THE PAEDIATRIC CONSULTATION AND CLINICAL CONSIDERATIONS

3.1 History

The importance of obtaining a thorough history for any paediatric patient cannot be overemphasised. Clues regarding potential injuries, disease predisposition and identification of management issues will assist in making a diagnosis or guide diagnostic planning.

Most Australian mammal paediatric patients are orphans, as a result of the death of the mother, illness of the young or mother, misadventure, maternal rejection or in some circumstances intentional removal and hand­rearing (McCracken 2008). How the animal became an

Fig.15.2.

Paediatric history-taking template.

orphan and its eventual proposed fate (e.g. housed in a zoo, returned to the wild or kept as a pet where that is legal) is valuable background information for clinical decision-making.

For animals being hand-reared, inspection of carer or owner notes on growth, behaviour, feeding and toileting is important. If records are not routinely kept, the carer/ owner should be encouraged to do so.

It is critical that any health evaluation or disease inves­tigation includes a detailed description of husbandry conditions. Mimicking the environmental factors neces­sary for normal development can be challenging for many species, especially if the owner/carer lacks experience. The method of housing and description of materials and substrate (e.g. cloth artificial pouch, grassed yard, indoor tiled or carpeted room), the environmental parameters (if known) such as temperature and humidity, formula type and preparation, volume/quantity and frequency of feeds and any recent changes are all aspects of care worth reviewing. In circumstances where feeding is problematic or aspiration of formula is suspected, inspection of the feeding equipment, including teat and hole size, is useful.

The duration and clinical progression of the present­ing problem and any treatment administered should be ascertained. It is common practice for carers to inappro­priately medicate animals on the basis of anecdotal advice from non-veterinary sources before the consulta­tion. The presence and health of in-contact animals should be discussed: contact with domestic or pest ani­mals may present disease and stress risks and impair post-release survival, whereas for some species rearing with a conspecific companion or in a creche is recom­mended, particularly if the goal is return to the wild.

2.8 Physical examination and assessment

Physical examination of most paediatric patients requires minimal restraint. If the animal is still with the mother,

Fig. 15.3. A koala (Phascolarctos cinereus) back young temporarily separated from its mother for examination. A toy 'parent' is used to provide a sense of security and facilitate examination. Photo: Taronga Western Plains Zoo

sedation or anaesthesia of the dam may be required. The examination should take place in a warm room (unless being performed in the field) with pre-warmed hands. For pouch-dependent young the bulk of the examination is best conducted while held within an artificial pouch. Koala back young feel more secure if given a toy ‘parent’ to cling to (Fig. 15.3).

Verifying the species, determining the stage of devel­opment (based on size, growth rate and physical charac­teristics) and assessing whether the animal’s behaviour is appropriate for the estimated age are important. Knowl­edge of expected growth trajectories and developmental milestones of the species is necessary for interpretation of findings (Table 15.1). In marsupials the age factor is defined as the age as a proportion of total expected pouch life (e.g. an age factor 0.7 PY has completed 70% of expected pouch life). McCracken (2008) provides a description of the physical features of PY at each stage.

Examination

• Demeanour

• Body temperature

• Hydration status (mucous membranes, skin turgor, peripheral circulation)

• Heart rate and respiratory rate and pattern (assess visually and by auscultation)

• Skin/coat inspection

• Abdominal palpation and auscultation

• Inspect cloaca/anus and any faeces/urine passed

• Eye/ear exam

• Palpate cervical thymus (if present) and/or lymph nodes

• Assess gait if ambulatory and inspect limbs for injuries

• Verify species and stage of development

• Measure bodyweight

Initial diagnostic tests

• Blood glucose and electrolytes if weak, dehydrated and/or anorexic (if collection of a small blood sample is feasible)

• Radiography (if history of trauma)

phase is substantial and the chance of successfully hand­rearing from this stage to adulthood is extremely low. Similarly, very young orphaned monotremes have a lim­ited chance of survival even in experienced hands.

The key components of a thorough physical examina­tion and initial assessment are summarised in Table 15.2. Hypothermia, hypoglycaemia and dehydration are common findings requiring rapid correction and are dis­cussed in more detail in sections 4.1-4.3.

