onto the surgical site and allowed to dry was equally as effective as chlorhexidine used according to manufacturer instructions. Make sure the alcohol has completely evaporated prior to using electrosurgery or a CO2 laser that can ignite the alcohol.
It is not necessary to scrub the patient's skin and actually may be contraindicated. Scrubbing not only irritates the skin, but it also exposes deeper and more pathogenic bacteria to the skin surface potentially contaminating the deeper tissues when the incision is made. A study in horses comparing mechanical and nonmechanical sterile preoperative skin preparation with chlorhexidine gluconate showed there was no difference between a five‐minute mechanical scrub and a five‐minute application with no scrubbing (Davids et al. 2015). The manufacturer's instructions for using chlorhexidine direct that it be applied to the site and allowed to remain for two minutes before wiping it off. Wiping it off with either saline or alcohol may remove the chlorhexidine negating its residual activity and should, therefore, not be done. A need for alternating between a preparation solution and saline or alcohol has never been established in any species. A newer skin preparation product, ChloraPrep™ One Step (BD Medical, www.bd.com) is applied to the skin for 30 seconds and left to dry for 30 seconds after which the skin is ready for incision. The World Health Organization Global Guidelines for Prevention of Surgical Site Infections states “The panel recommends alcohol‐based antiseptic solutions based on chlorhexidine gluconate for surgical skin preparation in patients undergoing surgical procedures” (www.who.int/gpsc/ssi‐guidelines/en/).
Patient Draping
Proper aseptic technique is indicated for all surgical patients regardless of size and species. Place quarter drapes around the surgical site and then cover with a patient drape with a fenestration around the site. Currently, disposable paper drapes are commonly used for both quarter drapes and patient drapes. Avoid the tendency to make a small sterile field as it is then easy to contaminate yourself by accidentally touching objects on the table outside the sterile field. Create a sterile field of the entire table top and take appropriate action to reestablish a sterile field if contamination occurs (Figure 1.2). When working with very small patients, it may be beneficial to use a clear plastic drape over the patient to allow respiration to be monitored; however, other respiratory monitoring devices such as end‐tidal CO2 monitors allow monitoring of respiration more accurately and do not require the ability to visualize the patient.
Figure 1.2 This 1.2 kg patient is being draped for a thoracotomy. First quarter drapes of Huck towels are placed to isolate the surgical field (a). Then the patient is covered with a patient drape large enough to create a sterile field of the entire table (b). The instruments are on the back table, and this is pulled up to the patient drape to complete the sterile field (c).
Thermal Support
Hypothermia during anesthesia is a major concern for many reasons including decreased metabolic functions and excretion of anesthetic agents. Many small exotic animals have a large body surface area/volume ratio predisposing them to developing hypothermia during anesthesia. The body temperature of a rat can drop 18 °F (10 °C) after 20 minutes of anesthesia (Harkness et al. 2010). Use an esophageal or rectal temperature probe to continuously monitor the patient's body temperature. The normal temperature for a given species may not be known; however, once the patient is anesthetized insert a temperature probe to determine its body temperature. Then monitor the temperature and how much it drops during anesthesia. Even in poikilotherms, this is very helpful and can help make decisions about the need to provide additional thermal support.
A short anesthesia and operative time accomplished by having all the necessary equipment ready and accessible will help to minimize hypothermia. It is best to use patient warming devices with temperature control such as forced warm air and warm water blankets. It can be difficult to place a warm air blanket around a small patient. These devices blow warm dry air, so pay particular attention to keeping the cornea lubricated to reduce the risk of creating corneal ulcers. This is especially important with small patients where the head is hard to visualize under the blanket. It is considered beneficial to use more than one patient warming device. For example combine a circulating warm water blanket under the patient and a forced warm air device around and over the patient where possible. For most small exotic animals set the circulating warm water blanket and forced warm air device at 104 °F (40 °C) because these patients have a high body temperature. Drape the patient as quickly as possible to help hold heat in under the drapes.
Use warm (101–103 °F; 39–40 °C) saline for abdominal and thoracic lavage. Fill the body cavity with the warm saline and do not immediately remove it. Allow it to dwell within the body for several minutes. Repeat this process until the body temperature begins to rise. Once the downward trend in body temperature reverses and the body cavity has been closed, in most cases, the temperature will continue to rise assuming other patient warming devices are in place. For most species, if the body temperature drops below 96 °F (35.5 °C) during the surgery, stop the procedure and instill warm saline into the body cavity before continuing the procedure. Repeat the process before closing.
Instrumentation and Equipment
Hemostatic Aids
The average cotton‐tipped applicator (CTA) holds approximately 0.1 ml of blood when completely soaked and a 4 × 4 gauze sponge holds 10 ± 2 ml (Hughes et al. 2007). The total blood volume of small mammals is 57 ml/kg of body weight (Jenkins 2000; Bennett 2009). If a patient loses 10–15% of total blood volume (approximately 1% of body weight), it is generally considered safe. Most mammals experience hypovolemic shock and release large amounts of catecholamines with loss of 15–20% of the total blood volume. Loss of 20–30% of the total blood volume can have life‐threatening consequences (Jenkins 2000; Bennett 2009). As an example, if a 50 g mouse loses more than five CTAs full of blood, it is equivalent to more than 20% of the blood volume (Harkness 1993). Table 1.1 shows approximately 20% of the blood volume of common rodent pets.
Magnification is an aid for hemostasis (see Chapter 3). What would seem a small amount of blood to the naked eye observer appears to be major blood loss when magnified drawing the surgeon's attention to the hemorrhage and the need to arrest it. Additionally, small vessels can be identified and controlled more easily when working under magnification.
Hemostatic clips are available in various sizes including microclips. These are very useful for controlling hemorrhage in small patients, where it is difficult to accurately place a ligature. Additionally, they can be applied in deep, hard‐to‐reach locations. With some types of hemostatic clips, both straight and right‐angled appliers are also available (Figure 1.3). This applier makes it easier to get under a hemostat to apply a clip to a severed vessel.
Table 1.1 Loss of approximately 20% of total blood volume results in cardiovascular compromise with potentially life‐threatening consequences.
Source:
