Midterm exam Flashcards
Acute Wound
- sudden loss anatomical structure in tissue following transfer of kinetic, chemical, thermal energy
- in recently uninjured, normal tissue
- acute wound healing within 6-12 weeks
- surgical wounds
Chronic Wound
- fail of wound healing
* prolonged tissue repair
When does healing arrest most commonly occur?
Inflammatory phase
failed epithelialization due to repeated trauma or desiccation may result in?
Chronic partial thickness wound
Primary healing
- tissue cleanly incised
- anatomically reapproximated
- healing by primary intention
- no complications, minimal scarring
Secondary Healing
- wounds left open through formation of granulation tissue, coverage by migration of epithelial cells
- healing by secondary intention
- infected wounds and burns
Delayed primary closure
- wound left open to heal under carfeully maintained, moist healing environment for abt 5 days
- closed primarily
- less likely to become infected → bacterial balance achieved, O₂ requirements optimized through granulation tissue
- third intention
Granulation tissue
- red, moist, granular tissue
* collagen, new blood vessels, fibroblasts, inflammatory cells, scar tissue
Mechanism of Wound Healing
• from coagulationa nd inflammation through fibroplasia, matrix deposition, angiogenesis, epithelialization, collagen maturation, wound contraction
What do wound healing signals include
peptide growth factors, complement, cytokine inflammatory mediators, metabolic signals (hypoxia & accumulated lactate)
What is redundant and pleiotropic in Wound healing
Cellular signaling pathways
What is the first step of Wound Healing Mechanism and until when does it last
- Hemostasis and Inflammation
* 0-5th day after injury
What happens in the first step of Wound Healing: Homeostasis and Inflammation
- stops bleeding
- immediately, coagulation products fibrin, fibrinopeptides, thrombin split products and complement components attract inflam. cells
- inflam cells increase metabolic demand
- local microvasc damaged → local energy ↓ , PaO₂ ↓ , Co₂ ↑
- oxidative stres triggers tissue repair
- Macrophages synthesize wound healing molecules, release lactate
- lactate stimulates angiogenesis and collagen deposition
- if not infected wound _> granulocyte population diminishes
- fibroblasts and new blood vessels
What factors are released by Platelets activated (by thrombin) in the 1st step of wound healing?
• insulinlike growth factor (IGF-1), transforming growth factor α (TGF- α), transforming growth factor β (TGF-β), platelet derived growth factor (PDGF)
What do IGF-1, TGF- α, TGF-β, PDGF attract to the wound?
leukocytes, macrophages, fibroblasts
what complement products are involved in the signal cascade which damaged endothelial cells respond to?
C5a, tumor necrosis factor α (TNF- α), interleukin-1 (IL-1), interleukin 8 (IL-8)
What happens in the second step of healing: Proliferation (Fibroplasia and Matrix Synthesis) 4-14d
- Fibroplasia, localize near wound edge → active tissue repair environment with tissue oxygen tension of 40mmHg, optimal for fibroblast replication
- smooth muscle cells progenitors of fibroblasts
- lipocytes, pericytes, stem cells may differentiate into fibroblasts
- Extracellular matrix depostion
- fibroblasts secrete collagen and proteoglycans
- extracelullar molecule sof matrix become physical basis of wound strength
- growth factors & metabolic products (lactate) regulate and stimulate synthesis of collagen
- collagen gene expression controlled by stress corticoids, TGF_β signaling pathway, retinoids
What is Fibroplasia stimulated by?
PDGF, IGF-1, TGF- β, later by peptide growth fsctor release
What stimulates fibroplasia?
• growth factors and cytokines: → fibroblast growth factor FGF → IGF-1 → vascular endothelial growth factor VEGF → IL-1, IL-2, IL-8 → PDGF →TGF- α, TGF- β → TNF- α
What do growth factors regulate regardless of collagen gene expression?
- glycosaminoglycans
* tissue inhibitors of metalloproteinase (TIMP), fibronectin synthesis
What happens in Angiogenesis?
