HOW TO PERFORM FIELD ANESTHESIA AND PAIN MANAGEMENT Horses are more difficult to anesthetize than the
other common domestic species. Total IV anesthe- sia may be safer than inhalant anesthesia, perhaps because it is usually of shorter duration.14 Both oxygenation and cardiovascular function are af- fected deleteriously when horses are placed in lat- eral recumbency, thus every step should be taken to minimize the duration of anesthesia. Suboptimal oxygenation is apparently well tolerated for up to 60 minutes of anesthesia but oxygen supplementation should be considered for all anesthetized horses. Typically, respiratory rate and depth of respiration and pulse rate and strength are the primary param- eters measured during field anesthesia. They should be assessed at 5-minute intervals and re- corded at least every 10 minutes. Respiratory rate and pattern are good monitors of anesthetic depth when horses are anesthetized with protocols incorporating ketamine. As the depth of anesthe- sia increases, respiratory rate slows and horses increasing “breath hold” at peak inspiration (ap- neustic breathing). If the “breath hold” lasts lon- ger than 2 to 3 seconds, the infusion rate should be slowed. Persons performing IV anesthesia on a regular basis routinely should consider the purchase of an oxygen tank and regulator in order to facilitate emergency oxygenation and ventilation of the pa- tient. Horses can be ventilated by adapting a nasogastric tube onto a pressure reducing valve attached to an oxygen tank. The tube is slid up one nostril and the nasal openings are occluded. The nostrils are released when the chest wall rises to a normal inspiratory level. The process is re- peated until spontaneous ventilation resumes. The techniques described produce tolerable levels of cardiovascular depression but as anesthesia is extended the importance of monitoring increases.
Acknowledgments
Declaration of Ethics The Author has adhered to the Principles of Vet- erinary Medical Ethics of the AVMA.
Conflict of Interest The Author has no conflicts of interest.
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