Chapter 26 - Skin Grafting Flashcards
What is the main reason for sking grafting?
The most common indication for applying a skin graft to a horse
is a wound so large that it cannot heal by any other means
A healed sking graft contains how many skin layers?
3 epidermis, dermis and adnexa including hair follicles
two basic types of skin grafts are the
pedicle graft and the
free graft
Definition of pedicle graft
pedicle graft remains connected to the donor site,
at least temporarily, by a vascular pedicle that sustains the graft,
ensuring its viability
pedicle graft is useful for covering a ___________ ___________ (2w) wound
poorly vascularized wound because the graft is not dependent
on the vascularity of the recipient site
cosmetic appearance
of wounds healed by applying a pedicle graft is
good
what is the name of the artery and veiin responsible for vascularization of flaps
direct cutaneous artery and vein
free skin graft is a piece of skin that
has been completely
separated from its local blood supply and transferred to a wound
at another site, where it must establish new vascular connections
to survive
Free grafts can be categorized in several different
ways, one of which is by their source. Name them
autograft (or isograft)
allograft (or homograft)
xenograft (or heterograft).
Free skin grafts can also be categorized according to their thickness. Name them
Full-thickness grafts
split-thickness (or partial-thickness) grafts
Definition of split-thickness (or partial-thickness) grafts
composed of epidermis and only a portion of the dermis
Definition Full-thickness grafts
composed of epidermis and the entire dermis
The percentage of dermis within the graft influences the
acceptance, durability, and cosmesis at the recipient site.
The thickness of dermis within the graft is directly proportional to the graft’s (name 2 factors)
durability
cosmesis
The thickness of dermis within the graft is indirectly proportional
to the graft’s ability to survive
Full- or split-thickness free skin grafts can be applied to the surface of wounds as:
1- solid
2- or meshed sheets,
or they can be embedded in granulation tissue
3- as pinch,
4- punch,
5- or tunnel grafts.
free graft cannot be expected to survive if placed on (3 structures)
1) on bone denuded of periosteum,
2) tendon denuded of paratenon,
3) or cartilage denuded of perichondrium,
Figure 26-2. Proliferating epithelium at the margin of a wound on the hip of a horse. Proliferating epithelium, represented by the pale ring around the edge of the wound, indicates that the wound is healthy enough to accept a skin graft.
A prime requisite for free grafting is a recipient bed that is (3 characteristics)
vascular
and
free of infection
and devitalized tissue.
Graft is initially adhered to the recipient site by
fibrin
Vessels and fibroblasts invade the fibrin matrix by
4th or 5th day and the graft is firmly united to the recipient bed by around the 10th day
newly applied graft is nourished by
plasma-like fluid
A thin skin graft is better/worse (choose 1 option) nourished during this phase of acceptance
better, because the quantity of nutrients able to permeate the graft is inversely proportional to the thickness of the graft.
new capillaries generated in the recipient bed traverse the fibrin layer to anastomose with those in the graft, a process called
inoculation
Organization (Organic Union) - epidermis of the graft becomes hyperplastic after grafting and can double in thickness during the first
2 weeks
Who has a more interrupted vascular area full-thickness or partial/split thcinkess?
full-thickness graft is less interrupted than that within the dermis of a
split-thickness graft
Dermis can be differentiated from granulation tissue by its ______________ color (1w)
paler color
Split-thickness grafts of horses, no matter the thickness at which the grafts are harvested, are likely to be devoid of ____________________(2w)
sebaceous glands
Hair begins to appear in split-thickness grafts at between ___ and ____ weeks
Hair begins to appear in split-thickness grafts at between 4 and 6 weeks
The growth of longer hairs may be related to a difference in _____________________ (1w) between the grafted limb and the donor site.
The growth of longer hairs may be related to a difference in temperature between the grafted limb and the donor site.
Reinnervation returns more rapidly, in split-thickness grafts or in full-thickness grafts?
Reinnervation returns more rapidly, but to a lesser extent, in split-thickness grafts than in full-thickness grafts
Split-thickness skin grafts of horses usually begin to develop pigment about _____weeks after grafting
Split-thickness skin grafts of horses usually begin to develop pigment about 4 weeks after grafting
After being harvested, grafts immediately shrink – referred to as
primary contraction
Primary contraction is greatest in full thcinkess grafts or decreased grafts?
Primary contraction is greatest in full-thickness grafts and decreases as grafts become thinner.
