Download management of dead space and associated fluid or

MANAGEMENT OF DEAD SPACE AND
ASSOCIATED FLUID OR GAS ACCUMULATION
IN SMALL ANIMAL SURGERY
Michael M. Pavletic, DVM, DACVS
Director of Surgical Services
Angell Animal Medical Center
Boston, Massachusetts
D
ead space, by definition, is a space left in the
body as a result of a surgical procedure. The term
is commonly used to describe spaces resulting
from the removal of a space-occupying mass or evacuation of fluid, tissue dissection resulting in disruption of tissue or fascial planes, and tissue separation or disruption
secondary to trauma (e.g., bite wounds, vehicular
trauma, high-velocity projectile wounds). Although less
common, dead space could also result from gas and/or
air accumulation (e.g., torn trachea, sucking wounds).
Dead space creates a pocket or cavity in which tissue fluid or blood can accumulate (e.g., seromas,
hematomas); excessive fluid accumulation separates
tissue planes, and its persistence can delay or prevent
normal healing. Moreover, fluid accumulation may
contribute to infection, especially in the presence of
contaminants. As a result, appropriate dead space
management is important to both the prevention and
management of infection.
There are several techniques used to manage dead
space, depending on the size, location, and cause of
the tissue pocket. These options include no treatment,
external bandage compression, suture closure, use of a
drainage system, and aspiration; each can be used
alone or in combination to control dead space.
DIAGNOSTIC CRITERIA
Historical Information
• The volume of a pocket or defect created when a
space-occupying mass (e.g., tumor, granuloma,
organized hematoma) is removed often approximates that of the lesion.
• Wide surgical dissection results in disruption of normal tissue planes, creating a potential space. Combined with surgical trauma and regional movement,
seroma formation may occur.
• Loose or elastic fascial planes are potential areas for
fluid accumulation, especially in the face of
regional trauma.
• Vehicular trauma is the most common form of blunt
trauma sustained by small animals. Both direct and
indirect trauma can cause soft tissue to stretch, tear,
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or avulse, thereby creating dead space.
• Orthopedic trauma and subsequent fracture repair
can result in variable degrees of soft-tissue disruption and dead space formation.
• Bite wounds often result in the crushing, stretching,
tearing, and laceration of the skin and underlying
tissue. Without appropriate wound management,
tissue trauma, circulatory compromise, contamination, and formation of dead space predispose the
patient to infection.
• High-velocity projectile wounds can cause significant tissue disruption and significant dead space
formation as a result of cavitation and tissue trauma
secondary to fragmentation of bone; frangible bullets also intensify local tissue trauma.
Physical Examination Findings
Dead Space Secondary to Trauma
• Vital signs should be immediately assessed, including the basic “ABCs” (airway, breathing, and circulation). Emergency treatment should be instituted in
critically injured patients.
• All trauma patients require a complete physical
examination, regardless of presentation.
• Patients should be assessed and treated for pain at the
time of presentation as well as pain anticipated for the
surgical procedure after assessment of the injuries.
• Disrupted tissue planes may include separation of
the skin from the underlying tissue attachments.
When grasped, the skin readily lifts away from the
underlying musculofascial layer. If a skin defect is
present, lifting the skin creates a vacuum effect,
which sucks air into the subcutaneous space.
• Palpation over areas of intact skin may reveal irregularities of the musculofascial tissue; suspected
areas of tissue disruption can be compared with the
corresponding area on the opposite side of the
patient (provided the area is uninjured). Muscle
tears and avulsion wounds are noted as gaps or
depressions with deep digital palpation. Herniation
of abdominal contents also may be noted.
• Depending on the age and condition of the wound,
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tissue fluid, blood, or pus may collect in the traumatized area and gravitate in a ventral or distal
direction. Palpable fluctuance may be noted with
significant accumulation of blood, serum, or pus.
This accumulation can further expand the dead
space by stretching or displacing adjacent tissues.
Tears in the pharynx and trachea may result in mild
to massive accumulation of air beneath the skin
(subcutaneous emphysema). Air distention displaces the skin, creating a dead space pocket of air.
