Ch. 75, 76, & 81 Wounds and Burns Flashcards
How is the vascular supply of the subcutaneous tissue divided?
Three divisions
superficial aka subpapillary plexus
middle aka cutaneous plexus
deep aka subdermal/subcutaneous plexus
what is a cutaneous angiosome
a given region of skin is supplied by a regional artery and vein is a cutaneous angiosome
Cats and dogs have different kinds of angiosomes - cats have a smaller number but wider distribution of cutaneous perforating vessels than dogs
How strong is wounded skin at 14 days after surgery
only 5-10% of its unwounded strength
and only 25% by 3-4 weeks
several months later it maxes out at 70-80%
How do cat wounds heal compared to dogs?
Cats have lower cutaneous perfusion immediately following surgery than dogs
Cat open wounds heal more by contraction whereas dogs heal more by fibroblasts and epithelialization
How should larger defects be closed in regards to tension lines as a general guideline
large defects should be created and closed PARALLEL to tension lines
How far will char penetrate when skin is incised by radiowaves vs CO2 laser vs monopolar
radiowave - 0.171 mm
CO2 laser - 0.215 mm
monopolar - 0.255 mm
Is the wound strength stronger or weaker with a blade vs cautery?`
Incisions made by sharp dissection with a scalpel blade had TWICE the wound strength at 10-12 days post incision
Scalpel incisions produced less drainage than laser and electrocautery incisions and had faster and stronger healing
Why should you primarily close traumatic wounds within 3-6 hours?
within 3-6 hours, bacteria within a minimally contaminated wound can multiply to 10^5 per gram of tissue or ml of exudate and that increases the risk of infection dramatically
What are the theoretical ways that low level laser therapy aids in wound healing
enhance leukocyte infiltration
increase growth factors, macrophage activity, neovascularization, and fibroblast and keratinocyte proliferation
promote early epithelialization
What is an abrasion
partial thickness epithelial injury usually from blunt trauma or shearing
minimal bleeding occurs and they heal rapidly by re epithelialization
What is a puncture wound
penetration of an object into the tissues and is characterized by a small skin opening with deep tissue contamination and damage
may include bite wounds, gunshot injuries, wounds cause by penetration of foreign bodies
What is a laceration
sharply incised skin edges and may extend into deep tissue such as muscle and tendons
usually minimal peripheral trauma to wound edges
What is a degloving injury
extensive loss of skin and underlying tissue
immediate or delayed exposure of the wound bed
a physiologic degloving is where the skin surface is intact but avulsed from the underlying SQ tissues and blood supply - delayed necrosis will occur
what is a thermal burn
the result of close proximity or direct application of heat to the skin
fire, cage dryers, heating pads, electrical cords, heat lamps, hot liquids, and malicious incidents
extent of the wound is difficult to predict because of delayed microvascular damage
what is a decubital ulcer
the result of compression of the skin and soft tissues between the bony prominence and a hard surface, resulting in skin loss over a bony protuberance
What is a more relevant conceptualization of the effect of the microbial burden on a wound than the usual greater than 10^5 CFU/gram of tissue or ml of exudate
(number of microorganisms x virulence)/host resistance
What is primary wound closure
first intention healing
wound edges are apposed
what is delayed primary wound closure
appositional closure but within 3-5 days after wounding (PRIOR to granulation bed forming)
what is secondary wound closure
appositional closure AFTER 3-5 days when there is granulation tissue
may also be called third intension healing which is dumb
what is second intention healing
healing by contraction and epithelialization
true or false
there is no difference in risk for infection with tap water vs sterile saline irrigation of a wound
true! no difference in people anyway in a prospective or a systemic review
there is no difference in development of wound infection with use of tap water vs distilled vs boiled
What constitutes as low pressure irrigation?
less than 5 PSI
what constitutes high pressure irrigation?