Full-thickness grafts from humans contract to nearly
half their original size after being harvested.
Split-thickness grafts that are about half the thickness of the whole skin contract to about
three quarters of their original size, and grafts composed solely of epidermis do not shrink at all.
Skin grafts inhibit wound contraction, to various extents, by accelerating the life cycle of the ___________(1w) within the wound.
myofibroblasts within the wound
Full thickness graftss tend to contract less or more than wounds receiving a split thickness graft?
Contract less in full thickness
contraction of wounds of horses, before or after grafting, should be considered beneficial
yes because it results in more rapid healing and smaller scars
A hematoma, a seroma, or exudate beneath the graft prevents ________(1w) from attaching the graft to the wound and acts as a barrier to the ingrowth of new vessels
A hematoma, a seroma, or exudate beneath the graft prevents fibrin from attaching the graft to the wound and acts as a barrier to the ingrowth of new vessels
graft can survive for only several _______ by imbibing nutrients from the hematoma or seroma
graft can survive for only several days by imbibing nutrients from the hematoma or seroma
Ideally, a hemorrhagic wound should not be grafted until hemorrhage has ceased - TRUE or FALSE
TRUE
Wgat is the concentration that seem to infect the tissue and exceed the ability of humoral and cellular defenses?
by quantitative bacterial analysis, to contain more than 105 bacteria per gram of tissue
Quantifying the concentration of bacteria in a wound is time-consuming and often impractical - what is very important to know?
Type of bacteria - most notably β-hemolytic streptococci and Pseudomonas spp., required to infect a wound is much less than 105 per gram of tis
most notably β-hemolytic streptococci and Pseudomonas spp., produce which type of proteolytic enzymes?
streptokinase and staphylokinase
What does the streptokynase and staphylokinase do?
they destabilize the fibrin network between the graft and the recipient wound by catalyzing the conversion of plasminogen to plasmin, which digests fibrin
Sprouting capillaries capable of rapidly revascularizing the graft develop in the wound within
48 hours
Factors to take in consideration when determining if the wound is prepared to receive a graft
wound vascularity
potential wound infection
Hgihgly vascular granulation tissue readily accepts a graft, but as the granulation tissue matures its vascularity and ability to accept a graft ___________(1)
diminish
Wounds allowed several days to develop sprouting capillaries before being grafted are referred to as
“prepared wound”
Removing streptococci from wound is relatively eay because they are susceptible to
penicillin
Occasionally, penicillin or other β-lactam antibiotics are ineffective in resolving a streptococcal infection, because other resident bacteria, particularly __________ and ________________ produce β-lactamase, an enzyme that inactivates β-lactam antibiotics.
Occasionally, penicillin or other β-lactam antibiotics are ineffective in resolving a streptococcal infection, because other resident bacteria, particularly staphylococci and gram-negative bacteria, produce β-lactamase, an enzyme that inactivates β-lactam antibiotics
Topical application of an antimicrobial drug to an infected, granulating wound is more effective for eliminating infection than is systemic administration of the same antimicrobial drug - TRUE or FALSE
TRUE
Which type of neoplasms resemble granulation tissue?
sarcoids or carcinomas
Figure 26-5. Burn wound on the back of a horse. (A) The wound contained exuberant, relatively avascular granulation tissue that was excised to skin level, with the horse standing, in preparation for grafting. (B) About 75% of a meshed, split-thickness skin graft, applied several days later, was accepted.
Pseudomonas spp. are usually sensitive to topically applied ___________, ____________ and______________(3w)
mafenide acetate, aminoglycosides, or polymyxin-B sulfate
Figure 26-6. A graft applied to a healthy-appearing, granulating wound on the dorsal aspect of a metacarpus was completely accepted, but a draining tract soon appeared in the healed wound (left). Drainage was caused by infection of bone beneath the wound and the development of a bone sequestrum (right).
How to prepare the recipient bed immediately before grafting? 4 steps
Remove hair form the skin surrounding the wound
Surgical scrub solution to cleanse the skin around the wound
Wound itself should be cleansed only by rinsing with physiologic salin
The graft should be cut slightly larger/smaller (choose) than the recipient sit
larger
Because subcutaneous tissue attached to the undersurface of the graft acts as a barrier to _____________________(2 w) and ________(1w) of new vessels, it must be removed to expose the dermis and its vasculature
Because subcutaneous tissue attached to the undersurface of the graft acts as a barrier to plasmatic imbibition and ingrowth of new vessels, it must be removed to expose the dermis and its vasculature
Figure 26-10. The Watson skin-grafting knife. Using this dermatome, a surgeon can harvest a graft 100 mm (4 in) wide. The knife uses disposable blades and is fitted with an adjustable roller in front of the blade to control the depth of the cut.