Wounds involving the flank and axillary regions occasionally result in the creation of a sucking wound, as
air enters the subcutaneous space during patient
ambulation. Normally, the air accumulation is comparatively milder than that associated with injuries of
the pharynx and trachea (e.g., holes, lacerations).
Open wounds are usually easier to examine preoperatively than are wounds covered by an intact skin
surface; dead space volume is assessed by the visible tissue disruption.
Tissue is initially assessed for degree of contamination and potential viability. However, intraoperative
assessment of the wound is more important in
determining the appropriate options for managing
dead space.
Dead Space Associated with Surgery
• Extensive debridement, dissection, excision, and
undermining of tissues may be necessary; this
should be followed by assessment to determine
how to manage the dead space created.
• The amount of excess skin present after removal of
a space-occupying mass is assessed to determine if
additional skin resection may improve dead space
control and the resultant cosmetic outcome.
Laboratory Tests
• In patients presenting with significant injuries, a complete blood count, serum chemistry profile, and urinalysis should be conducted (baseline assessment).
• A complete blood count and serum chemistry profile are indicated for older patients (>5 years of age)
or those with other medical conditions.
• A presurgical screening panel (glucose, alanine
aminotransferase, creatinine, total protein, total
leukocyte count, hematocrit) is recommended for
young (<5 years of age), healthy patients.
Other Diagnostics
• Needle aspirates may be collected for cytologic
examination of suspected tumors preoperatively;
biopsies may be advisable before removal of potentially problematic neoplasms (e.g., to help determine presurgical margins or the exact nature of the
neoplasm [prognosis]). Needle aspiration of fluid
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pockets can help identify seroma, infection, or primary accumulation of blood.
Radiography may be required to assess traumatized
patients:
— Thoracic, abdominal, and regional radiographs
may be necessary to assess patients for underlying injuries that may preclude anesthesia or
alter the surgical approach.
— Patients with potential malignancies may require
left lateral, right lateral, and dorsoventral thoracic radiographs preoperatively.
Additional diagnostic support (ultrasonography, computed tomography, magnetic resonance imaging) may
be required to better define the exact location of larger
and/or ill-defined masses and traumatized areas.
Lymph node biopsy or aspiration may be advisable to
help stage potential metastasis of malignant tumors.
In the presence of infection, representative bacterial
culture samples should be taken to determine the
most appropriate antibiotic regimen.
Summary of Diagnostic Criteria
• Preoperative assessment of the wound or surgical
area helps determine the most appropriate surgical
plan; intraoperative assessment of the wound better
enables the surgeon to select the most appropriate
method(s) to deal with dead space.
• Appropriate blood work and radiography are determined by the patient’s age and health status, preoperative assessment for metastatic disease, and
severity of trauma.
• Additional diagnostic tests may be advised to determine the cause of a dead space swelling or neoplasm.
• Staging, including lymph node biopsy or aspiration,
is advisable for tumors with the potential for metastasis. Results can help guide the surgical plan and
approach to the area as well as identify the dead
space potential.
• Bacterial cultures should be submitted if infection is
present.
Differential Diagnosis
Nonsurgical causes of dead space include traumatic
separation or tearing of tissue, hernias, and hematomas.
Without a history of trauma, swellings may require
differentiation from soft-tissue neoplasms.
TREATMENT
RECOMMENDATIONS
Initial Treatment Options
The primary goal of controlling dead space is to
prevent tissue fluid and blood from accumulating in
the disrupted tissue area. Their accumulation separates
the normal tissue planes, thereby delaying the normal
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GENERAL TIPS ON
USING PENROSE DRAINS
• The exit site is placed distal or ventral to the
surgical area, at or below the dead space pocket.
• A 0.25-inch Penrose drain is suitable for most
small animal patients.
• The exit site is created with a scalpel blade (“stab
incision”); the incision should be of sufficient size
to easily accommodate the exiting of the drain
and fluid exiting along the external surface of the
drain by capillary action.
• The drain normally exits the skin by 3–4 cm and is
typically secured to the skin with a single suture.
