Today's Veterinary Nurse

SEP-OCT 2017

Practical, peer reviewed, state-of-the-art companion animal nursing and technical educational articles with CE. Promotes better health for animals and career growth and development for veterinary technicians and veterinary assistants.

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CONTINUING EDUCATION TODAY'S VETERINARY TECHNICIAN | September/October 2017 | 45 the presence of pulsatile blood flow. Peripheral vasoconstriction, decreases in pulse amplitude, or arrhythmias are likely to affect signal quality. Respiratory function can be subjectively assessed by respiratory rate and depth. Capnography provides a measurement of the carbon dioxide content of respiratory gases and therefore is a good indicator of the adequacy of respiratory function. Accuracy can be hampered by small tidal volumes in pediatric patients as well as the dilutional effect of high fresh gas flow rates. Adapters for a capnograph are usually attached between the ET tube and breathing circuit and thus may contribute substantially to the apparatus dead space. This may be resolved by attaching a needle to the sampling tube and inserting it directly into the ET tube (sidestream sampling) (FIGURE 4) . If ventilation is required, care must be taken because the small tidal volumes of these patients increase the risk for barotrauma from overzealous ventilation. Airway pressures should not exceed 15 to 20 cm H 2 O (10–15 cm H 2 O in the open thorax). Fluid therapy is beneficial to provide hemodynamic support and replace insensible losses; however, it is advisable to use a fluid pump or a syringe pump that will deliver an accurate volume of fluid to decrease the risk of fluid overloading. If neither of these is available, a microdrip set with a burette is an acceptable alternative. Fluid rates should not exceed 10 mL/kg/h (unless in the setting of acute hemorrhage). Maintenance of adequate serum glucose may require fluids containing dextrose, such as 2.5% to 5% dextrose in lactated Ringer's solution. If solutions containing dextrose are not available, glucose can be added to the replacement or maintenance fluids. Regular monitoring of blood glucose while the animal is under anesthesia is advisable. Temperature probes placed into either the esophagus or rectum should be used and provide a reliable indication of body temperature. Hypothermia should be treated as soon as possible. Patients can begin to lose body temperature once they are premedicated. Many options to conserve body temperature exist. The use of temperature-controlled heating mats (eg, resistive polymer blanket), hot water bottles, or warm air blankets; wrapping extremities; and warming IV and irrigation fluids may all beneficial. Extreme care must be taken to avoid thermal burns, keeping all heating modalities close to body temperature if possible. Airway humidifiers and warmers must be used cautiously in pediatric patients because they may increase apparatus dead space. Warmed solutions should be used for presurgical skin preparation. Alcohol should only be applied to the animal immediately before surgery because it exacerbates heat loss via evaporation. Preinduction patient warming is well documented in human patients and is becoming more common in veterinary medicine. Veterinary studies have shown that patients prone to hypothermia, such as pediatric patients, benefit from forced-air warming 20 to 30 minutes before induction. Prewarming decreases the temperature gradient between the body's periphery and core, reducing the heat loss that typically occurs during the first hour of anesthesia 16 (FIGURE 5) . POSTANESTHESIA As with recovery of any patient, care must be taken to assess the adequacy of respiratory and circulatory function, and support should be provided if necessary. Hypothermic patients shiver on recovery, which may increase oxygen demands by up to 300%. 17 It is advisable to administer supplemental oxygen to shivering patients to maintain tissue oxygenation. Active warming must be instigated in hypothermic patients. Peer Reviewed FIGURE 4. To eliminate mechanical dead space from a mainstream adapter, (A) a surgical needle may be connected to sidestream sampling tubing and inserted directly into the lumen of the endotracheal tube, or (B) an endotracheal tube adapter with a sampling port may be used. B A

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