Which free graft provides the best cosmetic appearance?
full-thickness skin grafts
Full thickness grafts are not accepted as readily split thickness grafts, why? 2 reasons
because they have:
- fewer exposed blood vessels than do split-thickness grafts
- because their requirement for nourishment is greater
Figure 26-15. A Zimmer mechanical skin mesher. The mesher is capable of expanding the graft to many times its original area. The graft is positioned on a specially grooved plastic carrier, and the graft and carrier are fed through the mesh cutter by turning a hand crank.
Figure 26-14. A Padgett mechanical skin mesher. The mesher consists of an aluminum block with staggered, parallel rows of blades and a Teflon rolling pin. The graft is positioned on the block, dermal side down, and pressed into the cutting blades with the rolling pin.
Figure 26-13. Harvesting split-thickness skin from the ventral aspect of the abdomen using a free-hand knife. The ventral portion of the abdomen must protrude over the edge of the table to accommodate the handle of the hand-held knife. Slight, uniform tension is applied to the cut end of the graft as the graft is harvested.
Figure 26-11. Harvesting a skin graft with a drum dermatome. (A) Rotating the drum of a drum dermatome elevates skin to which it has been glued. (B) The skin attached to the drum is cut at a precise depth with a knife that oscillates back and forth on a piston.
Figure 26-12. Harvesting a split-thickness skin graft with a pneumatic dermatome. Although they are expensive, power-driven dermatomes allow the cutting of very uniform grafts by minimally experienced operators.
A split-thickness graft is composed of 2 portions name them
Epidermis and a portion of dermis
To obtain a split-thickness graft, a portion of the dermis and its overlying epidermis is harvested with a
Free hand knife
drum dermatome
power-driven dermatome
Donor sites for obtaining a split-thickness graft
ventral portion of the abdomen
ventrolateral aspect of the thorax, caudal to the elbow
How does the adjustable roller of the Watson knife affect the harvest of skin grafts?
It controls the depth of the cut, allowing for moderate practice to achieve uniform graft thickness.
What factors influence the thickness of the harvested skin graft?
The position of the roller, angle of incidence, and pressure applied during cutting.
What is the operational mechanism of a drum dermatome?
It uses an oscillating knife on a piston to split the dermis while the skin is glued to the rotating drum.
How does a drum dermatome allow for precise graft harvesting?
The depth of the cut is predetermined by the caliber of shims placed next to the blade.
What is a significant limitation of the drum dermatome when harvesting grafts for horses?
The length of the graft is limited by the circumference of the drum.
What types of power-driven dermatomes are commonly used?
The Stryker electric dermatome and the Brown pneumatic or electric dermatome.
What comparative advantage does a pneumatic dermatome have over an electric one?
The cutting head of a pneumatic dermatome oscillates more rapidly, leading to smoother harvesting.
Why might grafts obtained with the Davol-Simon dermatome be insufficient for horse wounds?
They are too thin (0.38 mm) to provide an adequate cosmetic appearance
What is a key advantage of using a free-hand knife over power-driven dermatomes?
It allows harvesting of consistently uniform grafts wider than 100 mm and is generally less expensive.
What preparation must be done before using a free-hand knife to harvest skin from a horse?
The horse should be anesthetized, and the abdomen positioned properly over the edge of the surgery table.
How can the operator’s hand position affect graft harvesting using a free-hand knife?
A right-handed operator finds it easier when the horse is in right lateral recumbency and vice versa for left-handed operators.
What technique helps to reduce friction during the use of a free-hand knife?
Lubricating the donor site with saline and the blade with mineral oil.
What is a subjective method to assess the thickness of the graft during harvesting?
Examining the graft for translucency and looking for the pattern of bleeding on the donor site.
How can the depth of cut be modified when using a free-hand knife?
By repositioning the adjustable roller, changing knife pressure, or altering the knife’s angle of incidence.
What is the benefit of using meshed grafts over solid sheet grafts?
Meshed grafts increase surface area for better coverage of larger wounds and allow exudate to escape.
What is a common way to create meshing in grafts?
