NEWARK RESEARCH ANIMAL FACILITY STANDARD OPERATING PROCEDURES
Title: Rodent Surgery
Section 3300
Date Issued:
Filename:
Keywords:
January 12, 1998
vetSURGERYrodent.doc
rodent, survival, surgery
Date Revised: April 1, 2002
Recommendations for the performance of rodent surgery are based on the 1996 edition of the Guide for the Use
of Laboratory Animals and 9 CFR, the Animal Welfare Act (AWA). This includes the use of sterile instruments,
sterile surgical gloves, and aseptic preparation of the surgical site in order to prevent postoperative infections. A
separate facility for rodent surgery is not necessary. A rodent surgical area can be a room or portion of a room
that is easily sanitized and not used for any other purpose during the time of the surgery.
Major Surgery
A major surgery includes invasion of the cranial,
abdominal or thoracic, cavities. Any procedure that
might leave the rodent with a permanent handicap
whether physical or physiological (e.g. limb
amputation) is considered as major surgery.
Provide a heat source such as a covered heating
pad, warm water bottle or heat lamp to prevent
hypothermia of the animal.
Minor Surgery
Minor survival surgery does not expose a body cavity
and causes little or no physical impairment (the
Guide, p 63). An example of a minor survival surgery
is placement of subcutaneous implants.
Procedures for Surgeries on Multiple Rodents
Investigators should begin with at least 2 sets of
sterile instruments. After the sterile instruments have
been used, they should be thoroughly cleaned to
remove all organic material (and dried if possible.)
Then the instruments should be treated with a high
level disinfectant at the appropriate concentration and
for the appropriate length of time before being used
on the next animal. (See Table 3)
Alternatively, a bead sterilizer may be used.
Subcutaneous Implants
The number and size of subcutaneous implants
should be the lowest number and smallest size
possible. The subcutaneous implants must not
impede normal mobility and physiologic function (i.e.
eating, defecation, urination or respiration) in the
animal.
Multiple, Major Survival Surgeries
All efforts should be made to avoid multiple major
survival surgery in animal studies. Two or more
major survival surgeries are considered as “multiple.”
However, there are instances when investigators will
have a scientific need for the performance of multiple
major survival surgical procedures. Such procedures
must be described in the protocol, scientifically
justified, and approved by the IACUC.
The Surgery Room/ Area
An area or portion of a room that is easily sanitized
and not used for any other purpose during the time of
surgery is acceptable. This must be kept free of
clutter. Be aware that materials stored on open
shelves above the surgery area are a likely source of
contamination during surgery i.e. dust dropping into
the surgery area.
Clean and disinfect the surface with a disinfectant
before each surgery (See Table 1).
Provide adequate lighting.
Rodent Surgery 04-2002
Sterilization of Instruments
See Table 2
Preparation of the Animal
A pre-surgical evaluation should be performed to
ensure that prospective patients are not overtly ill.
The withholding of food is not necessary in rodents
unless specifically mandated by the protocol or
surgical procedure. Water should NOT be withheld
unless required by the protocol. Withholding food for
greater than 6 hours should be discussed with a
veterinarian and approved by the IACUC.
Particular attention should be paid to maintenance of
the animal's body temperature, as hypothermia is a
significant cause of mortality in rodents undergoing
surgery.
Heating pads: Cover with a towel to avoid
direct contact. Use the lowest level of heat
possible. Circulating warm water heaters are
preferred for safety reasons.
Warm water bottles: Surgical gloves filled
with warm water or bags of fluids such as
those used to administer intravenous fluids
e.g. lactated Ringers solution or sterile saline,
warmed in the microwave may be used.
Monitor the temperature of the water as it
looses heat quickly. When the fluid bags
become cold they will draw heat away from
the animals’ body.
Newark Research Animal Facility Standard Operating Procedures
Heat lamp: Can produce too much heat—
the ears of the rodent are particularly
sensitive.
Monitor the rectal temperature—this should
not exceed 102oF in rats and 102oF in mice.
Monitor animal:
Check respiration rate and depth every 3-5
minutes.
Check pedal reflexes every 5 minutes.
Examine pedal reflexes by gently pinching
the animal's foot and determining whether the
animal pulls or moves its foot back. If the
animal has an elevated respiration rate or
positive pedal reflex, supplement the
anesthesia with one-half the initial dose, or
place a mask or cone, with a gas anesthetic
over the animal's face. Monitor the dosages
carefully to avoid overdosing.
Remove hair from the surgical site with clippers or
razor. Depilatory cream may be used when indicated,
however these products may complicate surgical
recovery due to dermatitis caused by these products.
To avoid contamination of the surgery area, hair
removal should be done at another location and the
loose hair should be vacuumed up or otherwise
removed from the environment (tape is a practical
and effective alternative for small amounts of hair.)
A non-medicated ophthalmic ointment needs to be
placed in the anesthetized animal's eyes to prevent
drying. Animals do not close their eyes when
anesthetized.
