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

Characteristics of chronic inflammation

Less swelling & exudate; more lymphocytes/macrophages/fibroblasts, tissue destruction, & collagen (→ more fibrous scar tissue formation)

MOA of Acetylsalicyclic Acid + containdication?

(Aspirin); Decreases prostaglandin synthesis, contraindicated in children (risk Reye’s Syndrome)

Key inflammation drugs? (4)

Acetylsalicyclic Acid, Acetaminophen, Nonsteroidal Anti-Inflammatory Drugs (NSAIDs), Steroids

Acetaminophen use for inflammation?

To manage pain/fever

MOA of NSAIDs + ones to know? (3)

Decrease prostaglandin synthesis; Ibuprofen, Piroxicam, & Diclofenac Sodium

MOA of steroids + ones to know (4) & key consideration?

Decrease histamine + prostaglandin release & block immune response; Prednisone, Triamciolone, Methylprednisone, & Dexamethasone; Long-term/high-dose → significant SE

Key herbs + spices to know for inflammation management?

Turmeric, black pepper, ginger root, rosemary

RICE acronym for inflammation

Rest Ice Compress Elevate

Define resolution healing + example

Minimal tissue damage, cells recover & tissue returns to normal; mild sunburn, epidermis abrasion

Define regeneration healing + example

Damaged tissue where cells are capable of mitosis (replacement w/ identical cells); skin regeneration from dermis cut

Define replacement healing + example

Tissue replaced w/ connective tissue (scar); brain, myocardium, deep skin wounds

What occurs during the injury + inflammation stage of healing by 1st intention?

Scab on top + blood clot forms, wound is sutured to hold edges together, inflammation begins as neutrophils arrive

What occurs during the granulation tissue & epithelial growth stage of healing by 1st intention?

Epithelium begins to regenerate, granulation tissue + new capillaries form, inflammation continues as macrophages & fibroblasts arrive

Final stage of healing by 1st intention?

Small scar remains (fibrous tissue)

What occurs during the injury + inflammation stage of healing by 2nd intention?

Scab on top + blood clot forms, inflammation occurs

What occurs during the granulation tissue & epithelial growth stage of healing by 2nd intention?

Epithelium begins to regenerate, granulation tissue + collagen & new capillaries form, inflammation continues as macrophages arrive

Final stage of healing by 2nd intention?

Large scar remains (fibrous tissue contracts)

Factors that promote healing?

Decreased age, increased mitosis, sufficient nutrition (protein, vit A & C), effective circulation, clean undisturbed wound, no infection/trauma to site, adequate hemoglobin

Factors that delay healing?

Increased age, decreased mitosis, anemia/circulatory issue, prolonged steroid use, infection/foreign material, irritation/excessive motility, comorbidities

Scar formation complications?

Loss of function, contractures, adhesions, and hypertrophic scar tissue

How does scar formation lead to contractures?

Scar tissue is inelastic, shrinks w/ time → decreased ROM of joint

What are adhesions in relation to scar formartion?

Scar tissue joins 2 normally separated surfaces

Define hypertrophic scar tissue

Overgrowth of fibrous tissue (keloid)

Burn classifications + diagnostic criteria?

Thermal (heat) or non-thermal (electrical) injury → acute inflammation; based on depth of skin damage & % of body surface area (BSA) involved

1st degree (superficial) burn criteria? (+ examples)

Epidermis & upper dermis; red, painful & heals w/o scarring; mild scald, sunburn

2nd degree (partial-thickness) burn criteria?

Destruction of epidermis + part of dermis; red, edematous, blistered, hypersensitive/painful; heal by regeneration

3rd degree (full-thickness) burn criteria?

Destruction of all skin layers; hard, dry eschar; skin graft necessary

4th degree burn classification?

Destruction of underlying tissue

BSA + Rule of 9s use?

Guideline for Tx + fluid replacement; rapidly calculate % of body burnt, each body part assigned multiple of 9

s/s of burns?

Shock, pain, infection, increased metabolic needs

Healing interventions for burns?

Debridement, skin grafts/substitutes, prevention of hypertrophic scarring

Phases of inflammation?

Vascular (5-10 min after injury) & Delayed (leukocytes infiltrate inflammed tissue)