Enteral fluid therapy Free choice water Free choice water is the simplest way to provide fluid therapy. It can be effective in replacing mild deficits and in providing fluids for maintenance. Clearly, free choice fluid intake is dependent on the willingness and ability of the patient to imbibe and absorb sufficient fluids. In hypovolaemia, blood is diverted away from the gastrointestinal tract to vital organs such as the heart, brain and muscles. This severely limits the ability to absorb fluids from the intestine. Furthermore, the thirst reaction is often blunted or absent in moderately to severely ill horses. For these reasons, free choice intake can rarely be relied upon to provide sufficient fluid intake during the early stages of hospital care. In horses with continued moderate fluid loss, such as mild to moderate diarrhoea, free choice fluids can be a useful source or adjunct source of fluids. Electrolytes can also be replaced in this way, and some horses will preferentially drink from water buckets containing electrolytes than from those containing plain water. When making water buckets containing electrolytes, it is extremely important not to make the fluids more concentrated than isotonic. Slightly hypotonic fluids are generally more palatable than isotonic fluids. Intra-gastric fluid administration Intra-gastric fluid administration, using a nasogastric tube, is an extremely effective way of ensuring adequate fluid intake, when the gastrointestinal tract is able to absorb fluids. It can also be used to hydrate the gastrointestinal contents, as a very effective method of treating primary large colon impactions. As outlined above, hypovolaemia may prevent effective gastrointestinal absorption of fluids, and therefore this route should be avoided in moderately to severely hypovolaemic animals. Delivery of nasogastric fluids Nasogastric administration of fluids is achieved through a soft plastic tube, passed along the ventral meatus of the nose, through the nasopharynx and into the oesophagus. It is important to ascertain that the tube is in the correct position prior to putting any fluid through it. This can be achieved most easily by palpation at the left base of the neck (deep to the jugular furrow), where the tube can be felt as a hard round object within the oesophagus, on the side of the trachea. Repeated administration of nasogastric fluids can be delivered through an indwelling tube. The tube should be plugged with a syringe barrel between administrations to prevent excessive air influx. Larger bore stomach tubes can result in pharyngitis if left in place. Continuous enteral fluids There are several advantages to continuous enteral fluid therapy over intermittent therapy. The most important is that giving 5-6L of fluid in a single dose can cause marked colic in some horses. Giving the same volume of fluids over 30 to 60 minutes does not seem to cause colic in these horses. Once the continuous enteral fluid system has been set-up, it can be monitored by a nurse or a competent owner. This decreases the time requirement for the vet to be with the horse. One potential downside of continuous enteral fluid delivery systems is if there is a small intestinal blockage or ileus, it might not be noticed that fluid is accumulating in the stomach. However, providing that the stomach is checked for reflux prior to starting fluids and only gravity is used to deliver the fluids, it is unlikely that serious consequences such as stomach rupture will ensue. If a horse shows any colic signs during continuous enteral fluid therapy, the fluids should immediately be stopped and the horse investigated for excessive build-up of fluids in the stomach (by refluxing the horse), as part of the investigation of the cause of the colic. If there is no build-up of fluid in the stomach 2
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