5-8 PSI
How can you consistently get about 7-8 PSI on an irrigation system
attach a 16-22 G needle to an IV fluid bag set and then place the fluid bag under 300 mmHg with a pressure bag and cuff
Topical wound dressings for open wounds: Hypertonic saline dressing
Stage of wound healing:
Indications:
Topical wound dressings for open wounds: Hypertonic saline dressing
Stage of wound healing: inflammatory, early repair, infected wound in aany stage
Indications: it is 20% saline and hypertonicity is antimicrobial and will facilitate autolytic debridement
Topical wound dressings for open wounds: honey
Stage of wound healing:
Indications:
Topical wound dressings for open wounds: honey
Stage of wound healing: inflammatory, early repair
Indications: antibacterial, enhances autolytic debridement, reduces edema and inflammation, enhances granulation tissue and epithelialization
Topical wound dressings for open wounds: sugar
Stage of wound healing:
Indications:
Topical wound dressings for open wounds: sugar
Stage of wound healing: inflammatory, early repair
Indications: hyperosmotic, questionable antimicrobial effect
Topical wound dressings for open wounds: enzymatic agents like collagenase
Stage of wound healing:
Indications:
Topical wound dressings for open wounds: enzymatic agents like collagenase
Stage of wound healing: inflammatory, debridement, early repair
Indications: enzymatic debridement, adjunct to surgical debridement, may be useful in poor granulation tissue in chronic wounds
Topical wound dressings for open wounds: maggots
Stage of wound healing:
Indications:
Topical wound dressings for open wounds: maggots
Stage of wound healing: inflammatory, debridement, early repair
Indications: maggots secrete digestive enzymes to dissolve necrotic tissue and may be useful when surgical debridement is prohibitive
Topical wound dressings for open wounds: topical antibiotic ointment
Stage of wound healing:
Indications:
Topical wound dressings for open wounds: topical antibiotic ointment
Stage of wound healing: inflammatory
Indications: reduces surface microbial burden
Topical wound dressings for open wounds: silver
Stage of wound healing:
Indications:
Topical wound dressings for open wounds: silver
Stage of wound healing: inflammatory, early repair, infected wound in any stage
Indications: infected wounds
Incorportaion of silver into hydrophilic dressings are more effective than silver alone - may have synergistic effect with alginate and together they will have improved binding affinity for elastase, matric metalloproteinase 2, TNF alpha, IL 8… however may be cytotoxic so use only for infected wounds
Topical wound dressings for open wounds: hydrogel
Stage of wound healing:
Indications:
Topical wound dressings for open wounds: hydrogel
Stage of wound healing: inflammatory, repair
Indications: provides exogenous moisture, good for wounds with minimal to no exudate like abrasions, keeps wound surface moist and promotes epithelialization
Topical wound dressings for open wounds: hydrocolloid or synthetic hydrophilic
Stage of wound healing:
Indications:
Topical wound dressings for open wounds: hydrocolloid or synthetic hydrophilic
Stage of wound healing: inflammatory, repair
Indications: wounds with moderate or copious exudates, absorbs exudate and keeps wound surface moist, enhances autolytic debridement, promotes granulation tissue formation
Topical wound dressings for open wounds: alginate
Stage of wound healing:
Indications:
Topical wound dressings for open wounds: alginate
Stage of wound healing: inflammatory, repair
Indications: wounds with moderate or copious exudates, absorbs exudates and keeps wound surface moist, enhances autolytic debridement, promotes granulation tissue formation
Topical wound dressings for open wounds: bioscaffolds
Stage of wound healing:
Indications:
Topical wound dressings for open wounds: bioscaffolds
Stage of wound healing: repair, chronic indolent wounds
Indications: semiocclusive dressing, provides scaffold for development of extracellular matrix, they stimulate matrix deposition, angiogenesis and epithelialization because of their collagenous and growth factor content
ex. porcine small intestinal submucosa
Topical wound dressings for open wounds: chitosan
Stage of wound healing:
Indications:
Topical wound dressings for open wounds: chitosan
Stage of wound healing: repair
Indications: linear copolymer of linked beta glucosamine and N acetyl D glucosamine derived from chitin rich crab shell
How does it work? enhances the function of inflammatory cells and increases granulation tissue through upregulation of TGF beta, PDGF, and IL 8
Topical wound dressings for open wounds: growth factors
Stage of wound healing:
Indications:
Topical wound dressings for open wounds: growth factors
Stage of wound healing: repair
Indications: only if wound is deficient in or contains excessive target cell or mediator
ex. Becaplermin or PRP
Topical wound dressings for open wounds: non adherent, semiocclusive
Stage of wound healing:
Indications:
Topical wound dressings for open wounds: non adherent, semiocclusive
Stage of wound healing: maturation
Indications: wound with intact surface. not for open wounds though because it will be non hydrophilic and drying
What concentration of 1:40 does chlorhexidine 2% dilution produce?
