Surgery of Exotic Animals. Группа авторов

Base

The ideal preoperative data base includes a complete blood count, serum or plasma biochemistry panel, and a urinalysis. Additional diagnostics may be indicated based on the species and the medical problem being addressed. For example, mice and rats are prone to mycoplasmosis pneumonia, and preoperative chest radiographs are indicated prior to anesthesia in these species. While it may be difficult to obtain a urine sample from a small rodent, they are prone to developing renal insufficiency later in life, so it is important to evaluate urine specific gravity and a dipstick for proteinuria. These can be done with two drops of urine that can be obtained by placing the patient in a plastic or glass container for several minutes. In ferrets, it is important to determine the blood glucose level prior to anesthesia because they are prone to forming insulinomas. In very small patients, it may not be feasible to take enough blood for all of the abovementioned diagnostics. At a minimum determine a hematocrit, total protein, blood urea nitrogen (azotemia test strip), glucose, and urine specific gravity.

      Preoperative Fasting

      Various species such as equids, rabbits, and rodents are not able to vomit for physiologic reason, so fasting to prevent aspiration pneumonia is not necessary. Additionally, if attempting to decrease gastrointestinal contents for a surgery, it can take days to make a difference because the majority of ingesta is within the hindgut. A short fast is recommended to allow these species to swallow any food material to reduce the risk of food entering the trachea during intubation. A prolonged fast in small mammals can result in a negative energy balance which increases their risk for developing complications after surgery (Jenkins 2000). Many small patients have low hepatic glycogen stores and may develop hypoglycemia during a prolonged fast (Harkness 1993; Redrobe 2002). Administer fluids containing dextrose subcutaneously (SC), intravenously (IV), or intraosseously (IOs) in patients prone to developing hypoglycemia. The gastrointestinal transit time in ferrets is rapid, and a prolonged fast is not recommended. An hour fast in ferrets is long enough for the stomach to empty minimizing the risk of developing aspiration pneumonia. On the other end of the spectrum, some reptiles may only eat once a week or even less often so there is no need for a fast.

      Hemodynamic Support

      Small patients have a small total blood volume and what may appear to be minimal hemorrhage can be life‐threatening. If the patient is anemic and surgery can be postponed, it should be postponed until the hematocrit is into the normal range. It would be a rare event that surgery made a hematocrit increase, typically the opposite is the norm. Consider a blood transfusion from a conspecific, if more than minimal hemorrhage is anticipated or if the patient is anemic preoperatively. Strict attention to intraoperative hemostasis is essential when performing surgery on any small patient.

      In patients experiencing serious blood loss during surgery, crystalloid or colloid fluid therapy should be administered as quickly as possible for cardiovascular support. More ideal, blood from a conspecific should be used, but often this is not available. Preplanning by having a conspecific blood donor available can be life‐saving. In ferrets, there are no blood types and no reports of transfusion reactions. It is safe to use any ferret as a blood donor. In many species, blood typing may not be known. If it is unknown whether a species has blood types, a crossmatch should be performed prior to administering a blood transfusion.

      Anesthesia results in loss of fluids because of dry gases making parenteral fluid administration vital for most surgical procedures. It can be difficult to achieve vascular access in small patients. Vascular access provides a route for the administration of fluids during anesthesia at the standard rate of 10 ml/kg/hr and, maybe more importantly, provides a route for administration of emergency drugs in the event of a crisis. An IOs catheter can be placed relatively easily in most species even in small patients. SC administration of fluids is much less effective than IV or IOs and is an ineffective route for administration of emergency drugs. A single dose of 10 ml/kg SC of 4% dextrose has been recommended for short procedures in healthy small exotic mammals (Redrobe 2002). Fluids administered subcutaneously or intraperitoneally are slowly absorbed and not appropriate for treatment of severely ill, dehydrated, or shocky patients.

      Maintain vascular access in the postoperative period if at all possible. Continue to administer fluid at least at a maintenance rate until the patient has completely recovered and is eating and drinking well.

      Perioperative Antibiotic Therapy

      The aim in administering perioperative antibiotics is that the blood level of antibiotic will be effective in preventing incision site infection from target organisms. In most cases, the target organisms are normal skin flora that cannot be completely eliminated during patient skin preparation. The antibiotic should be administered prior to making an incision, which is when the first exposure occurs and should continue until the surgery is complete so any blood clots that form will have therapeutic levels of antibiotic. If the patient is already receiving antibiotics for treatment of an infection and has therapeutic circulating levels of antibiotics effective against the target organisms, additional IV perioperative antibiotic is not needed. If the therapeutic antibiotic is not expected to be effective against the surgical target organisms, perioperative antibiotic administration of an antibiotic expected to be effective against the surgical target organisms should be administered perioperatively. For example, if a patient is receiving cephalexin for a skin infection, but the surgery is in the perineal area where fecal contamination is a concern, adding a perioperative antibiotic against which fecal flora are likely to be sensitive is appropriate. There is no evidence that continuing to administer a perioperative antibiotic for a brief period of time postoperatively is beneficial for preventing surgical site infections (SSIs) and may select for resistant organisms.

      Surgeon Aseptic Preparation

The goal of surgeon aseptic preparation is to reduce the incidence of SSI. In human medicine, SSI has been shown to delay wound healing, increase antibiotic use, increase hospital stay, and increase costs, and can result in fatal consequences. Minimizing the risk of SSI in exotic animals is essential for many reasons. Surgeons should wear a cap, mask, gloves, surgical gown, and shoe covers for all surgical procedures (Figure 1.1). Procedures should be done in the cleanest environment possible. A dedicated operating room is ideal, but avoid doing surgery in rooms where abscesses are treated, dirty procedures are performed, or there is fecal contamination.

      In one study, glove perforation occurred in 67% of surgeries underscoring the need for hand antisepsis to reduce skin flora before gloving (Verwilghen et al. 2011). Scrubbing is not recommended because it removes protective mechanisms on the skin surface and exposes more potentially pathogenic bacteria. Additionally, it causes small abrasions and excoriations damaging the surgeon's skin and increasing the risk of colonization by pathogenic organisms.

      Alcohol‐based hand rubs are recommended because they have rapid action, are faster to use, and cause less skin damage compared with antiseptic soaps. Alcohol‐based hand rubs do not require water. It has been estimated that on average 20 l of water are used per hand when using antiseptic soaps. Additionally, many water faucets and municipal water sources are contaminated with Pseudomonas sp. and other Gram negative organisms that can recontaminate the hands. There is no reason to do a one‐minute hand wash with a neutral soap before applying the hand treatment, and it has been shown that omitting hand washing prior to applying Sterilium® (Medline Industries, www.medline.com) increases its efficacy (Verwilghen et al. 2011). The World Health Organization recommends alcohol‐based hand rubs over antiseptic soaps because of their superior efficacy both in vitro and in vivo, better skin tolerance, lower environmental impact, and no risk of recontamination from rinsing with contaminated water.

      Patient Preparation

Regardless of the patient size or species, standard aseptic technique is essential for reducing the