By uniformly fenestrating the graft manually with a scalpel or mechanically with a meshgraft dermatome.
What is the role of the Padgett mechanical skin mesher?
It creates a staggered pattern in the graft, allowing for expansion and better fit over the wound.
What factor limits the harvesting width of grafts with a Zimmer mechanical skin mesher?
Grafts wider than 76 mm are difficult to mesh effectively.
Why is it challenging to mesh full-thickness grafts on commercial meshing instruments?
These grafts often must be meshed manually due to their size and thickness.
What is the ideal timing for excising exuberant granulation tissue before graft application?
24 hours in advance to ensure hemostasis and prepare the recipient site for rapid vascularization.
What types of instruments are mentioned as being ineffective for harvesting skin grafts from horses?
Scalpel blades, double-edged razor blades, and surgical straight razors.
Which knife is specifically highlighted for harvesting skin grafts from horses?
The Watson skin-grafting knife.
What is the maximum width of a graft that can be harvested using the Watson skin-grafting knife?
100 mm (4 in).
What feature of the Watson knife helps control the thickness of the graft?
An adjustable roller in front of the blade.
What factors influence the thickness of the harvested graft?
Position of the roller, angle of incidence, and pressure applied.
How does a drum dermatome harvest skin?
It uses an oscillating knife on a piston to split the dermis of skin glued to the drum.
What is a major advantage of using a drum dermatome?
It allows for harvesting grafts of exact dimensions.
What is a disadvantage of the drum dermatome for horses?
The length of the graft is limited by the circumference of the drum
Which drum dermatome is mentioned specifically in the text?
The Padgett Manual Dermatome (Z-PD-100R).
What is the function of power-driven dermatomes?
They use a rapidly oscillating blade to harvest split-thickness skin grafts with precision
What are the two commonly used types of power-driven dermatomes mentioned?
The Stryker electric dermatome and the Brown pneumatic or electric dermatome.
What is the width and thickness of grafts from the Davol-Simon dermatome?
33 mm (1.3 in) wide and 0.38 mm (0.015 in) thick.
What drawback is associated with grafts harvested with the Davol-Simon dermatome?
The grafts are too thin for a cosmetic appearance.
What is an advantage of using a free-hand knife compared to power-driven dermatomes?
It can excise grafts that are consistently uniform and wider than 100 mm (≥4 in).
How does using a free-hand knife impact costs and maintenance compared to power-driven dermatomes?
Free-hand knives are less expensive, require less maintenance, and have fewer parts that can malfunction.
Why must harvesting a split-thickness graft be done under anesthesia?
It is painful to the unanesthetized horse.
What technique is used when harvesting grafts with a free-hand knife?
A sawing motion is used while keeping the blade at an acute angle.
What type of graft is preferred for covering larger defects?
Split-thickness grafts.
What characteristics indicate whether a graft cut is too thick?
If subcutaneous tissue is exposed, the graft is considered full thickness.
What type of instrument is the Padgett mechanical skin mesher?
A mesh graft dermatome.
What are the advantages of using a mechanical skin mesher?
It can expand grafts to increase their application over larger areas.
What is a potential issue when using a Zimmer mechanical skin mesher?
Grafts wider than 76 mm are difficult to mesh.
What aspect of the wound must be managed before applying a graft?
Excess granulation tissue 24 h before
When securing the graft with sutures, the suture needle should pass from the graft to the surrounding skin or from the surrounding skin to the graft?
graft when securing the graft with sutures, the suture needle should pass from the graft to the surrounding skin, rather from the surrounding skin to the graft
Advantages of the graft being sutured/stapled/glued standing?
Applying the graft with the horse standing reduces the time of general anesthesia and eliminates the possibility of damage to the graft that may occur while the horse recovers from general anesthesia
A graft need only be fixed to the wound’s margin, because fibrin produced by the wound fixes the graft to the wound’s surface within __________ (1w) after the graft is applied
A graft need only be fixed to the wound’s margin, because fibrin produced by the wound fixes the graft to the wound’s surface within minutes after the graft is applied
Places of haverst of punch graft
Perineum (caudal epidural anesthesia)
ventrolat aspect of abdomen
neck beneath the main
In punch tx the holes are obtained in the pectoral region?
No, full thickness sheet of skin harvested from pectoral region and than biopsy punch 6-7 mm diameter
How big should be the full thickness sheet of skin?
