worthwhile in this situation. If the animal needs less than 20ml/kg of fluids, nasogastric fluid administration should be strongly considered. In adult horses, where the transport time to the hospital is less than 2 hours, hypertonic saline (7.0-7.5% sodium chloride) can be given instead of isotonic crystalloid fluids. The dose of hypertonic saline is 2-4mg/kg. This always needs to be followed up with large volume isotonic crystalloid fluids within two and a half hours. An alternative to hypertonic saline is to give 2-6ml/kg colloid solution such as Tetrastarch (Voluven®). The advantage of a colloid to hypertonic saline is that the effects last longer, perhaps as long as four to five hours, and that the colloid oncotic pressure is supported. The disadvantage is that colloid solutions are considerably more expensive than hypertonic saline. Hypertonic saline solutions should never be given to foals less than one month old, and colloids should only be given to this age group with extreme caution. In the second situation, where all the treatment is to be done in the field, isotonic crystalloid solutions are the fluids of choice. An initial 20-80ml/kg bolus should be given to reverse hypovolaemia. Thereafter, fluids need to be given to provide for maintenance (approximately 2.5ml/kg/hr) and replace any ongoing losses. Constant rate fluids are preferable to intermittent fluids, as they replace losses as they happen. The risks with leaving a catheter in are thrombophlebitis, displacement of the catheter and subcutaneous delivery of fluids and drugs. Long-term, over-the-wire, catheters can be placed in the field and should be covered with a clean or sterile swab and elastoplast. If giving fluids intermittently, dividing the total daily requirement into a minimum of three bolus doses is probably a reasonable compromise. Giving the total daily fluids as a single bolus is not appropriate, and if it is truly only possible to give fluids to a foal once daily, only one third to one half of the daily requirement should be given. One last thing to remember is that fluids will freeze, especially in giving sets, in subzero ambient temperatures. 4
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