0.05 to 0.1%
What concentration of 1:100 or 1:1000 does povidone iodine 10% dilution produce?
0.1 to 0.01%
How does the subcutaneous tissue influence epithelialization in the dog and cat
When subcutis was left in place, the percentage of epithelialization of experimental wounds at day 21 was 34% in cats and 89% in dogs. Without the subcutis though, it was 20% in cats and 61% in dogs
What is the inhibin number in regards to honey
the amount of dilution to which the honey will retain its antibacterial properties and is measured at dilutions of 25, 20, 15, 10 and 5%
What species of maggots is used for medical debridement and why
the green blow fly, Lucilia sericata, is used because these larvae will not damage heatlhy dermis or SQ tissue (but will damage epidermis)
How may a bioscaffold be of particular use in a chronic wound over an acute?
Acute vs chronic wounds have imbalances of metalloproteinases
Collagen or collagen/oxidized regenerated cellulose bioscaffold dressings can act as competitive substrates for matrix metalloproteinase 2 and 9 and also bacterial collagenases
This will favor the wound toward inhibiting metalloproteinases so that the extracellular matrix can form
What pore size is recommended for negative pressure wound therapy in an open wound
400 to 600 um
How does NPWT increase oxygenation in a wound bed if it actually reduces the PaO2
Theory is that macrodeformations in the tissue due to differing forces at the surface and depths of the wound may change pressure gradients, flow, and then oxygenation which then could release growth factors like VEGF
What is the NPWT pressure recommended by the Morykwas study
Negative! -125 mmHg
The study showed that this pressure increased blood flow to four times above baseline
Another study suggested a different pressure for NPWT for less dense tissues to stimulate blood flow while minimizing marginal hypoperfusion - what pressure was that
-75 to -100 mmHg
General recommend pressure for NPWT for gauze based vs foam based systems
- 80 mmHg for gauze
- 125 mmHg for foam
the biggest wound contraction is seen at pressures from 0 to -50 mmHg though
What two cytokines are significantly higher with NPWT treatment over regular foam dressing?
VEGF
IL 8
but recent studies show that it may also upregulat IL 1beta too
what NPWT pressure is reommended for placement over skin grafts
-65 to -75 mmHg
Will intermittent or continuous NPWT have a greater effect on promotion of vascular proliferation within a wound
Intermittent apparently
What are the four burn categories based on their energy source
thermal
chemical
electrical
radiation
definition of a thermal burn
caused by tissue exposure to temperature extremes (high or low) that will cause cellular damage
How is heat transferred in a thermal burn
conduction - direct contact with hot object
convection - airborne heat transfer
radiation - electromagnetic energy is converted to heat
At what temperature will a cell membrane sodium pump fail
40-44 degrees celsius or 104 to 11 degrees F
At what temperature will epidermal and dermal necrosis occur if the skin temp reaches it for 1 sec
epidermal necrosis will occur at 60 C/140 F for one sec
full thickness through the dermis will occur at 70 C/158 F for less than one sec
How is an animal’s body divided with the rule of 9
head and neck = 9 each forelimb = 9 each hindlimb = 18 dorsal trunk = 18 ventral trunk = 18
How do you use the veterinary burn card
the card is the same dimensions as a credit card and is 45 cm^2
Measure the burn with the card and count how many cards cover the burn
weigh the patient and then convert the weight to surface area m^2 (like chemo dosing)
use this formula:
% total body surface area that is burned = ((# of cards) x 0.45)/m^2
What are the three zones of a burn
zone of coagulation (or necrosis or destruction)
zone of stasis (reduced perfusion)
zone of hyperemia (primary area that will have inflammation)
What is the role of nitric oxide in burns
it is upregulated within the area of thermal injury
acts as a vasodilator via direct effects on smooth muscle but also indirectly by stimulating other vasodilatory compounds like substance P
what leads to post burn edema
increased perfusion to the area (courtesy of NO and substance P)
increased capillary permeability
What is the majority of injury from smoke inhalation caused by?