• The proximal or dorsal end of the drain can be
secured with a single 2-0 suture loop passing
through the skin and capturing the drain. Some
veterinarians prefer to “tack” the buried end of the
drain with a fine (4-0) absorbable suture to an
adjacent musculofascial layer; the suture will break
or pull out of the tissue when traction is applied to
the external end of the drain. (Note: There is a
small risk of a drain tearing with this latter
technique, resulting in the retention of a segment.)
• It is preferable to insert any drain before wound
closure to assure proper positioning.
• When possible, a Penrose drain should not cross
or lie beneath the incision.
• Care must be taken to avoid accidental suture
entrapment of the Penrose drain during closure of
the incision.
• Penrose drains are radiopaque; radiography can
confirm the position or presence of a drain or
fragment.
• Most Penrose drains are removed within 5 days
after insertion.
• Timing of drain removal is assessed by the volume
of fluid exiting the site.
• Penrose drains may be covered with a sterile
dressing, especially when the drain is likely to
come into direct contact with contaminated
surfaces. The relative discharge in the bandage
can be used to assess the volume of drainage.
• Exposed drains can be maintained by cleansing
around the exit incision with antiseptic solution,
followed by application of a thin layer of
antimicrobial ointment.
• An Elizabethan collar should be considered to
prevent the patient from removing the drain. Fluid
volume is assessed by the amount of drainage
noted on absorbent cage mats.
healing process. Moreover, the risk of infection is
increased, especially in the presence of contaminants.
Connective tissue restoration (fibroplasia, collagen
deposition) can be accomplished more effectively by
controlling dead space.
There are several surgical and nonsurgical options
that can be used alone or in combination to control
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dead space in wounds. Drains are generally used for
the more substantial dead space regions but may be
combined with compressive wraps and basic suture
apposition techniques employed in wound closure. In
some cases, the presence of a small, self-limiting
seroma may require little or no treatment; over time,
the body reabsorbs serum. Because excessive activity
can impair dead space management, exercise restriction and the appropriate use of bandages can reduce
regional motion at the surgical site.
Closure of small skin defects involving the mid to
lower extremities normally demonstrates a variable
degree of incisional tension at closure. Slight tension
helps prevent the development of seromas.
Minimizing surgical trauma reduces the likelihood
of postoperative inflammation that contributes to
seroma formation in the surgical dead space created.
Postoperatively, small incisional seromas normally
resolve without treatment. Warm compresses applied
for 10 to 15 minutes two or three times daily over a 1week period may facilitate fluid resorption.
Additional treatment options include the following.
Compressive Bandages
Application of mildly compressive bandages can be
used to compress dead space areas, reduce regional
motion, and protect the wound while helping to limit
postoperative swelling. Fibrin deposition and subsequent
collagen deposition will occur between apposed tissue
layers during the reparative phase of wound healing.
Note: Caution is required when using compressive
wraps to manage dead space. Circulatory impairment
may occur if bandages are applied under excessive
tension or compression; extensive swelling and subsequent necrosis may occur if bandages are improperly
applied to the extremities. Similarly, compressive
wraps applied to the thorax, abdomen, or cervical area
have the potential to compromise normal respiration.
Compressive bandages are difficult to apply to the axillary and inguinal areas and are not normally used in
these body regions. Compression bandages are marginally effective in controlling dead space but should
be limited to those areas where simple application and
compression can be accomplished (mid to lower
extremities, central trunk region). They may be useful
in conjunction with suture closure of dead space (see
page 9) or in combination with an active or passive
drainage system for large dead space pockets.
Penrose Drains
Penrose drains have been used in the management of
dead space and dead space seroma formation for
decades. They are most commonly used to control small
to moderate-sized areas of dead space. They function by
directing fluid by capillary action over their external surface; the drain exits in a dependent position, allowing
fluid to exit the body by gravity. Such drains normally are
used to manage dead space for 3 to 5 days, unless significant drainage persists after this time. Drains can be
purchased in a variety of sizes, although the 0.25-inch
drain is best in small animals. I anchor the dorsal or proximal end of the drain with an external skin suture and a
single suture placed into the drain and exit incision. The
drain can be covered with a protective or compressive
wrap, depending on the body region affected.
