LA Wound Healing & Surgical Inflammation (11) Flashcards
Dr. Devine
What are the phases of wound healing?
inflammation (4-6 days)
proliferation (4-24 days)
remodeling (21 days - 2 years)
What is the goal of hemostasis?
to stop bleeding while maintaining perfusion
What happens with endothelial cell disruption in hemostasis?
immediate vasoconstriction —> exposure of vWF —> platelet activation and aggregation —> coagulation cascade
Hemostasis leads to inflammation. How?
- endothelial cells release vasodilators mediated by histamine, etc
- post-capillary venue leakiness
- protein leakage
What is the purpose of edema?
facilitates delivery of soluble factors and cells
What are the two phases of inflammation (the debridement phase)?
early: neutrophil recruitment
late: monocyte transformation
How do leukocytes respond to inflammation?
are recruited from circulation by chemoattractants (from coagulation)
rolling, activation, tight adhesion, transmigration of cells through microvascular endothelium
What is diapedesis?
the passage of blood cells through intact capillary walls
What is neutrophil diapedesis encouraged by and how long does it take?
encouraged by capillary permeability, minutes and peaks 1-2 days after injury
What are the functions of macrophages?
- pro-inflammatory functions
- stimulate proliferation of firm, endodermal, and epithelial tissues
- helps with remodeling phase
What is the resolution of inflammation?
each of the pathways needs to be halted or reversed - apoptosis of cells
Why is the inflammatory phase most easily modulated by clinicians?
- good surgical debridement
- good hemostasis
- adequate drainage
- NSAIDs and steroids
What do steroids do?
inhibit phospholipases
What happens in the proliferation phase of wound healing?
- fibroplasia
- angiogenesis
- epithelialization
What is fibroplasia?
formulation of granulation tissue by fibroblasts
- scaffold
- temporary barrier of infection
What is granulation tissue made of?
- macrophages
- fibroblasts
- blood vessels
When do you start to see granulation tissue?
around day 5
What are fibroblasts directed by? What do they produce?
directed by macrophages via cytokines and growth factors
- produce extracellular matrix - initially more type III immature collagen, later more type I collagen
What is the time of increasing wound strength?
rapid gain 7-14 days (corresponds to time of suture removal)
How does angiogenesis occur?
regulated by macrophages and endothelium (vascular endothelial growth factor)
What is epithelialization? Which direction does it cover?
- epithelium covers wound
centripetally
What happens to fibroblasts regarding maturation?
wound contraction - fibroblasts differentiate into myofibroblasts under influence of growth factors and cytokines
What is involved in remodeling?
conversion of granulation tissue into scar tissue
matrix metalloproteinases (collagenases, gelatinases, stromelysins) - demolition team
How long can remodeling take?
up to 1-2 years, depending on size of wound
When does healing stop?
wound edges meet (good)
- tension surrounding skin > force of myofibroblasts (not ideal)
- reduced #s of myofibroblasts (not ideal)
- granulation tissue is proliferative
What is shock? What can it lead to?
cascade of events that begins when cells/tissue are oxygen deprived from inadequate perfusion
can lead to systemic inflammatory response syndrome and multiple organ dysfunction
What is systemic inflammatory response syndrome?
generally considered excessive response - cytokine storm, leukocyte dysfunction, delayed resolution of inflammation
When do you classify something as SIRS?
must meet any 2 with underlying pathologic cause
- hyper or hypothermia
- tachycardia
- tachypnea
- leukocytosis or leukopenia
- depression
- DIC
What happens with hyperthermia?
pro inflammatory cytokines
act on hypothalamus
What happens with hypothermia?
hypoperfusion, central blood sequestration
What happens with tachycardia?
dehydration —> hypotension
or pain increases heart rate
shift fluid between spaces
What happens with tachypnea?
PAIN
leads to metabolic acidosis
What are the CBC alterations for shock?
primarily from change in neutrophils
- leukopenia - increased use
- leukocytosis - released from sequestered areas
- left shift
What happens with depression and SIRS?
cytokines, eicosanoids
What effect do corticosteroids (stress) have on surgical healing?
reduce healing - anti-inflammatory, reduce activity/production of growth factors
What is multiple organ dysfunction syndrome?
progression or sequelae of SIRS
presence of altered organ function in an acutely ill patient such that homeostasis cannot be maintained without interruption
