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Policy
for Performing Survival Surgery on Vertebrate Animals at Indiana University
All survival surgery
in vertebrate animals must be performed using aseptic procedures, including
surgical gloves, masks, sterile instruments and aseptic techniques. Non-rodent
mammalian survival surgery must be performed in a dedicated operating
room. Survival surgery on rodents does not require a special facility
but should be performed using sterile instruments, surgical gloves and
aseptic procedures to prevent clinical infections.
Guidelines
for Aseptic Surgery in Rodents
The following guidelines
for performing aseptic surgery on rodents were developed by the IUPUI
Animal Care and Use Subcommittee. These guidelines are intended to provide
those persons performing survival surgical procedures on rodents with
sufficient information so that procedures done in their areas are in compliance
with the IU Survival Surgery Policy.
A. Pre-operative
preparation
Rodents should
be in optimal health prior to performing surgery. The veterinary staff
of the facility should be contacted anytime rodents appear ill, and
surgery should not be performed until the health status of animals has
been determined. Recently shipped animals should be given a period of
adaptation of 3-7 days before surgery is performed in order to allow
them to become familiar with their new surroundings and to allow them
to become familiar with new food and sources of water. If animals will
be placed into a different environment following surgery, it is advisable
to adapt them prior to performing surgery (ie., group housing to single
housing, conventional cage to metabolic cage).
Pre-surgical fasting
is not generally required for rodents. However, it may be desirable
to withhold feed if surgery is to be performed on the gastrointestinal
tract in order to reduce the volume of intestinal contents.
B. Anesthesia
Appropriate anesthesia
should be induced and maintained during the surgical period. An adequate
depth of anesthesia is indicated when the animal:
(a) is breathing
regularly,
(b) has pink ears and mucous membranes,
(c) will not withdraw its foot when the toes are pinched, and
(d) will not blink when the eye or eyelid is touched. The veterinary
staff should be consulted for advice in selection of appropriate anesthetic
agents, routes of administration and dosages.
Hypothermia is a
major complication of anesthesia in rodents, and where required, it
should be prevented by providing supplemental heat. Placing a circulating
water heating pad under the rodent at the time of surgery is ideal,
but plastic bottles filled with warm water or suspending a 75-watt bulb
approximately 2 feet above the animal can also be used. Extreme care
must be used when placing unconscious animals under a light source,
since severe thermal burns can be produced if animals are not closely
monitored until they have regained mobility.
C. Surgical
procedures
Surgical facility:
Areas where rodent surgeries are performed must be adequately sanitized.
In most cases, rodent surgeries are performed on a table or portion
of a lab bench that has been appropriately sanitized and is not used
for any other purpose during the time of surgery.
Preparation of
the incision site:
Hair should be removed from the incision site and the skin should be
aseptically prepared prior to surgery. For larger rodents, hair can
be removed by clipping with electric clippers using a #40 blade. For
smaller rodents, hair can be plucked from the incision site of anesthetized
animals. The incision site should be scrubbed free of debris using a
standard surgical skin cleanser. The use of isopropyl alcohol alone
is not a suitable means of preparing skin for aseptic surgery. Care
must be taken not to wet large areas of the rodent's body when prepping
the incision site--this will predispose the animal to-hypothermia. For
small rodents, cotton-tipped applicator sticks can be used to cleanse
the incision site. Sterile gauze sponges can be used for skin preparation
in larger rodents.
When there is extensive exposure of tissues (laparotomy, thoracotomy),
the surgical site should be draped after it has been prepped. Drapes
can be made from impervious materials that can be sterilized; plastic
sheets, plastic-backed paper, double layered cloth, aluminum foil. Sheets
of clear plastic make excellent drapes because the animal can be visualized
through the drape.
Surgical instruments:
The surgical instruments should be matched to the size of the rodent and
the procedure in order to minimize surgical trauma. Surgical procedures
in small rodents require delicate instruments such as those designed for
micro or ophthalmic surgery.
All instruments, sutures, catheters, etc. that will have contact with
the surgical site must be sterile. Suitable methods for preparing surgical
materials include the following:
a. Steam autoclaving--the
most common means of sterilizing surgical equipment (items are exposed
to moist heat at 27ºF for 15-30 minutes)
b. Gas sterilization (ethylene oxide)--used to sterilize heat sensitive
materials.
c. Liquid chemical disinfectant (ABQ, novalsan, zephiran, povidone
iodine solutions)--when materials are disinfected by immersion in
chemical solutions, they must be accurately mixed and used according
to the manufacturer's instructions. Immersed materials must be rinsed
with sterile saline prior to contacting tissues of live animals. Failure
to rinse caustic chemicals from instruments has produced severe chemical
burns in rodents.
Surgeon preparation:
Anyone touching the sterile surgical equipment or the operative site
should wear sterile gloves. Once gloved, care should be taken to touch
only the sterile operative field and equipment. In addition to sterile
gloves, caps and masks must be worn, and the arms of the surgeon must
be covered (clean lab coat or surgical gown).
Advice for "Multiple
Run" Procedures:
"Multiple run" refers to the same procedure being performed on a group
of rodents sequentially using the same surgical instruments. One way
to minimize transfer of skin bacteria to deeper tissues and between
animals is to separate the instruments by function when the instrument
tray is prepared. For example, a pair of scissors and forceps are assigned
to skin incisions. A second scissors and forceps are assigned to subcutaneous
and abdominal wall incisions. Additional instruments are used to manipulate
abdominal organs. Blood and tissue debris are removed from instrument
tips by rinsing them with sterile saline between animals. The pack should
be re-sterilized after it has been used on 4-5 rodents.
D. Postoperative
recovery
Anesthesia recovery:
Most rodents recover rapidly and uneventfully from most surgeries. Animals
should be kept comfortable and warm, and they should be observed at
frequent intervals (every 15-30 minutes) until mobility has been regained.
Anesthetized animals should be positioned with their heads and necks
extended in order to maintain a patent airway. If there were significant
fluid losses during surgery, or the duration of the surgical procedure
was long, administration of warmed sterile saline or lactated ringer's
solution (1 ml/100 g body weight/anesthesia hour) by subcutaneous injection
is recommended. Systemic analgesics should be administered to rodents
that have undergone orthopedic or invasive procedures. The facility
veterinary staff can be consulted for appropriate analgesic drugs and
dosages.
Clinical recovery:
Animals should be examined daily until incisions are healed and sutures/wound
clips have been removed. Sutures are usually removed approximately 6-10
days following surgery. Care should be taken to ensure proper food and
water intake, to provide analgesic drugs for pain relief, and to clean
surgical sites to ensure proper wound healing. During this period, it
is the investigator's responsibility to check their animals each day,
including weekends and holidays. Any clinical problems must be promptly
reported to the veterinary staff.
It is best to keep post-surgical patients separated from non-operated
animals until the incisions are healed because non-operated rodents
may cannibalize the incision of the recovering animal.
E. Recordkeeping
requirements
Records of surgical
procedures performed on rodents must be maintained. These records should
include: 1) a description of - the surgical procedure performed; 2)
the anesthetics used (including dosages and routes of administration);
3) monitoring procedures that were done during surgery and in the postoperative
recovery period (observations must be recorded, at least daily, from
the date surgery was completed until the date the incision has healed);
and 4) a description of any adverse anesthetic reactions or complications
that were encountered. Groups of rodents undergoing surgery on the same
day can all be kept on a single record. These records must be accessible
to the Animal Care and Use Committee during their semi-annual inspections
and to the veterinary staff upon their request.
reviewed & approved
by IU IACUC in August, 1993
drafted by C.M. Vogelweid
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