- 2nd to 4th day after injury
- earlier than 4 days when new capillaries sprout from preexisting venules and grow towards injury in response to chemoattractants
- budding vessels soon meet and fuse with counterparts
- blood flow establishment across wound
- in left open wounds, new capillaries connect with adjacent capillaries in same direction → granulation tissue
Where are the dominant angiogenic stimulants in wounds derived from?
- platelets in response to coagulation
* then from macrophages in response to hypoxia or ↑ lactate, fibrin
What growth factors are involved in Angiogenesis?
PDGF, FGF, TNF α, TGF β, VEGF
What happens in Epithelization
- starts from wound edges
- new migrate to unhealed area, anchor to first unepithelialized matrix encountered
- PaO₂ low under cell at anchor point → further mitosis
- epidermal mesenchymal communication continues until wound closed
What regulates epithelial cell replication?/ are potent epithelial mitogens
- TGF α, keratinocyte growth factor (KGF)
* TGF- β which blocks epithelial cells from differentiating and therefore is a potent mitogen
What triggers TGF- β production from squamous epithelial cells?
low PaO₂
When does Squamous epithelialization and differentiation proceed maximally
- when surface of wound kept moist
* e.g exudates froma cute uninfected wounds also contains growth factors and lactate
What impairs process of epithelialization and differentiation
drying of wound
What happens in Maturation and Remodeling?
- 8d to months
- fibroblasts replace fibrin matrix with collagen monomers
- extracellular enzymes, some PaO₂ dependent, polymerize monomers, collagen fibrils and cross link them to collagen fibers
- random pattern, predispose early aournd joints → disabling
What might prevent disabling wound contractures?
Skin grafts, especially thick ones, dynamic splints
What are wounds vulnerable to during rapid turnover?
contraction and stretching
What do wound myofibroblasts express which also contributes force to fibroblast-mediated wound contraction?
express intracellular actin filaments
Which part of the GI is least reliably and more likely to leak compared to the stomach or small intestine anastomoses with rare leakage
colon, esophageal
Does Intestinal anastomoses or skin wounds regain strength rapidly?
intestinal anastomoses
what part of GI lacks serosal mesothelial lining (source of repair cells) which might contribute to failed wound healing?
esophagus, retroperitoneal colon
When is danger of leakage the greatest?
4th to 7th day, when tensile strength could be impeded by impaired collagen deposition or ↑ lysis
From where does Injury (fracture) cause hematoma formation?
damaged blood vessels of periosteum, endosteum, surrounding tissue
What do monocytes and granulocytes debride and digest on fracture surface?
necrotic tissue and debris including bone
What is callus?
- thickened and hardened part of skin or soft tissue, especially in area of friction
- composed of fibroblasts, endothelial cells, bone-forming cells (chondroblasts, osteoblasts)
What is endochondral bone formation?
•osteocytes (fibroblasts) deposit collagenous matrix, chondroblasts deposit proteoglycans
What is the most frequent cause of healing failure?
- impaired perfusion
* inadequate oxygenation
Which factors lead to failure to heal
- anti-inflammatory corticosteroids, immune suppressants, cancer chemotherapeutic agents that inhibit inflam. cells
- malnutrition
- weight loss
- protein depletion
Where is upregulation of fibroblast growth factor like TGF-β implicated?
hypertrophic & keloid scar formation
The PaO₂ of wound fluid in human incision is about…?
30-40 mmHg
critical collagen oxygenases involved have Km values for oxygen of…?
20 mmHg → 200mmHg
What are the most common acute wound complications?
• pain, infection, mechanical dehiscence, hypertrophic scar
How do venous ulcers occur?
- largely of lower leg
- reflect poor perfusion & perivascular leakage of plasma into tissue (stimulates inflammation)
- most heal of venous congestion and edema relived by leg elevation, compression stockings, surgical procedures
Arterial or ischemic ulcers?
- lateral ankle or foot
- treated by revascularization
- hyperbaric oxygen expensive treatment of O₂ delivery
Diabetic ulcers
- ischemic disease (with neuropathy or not): at risk for gangrene
- neuropathy if trauma
- amputation if revascularisation not possible, protection of ulcer
Wat are pyoderma gangrenosum, granulomatous inflammation excess cytokine release leads to? what are these ulcers associated with?
