Use of Expired
Rodent Surgery SOP
Guidelines for Prevention of Intravascular Device-Related Infections
Guideline for Prevention of Surgical Site Infection
Copyright 2008, University of Minnesota Board of Regents.
The University of Minnesota is an equal opportunity educator
General Issues and Requirements
Surgery is defined as any procedure
that exposes tissues normally covered by skin or mucosa. Experimental
surgery has great potential for causing pain or distress to animals if
not performed properly. Surgery can result in pain, damage to tissue
and post-operative infections. Therefore stringent guidelines for
surgical facilities, asepsis,
surgical preparation, anesthesia, intra-operative records, analgesia, surgical technique, and post-operative monitoring have been established.
Surgery is classified in
several ways. There are different requirements depending on the type
of surgery being performed.
- Surgery is major if it
enters a body cavity (thorax, abdomen, calvarium), or has the potential
for having significant complications. Included would be orthopedic
procedures and extensive cannulation procedures.
- Other surgery is classified
as minor. Minor procedures include peripheral vessel cannulations
and skin incisions.
- Surgery is also classified as
survival vs. nonsurvival. Asepsis and sterility are not required
for non-survival procedures, unless the procedures are of sufficient duration (eg. over 6 hours)
to allow bacterial infections to affect the outcome of the study.
- There are also different
regulatory requirements for surgery performed on large animals such as rabbits, dogs,
pigs and monkeys versus rodents and non-mammals. See Rodent Survival Surgery Sample SOP for further information.
Surgical facilities used for
survival surgery must be designed and maintained in such a way that they
help prevent the development of post-procedural infections. Design
- Separation of the preparation
areas from the surgery area
- Minimization of personnel traffic
flow through the surgery area
- Air flow should be away from
the surgery area (e.g. positive room pressure, use of filtered, laminar
flow air). It may be desirable to have HEPA filtered air for high-risk
- Room surfaces should be non-porous
and easily sanitized
- A regular room cleaning and
disinfection schedule should be established for dedicated surgical suites (i.e. daily cleaning of floors
and work surfaces, weekly to monthly cleaning of walls and cabinets)
- The surgery area should be free
of all equipment and materials not necessary for the procedure. Any
stored items should be in cabinets or drawers.
How these goals are achieved
will vary somewhat depending on the type of surgery.
- An approved surgery suite
is needed for large animal major survival surgery, with separate rooms
for preparation of the patient, preparation of the surgeon, the operating
room and a recovery of the animal from anesthesia.
- Non-survival surgery, minor
surgery or rodent/non-mammal surgery may be performed in a dedicated
work area. This is a room or bench top which from which all materials
are removed at the time of the surgery. The same concepts described
above are important for a dedicated area.
The IACUC will review all surgical areas semi-annually.
Principles of Asepsis
Asepsis is defined as preventing
exposure to microorganisms and prevention of infection. Three things
that are extremely important in achieving asepsis are the reduction
of time, trauma and trash.
- Time of surgical procedure
is an important factor, as the longer a procedure takes the greater the
possibility of contamination and therefore infection.
- Trauma that is sustained
by the tissue as a result of rough handling, drying out upon exposure to
room air, excessive dead space, implants or foreign bodies or non-optimal
temperatures will contribute to infections.
- Trash refers to contamination
by bacteria or foreign matter.
It may be possible to follow
slightly different procedures for achieving asepsis when performing surgery
on small patients such as rodents, birds, reptiles and amphibians.
Typically, surgical times are short, incisions are small and the amount
of tissue trauma is minimal. These all minimize the risk of infection.
Preparation: Surgeon, Patient, Instruments and
It is essential that anything
that will contact the subcutaneous tissues of an animal be appropriately
sterilized to prevent post-procedural infections. These will be
discussed below. Videos on many of these techniques are available
from the central animal facilities and the University library system.
The RAR veterinary staff can provide
training as well. Other aspects of preparation include pre-operative
fasting, if necessary, a decision about prophylactic
antibiotics, appropriate anesthesia of
the patient, and a plan for post-operative pain
control and supportive care.
Preparation of Instruments
Surgical instruments and supplies
must be sterilized before they are used for survival surgery. There
are a number of ways that this can be achieved.
Durable instruments and supplies
may be autoclaved. This an extremely reliable and cost-effective
method for sterilization. The disadvantage is the time that it takes
to perform (from 15 minutes to 1 hour). Normally a wrapped "pack"
of instruments is prepared and is opened the day of surgery. Packs
may be stored if they are kept away from moisture. A preparation date should be put on each prepared pack and packs should not be used if they are more than six months old.
