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Burns part 2 - pathophysiology
Integrated pathophysiology for nurses (HTHSCI 3PA2A)
McMaster University
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BURN PATHOPHYSIOLOGY - OVERVIEW
Burn injuries causes both local and systemic response
Local responses described as 3 zones of burn:
- Zone of coagulation (necrosis)
- Tissue necrosis is irreversibly lost due to coagulation of skin proteins
- Evidenced by clotted blood and thrombosed blood vessels
- Zone of stasis (injury)
- Located deep and peripheral to the necrosis zone
- Area at risk due to decreased blood flow but potentially salvageable if perfusion is maintained and infection or edema is prevented
- Zone of hyperemia
- Peripheral to and below the zone of stasis
- Characterized by minimal cellular injury with increased blood flow and should recover unless an invasive infection or profound tissue inflammation occurs
- Zone of coagulation (necrosis)
When burn injuries occur, local mediators (histamine, serotonin, kinins, arachidonic acid metabolites, complement, cytokines, catecholamines) are released by the body
These local mediators cause vasodilation and increase capillary permeability allowing plasma proteins to escape the intravascular space - This increases tissue oncotic pressure (pulls water towards higher concentrations of proteins) and creates local tissue edema. - A burn injury is also associated with increased levels of profound vasoconstrictor thromboxane A2, which may compromise perfusion, decreasing blood flow thus enlarging the zone of stasis and creating a larger burn injury - The coagulation system (blood clotting) is activated concurrently, causing platelet aggregation (clustering of platelets to form a plug to stop bleeding). - Neutrophils and macrophages release multiple cytokines to promote wound healing - Together, all of these intense inflammatory responses lead to vascular stasis and rapid tissue edema BURN PATHOPHYSIOLOGY
The release of cytokines and other inflammatory mediators at the site of injury has systemic effects once the burn reaches 30% of total body surface area. Thus Causing alterations in organ function remote from site of injury
- SYSTEMIC CHANGES:
- Cardiovascular changes:
- Increased capillary permeability causing loss of intravascular proteins and fluids into the interstitial compartment
- Peripheral and splanchnic (stomach, intestine, liver..) vasoconstriction occurs
- Decreased Myocardial contractility due to release of tumor necrosis factor alpha (TNF alpha)
- ^these changes along with fluid loss from burn wound, results in systemic hypotension (low bp) and end organ hypoperfusion (decreased blood flow and oxygen delivery to organs/tissues)
- Respiratory changes
- Inflammatory mediators cause bronchoconstriction and in severe burns, adult respiratory distress syndrome can occur (ARDS)
- Metabolic changes
- Includes increase of basal metabolic rate (energy needed) up to 3x it's original rate
- ^this coupled with splanchnic hypoperfusion (reduced blood flow to abdominal organs), necessitates early and aggressive enteral feeding to decrease catabolism (breakdown of tissues/muscle proteins) and maintain gut integrity
- Immunologic changes
- Immunologic changes leads to non-specific down regulation of the immune response, affecting cell mediated and humoral pathways
- Non-specific down regulation of cell mediated and humoral pathways (diminished production and effectiveness of antibodies)
*basal metabolic rate: amount of calories body needs for life sustaining functions *enteral feeding: thru the nose *catabolism: breakdown of complex molecules like organ tissues or muscle proteins *splanchnic perfusion: describes blood flow to abdominal gastrointestinal organs (stomach, liver, spleen, pancreas, small/large intestine) *non-specific down regulate: decreased surface receptors for neurotransmitters= decreased cell sensitivity Humoral response: production and action of antibodies by B cells to neutralize and eliminate foreign substances and pathogens circulating in the body fluids
SPECIAL CONSIDERATIONS FOR PEDIATRIC AND GERIATRIC POPULATIONS
- Pediatric:
- Sustains more injuries than adults due to their thin skin
- They have proportionally larger body surface area in relation to their height/weight = greater risk for fluid and heat loss - Large body surface to mass ratio
- Achieving a delicate balance between dehydration and overhydration is important
Burns part 2 - pathophysiology
Course: Integrated pathophysiology for nurses (HTHSCI 3PA2A)
University: McMaster University