Patient Scrub (See Table 4)
Scrub with chlorhexidine or providone-iodine scrub a
minimum of three times or until clean. The scrubs
may be alternated with alcohol.
Scrub in an enlarging circular pattern from the center
of the shaved area to the outside. Finish with an
alcohol wipe then apply chlorhexidine or providoneiodine solution.
Caution: evaporation of alcohol can cause
hypothermia so limit the alcohol scrub to the surgical
site and use sparingly.
Preparation of the Surgeon
Wear a clean lab coat of scrub top and remove all
jewelry (rings, bracelets, watches) on the hands and
wrists.
A mask and hair bonnet or cap is required for all
surgeries. .
Wash and scrub hands with a disinfectant soap and
dry with clean paper towels.
It is acceptable to use clean latex gloves disinfected
with Clidox or another strong disinfectant and then
Rodent Surgery 04-2002
rinsed with sterile water or saline. Fresh sterile gloves
are recommended for each animal.
Draping
After disinfecting the skin, the animal should be
moved to the surgical area, placed on a clean
absorbent pad over a heating pad or warm water
bottle.
Position with tape. Do not overstretch the legs or
bind them in such a way as to restrict circulation.
Cover with a sterile drape with a fenestration over
the proposed incision site.
The drape minimizes contamination of the surgical
area and surgical instruments.
To perform sterile draping, the surgeon must already
be aseptically prepared including use of sterile
gloves.
Surgery
Training is available on basic surgery technique.
Please contact RAF veterinary staff if training in
surgical technique is needed.
See Table 5 for suture selection. The smallest
gauge suture should be selected to perform
closure/ligation adequately. Cutting and reverse
cutting needles provide edges that will cut through
dense difficult to penetrate tissue such as skin. Noncutting, taper point or round needles have no edges
to cut through tissue, used primarily for suturing easily
torn tissues such as peritoneum or intestine.
Anything touching the drape or the animal should be
sterile. If forceps are used to check the toe pinch
response, the tips are contaminated. The handle end
of the forceps can be placed on the drape with the
tips hanging over the edge.
Postoperative Care
Check the animal regularly until it is fully ambulatory.
The animal must be monitored daily following
surgery, assessing such parameters as appetite, and
wound healing. Any complications should be reported
to the RAF veterinary staff.
The three major threats to a rodent recovering from
anesthesia are:
 Hypothermia. This may be
minimized by housing the animal in a
warm room, use of a heating blanket,
warm water bottle or other source of
warmth.
 Dehydration. In prolonged or very
invasive surgeries, 1-2 cc in mice
and 10cc in rats of warm (not hot)
sterile saline or LRS can be given
subcutaneously after surgery to help
Newark Research Animal Facility Standard Operating Procedures

prevent dehydration. More may be
needed if there was much bleeding
during surgery. Additional fluids may
be given if the animal has not
recovered from anesthesia within
several hours.
Cagemates.. House rodents singly
after surgery. Rodents tend to
cannibalize nonresponsive
cagemates. Even if all of the rodents
in a cage were anesthetized, some
will be slower to recover than others,
and they may be injured by more
alert animals. Therefore, it is best to
recover rodents in separate cages
until they are fully ambulatory.
Never place rodents on antibiotics postoperatively without consulting the
veterinarian and IACUC approval. Many
are susceptible to fatal enterocolitis due
to bacterial overgrowth of Clostridium
difficile when certain antibiotics are
administered.
Table 1. Recommended Hard Surface Disinfectants (e.g. table tops, equipment) Always follow
manufacturer's instructions.
NAME
EXAMPLES
COMMENTS
Alcohols
70% ethyl alcohol
Contact time required is 15 minutes.
70%-99% isopropyl alcohol
Contaminated surfaces take longer to
disinfect. Remove gross contamination before
using. Inexpensive. Flammable.
Quarternary Ammonium
Rapidly inactivated by organic matter.
Roccal, Cetylcide
Compounds may support growth of gram
negative bacteria.
Chlorine
Sodium hypochlorite (Clorox Corrosive. Presence of organic matter
10% solution) Chlorine dioxide reduces activity. Chlorine dioxide must be
fresh (<14 Days old); kills vegatative
(Clidox, Alcide)
organisms within 3 minutes of contact. A rinse
with water or alcohol is required after solid
surface disinfection.
Aldehydes
Rapidly disinfects surfaces. Toxic Exposure
Gluteraldehyde (Cidex, Cide
limits have been set by OSHA.
Wipes)
Phenolics
Less affected by organic material than other
Lysol , TBQ
disinfectants.
Chlorhexidine
Presence of blood does not interfere with
Nolvasan , Hibiclens
activity. Rapidly bactericidal and persistent.
Effective against many viruses.
Rodent Surgery 04-2002
Newark Research Animal Facility Standard Operating Procedures
Table 2. Recommended Instrument Sterilants
AGENTS
Physical: Steam sterilization
(moist heat)
EXAMPLES
Autoclave
COMMENTS
Effectiveness dependent upon temperature,
pressure and time (e.g. 121C for 15 min vs.