Penrose drains are a potential source of wound contamination; they also allow air to enter the subcutaneous area. When used in the axillary or inguinal
areas, a “sucking wound effect” is occasionally noted,
whereby air is “pumped” beneath the skin. The resultant subcutaneous emphysema normally is minimal but
could become more substantial if the drain is retained
over an extended period. Under these circumstances,
air is slowly reabsorbed once the drain is removed.
Precautions: Penrose drains are not advisable for
wounds involving the thoracic wall or inlet, where there
is potential for air entry into the thoracic cavity. They are
ineffective for management of dead space in areas where
the drain cannot exit in a ventral or distal position.
Although Penrose drains may be used to manage dead
space in the presence of contamination or localized
infection, infected wounds may often best be managed
by delayed primary or secondary closure rather than by
closing the wound with a drain. Dead space can then be
managed with a Penrose or closed suction drainage system at the time of final closure (see box on page 8).
Closed Vacuum Drainage Systems
Closed vacuum drainage systems have gained
increasing popularity in veterinary medicine to control
moderate to large dead space pockets. The continuous
vacuum effectively draws tissue planes together, creating a “shrink wrap” or “vacuum pack” effect as residual
air and fluid are removed from the dead space pocket.
Unlike Penrose drains, vacuum drains function without
relying on gravity to facilitate fluid removal; they can be
placed in a variety of areas, including deeper dead
space areas (e.g., deep pockets, orthopedic surgeries
with extensive soft-tissue trauma). A vacuum reservoir
(100- to 150-ml capacity) attached to a fenestrated
drain aspirates serum that normally accumulates in the
dead space postoperatively. The nonfenestrated portion
of the tube exits the skin through a small stab incision;
a purse-string suture secures the tube to the skin. The
external end of the drain is connected to the fluid reservoir; in most models, a one-way valve prevents reflux
of the reservoir contents and accumulated contaminants back into the wound. Most commercial reservoirs
either use an internal spring to create a vacuum by forcing the chamber walls apart or rely on the inherent
“rebound” elastic properties of the chamber to create
the vacuum. All reservoirs have a spout to evacuate
CHECKPOINTS
— Beyond the guidelines given, surgical
experience with dead space management
influences the technique(s) selected for a
given patient.
— Penrose drains are best used for smaller
wounds. Some surgeons continue to use
Penrose drains as the primary form of dead
space management, despite the multiple
advantages of using closed vacuum
drainage systems.
air and accumulated fluid, with a milliliter scale to
measure the fluid accumulated. Drains are normally
removed when fluid volumes become minimal.
Should the drain become obstructed with a blood
clot, sterile saline can be flushed through the drain
with a sterile syringe using strict aseptic technique.
Surgical gloves are advised to further reduce the risk of
contamination. The drain is then reconnected to the
reservoir and reactivated. “Y” adaptors allow for the
simultaneous use of two drains with a single reservoir.
Because the risk of ascending infection is minimal
when drains are properly maintained, vacuum drains
may be used to prevent or control dead space seroma
formation for extended periods (2 to 3 weeks). Vacuum drains also minimize the nursing care required.
The reservoir vacuum can be inactivated by air entering the wound, often as a result of small incisional gaps
between sutures. Surgical glue or topical ointment may
be used to seal an incisional leak until fibrin deposition
and early connective tissue naturally plug these sites.
Although “homemade” vacuum drainage systems
using a syringe or vacutainer tube have been described
in the literature, they are not particularly effective
compared with commercially available units. Such
systems also have limited reservoir capacity and thus
are inappropriate except for fairly small dead space
areas. The small “butterfly” set used as the drainage
tubing for the vacutainer frequently becomes obstructed
and cannot be recommended. The lack of an antireflux
valve increases the risk of wound contamination. The
cost of vacuum drain systems has decreased considerably over the past few years, and silicone reservoirs
and tubing can be cleaned and autoclaved for further
use if so desired.
