Preanesthetic Considerations and Tranquilization
Anemia from endoparasitism is relatively common in goats. The color of the mucous membranes, specifically the conjunctiva, should be evaluated as part of the preanesthesia physical examination.
Determination of a packed cell volume aids in detecting anemia if there is doubt, and it may be prudent to postpone elective surgery until after anthelmintics and good nutrition have corrected the anemia. Alternatively, a blood donor can be secured prior to emergency surgeries that cannot be postponed.Preoperative starvation reduces the volume of digesta in the rumen. The activity of the microfloral population is also reduced; gas production (bloat) during surgery is then reduced. An undesirable effect of starvation is that it makes the digesta more fluid, increasing the risk of regurgitation. The decrease in total rumen volume and the decrease in intra-operative bloat outweigh the risk of digesta consistency change. Lactation decreases, and there is a risk of pregnancy toxemia in late pregnancy. In general, adults should not be held off feed longer than 12-18 hours, and 4 hours is adequate for unweaned kids. Longer periods without food slow the recovery of ruminal activity and appetite of adults and predispose kids to hypoglycemia and hypothermia. Neonatal kids should not be fasted (Riebold 2015) and all neonates and pediatric goats should undergo close blood glucose monitoring.
Premedication with atropine is generally considered unnecessary. A dose small enough to avoid undesirable tachycardia and pupil dilation does not prevent salivation, but merely makes the saliva more viscid and more difficult to clear from the airways (Clarke et al. 2014). Some anesthetists use glycopyrrolate as an anti-sialogogue. Rarely, therapeutic use of atropine at 0.02mg∕kg IV has been recommended if bradycardia develops during anesthesia (Trim 1987), although care must be taken to ensure that this is not in the face of normotension or hypertension, especially if the goat has been premedicated with an alpha2 agonist.
Preanesthetic sedation with acepromazine maleate (0.05-0.10 mg/kg IV), midazolam (0.4 mg/kg IV), or diazepam (0.50 mg/kg IV) has been recommended to simplify restraint and reduce the dose of drugs needed to achieve induction (Gray and McDonell 1986b; Larenza et al. 2005). These drugs are considered to cause less cardiopulmonary depression than xylazine. A chlorpromazine dosage of 2-2.5 mg/kg IV has been suggested for preanesthetic tran- quilization of goats (Nawaz 1981). At decreased doses, both diazepam (0.04 mg/kg IV) and chlorpromazine (0.5 mg/kg IV) have been used to stimulate appetite in goats (Anika 1985). The positive effect on feeding lasts approximately 30 minutes.