Transcript Slide 1

Pain, Temperature, Sleep,
and Sensory Function
Pain
“one of the body’s most important adaptive
mechanisms”
“an unpleasant sensory or emotional
experience associated with actual or potential
tissue damage, or described in terms of such
damage” Amer. Pain Society
“whatever the experiencing person says it is,
existing whenever he says it does”
- Margo McCaffrey
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“one person cannot judge the perception of
pain in another”
“culture influences a people’s response to
pain”
“pain occurs with tissue damage, there is no
correlation between the amount of tissue
damage and the degree of pain
experienced”
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“a clear distinction among pain types may
not be always possible”
Two major types: Stimuli –Table 13-1
1.Nociceptive
 A. somatic-joints, muscle, skin
 B. visceral-organs(tumors/obstruction)
2.Neuropathic
 A. Central-central or peripheral NS
 B. Peripheral-neuropathies(DM/GB disease)
Neuroanatomy of Pain
“Nociception”
1)
2)
3)
Afferent pathways – peripheral (PNS) →
spinal gate (dorsal horn) → higher centers
(CNS)
Interpretive centers – brain stem, midbrain,
diencephalon and cerebral cortex
Efferent pathways – CNS → dorsal horn of
spinal cord (modulate pain)
Nociceptors
“free nerve ending”
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Free 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
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A delta fibers: touch, vibration, thermal & pain
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Unmyelinated C polymodal fibers: pain
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Skin and its
accessory structures
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structure
function
growth and repair
development
aging
disorders
1.Transduction
2.Transmission
3.Perception
4.Modulation
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Sensitizing substsnces
◦ Prostaglandins, bradykinin, serotonin, substance P,
histamine
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Action potential
◦ “wave of depolarization”
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Tissue damage
Spinal cord
Brain stem & thalamus
cortex
“conscious experience of pain”
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“inhibition of nociceptive impulses”
Brain stem
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Spinal cord
*Endorphins, serotonin, NE
Gate Control Theory
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– Melzack &
Wall 1965
Small c fibers – pain( diffuse,burning,aching)
Large A fibers – touch, vibration or thermal
stimulation(localized,sharp)-pain
Inhibitory interneurons – dorsal horn
“ balance between c fibers and nonnocieptive A fibers(touch,vibration,thermal)
Neuromodulation of Pain
Located in pathways of nervous system
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Hypothalamus, pituitary gland, spinal cord, brain
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Triggered by tissue injury/inflammation
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Excitatory
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Substance P, glutamate, somatostatin
Inhibitory
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GABA, serotonin, norepinephrine, endorphins
“OLDCART”
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O…onset
L…location
D…duration
C…characteristics
(sharp,crampy,burning,dull…)
A…aggravating/alleviating/associated
R…radiation
T…treatment
Clinical Descriptions of Pain
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Acute – immediate, harmful alert, acute
anxiety: tissue damage, self-limiting, ends
with healing
◦ Somatic
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superficial, sharp, well localized
dull, aching, poorly localized, nausea
and vomiting
◦ Visceral
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internal organs, abdomen or skeleton,
poorly localized (↓ # receptors)
nausea and vomiting, hypotension,
restlessness and shock
“generalized stress response”
“physiologic signs associated with pain”
low/moderate/superficial
sympathetic nervous system
HR, BP, RR, muscle tension, dilating pupils,
diaphoresis
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Severe or deep pain
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Parasympathetic nervous system
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Pallor, muscle tension, HR, irreg RR, N/V,
weakness & exhaustion
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Acute
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Referred
 Area distant from the point of
origin, same spinal segment as
the actual site of pain, more
receptors in the skin
Chronic Pain-Neuropathic
“lasting 3 to 6 months”
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Injury to the nervous system
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Persistent (low back pain) or intermittent
(migraines)
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Produces significant behavior of psychologic
changes
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Types
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Myofascial – muscle, fascia
Chronic postoperative pain
Cancer pain (Chapter 10)
Neuropathic Pain
“increased sensitivity to painful stimuli”
do to: abnormal processing of sensory input
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Chronic
◦ 1.Peripheral pain – nerve
entrapment or diabetic neuropathy
◦ 2.Central – lesion/dysfunction in
the CNS – phantom limb
Aging and Pain
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Increase in pain threshold
◦ Peripheral neuropathies
◦ Skin thickness changes
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Decrease pain tolerance
Alteration in metabolism of drugs and
metabolites
Temperature Regulation
“heat production ↔ heat conservation ↔
heat loss”
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Extremities are cooler than the core
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Daily fluctuation (circadian rhythm)
(0.2 – 0.5° C)
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Peak at 6:00 p.m.