Assessment, treatment and prompt return to a healthy mother capable of providing adequate care, is preferable to hand-rearing where appropriate. If a marsupial PY has been removed from a pouch and is returned after assessment, partial temporary closure of the pouch opening with tape may reduce the risk of the PY being expelled in the imme­diate recovery phase. In a managed care setting it may be possible to provide ongoing supplemental nutrition to the juvenile after it returns to the care of the mother, as demon­strated by Shibata et al. (2017) in two koalas failing to thrive.

For orphans of free-ranging animals the species’ conser­vation status may be a factor in deciding whether an indi­vidual should be hand-reared, particularly when resources are scarce. In some cases the hand-rearing and release of abundant species may be detrimental to the health and welfare of other free-ranging animals and/or the individual being released. For sub-adult free-ranging animals some consideration should be given to whether separation or injury occurred as a result of natural dispersal, as this may influence decision-making in relation to release criteria and location following assessment and treatment.

2.9 Clinical pathology

At birth, neonates have reduced functional capacity of many organ systems because of incomplete development. As they age, organ function develops and there are varia­tions in the levels of enzymes and metabolic products. Because of these variations, as well as differences in immune function and nutrition, care must be taken when interpreting clinical pathology results using adult refer­ence ranges (Kutzler 2013).

Lower red cell values in juveniles have been reported in the koala, greater bilby, common brush-tailed possum and tammar wallaby (Presidente and Correa 1981; Spen­cer and Canfield 1994; McKenzie et al. 2002; Warren et al. 2015), but Vaughan et al. (2009) documented a higher PCV in juvenile Gilbert’s potoroos (Potorous gilbertii) compared with adults. In general, neonatal cetaceans have a relatively high PCV that decreases during growth as they start to dive (Reidarson 2003).

Sub-adult bilbies have been shown to have higher WBC, segmented neutrophil and monocyte counts (Warren et al. 2015), whereas sub-adult Gilbert’s potoroos have higher WBC, lymphocyte and basophil counts than adults (Vaughan et al. 2009).

Elevated calcium, phosphorus and ALP are typical in the growth phase of many species (Stannard 2012; Peck et al. 2015; Warren et al. 2015) and lower globulin levels may reflect underdeveloped and unchallenged immune sys­tems, with wide variability among species in age-related differences.

2.10 Pharmacology and toxicology

In the absence of specific studies it is difficult to predict the effect of age on pharmacokinetics and toxicology (Smits et al. 2012). For example, in addition to factors mentioned in sections 2.3 and 2.4, smaller amounts of body fat and greater water volume may result in more rapid absorption of drugs and toxins relative to adults (Petersen 2011), and milk diets may interact with toxins and reduce or enhance uptake.

2.11 Anaesthesia

Neonates and juveniles generally have a tissue oxygen demand that is greater than that of adults (with the excep­tion of early marsupial PY that have yet to achieve endothermy). Therefore, there is a higher risk of hypoxae­mia and rebreathing of carbon dioxide. To help combat this during anaesthetic procedures, higher fresh gas flow rates and non-rebreathing systems should be used. The higher minute volume of young animals can influence inhalational anaesthetic agent absorption.

Paediatric patients are predisposed to hypoventilation and airway collapse in the presence of respiratory depres­sant drugs such as opioids and inhalational anaesthetics, so careful monitoring and respiratory support are required when using these agents. A small trachea makes intubation challenging and if achieved, the clinician needs to be mindful that tubes can readily become obstructed with very small amounts of mucus (Sisak 2007).

Given that cardiac output is rate-dependent and many anaesthetic drugs cause bradycardia, paediatric patients undergoing veterinary procedures are predisposed to hypotension. It is critical to keep the heart rate at a normal to high normal rate during anaesthetic events. Dose­dependent cardiac depression associated with inhala- tional agents can be minimised by maintaining the lightest plane of anaesthesia appropriate for the proce­dure, providing adequate analgesia and considering the use of anticholinergic drugs. Close monitoring of cardiac function will facilitate timely dose adjustment. For pro­longed procedures, recommended intraoperative moni­toring includes electrocardiography, pulse oximetry, blood pressure assessment and capnometry.

Prolonged fasting before anaesthesia should be avoided in paediatric patients. Similarly, a feed should be given as soon as it is safe to do so after an anaesthetic event. Hypo­glycaemia is common during lengthy anaesthetic periods and dextrose supplementation in IV crystalloid fluids may be required (Archer 2019). It is recommended that blood glucose is checked q 30 min during and directly after anaesthesia where this is feasible. Chemical restraint is covered in more detail in Chapter 9.

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