- cause skin necrosis
* associated with inflammatory bowel disease
Decubitus ulcer
- immobilization
- prolonged pressure, reduces tissue supply, irritative or contaminated injections, prolonged contact with moisture, urine, feces
- poorly nourished patients, immobile elderly, ICU patients
- greater trochanter, sacrum, heels, head
- treated with drainage of infected space, excision of necrotic tissue, musculocutaneous flap
What is the treatment of chronic wounds and ulcer
- control infection with antibiotics
- treat underlying circulatory disease
- moist
- debridement of unhealthy tissue
- reduce autonomic vasoconstriction
Peritoneal scarring (adhesions)
- bands of scar tissue connecting organs
- fibrin, fibroblasts, collagen = filmy adhesions
- fibrinolysis within 1 week
- migration of capillaries, nerves, connective tissue = solid adhesions
silk suture
- soft tissue
- is an animal protein, inert in human
- loses strengt over period of time
- unsuitable for arteries, insertion prosthetic cardiac valves
- multifilament
- provide immune barriers for bacteria
synthetic non absorbable sutures
- inert polymers → strength
- knotted at least 4 times
- incr amount of retained foreign material
- may become infected
- no harbour of bacteria
- nylon extremely unreactive, but hard to tie
synthetic absorbable sutures
- strong, predictable loss of strength
- minimal inflammation
- useful in contaminated GI, urologic, gynecologic operations
stainless steel wire
- inert, maintains strenght for long time
- difficult to tie
- painful
- no harbour of bacteria
- can be left in granulating wounds
Staples
- steel-tantalum alloys
- min tissue reaction
- skin closure
surgical glues, tissue adhesive
- safe and effective for repair of small skin incisions
- cryanoacrylate based glues
- seal serves as wound dressing
What is the goal in surgical technique/incisions/operations
- anatomic tissue approximation achieved but optimum tissue perfusion preserved
- fine instruments!!
- proteCt tissue from drying and contamination!
What is the optimal suture length to wound length ratio in laparotomy closure?
4:1
What happens, when wound closure is excessively tight?
- strangulates tissue
- impair wound perfusion & oxygen delivery
- hernia formation or infection
delayed primary closure
- wound left open 4-5 days
* angiogenesis and fibroplasia start, bacteria cleared from wound
What are examples of wounds that should be left open for secondary closure?
• fibrin-covered or inflamed wounds
What level of β-hemolytic streptococcal wound infection predicts delayed wound healing
any level
What do highly incompatible material like wood splinters elicit
• acute inflammatory process, massive release of proteolytic enzymes
What influence has Negative Pressure Wound Therapy on Wounds
- stabilizes distractive forces of an open wound and supports healing
- distractive forces keep wound open with force vectors opposing wound contraction, impair healing
What treatment is done when chronic infection and significant tissue loss are combined?
Musculocutaneous flaps
What are pros and cons of Adhesive tapes?
