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IACUC Training
Anesthetic Drugs

Many of these drugs are controlled substances and must be used according to University policy. Sedatives such as acepromazine, xylazine, medetomidine, opiates, diazepam, midazolam and others can be used by themselves for performing minor procedures. Usually sedatives can not be used for painful procedures, although xylazine, medetomidine, and the opiates do provide pain relief. These sedatives are also useful adjuncts to general anesthesia. They can be used to smooth induction and recovery, and to decrease the dosages of other drugs being used.

Local anesthesia

Drugs such as lidocaine or bupivicaine can be used for localized anesthesia. Normally, some type of sedative or physical restraint is needed to allow procedures to be performed. Several methods of local anesthesia can be used:

Topical - this includes topical ophthalmic anesthetic, application to the skin before a procedure, or within an incision during a procedure. Generally, topical anesthesia is only short-lived.

Regional anesthesia - is a technique whereby an area is infused with the anesthetic 10-15 minutes prior to the procedure. This may be used for small or large areas.

Spinal anesthesia - this technique involves an intrathecal or epidural injection of the drug to block sensation from a large part of the body. Xylazine has been used for this purpose, as well as the more traditional local anesthetics. This technique is very useful for caudal abdominal, perineal or hind limb surgical procedures. The amount of anesthetic injected can be increased to increase the area that is anesthetized. Overdosing using this method can result in paralysis of the respiratory muscles, requiring mechanical ventilation until the drugs have worn off. Considerable training is necessary for proper needle placement and drug dose calculations.

Nerve block - this technique involves injecting a relatively small volume of drug in the area of a peripheral nerve 10-15 minutes prior to the procedure. This allows for very precise anesthesia localization, retaining function in adjacent areas. A good knowledge of nerve locations is necessary to make this technique work.

General anesthesia - these drugs cause generalized depression of the central nervous system, resulting in loss of consciousness, loss of pain perception, immobilization, amnesia, as well as side effects such as cardiopulmonary depression and loss of thermoregulation.

Inhalant Anesthetics - include low vapor pressure drugs such as ether and methoxyflurane that may be used in a bell jar or with a drop system, or the high vapor pressure drugs such as halothane or isoflurane which require a precision vaporizer or vernitrol delivery system. These can be used as sole agents for surgery. Inhalant anesthetics must be used with a scavenging system or fume hood to prevent hazards to personnel.

Barbiturates

Barbiturates such as pentobarbital, thiopental or methohexital can be used as sole agents for surgery. Dissociatives such as ketamine and tiletamine do not provide adequate analgesia or muscle relaxation for many procedures, and must be combined with other drugs. Their use as sole agents is limited to restraint for non painful procedures, or in some species such as cats and monkeys, for minor skin procedures.

Neuroleptanalgesia

Neuroleptanalgesia refers to the use of several drugs to provide a trance like state with analgesia. Typical combinations of drugs include dissociatives or opiates with an analgesic and/or sedative added. Examples include Telazol/xylazine, ketamine/xylazine, ketamine/diazepam, ketamine/acepromazine/butorphanol, or fentanyl/acepromazine.

Paralytics

Paralytics such as succinyncholine or gallamine require concurrent use of an anesthetic, as they provide no analgesia or loss of consciousness. Monitoring anesthetic depth must
focus on physiological parameters, such as heart rate and blood pressure, as normal reflexes may not be used.

Experimental Surgery

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 postoperative infections. Therefore stringent guidelines for training, surgical facilities, anesthesia, analgesia, asepsis, and postoperative monitoring have been established.

Survival vs. Nonsurvival

There are different requirements for nonsurvival surgeries than for survival surgeries. For short nonsurvival procedures, dedicated surgical facilities and aseptic techniques are not needed. Asepsis is still required for longer nonsurvival surgeries, as infections can begin affecting the animals within several hours. Anesthetic requirements are identical between survival and nonsurvival procedures, except that certain anesthetics such as urethane may not be used for survival procedures because of carcinogenicity or toxicity to the animal. Postoperative analgesia, monitoring and care is obviously not a requirement for nonsurvival procedures.

Major vs. minor Major surgical procedures

Major vs. minor Major surgical procedures - are defined as those that enter a body cavity (thorax, abdomen, calvarium), or that have the capacity for having significant complications. Included would be orthopedic procedures and extensive cannulation procedures. Minor procedures include peripheral vessel cannulations and skin incisions. There are more stringent requirements for asepsis and postoperative care for major procedures, because of the increased potential for serious complications.

Rodent Surgery

Rodent Surgery - has less stringent requirements than for large animals. Incision size is smaller, reducing the potential for contamination. Asepsis in rodent surgery includes using sterilized instruments (autoclaved or a high-level disinfectant, not just alcohol), clipping the surgical site, scrubbing with a disinfectant such as betadine or chlorhexidine (not just alcohol), draping for major procedures, and use of sterile gloves. A dedicated work area is required. This is a room or bench top which from which all materials are removed at the time of the surgery. The area should be disinfected before starting the procedure.

Postoperative care

Postoperative care - includes support of body temperature, cardiovascular and respiratory function, monitoring, analgesics and record keeping. Large Animal Surgery including rabbits, dogs, cats, farm animals and primates has more specific requirements. Asepsis in larger animals requires using sterilized instruments (autoclaved or a high level disinfectant, not just alcohol), clipping the surgical site, scrubbing with a disinfectant such as betadine or chlorhexidine (not just alcohol), draping, and use of sterile gloves.
Requirements for asepsis are similar for major or minor procedures in large animals.

Approved Area

An IACUC approved area is required for large animal surgery. For minor or nonsurvival procedures, this is a dedicated work area, similar to that used for rodents. For major procedures, there must be separation of the operating room from preparation and instrument cleaning areas, and an adjacent, but separate area for surgeon preparation. The area must be inspected by the IACUC and approved prior to starting any animal procedures. Postoperative care includes support of body temperature, cardiovascular and respiratory function, monitoring, analgesics and record keeping.

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