Patho Chapter 14


is an unpleasant sensory and emotional experience associated with actual or potential tissue damage or described in terms of such damage


cannot be defined, identified, or measured by an observer


is subjective


is whatever the experiencing person says it is, existing whenever he says it does


Perception of pain


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

A-delta fibers

are medium sized and thinly myelinated transmit sharp, well localized fast pain sensations. These fibers are responsible for the reflex withdraw of the affected extremity even before the pain is felt.

C fibers

transmit pain slowly are dull, aching or burning sensation that are poorly localized and constant.

A-beta fibers

are large myelinated fibers that transmit touch and vibration sensations. They do not normally transmit pain.

Pathways of Nociception

pain travels up the fibers and ends up in the brain stem, reticular formation and cerebral cortex


Located in pathways of nervous system; Triggered by tissue injury(bradykinin, prostaglandins) and/or inflammation (lymphokines).

Excitatory neuromodulation

substances that are triggered after the tissue injury that reduces the pain threshold (increases sensitivity to pain); Substance P, glutamate, somatostatin

Inhibitory neuromodulators

(Serotonin, norepinephrine, and endogenous opioids) Increases the pain threshold (reduces sensitivity to pain) by binding with opioid receptors which in turn inhibits the release of excitatory neurotransmitters.
Morphine (exogenous opioids) are given to r

Morphinelike neuropeptides

Bind with opioid receptors to inhibit pain impulses in periphery, spinal cord, and brain ; Opioid receptors throughout body; Responsible for sensations of well-being and modulation of many physical processes

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

Pain threshold and tolerance is influenced by

genetics, gender, cultural perceptions, expectations, role socialization and physical and mental health

Pain tolerance varies among

Pain tolerance varies among

Tolerance generally decreases with

repeated exposure to pain, fatigue, anger etc. and may increase with alcohol consumption, opioid medications etc.

Acute Pain

Begins suddenly and relieved after pain stimulus removed; transient; protective mechanism

Protective Mechanism

Alerts an individual to a condition or experience that is immediately harmful to the body

Acute Pain 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

In unconscious patients the vital signs

may be the only sign we have that indicates that a patient may be in pain.
Explain patient in ICU with full bladder.

Acute somatic

Arises from connective tissue, muscle, bone, and skin; A delta 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 as a result of the lesser number of nociceptors:may be aching, gnawing, throbbing, or cramping

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; example: Myocardial infarction pain

Chronic Pain

-May be persistent or intermittent
-May be sudden or develop insidiously
-Usually defined as lasting at least 3 to 6 months
-Response patterns vary
-Produces significant behavior and psychologic changes
-Usually do not see physiological signs as in acute

Changes in the peripheral and central nervous systems that cause dysregulation of nociception and pain modulation processes are thought to lead to

chronic pain

Intermittent chronic pain

produce similar physiological responses as those of acute pain.
Persistent pain allows for physiologic adaptation (normal heart rate, blood pressure)
This is important for nurses to remember. Just because they are not having the physiologic changes (incre

common types of chronic pain

Myofascial pain syndromes; Chronic postoperative pain; Cancer pain; persistent low back pain

Persistent low back pain

Most common chronic pain condition.
Results from poor muscle tone, inactivity, muscle strain, or sudden vigorous exercise

Neuropathic Pain

-Result of trauma or disease of nerves (non-nociceptors)
-Most often chronic
-Peripheral (Problems with nerves)ex:Painful diabetic neuropathy
-Central (caused by problem in brain or spinal cord) ex:Phantom limb
-Often described as burning, shooting, shock

young age and pain

Pathways and chemicals associated with pain are functional in preterm and newborn infants

old age and pain

-May have lower pain threshold
-Peripheral neuropathies
-Skin thickness changes

Temperature regulation varies in response to

-Circadian rhythm

Normal range for body temperature

96.2 to 99.4 F

Extremities are cooler than the


Core temp (rectal) is higher than

skin temp (oral)

Different ways to take temp

-Oral (by mouth)
-Rectal (by anus)
-Tympanic (by ear)
-Axillary (under the arm)
-Temporal (by forehead )

Temperature peaks at

around 6pm

temperature is lowest when

you are sleeping

Peripheral and central thermoreceptors

provide the hypothalamus with information then it acts to conserve or get rid of the heat.

Heat production and conservation

-Chemical reactions of metabolism
-Skeletal muscle contraction
-Chemical thermogenesis
-Voluntary mechanisms

Chemical thermogenesis

epinephrine is released that greatly increases metabolic rate this increasing heat production.
Heat is distributed through the by the circulatory system.
Vasoconstriction shunts blood away from the skin to the core to keep the core warm.