10 cm long x 4 cm wide
Spraying the wound with phenylephrine before creating the recipient holes may improve visibility by decreasing
hemorrhage
Creating the recipient holes ___hours in advance with ____ mm biopsy punch
24 hours in advance with 5mm biopsy punch
the graft itself should be 7 mm biopsy punch
In punch grafts the holes should be ____ mm apart
6mm
By 3 weeks each plug of skin is surrounded by a red ring, what is it?
epithelium
What is the % survival of puch graft?
60 to 75%
Pinch graft are
small disc harvested by excising an elevated cone skin
optmial size of a pinch graft?
3 mm size in diameter
Thinckness is the same all over the 3 mm pinch graft?
No, it is more thick in the center and diminishes toward periphery
Recipient site of pinch graft prepared 24 h advance with blade number
Nº15
Each disk of pinch graft is surrounded by red ring by ____ weeks. What is the red ring?
3 weeks and is epithelium
What is the prognosis of pinch graft to survive?
50 to 75% grafts survive
advantages and disadvantes of pinch graft
Inexpensive, little expertise
Poor cosmetic apperance
Tunnel grafts are strips of split-thickness or full-thickness?
both
Prognosis of acceptance of tunnel grafts
60-80%
Harvest sites
Neck beneath mane
Ventral aspect of flank
What is the size of the linear wheals in tunnel graft?
2-3 cm wide
in tunnel graft the grafts should be embeded in
2cm apart
In tunnel grafting when do you remove the roof of granulation tissue?
6-10 days
Modiefied Meek Grafting Tx is a combination of 2 types of grafting name them
island grafting
split thickness skin or micrografts
What are the size of the islands in the Modified Meek Graft?
3-mm2 islands of split-thickness skin
Can the tx of Meek Graft expand more with micrografts than with meshed sheet?
Yes, the technique is particularly useful for grafting large wounds because the donor skin can be expanded more with micrografts than with meshed sheet grafts
In which particular case this technique of Modified Meek Graft is useful?
This technique of grafting is particularly useful when the donor skin is in short supply, as may be the case for horses with extensive burns.
Name the pieces of Meek graft (3 pieces)
frame
cutting block
pneumatic or hand-driven motor
What is the size of the cork plate in Meek Graft tx?
42 x 42 mm cork p+lat
The cork plate, containing the graft, is placed onto a ______ __________(2w), which is placed in a ____________ (1w)block
The cork plate, containing the graft, is placed onto a cork holder, which is placed in a cutting block
The cork, covered with graft, is then passed through a machine that contains ____ rotating circular blades that cut the graft, but not the cork, into ___strips of ____ mm width
The cork, covered with graft, is then passed through a machine that contains 13 rotating circular blades that cut the graft, but not the cork, into 14 strips of 3 mm width
Figure 26-30. A Meek micrograft machine shown with a hand-drive (a machine with a pneumatic motor for turning the knives is also available). The cutting block with the cork template and graft are passed through the Meek micrograft machine, which contains 13 circular knives that
cut the graft into 14 strips of 3 mm width. The cork holder is rotated 90 degrees and replaced onto the cutting block, and by passing it through the machine again, the strips of graft are cut into 196 (14 × 14) micrografts of 3 × 3 mm size.
The cork and graft are rotated _____(1 number) degrees, replaced onto the cutting block, and again passed through the machine, which cuts the strips of graft into ____ (14 × 14) grafts measuring 3 × 3 mm.
The cork and graft are rotated 90 degrees, replaced onto the cutting block, and again passed through the machine, which cuts the strips of graft into 196 (14 × 14) grafts measuring 3 × 3 mm.
The ____________ surface of the graft is sprayed with an adhesive, which is allowed to dry until it becomes tacky.
The epidermal surface of the graft is sprayed with an adhesive, which is allowed to dry until it becomes tacky.
The cork plate, covered with graft, is pressed onto a pleated _________ __________(2w) backed by aluminum foil
The cork plate, covered with graft, is pressed onto a pleated polyamide gauze backed by aluminum foil
when unfolded expands the graft in a ratio of 1 : __, 1 : ___, 1 : __, or 1 : __
when unfolded expands the graft in a ratio of 1 : 3, 1 : 4, 1 : 6, or 1 : 9
What is in the Meek graft the most used pleated gauze?
