleep apnea syndromes, and alterations in thyroid hormone secretion • Sleep-provoked disorders • Sleep stage alterations produced in certain disease states

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