Explain what happens to patients blood pressure after surgery and why we warm them up



When the body is warmer than the surrounding air. (decreased environmental temp.)


Direct transfer from one object to another (cooling blanket)


Transfer heat through currents of gases or liquids from warmer body to cooler air


Converts core warmed blood to the surface for heat release

Decreased muscle tone

muscles become exhausted and have reduced muscle tone


sweating. Major form of heat loss

Increased respirations

does not work well

Voluntary measures

clothing that increases body surface area available for heat loss

Adaptation to warmer climates

A body will gradually adapt to the warmer climate and with time you develop a heat tolerance.

Infants temperature regulation

-Produce sufficient body heat but are unable to conserve heat produced
-Small body size and high body surface to weight ratio
-Thin subcutaneous layer

elderly and temperature regulation

-Slow blood circulation, vasoconstrictive response, and decreased metabolic rate
-Decreased sweating, shivering, and perception of heat and cold


-Temporary resetting of the hypothalamic thermostat
-Activate heat production and conservation measures to a new set point

Exogenous pyrogens

Toxins that are produced by the invading pathogen; turn stimulate the production of endogenous pyrogens

endogenous pyrogens

produced by the bodies own phagocyte cells (tumor necrosis factor, interleukins and interferon).
The presence of these pyrogens then tells the hypothalamus to reset the body temp. at a higher level. The body then tries to maintain the higher temp. level.

Fever of unknown origin (FUO)

-Body temp of greater than 101 that remains undiagnosed after 3 days of hospital stay or 2 or more outpatient visits.
-Usual cause are infections, inflammatory response, cancer, neuro disorders.

Benefits of fever

-Kills many microorganisms:
-Decreases serum levels of iron, zinc, and copper: Minerals needed by the microorganisms to reproduce.
-Promotes lysosomal breakdown and autodestruction of cells: Prevents viral replication in infected cells.
-Increases lymphoc

Effects of fever on children

-Develop high temps even with minor infections
-Febrile seizures before the age of 5 are not uncommon

effects of fever on the elderly

-Show decreased or no fever responses to infection (Do not get the benefits of fever)
-High morbidity and morality results from lack of benefits of fever


Elevation of the body temperature without an increase in the hypothalamic set point; Can produce nerve damage, coagulation of cell proteins, and death; May be therapeutic, accidental, or associated with stroke or head trauma


is caused by increased environmental temp or hard work in such an environment; can from cramps, heat exhaustion, heat stroke, malignant hyperthermia

Temperature where nerve damage produces convulsions

105.8 F

Temperature where death results

109.4 F

Heat Cramps

-Severe spasmodic cramps in the abdomen and extremities
-Following prolonged sweating and associated sodium loss causing dehydration
-Common in individuals not accustomed to heat or those performing strenuous work in warm climates
-Fever, rapid pulse, and

Heat Exhaustion

-Result of prolonged high core or environmental temperatures
-Prolonged vasodilation and profuse sweating
(Dehydration, depressed plasma volumes, hypotension, decreased cardiac output, tachycardia)
(Dizziness, weakness, nausea, confusion,

Heat stroke

-Potentially lethal result of an overstressed thermoregulatory center
-Brain cannot tolerate temperatures >40.5o C (104.9o F)
-Cardiovascular and thermoregulatory centers may cease functioning with higher temperatures
-They loose the ability to regulate b

Malignant Hyperthermia

-Complication of a rare inherited muscular disorder
-Precipitated by inhaled anesthetics and neuromuscular blocking agents (Causes sustained muscle contractions; Increased oxygen consumption and lactic acid production)
(Symptoms include absent reflexes, f


-Body temperature less than 35 C (95 degree F)
(Ice crystals, which form inside the cells, causing them to rupture and die)
-Tissue hypothermia
(Slows the rate of cellular metabolism; Increases blood viscosity and slows blood through the microc

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 in tissue during surgery or limb reimplantation
-May lead to ventricular fibrillation and cardiac arrest
-They are not dead until they are warm and dead

CNS trauma

-leads to central fever off greater than 102.2
(Inflammation, increased ICP, intracranial bleeding)
Accidental injuries
Hemorrhagic shock
Major surgery
Thermal burns

Central fever

not caused by an infectious agent; other causes of temperature changes are accidental injuries, shock, surgery, and burns.