131 C for 3 min).
Dry Heat1
Hot Bead Sterilizer
Fast. Instruments must be cooled before
Dry Chamber
contacting tissue.
Ionizing radiation
Gamma Radiation
Requires special equipment
Chemical: Gas Sterilization
Ethylene Oxide
Requires 30% or greater relative humidity for
effectiveness against spores. Gas is irritating
to tissues, all materials require safe airing
time. Carcinogenic. Use only for materials
which cannot be sterilized with any other
method.
Hydrogen Peroxide
Not useful for "delicate" items.
(Sterad )
Chlorine2
A minimum of 6 hours required for
Chlorine Dioxide (Clidox,
sterilization. Presence of organic matter
Alcide)
reduces activity. must be freshly made (<14
days)
Aldehydes2
Formaldehyde (2% sol.)
For all aldehydes: many hours required for
Gluteraldehyde
sterilization. Corrosive and irritating. Consult
safety representative on proper use.
Glutaraldehyde is less irritating and less
corrosive than formaldehyde.
1Instruments must be cleaned and rinsed before being placed in the bead sterilizer.
2Instruments must be rinsed thoroughly with sterile water or saline to remove chemical sterilants before
being used.
Table 3. Recommended Instrument Disinfectants
AGENT
Alcohols
Primary use is as a
disinfectant- soak between
animals when starting with
sterilized instruments.
Chlorine1
EXAMPLES
70% ethyl alcohol
70%-99% isopropyl alcohol
COMMENTS
Contact time required is 15 minutes.
Contaminated surfaces take longer to
disinfect. Remove gross contamination before
using. Inexpensive. Flammable. Low level
disinfectant.
Sodium hypochlorite (Clorox
10% solution) Chlorine dioxide
(Clidox, Alcide)
Corrosive. Presence of organic matter
reduces activity. Chlorine dioxide must be
fresh (<14 Days old); kills vegatative
organisms within 3 minutes of contact.
Corrosive to instrument surfaces. Must be
thoroughly rinsed from instruments before
use.
Presence of blood does not interfere with
activity. Rapidly bactericidal and persistent.
Effective against many viruses.
Peracetic Acid/ Hydrogen
Peroxide
Spor - Klenz
Chlorhexidine
Nolvasan, Hibiclens
1Instruments
must be rinsed thoroughly with sterile water or saline to remove chemical sterilants before
being used.
Rodent Surgery 04-2002
Newark Research Animal Facility Standard Operating Procedures
Table 4. Skin Disinfectants Alternating disinfectants is more effective than using a single agent. For
instance, an iodophore scrub can be alternated 3 times with an alcohol, followed by a final soaking with a
disinfectant solution. Alcohol, by itself is not an adequate skin disinfectant. The evaporation of alcohol or
alcohol based products can induce hypothermia in small animals.
NAME
Alcohols
EXAMPLES
70% ethyl alcohol
70-99% isopropyl alcohol
Iodophors
Betadine, Prepodyne,
Wescodyne
Chlorhexidine
Nolvasan , Hibiclens
Table 5. Suture Selection*
SUTURE
Vicryl, Dexon
PDS or Maxon
Prolene
Nylon
Silk
Chromic Gut
Stainless Steel: Wound Clips, Staples
COMMENTS
NOT ADEQUATE FOR SKIN
PREPARATION! Contact time required is 15
minutes. Not a high level disinfectant. Not a
sterilant. Flammable.
Reduced activity in presence of organic
matter. Wide range of microbe killing action.
Works best at pH 6-7.
Presence of blood does not interfere with
activity. Rapidly bactericidal and persistent.
Effective against many viruses. Excellent for
use on skin.
CHARACTERISTICS AND FREQUENT USES
Absorbable; 60-90 days. Ligate or suture tissues where an
absorbable suture is desirable.
Absorbable; 6 months. Ligate or suture tissues especially
where an absorbable suture and extended wound support is
desirable
Nonabsorbable. Inert.
Nonabsorbable. Inert. Recommended for skin.
Nonabsorbable. (Caution: Tissue reactive and may wick
microorganisms into the wound). Silk is very easy to use and
knot. Silk is not acceptable for suturing skin.
Absorbable. Versatile material. causes mild inflammation, but
is absorbed more rapidly than synthetics. Chromic gut is not
acceptable for suturing skin.
Nonabsorbable. Requires instrument for removal from skin.
*Suture sizes for most general purposes for mice are 4-0 or 5-0 and for rats is 3-0 or 4-0. Sutures or staples must be
removed from the skin after the incision is healed; this is generally 10-14 days.
REFERENCES:
1.
2.
Forman, L.A., 2000; Rodent Surgery guidelines, Northwestern University, Chicago, IL.
Slatter, D., 1993; Textbook of Small Animal Surgery, Philadelphia, W.B. Saunders and Co.
DBL
EBR
Rodent Surgery 04-2002