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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PEER REVIEWED 40 | TODAY'S VETERINARY TECHNICIAN | September/October 2017 pediatric patients are highly dependent on heart rate to maintain cardiac output and blood pressure. 4 They have less functional contractile tissue, limited cardiac reserve, and low ventricular compliance and therefore a reduced ability to increase stroke volume. 5 The sympathetic nervous system is underdeveloped, and these patients may have poor vasomotor control and reduced baroreceptor reflexes, which make them less able to tolerate blood loss and maintain blood pressure. 6 Bradycardia may therefore profoundly affect cardiac output and subsequently blood pressure. Although they are likely to rapidly respond to fluid loading, pediatric animals are less tolerant of fluid overload than adult dogs and cats. Pulmonary reserve is also limited in pediatric patients. Compared with adults, anatomic differences such as a large tongue and less rigid airway cartilage can predispose pediatric patients to upper airway obstruction. Additionally, the ribcage is more pliable, the intercostal muscles weaker, the lungs less compliant, and the overall work of breathing is greater than in adults, thus facilitating airway collapse and respiratory fatigue. 3,7 Neonates have a reduced inspiratory reserve volume compared with adults, and increases in minute volume are achieved by increasing respiratory rate. 3 Functional residual capacity is reduced, respiratory chemoreceptors are immature, and oxygen demand is decreased, all of which predispose young animals to be at risk for rapid desaturation and hypoxemia during the perianesthetic period. 7 The susceptibility of young puppies and kittens to hypoxemia and respiratory fatigue necessitates oxygen supplementation throughout the anesthetic period and highlights the importance of careful monitoring of the respiratory system so that intermittent positive-pressure ventilation can be swiftly commenced if required. The renal and hepatic systems are immature in very young patients. One of the main considerations for sedation and anesthesia is the metabolism, biotransformation, and excretion of drugs. An exaggerated effect and prolonged duration of action may be observed, and the technician may need to adjust and reduce dose rates and dosing intervals accordingly. Pediatric patients are prone to hypoglycemia because of minimal glycogen stores and poor gluconeogenesis. 8 Blood glucose monitoring and the administration of glucose-containing fluids may be beneficial during anesthesia. Renal function is also reduced compared with adult dogs and cats, adding to the reduced tolerance of fluid overloading and hypotension. Thermoregulation is impaired in pediatric patients, and their larger body surface area relative to body weight and minimal fat reserves make them extremely vulnerable to hypothermia. In addition, most anesthetic agents affect the thermoregulatory center, and hypothermia may result. This can produce many deleterious effects, including decreased metabolic rate, increased susceptibility to infection, myocardial depression, respiratory depression, and delays in drug metabolism. Hypothermia significantly reduces the minimum alveolar concentration (MAC) of inhalational agents because of the decrease in metabolic rate. PREANESTHESIA PREPARATION A complete physical examination is the cornerstone for any animal undergoing sedation or anesthesia. From the observations that are noted during this examination, the technician will be able to formulate the appropriate anesthetic plan. Because of the minimal glycogen stores in the liver of the pediatric patient, withholding of food should be kept to a minimum. Unweaned puppies and kittens should not be fasted, and patients older than 6 weeks of age that are eating solid food need to be fasted only for a maximum of 3 to 4 hours before general anesthesia. 5 Prolonged fasting of these patients may result in hypoglycemia and dehydration and predispose them to hypothermia. Withholding of water is unnecessary. The minimum laboratory evaluations should include packed cell volume, total protein, and blood glucose. Further evaluation of the patient's biochemical and hematologic status should be performed if indicated. Any fluid deficits or electrolyte imbalances should be corrected before anesthesia if possible. If possible, avoid repeated blood sampling, which may cause volume depletion in a very small patient. Equipment When planning to induce anesthesia in a pediatric patient, the correct equipment must be available. A selection of ET tubes of appropriate sizes should be readily accessible, along with a laryngoscope with a good light source and an appropriately sized blade. In very small patients, an uncuffed ET tube Anesthesia for Pediatric Patients T E C H P O I N T In very small patients, an uncuffed ET tube may be preferable to maximize airway diameter and decrease resistance of breathing.

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