+ rapid, simple, no risk of needle injury
- needs dry skin, poor adherence, poor hemostasis, accidental removal
What are pros and cons of skin glue
+ rapid, simple, reduced pain, good aesthetic result
- poor approximation of deep layer, poor hemostasis
Pros and cons of Surgical skin staples
+ fast closure of large wounds, less reaction than sutures
- poor hemostasis
example cutting instrument
- scalpels
* scissors for sutures or tissues
examples grasping instruments
- tissue forceps
- ratcheted tissue forceps
- needle-holder
example retracting instruments
- hand-held retractors
- self- retaining retractors
- large (complex) self-retaining retractors
Surgical staplers
- skin stapler
- linear stapler
- GI anastomosis stapler
- circular stapler
Local anesthetics mechanism
• nerve conduction relies on cell membrane depolarisation (Na⁺ inflow) and repolarization (K⁺ outflow)
→ local anesthetics inhibit electrical conduction along neurones
• transient blocking of Na⁺ transport channels → blocking depolarization
→ sensory neurons more sensitive than motor neurons
Examples Local Anesthetics
- Lidocaine (Xylocaine 2%-20mg/ml) with or without adrenaline
- Bupivacine (Marcaine 0.5%-5mg/dl)
- Ropivacaine (Naropaine 0.75%-7.5 mg/ml)
onset = 5-10 min duration = 1-6 hours
Method local anesthetics: Topical
- lipid soluble cream
* skin and mucosa up to few mm deep
Method local anesthetics: Local infiltration
- injected into tissue
* local nerves
Method local anesthetics: Nerve block
- injected around nerve or plexus
* distribution of nerve blocked
Method local anesthetics: Intravenous block
- IV injection in arterial turniqueted limp
* nerve tissues within limb
Method local anesthetics: centrineural block
- epidural or spinal injection
* multiple dermotomes
Method local anesthetics: Cavity administration
- intrapleural or intraperitoneal administration
* local nerves in cavity
What are side effects of local anesthesia toxicity
- mouth and tongue numbness
- anxiety
- tremor
- drowsiness
- tachypnea
- hypotension
- nausea & vomiting
- allergy
Lidocaine
- onset 5-10min
* max dose 300mg for 70kg person
Name the total body water distribution
• 30-40% intracellular
• 15-20% extracellular
→ 80% (12-16% of TBM) in interstitial compartment, 20% (3-4%) in intravascular(1/4 proximal to arterioles, 3/4 distal to arterioles)
what is the main intracellular cation?
potassium ion K⁺
what is the main extracellular cation?
sodium ion Na⁺
what are intracellular cations electrically balanced by?
polyatomic ion phosphate (PO₄³⁻ ) and negatively charged proteins
what are extracelullar cations balanced by?
chloride ion (Cl⁻)
what is the main cause for high colloid pressure in serum, which in turn is chief regulator of fluid distribution between 2 extracellular compartments?
albumin, protein in intravascular fluid
What does the relationship between colloid osmotic pressure and hydrostatic pressure govern?
movement of water across capillary membrane
how is the body’s voluem status and electrolyte composition dtermined by kidneys?
• maintain constant volume and osmolality by modulating amount of free water and Na⁺ being reabsorbed from renal filtrate
What is the chief regulator of osmolality?
Antidiuretic hormone, or arginine vasopressin
Is following true:
collecting duct is permeable to water leading to water accumulation and production of dilute urine
NO
impermeable to water, leading to water loss and prod of dilute urine
at high levels ADH(antidiuretic hormone) has what effect on arterioles
vasoconstriction
where is most filitered Na⁺ reabsorbed into? (60-70%)
proximal tubule
20-30 into thick ascending limb LOH
5-10% reabsorbed by distal tubule
what is osmolality
- total solute concentration
* 290-310 mOsm/Kg
Hypovolemia
• surgical patients
• loss of isotonic fluids in setting of hemorrhage, GI losses, sequestration of fluids in gut lumen, burns, excessive diuretic therapy
• in poor settings: sweat as well
• loss of Na⁺ and water without affecting osmolality of extracellular fluid, little shift of water
• stimulation aldosterone secretion from zona glomerulosa (adrenal cortex)
→ ↑ reabsorption of Na⁺ and water from renal filtrate, excretion of low vol of hypertonic urine (oliguria)
Clinical Presentation of Hypovolemia & laboratory
- longitudinal furrows on tongue, dry oral and nasal mucous membranes
- ↑ capillary refill time, unclear speach, upper & lower extremity wekaness, dry axilla, postural hypotension
- elevated blood urea nitrogen (BUN)
- disproportionate rise in BUN compared to creatinine (Cr)
what is 91-100% sensitive clinical finding for severe Hypovolemia
postural incr in heart rate of at least 30 beats per min with postural dizziness
Treatment hypovolemia?
isotonic fluid
Metabolism of what is decreased by liver disease
• circulating aldosterone and ADH
Hypervolemia
- surgical patients
- after treatment of shock with colloid and crytalloid fluids
- postoperative period when ADH secreted, disrupting role in regulation of osmolality
- high ADH → vasoconstrictive