Instruments and less durable
supplies may be sterilized by ethylene oxide. This is also
a reliable method for sterilization. However, it is more costly than
autoclaving and also takes time to perform (overnight). Ethylene
oxide is hazardous and must be performed using appropriate procedures and
Instruments and some materials may be sterilized in a cold sterilant
solution. There are several acceptable commercial sterilants available.
Only products classified as sterilants are to be used for sterilizing
instruments and implants for surgery and they must be used according to
the manufacturer's recommendations for sterilization.
examples of four commercial products listed by brand names:
Cidex: active ingredient: glutaraldehyde* - a minimum of 10 hours is required for sterilization. Cidex comes in two formulations, Cidex and Cidex-7 (long-life). The shelf life of activated Cidex is 15 days and of activated Cidex-7 is 28 days.
Sporicidin: active ingredients:
phenol and sodium phenate - a minimum of 12 hours is required for sterilization. The shelf life of the activated solution is 14 days.
Alcide: active ingredients: sodium chlorite and lactic acid which, when mixed, form chlorine dioxide - a minimum of 6 hours is required for sterilization. The shelf life of the activated solution is 14 days.
Sporclenz: active ingredient: hydrogen peroxide - for a minimum of 6
hours. Estimated shelf life is 7 days.
Non-commercial solutions that are acceptable include:
glutaraldehyde 2% for a minimum of 10
formaldehyde 8% + 70% ethyl alcohol for a minimum of 18 hours*
stabilized hydrogen peroxide 6% for a minimum of 6 hours
*Note: DEHS guidance is that these cold sterilants should be kept in covered trays and only opened inside a fume hood or externally vented biosafety cabinet.
both interior and exterior, must be exposed to the sterilant. Tubing
must be completely filled and the materials to be sterilized must be
clean and arranged in the sterilant to assure total immersion. The items
being sterilized must be exposed to the sterilant for the prescribed
period of time. The sterilant solution must be clean and fresh. Most
sterilants come in solutions consisting of two parts that when added
together form what is referred to as an "activated" solution. The shelf
life of activated solutions is indicated on the instructions for
commercial products. Instruments,
implants, and tubing (both inside and out) that have been chemically sterilized should be rinsed with sterile
saline or sterile water prior to use to avoid tissue damage. Note:
chemicals classified only as disinfectants (for example, 70% alcohol)
are not adequate for initial instrument sterilization.
If starting with sterilized instruments, the same instruments can be used for multiple animals (up to six) (mice, rats and non-mammal only) if the instruments are cleaned of organic material and disinfected between animals, for example with ethanol or a hot bead sterilizer. When using a hot bead sterilizer, only the tips of the instruments are sterilized, and thus the surgeon must constantly be aware of instrument handling and aseptic technique. The pack of instruments must be fully re-sterilized (autoclaved) if the sterile field is broken, e.g. instruments are set down on a table or other non-sterile surface between surgeries. The efficacy of the hot bead sterilization is high and it sterilizes in a very short time (10 sec) but it is necessary
to allow the instruments to cool before handling tissue to prevent thermal
injury. [Ref: Callahan, et. al, 1995. A comparison of four methods for
sterilizing surgical instruments for rodent surgery. Contemp. Top. Lab.
Anim. Sci, 34:2, 57-60.]
Instruments and materials are
often available pre-sterilized. The packages should have an
expiration date on them. Surgical supplies may not be used for survival
surgery when they have passed the expiration date.
Use of Expired
Expired medical materials
such as drugs, fluids and sutures may not be used on an unanesthetized research animal
or one that is to recover from an anesthestic procedure.
The use of such materials under these conditions constitutes inadequate
veterinary care under the Animal Welfare Act.
The IACUC has established
the following guidelines for the use of expired medical materials during non-survival procedures:
- It is never acceptable to use
outdated anesthetics, analgesics, euthanasia agents, or emergency drugs on any animal.
- Examples of acceptable
expired materials for use in non-survival surgery include IV fluid solutions, non-emergency drugs (diuretics, contrast
material, antibiotics), IV catheters, bandage materials, surgery gloves
and suture materials.
- All expired materials must be
clearly and individually labeled as: Expired--for acute use only, and are
kept together in an area physically separate from all other medical materials
and drugs. The area (box, shelf etc.) they are kept in must be labeled: Expired--for acute use only.
Preparation of the Patient
The majority of post-procedural
infections are the result of contamination of the surgical site with resident
or transient skin bacteria from the patient. Therefore, decontamination
of the surgical site and prevention of contamination from other areas is
the best means of preventing post-procedural infections.