Lowest with sleep
Hypothalamic Control: “conserve
heat”
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Thermoreceptors
– Peripheral – skin
– Central – hypothalamus, cord, abdominal organs
1.Endocrine System
– TSH-RH → Thyroxine → adrenal → Epinephrine
– vasoconstriction, glycolysis & ↑ metabolic
rate →↑ heat production
2.Sympathetic Nervous System
– ↑ skeletal muscle tone
– Initiates shivering
– Vasoconstriction
3.Cerebral Cortex – “voluntary”
– ↑ body movement, bundle up, curl in a ball
Fever
“resetting of the hypothalamic
thermostat”
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Active heat production and
conservation measures a new “set
point”
Exogenous pyrogens
(endotoxins)
Endogenous pyrogens TNF,IL6,IF
Benefits of Fever
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Kills many microorganisms
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↓ serum levels of iron, zinc and copper
◦ Needed for metabolism of bacteria
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Promotes lysosomal breakdown and
autodestruction of cells # viral replication
↑ lymphocytic transformation and phagocyte
motility
Augments antiviral interferon production
Hyperthermia
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Not mediated by pyrogens
No resetting of the hypothalamic set point
41°C (105.8°F) nerve damage produces
convulsions
43°C (109.4°F) results in death
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Forms
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– Heat Cramps – fever, ↑ pulse, ↑ blood pressure
– Heat Exhaustion – dizziness, weakness, nausea,
confusion and syncope
– Heat Stroke – core > 40°C-104F :cerebral edema,
degeneration of the CNS, renal tubular necrosis and
death
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Damage to the CNS,inflammation, increased
intracranial pressure or intracranial bleeding
Body Temperature> 39/102.2 degrees
◦ “central fever”
◦ +/- bradycardia
◦ Resistant to antipyretic therapy
Malignant Hyperthermia
“rare inherited muscle disorder”
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Precipitated by inhaled anesthetics and
neuromuscular blocking agents
◦ ↑ Ca++ release or ↓ Ca++ uptake with muscle
contraction
◦ Sustained muscle contraction (↑O2 use, ↑ lactic acid)
◦ Symptoms – resemble those of coma with anuria
(children and adolescents)
Hypothermia
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Body temperature < 35°C
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Produces
◦ Depression of the CNS and respiratory systems,
vasoconstriction,
in microcirculation,
coagulation and ischemic tissue damage
◦ Severe → ice crystals within the cells → rupture and
death
Sleep
“temporary
state of restful
unconsciousness with spontaneous
arousal”
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Two stages – alternate
◦ Rapid eye movement sleep (REM) :dreams
◦ Non-REM sleep
 Stage I-IV
REM Sleep
 20
– 25% of sleep time
 Paradoxic
sleep – EEG pattern –
awake – very active brain
 Occurs
every 90 minutes
beginning after 1-2 hours of
sleep
Non-REM Sleep
 75
– 80% of sleep time
 Initiated
when inhibitory signals
are released from the
hypothalamus - ↑
parasympathetic tone
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stages - EEG
Sleep Disorders
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Dyssomnias
◦ Insomnia: inability to fall or stay
asleep (mild, moderate or severe)
◦ Sleep disordered breathing:
obstructive sleep apnea syndrome
◦ primary hypersomnia (narcolepsy)
◦ Disorders of the sleep-wake
schedule: jet lag, sleep schedule
Sleep Disorders
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Parasomnias – unusual behavior during sleep
◦ Sleepwalking, night terrors, rearranging furniture,
eating food, violent behavior and restless leg
syndrome
Visual Dysfunction
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Ocular movement – III, IV, VI CN (Figure 1222)
◦ Strabismus
 Diplopia (weak or hypertonic muscle)
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Nystagmus
◦ Pedular – regular to-and-fro
◦ Jerk – one phase faster
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Causes: inner ear, cerebellum, CN, drugs,
retinal disease, cervical cord disease
Dysfunction of Acuity
“ability to see objects in sharp detail”
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Glaucoma - ↑ intraocular pressure (> 1220 mmHg) upon optic nerve → death
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Cataract – cloudy or opaque area in ocular
lens
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Age-related macular degeneration – loss of
vision (risk factors: HTN, cigarettes, DM)
Alterations in Refractions
 Myopia – nearsightedness: focus in front of
the retina (long eyeball)
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Hyperopia – farsightedness: focus behind
retina (fat eyeball)
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Astigmatism – uneven corneal curvature –
no single retinal focus
Auditory Dysfunction
“5% - 10% population has impaired hearing”
 Conductive – change in outer or middle
ear impairs conduction
◦ Impacted cerumen, foreign bodies, tumors (middle
ear, canal), eustachian tube, otitis media
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Sensorineural – impairment of the organ of
Corti or its central connections
◦ Congenital, noise, aging, meniere's disease,
ototoxicity, systemic disease (syphilis, diabetes,
others), and neoplasms.
Ear Infections
 Otitis
externa
◦ Infection of the outer ear
◦ Prolonged moisture exposure (swimmer’s ear) and
bacteria
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Otitis media – infants and children
◦ Acute – pain, fever, inflamed TM with middle ear
fluid
◦ With effusion – fluid in middle ear without
symptoms
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Page 340 Geriatrtic Considerations
Olfaction and Taste
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Olfaction (smell) – CN I
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Taste (gustation) – CN VII & IX
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Strong relationship between taste and smell
◦ Sour, salt, sweet, bitter, umami
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Umami?
Olfaction and Taste Dysfunctions
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Olfactory ( 7 classes)
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Hyposmia – impaired
Anosmia – loss
Hallucinations – odors not present
Parosmia - abnormal
Taste (5 classes)
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Hypogeusia - ↓ taste
Ageusia – absence of taste
Dysgeusia – unpleasant flavor
Page 341
Somatosensory Function
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Touch
◦ 4 afferent fiber types – touch, vibration pressure,
stretch, joint position
◦ Fusion of intensity, location and duration of
stimulus to higher CNS centers
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Proprioception – body position
◦ Depends upon inner ear, vision, and receptors in
joints and ligaments
Proprioceptive Dysfunction
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Vestibular nystagmus
◦ eyeball movement 2° to overstimulation of the
semicircular canals
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Vertigo
◦ spinning sensation 2° to inflammation of the
semicircular canals
◦ Meniere’s disease