SAEVA Proceedings 2015 | Page 12

South African Equine Veterinary Association Congress 2015  Protea Hotel  Stellenbosch (3-7%), it is reasonable to initially treat horses with a dose of enteral fluids (10 litres via a nasogastric tube would correct ~2% dehydration) and oral electrolyte pastes. Because the goal of electrolytes administered orally would be to stimulate further drinking, NaCl should be the predominant electrolyte administered and it can be given alone or mixed with KCl in a ratio of 2:1 to 3:1. As for enteral fluids, oral pastes can be made from table salt and lite salt (a 1:1 mixture of NaCl and KCl). KCl can also be obtained in larger quantities from chemical supply companies or in bulk from feed mills. Administration of 30 g of NaCl (~500 mEq of Na+ and Cl- [1 g of NaCl provides ~17.1 mEq of both Na+ and Cl-]) as an oral paste provides an amount of NaCl similar to that in 3-4 litres of an isotonic polyionic crystalloid fluid. Thus, dosing oral pastes at 6-hour intervals should provide a similar amount of electrolytes as a maintenance rate of intravenous fluids and more frequent administration could be used to replace electrolytes lost by disorders producing dehydration. Again, use of oral electrolyte pastes will only be beneficial if horses voluntarily drink water to replace the concurrent water need. Although use of oral pastes has both practical (e.g., can also be administered by a client on the farm) and economical advantages, their administration may be accompanied by transient interruption of feeding, apparently due to poor palatability of the pastes. In an attempt to lessen this problem, salts can be mixed with corn oil, molasses, applesauce, or yoghurt rather than water. Irritation of oral membranes, and possibly gastric mucosa, are further potential adverse effects of hypertonic oral electrolyte pastes. A final option to increase electrolyte intake is to dissolve NaCl and KCl in drinking water. Adding 30 g of NaCl, or a mix of NaCl and KCl, to each gallon of drinking water would make a nearly isotonic solution that may be consumed by some horses. However, voluntary drinking of water containing electrolytes is variable between horses; thus, plain water should also be made available in addition to water containing electrolytes. Monitoring response to treatment: Response to fluid therapy is practically monitored by reassessing the patient‟s attitude and clinical parameters of hydration, including heart rate; moistness of oral membranes; temperature of the nose, ears, and extremities; skin tent response; PCV; and TS. In addition, an obvious, but easily overlooked, assessment is the frequency of urination. Most horses should be observed to pass substantial amounts of dilute urine within 6-12 hours after onset of fluid administration and horses with mild dehydration (5-7%) may start to pass urine within 2 hours. Once an increase in urine output is observed, the rate of fluid administration should be reassessed and usually reduced. At times, improvement in other clinical parameters (e.g., heart rate or PCV) is less than desired despite increased urine output. Rarely does maintenance of a high fluid administration rate correct these clinical abnormalities once urine output has increased. More often, patients with this response may need further supportive care such as treatments to increase oncotic pressure (e.g., plasma or hetastarch) or that provide further analgesia for the underlying disease. Observation of urine output is also warranted to assess for potential development of acute renal failure in moderately to severely dehydrated horses. Two signs that should increase suspicion for acute renal failure are a greater than expected degree of lethargy/anorexia for the primary disease and oliguria – decreased urine output. The latter is most easily assessed by monitoring wetness of bedding in the stall, rather than by continuous observation for urination. Next, horses in the incipient stage of acute renal failure will also gain excessive weight due to fluid retention. Discontinuation of fluid therapy: It is often easier to decide when a horse needs fluid therapy than to determine when this aspect of supportive care can safely be discontinued. In reality, fluid support is probably continued longer 12