Pain, Inflammation, and Healing

Define pain threshold

Amount of pain required to perceive

Define pain tolerance

Amount of pain a person is willing to bear

Define intractable pain

Resistant pain that cannot be controlled by meds

Define referred pain

Pain perceived at site distant from source

Pain pathway steps overview?

Stimulus → nociceptor stimulation → peripheral nerve → synapse → spinal decussation → lateral spinothalamic tract → reticular formation → thalamus → somatosensory cortex → hypothalamus → limbic system

Types of nociceptor stimulators?

Thermal, chemical (i.e. Bradykinin), mechanical/physical (i.e. pressure)

Types of peripheral nerves (afferent fibers)?

A delta fibers & C fibers

What type of pain are A delta fibers associated with?

Rapid, acute pain (myelinated fibers); thermal & physical stimuli to skin & mucous membranes

What type of pain are C fibers associated with?

Slower pain responses (non-myelinated); thermal, physical, & chemical stimuli to muscles, tendons, myocardium, GI tract, & skin

Function of a synapse in pain transmission? (What reflex occurs?)

Reflex response sends motor impulse (efferent) to muscles to contract body away from harmful stimulus

Function of spinal decussation in pain transmission?

Crosses the signal over to the spinal cord

What is the lateral spinothalamic tract in pain transmission?

Ascending tract leading to the brain

Location + function of reticular formation in pain transmission?

W/n pons & medulla; RAS (reticular activating system) → brain awareness of incoming pain stimuli

(Lecture 1) Where do many analgesics act in the pain pathway to depress pain?

Reticular formation (block awareness of pain stimuli)

Function of the thalamus in pain transmission?

Sensory relay center

Location & function of the somatosensory cortex in pain transmission?

W/n parietal lobe; locate pain site

Roles of hypothalamus & limbic system in pain transmission?

Hypothalamus → stress response, limbic system → emotional response

Define the Gate Control Theory

Built-in “gates” in the spinal cord regulate pain; when fast sensory signals (A delta fibers, touch/cold) activate them, the gates close and reduce the slower pain signals (C fibers)

How does icing a would relate to Gate Control Theory?

Ice = strong input from large A-beta fibers → gate closes → pain signals from C-fibers can’t get through → less perceived pain

Define endorphins

“endogenous morphine;” body’s own endogenous analgesic

MOA of endorphins + types? (3)

CNS releases endorphins to block pain conduction; Enkephalins, Dynorphins, & Beta-Lipotropins

How does Serotonin relate to endorphins? And Depression?

Serotonin can increase enkephalins release; Depression → decreased Serotonin → chronic pain

Body response (s/s) to acute pain?

Increased pulse, BP, N/V, & cool/moist skin

Body response (s/s) to chronic pain?

Disabling fatigue, depression, irritability

Common mild analgesics?

Acetaminophen, Acetylsalcylic Acid (Aspirin)

Common moderate analgesics?

Codeine, Oxycodone (both combined w/ mild analgesics)

Common severe analgesics?

Morphine, Hydromorphone

What are adjunct treatments? Common pharmacological adjunct for pain?

Secondary treatments used alongside primary analgesic; sedatives & anti-anxiety agents often utilized

What is a Rhizotomy/Cordotomy?

Surgical procedure to sever sensory nerve pathway for intractable pain

Surgical implant options for pain?

Intrathecal drug delivery direct to spinal cord, spinal cord stimulation implant (low-level electrical signal blocks pain signal from brain)

Define Transcutaneous Electrical Nerve Stimulation (TENS)

Low-volt electric current through skin to decrease pain signals to brain

Define trigger point injections

Local anesthetics, steroids, or botox → muscle relaxation & decreased pain

Define local anesthesia + example?

Injection or topical application to skin/mucous membranes → blocked pain transmission; ex: Lidocane at dentist

Define regional anesthetic

Block pain impulses from the legs or arms

Define spinal anesthesia

Inject into epidural space/CSF → blocked conduction at/below injection level

Define general anesthetic + common combination

Inhaled gas or IV injection → partial or total LOC; combined w/ analgesics to reduce pain

Define Inflammation + suffix?

Normal, nonspecific defense mechanism intended to localize & remove an injurious agent; “itis” = inflammation

What is the relationship between inflammation and infection?

Inflammation does not = infection; infection can cause inflammation, but inflammation does not always indicate infection

Overview of inflammation mechanism steps?

Injury → cells releasing chemical mediators → vasodilation & increased blood flow → increased capillary permeability → leukocytes to injury site → phagocytosis

What chemical mediators are sent to the site in inflammation?

Histamine, serotonin, prostaglandins, & leukotrienes → interstitial fluid & blood

Define hyperemia

Increased blood flow to an area

Function of increased capillary permeability in inflammation?

Allow fluid & plasma proteins to move to interstitial space; fluid dilutes toxic materials, globulins (antibodies, fibrinogen) localize site

Role of phagocytosis in inflammation?

Debris removal to prepare for healing

4 cardinal signs of acute inflammation + causes?

Redness (rubor/erythemia) → increased blood flow; Heat → increased blood flow; Swelling → shift of protein & fluid into interstitial; Pain → fluid increases P on nerves & local irritation from chemical mediators

Define exudate related to inflammation

Collection of interstitial fluid in inflammed area

Define serous exudate + examples?

Small amounts of protein & WBCs; allergic rxns, burns

Define fibrinous exudate + associated risk

Thick, sticky, high cell/fibrin content → increased risk scar tissue

Define purulent exudate + indication

“Pus;” thick, yellow-green w/ leukocytes, cell debris, & microorganisms; Infection indication

Define an abscess

Localized pocket of purulent exudate or pus in a solid tissue

Fever (Pyrexia) MOA?

WBCs/macrophages release pyrogens, pyrogens w/n blood → hypothalamus to increase temperature → impaired pathogen production

How does shivering function in relation to pyrexia?

Shivering increases cell metabolism to produce heat until body reaches new set-point temperature

Non-specific diagnostic test results for acute inflammation

For general screening/monitoring; Increased WBC count (Neutrophils), serum C-Reactive Protein (CRP), & Erythrocyte Sedimentation Rate (ESR)

Specific enzymes present in acute inflammation?

Creatine Kinase (CK-MB, MI specific) & Alanine aminotransferase (ALT, liver specific)

Complications for lung & joint inflammation?

Lung → impaired lung expansion & decreased O2; Joint → Decreased ROM

How can acute inflammation lead to infection?

When tissue damage, swelling, or necrosis create openings or weakened defenses that allow microbes to enter and grow

How can acute inflammation lead to skeletal muscle spasms?

Pain, nerve irritation, swelling, and reduced blood flow trigger reflex muscle guarding and involuntary muscle contractions