1:3 ratio
The pleats are unfolded, separating the grafts at a set uniform distance by applying traction to all of its _____(1number) sides
The pleats are unfolded, separating the grafts at a set uniform distance by applying traction to all of its four sides
After unfolding the support aluminum backing in the Meek Graft what are the next steps?
the supporting aluminum backing is peeled off and discarded, leaving the expanded gauze with the separated islands of graft. The expanded gauze to which the grafts are attached is trimmed appropriately, applied graft side down to the wound, and secured to the margin of the wound with staples or sutures
When do the grafts become attached to the wound?
6 days after
Most wounds that receive Meek micrografts are healed within (1 word)
a month
What is the acceptance % of Meek Graft?
95% - it appears to be better than other skin grafts tx
disadvantage of the modified Meek micrografting technique over other methods of island grafting
is that the horse must be anesthetized to harvest the split-thickness donor skin. Equipment to harvest the split-thickness skin and the micrografting machine are relatively expensive
Figure 26-33. (A) A nonhealing wound on the palmar aspect of a metatarsus is almost healed after receiving Meek micrografts 24 days earlier. The original square Meek micrografts from which epithelialization proceeds can still be seen. Only tiny areas remain to be epithelialized. (B) Five months after grafting, the grafted site is covered with hair the same color as that at the donor site. The hair coat is somewhat sparser than the surroundings because the newly formed epithelium between the micrografts does not produce hair
The donor site of a split-thickness graft retains a portion of the
dermis
The donor site of a split-thickness graftis comparable to a ________ ___________(2w)
deep abrasion
The new pink epithelium covering the donor site begins to develop pigment within a month after it forms, causing the epithelial scar to become _________(1w)
black
Figure 26-34. The donor site of a split-thickness graft 2 weeks after the graft was harvested. The donor site is nearly covered by epithelium. The new, pink epithelium will begin to develop pigment within a month, causing the epithelial scar to become black.
The wound at the donor site is usually covered by epithelium within __ to ____ weeks
The wound at the donor site is usually covered by epithelium within 1 to 3 weeks, depending on the depth of the cut
Pain caused by exposure of nerves at the donor site of a split-thickness graft can be reduced by
bandanging the donor site with a moist dressing (honey impregnated or hydrocolloid)
Time to healing of wounds dressed with honey-impregnated gauze was similar to that of wounds covered with a hydrocolloid dressing - TRUE or FALSE
TRUE
The horse should receive before and after harvest an analgesic drug, which one?
phenylbutazone for at least several days after surgery
Figure 26-35. A recently applied graft destroyed by streptococcal infection.
In the after care of the recipient site the grafted wound shoulb be covered with which type of bandage?
cotton nonadherent film dressing (Telfa Sterile Pads),
rayon polyethylene dressing (Release),
or petrolatum-impregnated gauze dressing (Adaptic).
Primary dressing of recipient should be immobilize with primary dressing with
staples or with elastic adhesive tape rather than rolled gauze to immobilize in joint zones to decrease shear forces
When should you immobilize the limb with a cast?
dorsal aspect of MCP/MTP joint
but Robert jones or splint should be enough
The bandage should not be changed for __ or __ days after grafting to avoid disturbing the graft’s delicate attachment to the woun
The bandage should not be changed for 4 or 5 days after grafting to avoid disturbing the graft’s delicate attachment to the woun
Which 2 bateria rapidly destry graft
Streptococci or Pseudomonas spp
Infection caused by Pseudomonas spp. is characterized by the presence a
bluish-green exudate on the surface of the wound and an odor similar to that of grape juice.
Until the results of culture from the receipt wound in case of signs of infection waht should you give/apply?
effective against both β-hemolytic streptococcus and Pseudomonas spp., such as a combination of:
ticarcillin disodium
and clavulanate potassium
or an antimicrobial dressing containing silver topically in the wound
Negative pressure wound therapy is good in case of grafts why?
decreases shear forces and accumulation of fluid, and reduces edema in tissue surrounding the wound. Cells exposed to negative pressure experience microstrain, or stretching, which causes them to rapidly divide and proliferate. Negative pressure also results in the production of growth factors conducive to healin
In case of infection of the graft the bandage should be changed how often?
daily or twice daily for at least 5 days
Exuberant granulation tissue that inhibits
Exuberant granulation tissue that inhibits epithelial migration may grow through the latticework of a meshed graft, especially if the graft was applied to the wound fully expanded
What can be applied in exuberant granulation tissue?
corticosteroid applied to the grafted wound causes the exuberant granulation tissue within the graft to regress, allowing epithelial migration to proceed, even if at a slower than normal pace.