- Normally, the patient's hair
should be removed from the surgical site. This should be done with
an electric clipper or depilatory rather than a razor. Hair removal
should be performed immediately prior to the surgery.
- The patient's skin should be scrubbed with a disinfectant such as povidone iodine or chlorhexidine. Scrubbing should start at the center of the surgical site and move to the outside in a linear or circular manner. Scrub the surgical site with a disinfectant and rinse/scrub with alcohol or sterile water or saline to remove debris. Repeat at least three times or until site is free of visible debris. Often a disinfectant solution is then painted onto the surgical site and left to dry. The amount of scrub fluid used should be carefully controlled to prevent hypothermia. It may not be appropriate to scrub the site of some patients. Scrubbing the skin of a fish or amphibian will remove the protective bacterial slime layer, and may actually increase the risk of infection.
- A sterile surgical drape
should be used whenever possible to isolate the disinfected area from surrounding
areas. To be effective, a drape must fit tightly to the skin and
must be impermeable to moisture. Clamps or sutures may be used to
fix the drape in place. Self-adhesive drapes are also useful and
are particularly recommended for use in small patients. In some cases
a drape may not be practical or necessary. When a drape is not used
is places extra responsibility on the surgeon to perform excellent
Preparation of the Surgeon
The patient must be protected
from organisms that can be carried and shed by the surgeon. These
organisms reside on the surgeon's skin, hair, in the nose or mouth, or
may be carried on dust particles from the floor or room surfaces.
This route of contamination is minor compared to the patient's own flora,
however, it is a significant source of contamination is some types of surgery
such as orthopedic and central nervous system procedures. See also http://www.ohs.umn.edu/ppe/home.html.
- Sterile gloves must
be used for all survival surgical procedures; examination gloves are not sterile and are only acceptable for non-survival surgery. For rodent
and non-mammal surgeries (other than aquatics) gloves may be disinfected between surgeries with a cold sterilant.
- The surgeon's hands and arms
should be scrubbed for 3 minutes with a disinfectant such as povidone
iodine or chlorhexidine, rinsed with water and dried prior to gloving for
any large animal survival surgery. As much as 30% of the time gloves
become perforated during surgery, exposing the animal's tissues directly
to the surgeon's skin. If that happens, the surgeon should reglove with sterile gloves.
- A cap/hair cover, face mask, shoe covers
and sterile gown must be worn for all large animal major survival surgeries.
- Sterile gloves hair cover, surgical mask and a clean top (surgical gown/lab coat/smock/scrub top etc.) must be worn for survival surgery on rodents and non-mammals (other than aquatics).
- Minimizing traffic flow and
conversation in the operating room significantly reduces the risk of
contamination of the surgical site.
It has been recognized that
one of the greatest influences on the incidence of post-procedural infection
rates is the surgeon themselves. Prolonged surgical times expose
tissues to contaminants, dry out tissues and compromise the blood flow
to tissues. Tissues damaged by crushing or drying, suture and other
surgical implants serve as a nidus for infection. There are a number
of things that surgeon's can do to prevent post-procedural infections.
Be aware of instrument and
hand position at all times. If an instrument or hand touches
something outside of the sterile field (the are delimited by the drape
or the inside of the opened instrument pack) the instrument or glove should
be replaced immediately.
Be gentle when handling tissues.
Do not use toothed or crushing
instruments if it is not necessary.
Hold the cut edge rather than
grasping in the middle of a tissue layer.
When tying off vessels include
only a minimum of surrounding tissues.
Use electrocautery or electroscalpels
sparingly. They cause significant tissue necrosis.
Use appropriate suture techniques
Any suture that will be buried
in tissues should be either absorbable or monofilament (non-absorbable
braided suture is irritating and can harbor bacteria)
Sutures should be placed evenly
and as close to the tissue edge as possible to prevent obstruction of blood
flow- typically no more than 1 cm from the edge is necessary in large animals
and 0.2 cm in small animals.
Sutures should only be tightened
enough to appose the tissue edges. Any tighter will obstruct blood
supply, retard wound healing and may result in dehiscence.
Skin sutures are often unnecessary.
They may cause the animal to chew or scratch at the incision site.
Alternatives include use of subcutaneous/intradermal closure techniques
or tissue adhesive.
Ablate all "dead space" during
closure. Any pockets or potential space that remains between
tissue layers will fill with extracellular fluid or blood. This is
an abscess waiting to happen. However, it is important not to place excessive tension on the suture line or the incision may not heal. Tacking down tissue layers can be used.