Suture Closure of Dead Space
Often, surgical and traumatic dead space can be
closed by reapposing fascial planes and adjacent softtissue structures. Suture closure can avoid the postoperative care and overall cost factors associated with the
use of surgical drains. Suture apposition is particularly
useful for moderate-sized dead space areas involving
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the trunk. However, not all dead space regions can be
effectively eliminated by suturing, especially in those
areas lacking fascia and soft-tissue structures for suture
apposition. Many of the synthetic, monofilament
absorbable or nonabsorbable suture materials on the
market may be used for tissue apposition; preferences
vary with individual surgeons. When possible, the
adjunctive use of bandages may reduce motion to facilitate healing. In the inguinal, flank, and axillary areas,
where elastic skin and underlining subcutaneous tissue
accommodate limb motion, aggressive attempts at
suture closure can impair this normal gliding function,
and vacuum drains are preferred in these areas.
In the presence of contamination and infection,
excessive use of suture material also can promote
infection; in some cases, separate infected pockets
may be created, making simple wound drainage problematic. Suture apposition should be used sparingly in
contaminated wounds. Contamination or potential
contamination is also a good argument for using a
monofilament absorbable suture (or nonabsorbable
monofilament nylon/Prolene) of the smallest practical
size. Open wound management alone or combined
with drains is best for infected wounds.
Alternative/Optional
Treatments/Therapy
Aspiration of Dead Space Seromas
Hypodermic needle aspiration may be used alone or
in combination with a compressive wrap in the management of moderate-sized seromas, provided that an
effective compression bandage can be applied to the
area. Aspiration requires standard surgical preparation
of the skin and sterile technique to reduce the likelihood of infection. If a seroma rapidly (within 24 to 48
hours) re-forms after aspiration, it is an indication that a
surgical drain is best employed to resolve the problem.
In some cases, dead space seromas slowly re-form to a
variable degree within 5 to 7 days of the initial aspiration. Under these circumstances, one or two additional
outpatient aspirations usually resolve seroma formation. The primary advantages of aspiration are that it
allows outpatient management and has a low cost.
Bandages
Some surgeons recommend that all Penrose drains
be covered with a bandage because of the risk that contamination could result in ascending infection. Bandages with a thicker secondary layer may be needed to
retain large volumes of fluid exiting the drain sites, and
frequent bandage changes would be indicated. Penrose
drain placement in the flank, inguinal, and axillary
areas normally precludes simple bandage coverage. In
my experience, the risk of ascending infection is low
without the use of a bandage cover, especially when
the drain can be removed a few days after insertion.
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However, bandage coverage is advisable for body
regions in direct contact with soiled or contaminated
surfaces (e.g., ventral thorax, abdomen, paws).
Management of Subcutaneous Emphysema
Subcutaneous emphysema normally is self-limiting;
the air is typically absorbed once the source of the air
entering the wound is eliminated. In cases in which there
is a tear in the trachea, large volumes of air may enter the
subcutaneous tissue, with dramatic expansion of the
elastic skin from the underlying musculofascial layers.
Tears of the pharynx, rhinotomy, and cutaneous sucking
wounds also cause subcutaneous emphysema, but rarely
on the order of magnitude noted with open tracheal
wounds. When significant stretching of the skin is present, air can be removed with a large-gauge hypodermic
needle connected to a vacuum pump; however, this
maneuver is rarely needed. Despite the dead space created, drains are not needed; most air is absorbed within
days of eliminating the air leak.
Supportive Treatment
• Supportive care depends on the health status of the
individual patient.
• A sterile dressing and protective bandage can be
applied over exposed Penrose drains, as noted above.
Depending on the volume of discharge, bandages
may require changing one or more times daily.
• Exposed Penrose drain sites can be maintained with
the application of a broad-spectrum antimicrobial
ointment. Any debris or discharge can be swabbed
with antiseptic solutions before the ointment is
applied. Care should be taken not to occlude the
drainage area with too much antibiotic ointment.
• Vacuum drains are emptied on an “as needed”
basis. Large effusions may require emptying of the
reservoir several times daily, depending on its
capacity. More commonly, fluid reservoirs are emptied two to four times per day. The quantity of fluid
accumulated should be recorded each time the
reservoir is emptied. Quantitating the volume helps
determine the optimal time to remove the drain
(provided the drain is not obstructed).
• Elizabethan collars are strongly recommended to
prevent patients from damaging or removing drains.
Patient Monitoring
• Normal health parameters should be assessed daily;
critical care patients require intensive monitoring
and supportive care.