Pressure on a graft from a bandage is necessary for the graft to be accepted?
NO, pressure on a graft from a bandage is not necessary for the graft to be accepted, so, for areas that are difficult to bandage or for wounds that are chronically plagued with infection, the grafted wound can be left uncovered
How do you prevent movement in open
tying the horse or applying a neck cradle must be taken to prevent the horse from disturbing the exposed graft
Some horses probably suffer from hyperesthesia at the grafted wound, so when bandaging is discontinued, temporarily applying precaution with _____ _________ (2 w) might be necessary
neck cradle or tying the horse may be prudent to prevent the horse from mutilating its grafted wound
Drying and scaling the healed donor and recipient sites cause by reduced [] eccrine and sebaceous glands can be lessened by applying
ointment containing lanolin
Viable cutaneous allografts can be obtained from refrigerated cadavers____ (number) hours or longer after death
Viable cutaneous allografts can be obtained from refrigerated cadavers 24 hours or longer after death
Allografts applied to wounds of horses seem to survive between __ and __ weeks,
Allografts applied to wounds of horses seem to survive between 2 and 3 weeks,
An allograft or xenograft encourages healing by promoting (4 things)
epithelialization
angiogenesis
retards formation of exuberant granulation tissue
acts as a bacterial barrier
allografts are superior or inferior to xenografts?
superior according to human medicine trials
bacterial colonization decreases even beneath nonviable grafts, perhaps because
the fibrin that forms between the graft and the wound enhances phagocytosis
Autografts or allografts can be applied successfully to wounds after being stored for _____ weeks at _____temperature in gauze that has been soaked in either ________ solution or lactated Ringer solution
Autografts or allografts can be applied successfully to wounds after being stored for several weeks (3 weeks) at refrigeration temperature (4ºC) in gauze that has been soaked in either physiologic saline solution or lactated Ringer solution
In order to refrigerate the skin need to be stored with nutrient medium such as
McCoy’s 5A Medium, to which serum has been added, for much longer periods
What is McCoy’s 5A Medium
is a tissue-culture medium composed of a balanced electrolyte solution, to which amino acids, vitamins, dextrose, and a pH indicator (phenol red) have been added
How can you extend the time a graft can be stored?
Adding vitamins, amino acids, dextrose, and serum to the electrolyte solution greatly extends the time
wounds of some horses have been grafted successfully using skin stored for as long as ___ weeks.
wounds of some horses have been grafted successfully using skin stored for as long as 12 weeks.
The concentration of serum in the storage medium should be between ___% and ___%.
The concentration of serum in the storage medium should be between 10% and 33%.
A concentration of serum greater than ____% stimulates the metabolic activity of the graft
A concentration of serum greater than 33% stimulates the metabolic activity of the graft
Antigenic reaction of the serum to the graft is avoided by using a
commercially available antibody-free serum (GG -Free Horse Serum), pooled homologous serum, or the horse’s own serum
Should the allografts be allowed access to air?
Yes
To prepare a meshed split-thickness skin graft for storage, the graft is laid on a sterile gauze swab or gauze dressing, with the epidermis of the graft ____ (1w) to the gauze.
To prepare a meshed split-thickness skin graft for storage, the graft is laid on a sterile gauze swab or gauze dressing, with the epidermis of the graft next to the gauze.
The gauze-graft composite is rolled up, with the gauze to the outside/inside (choose 1) of the roll
he gauze-graft composite is rolled up, with the gauze to the outside of the roll
The gauze graft is place in a sterile container that contains how many ml of storage medium per square cm of graft?
1 to 2.5 mL
A color change in the McCoy’s 5A Medium from cherry-red to orange-yellow indicates
excessive accumulation of catabolites
What does it mean when a color change is observed in the McCoy’s 5A Medium?
need for immediate application of the graft or replacement of the medium.
When there is a change of color of the medium and you need to change the medium, how much should you change?
Only half of the volume of medium should be replaced, because total replacement affects the graft deleteriously
Storing the graft, so that it can be applied with the horse standing has advantages name them
shortens the anesthetic period and eliminates the risk of the graft being disturbed during recovery
A stored graft is often more readily accepted than a fresh graft?
YES because grafts stored for 24 hours or more release anaerobic metabolites that stimulate rapid revascularization of the graft.