If this is not possible, use of a drain for 3 to 5 days following the procedure
It is required that animals be cared
for after procedures to ensure their full recovery. Post-procedural care
for dogs, cats, swine, sheep and goats is provided
by RAR. Post-procedural care for other animals such as small animals,
nonhuman primates and in some circumstances, sheep, may be provided by
the investigator under RAR supervision, or by RAR if arranged.
Projects outside of the core
Minneapolis facilities must make arrangements to either have RAR provide
post-op care service if practical or do the care themselves under guidance
and oversight from RAR. In either case, the principal investigator should
budget accordingly when planning the project. Post-operative care is not
included in routine husbandry procedures or the per diem fees.
Post-procedural care includes
Someone must be present
with any animal recovering from anesthesia until that animal is able to
hold itself in a sternal position (on its chest, able to hold its
head up). Rodents and rabbits must be ambulatory, since even an anesthetized rodent is stable enough to rest on its chest.
Endotracheal tubes should
be kept in place as long as possible; they must be removed when the animal
begins to chew or swallow
The animal must be able to maintain
normal physiology. Heart rate, respiration, and hydration should be stable and within normal limits for the species.
monitoring and care
- Provide analgesia
as described and approved in your IACUC approved Animal Care and Use Protocol. See standard RAR post-operative analgesic regimens for pigs. sheep, and dogs and for rats and mice.
- Provide nursing support which may include a quiet, darkened recovery or resting place, timely wound and bandage maintenance, increased ambient warmth, a soft resting surface, rehydration with oral or parenteral fluids, and a return to normal feeding through the use of highly palatable foods or treats.
- Consider the administration of antibiotics
to prevent post-procedural infections (consult you area veterinarian)
- Monitor incisions for
swelling, exudate, pain or dehiscence
- Monitor catheters & devices
- Monitor for procedure-related
complications such as organ failure, thrombosis, ischemia
3. Maintaining records
- Records must include a daily assessment and
treatments given. Other items that could be included in the record
are anesthetic agents and time administered, intra-operative assessments
and recovery observations.
- Post-operative records are required on all animals and must be readily available
for review. Records on rats and mice may be somewhat abbreviated,
and can be included as part of research data collected, but should also
be available for review. For more information, contact RAR at 624-9100.
- Sample recordkeeping forms can be viewed and downloaded from the IACUC guidelines page.
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If antibiotics are being used,
they should be administered before surgery so that they are in tissues
when the surgeon is.
An appropriate antibiotic should
be administered at an adequate dose at the recommended frequency to minimize
the development of resistance.
Antibiotics should not be used
in place of surgical asepsis and good tissue handling techniques. Tissue
trauma contributes to post-operative infections.
If a culture and sensitivity
is not available, select antibiotics based on probable organism and probable
sensitivity. For example, normal skin flora are usually Gram +, so for
a a skin incision, select something with a Gram + spectrum, e.g., amoxicillin/clavulanate
or a potentiated sulfonamide. If GI surgery is performed, an antibiotic
with a Gram - spectrum is more appropriate, e.g. an aminoglycoside or ceftiofur.
Indwelling catheters tend to become infected with skin or fecal contaminants,
including anaerobes. Thus a broad spectrum and anaerobic spectrum is required,
e.g. amoxicillin/clavulanate, ceftiofur or ticarcillin. Pseudomonas
is an opportunist with a high likelihood of a multiple antibiotic resistance
phenotype. An extended spectrum penicillin (ticarcillin), a fluoroquinolone
(enrofloxacin) or an aminoglycoside (amikacin) may be necessary.
Antibiotic activity is classified
as being either bacteriostatic (inhibits cells from dividing) or bacteriocidal
(kills bacteria even if they are not dividing). In general, combining
two bacteriostatic drugs results in additive effect, combining two cidal
drugs results in synergistic effect. Combining cidal and static agents
can result in impairment of bacteriocidal activity. If you are treating
a specific infection, select two drugs with activity against the organism
in question. If you are looking for broad spectrum activity, select drugs
with complementary activity, eg. penicillin and an aminoglycoside, or enrofloxacin
Dosages for antibiotics and
a description of their activities are listed in RAR's drug
The information contained in this site is intended as
a reference for University of Minnesota investigators, and animal husbandry
and veterinary staff. Drug information and dosages are derived from a variety
of sources and do not necessarily guarantee safety or efficacy. Information
obtained through this site should not be relied upon as professional veterinary
advice. Any medications administered or procedures performed on animals
should only be performed by or under order of a qualified, licensed veterinarian.