• Compression bandages require periodic assessment
to ensure circulation is not impaired. For bandages
on the extremities, the central toes may be exposed
to assess for swelling. Bandages that may restrict normal respiration must be closely examined. Problem-
atic bandages may need to be adjusted or removed.
• The quality and volume of accumulated fluid should
be monitored and recorded.
• The surgical site should be assessed for dehiscence,
infection, necrosis, and self-mutilation.
• The integrity of the drain should be assessed; closed
suction drainage systems should be checked for air
leaks and obstructions that can negate their function.
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Home Management
• Patients sent home with drains in place require the full
attention of the owner to prevent contamination and
drain removal by the patient.
• Owners can master the use of vacuum drain systems with written instructions and a demonstration
before their pet is discharged.
• Owners should record the volume of fluid collected.
• Standard bandage care is indicated; bandages
should be changed when they become soiled.
• Bandages applied to the extremities require close
assessment for irritation and edema; owners should
be instructed to examine the middle two toes for
swelling, color, and warmth. Bandages should be
reassessed by a veterinarian if the patient is in pain
or chews at the bandage.
• Exposed surgical areas should be examined daily
for swelling, discharge, inflammation, discoloration,
necrosis, and dehiscence.
• Until healing is complete, the patient’s activity
should be kept to a minimum.
• Owners should be advised to keep the Elizabethan
collar on their pet to prevent chewing on or
removal of exposed drains.
Milestones/Recovery Time Frame
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abscess pockets can be effectively managed with
vacuum drains.
Penrose and closed suction drainage systems cannot provide optimal wound support in the presence
of necrotic tissue.
Penrose drains require a lower, dependent exit site for
proper gravitational flow from the wound. If this cannot be provided, closed vacuum drains are advisable.
Penrose drains allow air to enter the subcutaneous
space through the exit site. They should therefore be
avoided in thoracic wall and inlet areas if there is
potential for air to enter the thoracic cavity (e.g.,
through intercostal muscle tears, incisions).
Vacuum drain systems must be closely monitored
when used to control dead space associated with
thoracic wounds. Drain tube displacement from the
reservoir and a patient’s chewing the tube are
potential ways for air to enter the thoracic cavity.
Vacuum drains are contraindicated in wounds in
which an airtight seal cannot be maintained.
Patients must be prevented from chewing drains. A
retained drain becomes a surgical foreign body and
can result in the development of draining tracts until
it is removed. Penrose drains are radiopaque, and
thus radiography can be used to determine if a drain
fragment is within the body. Drains also can be
measured before placement and at removal to
ascertain if any is missing.
PROGNOSIS
Favorable Criteria
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Progressive reduction in drainage; drain removal.
Complete healing.
Absence of infection.
No seroma formation after drain removal.
• Skin sutures are normally removed in 8 to 10 days.
• Drains can be removed when the volume of
drainage decreases to minimal amounts.
— Most Penrose drains can be removed within 3 to
5 days. If little or no drainage is noted after 48
hours, the drain can be removed at that time.
— Intact closed suction drains normally can be
removed in less than a week after insertion. The
volume of drainage dictates the appropriate
time for its removal. I have used vacuum drain
systems for up to 3 weeks.
Unfavorable Criteria
Treatment Contraindications
Miller CW: Bandages and drains, in D Slatter (ed): Textbook of
Small Animal Surgery, ed 3. Philadelphia, WB Saunders, 2003,
pp 247–249.
• Excessive use of appositional (“tacking”) sutures to
control dead space in the face of wound contamination or infection.
• In cases of infection, open wound management
may provide optimal drainage. Deeper or recessed
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Persistent, excessive fluid drainage.
Development of infection.
Tissue necrosis.
Partial or complete dehiscence.
Repeated vacuum drain obstruction.
Seroma formation despite treatment to control dead
space.
RECOMMENDED READING
Pavletic MM: Atlas of Small Animal Reconstructive Surgery.
Philadelphia, WB Saunders, 1999, pp 36–39.
Swaim SF, Henderson RA: Small Animal Wound Management.
Philadelphia, Williams and Wilkins, 1997, pp 29, 31.
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