two types - thermal and toxic
thermal is generally only the upper airways because the air is cooled fast enough in the trachea to not be too hot by the time it reaches the lungs
therefore, TOXIC is where most effects are from
What are the toxic compounds that contribute to smoke inhalation damage
carbon monoxide
hydrogen cyanide from nitrogen contaning products (like Formica, wool)
inorganic acids
free hydroxyl and carbon radicals
How is carbon monoxide toxic? three mechanisms
- preferentially binds to hemoglobin (making carboxyhemoglobin) which reduces RBC oxygen carrying capacity
- carboxyhemoglobin formation results in a LEFT shift of the oxyhemoglobin dissociation curve which makes it a higher affinity and reduces oxygen delivery to the tissues
- binding of carbon monoxide with myoglobin will reduce oxygen availability to muscle
How is hydrogen cyanide toxic?
binds with mitochondrial cytochrome oxidase which disrupts electron transport chain and prevents cellular respiration
How are hydrochloride and other diatomic halide acids toxic in smoke inhalation
irritating to respiratory mucous membranes, produce laryngospasm and bronchospasm
What is the lung’s response to smoke inhalation
increased pulmonary vascular permeability
venoconstriction
rapid accumulation of fluid, mucus, neutrophils within the alveoli and airways (pulmonary edema)
atelectasis
decreased alveolar ventilation
deactivation of pulmonary surfactant
decreased lung compliance
All leading to ARDS
how does thromboxane A2 play a role in pulmonary response to smoke
TxA2 is also made by pulmonary macrophages and gets released in smoke inhalation
they lead to an increase in pulmonary transvascular flux and vascular resistance secondary to marked pulmonary venoconstriction
Why do burn patients get hypovolemic
combo of extreme systemic extravasation and evaporation
Why does the body’s blood become hyperviscous in burn patients
profound hypovolemia in concert with erythrocyte deformability
this effect is then worsened by systemic vasoconstriction and it leads to tissue hypoxia and metabolic acidosis
What effects do large burns have on myocardial function
direct effects!
decreased left ventricular contractility because of increased Ca2+ in cardiac myocytes due to oxidative injury (calcium leaks) and cytosolic sodium accumulation in myocytes
How is the GI system affected in burn patients
barrier function is compromised
increased apototic rate of gut mucosal cells with no increased in mucosal proliferation
decreased motility
oxidative stress in hepatocytes and upregulation of acute phase proteins while albumin production decreases
Why do burn patients become anemic
first, they have RBCs trapped in the wound, about 10% of RBC mass but that doesnt account for all of the anemia
Within 1 hour of a burn, the concentration of free hemoglobin in the plasma increases and that signals intravascular hemolysis which then occurs because of membrane damage that increases erythrocyte fragility and decreases erythrocyte deformability
The body will make more erythropoetin released but it usually isnt enough because of decreased iron availbility. For whatever reason though, the book does say that supplemental exogenous erythropoetin will help
What are the metabolic effects of a burn
increase in body temp setting of the hypthalamus so the body wastes energy making the body tempertuare higher than usual
change in the utilization of predominantly fat in normal state to more protein catabolization in burn state
upregulation of gluconeogenesis and relative insulin resistance –> persistent hyperglycemia and catabolic state (“burn diabetes”)
Burn wounds have an increased rate of glucose uptake because of the high rate of anaerobic glycolysis by inflammatory and endothelial cells
