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Definition

Overhydration and gastrointestinal rupture

Risk factors

 Small patients (ponies, neonates) where the capacity of the stomach is overestimated

 Horses with reflux

 Horses with gastric impaction

Pathogenesis

Similar to intravenous fluid therapy, enteral fluid therapy can lead to overhydration. Experimental administration of large volumes (20 ml/kg/h) has been shown to lead to overhydration [52, 53]. Systemic overhydration depends on the capacity of fluid absorption from the gastrointestinal tract and it is therefore less likely to occur compared to systemic intravenous fluid therapy. See earlier in this chapter for more details.

Horses have no capacity to vomit due to a strong external sphincter at the cardia. Administration of large amounts of fluid with or without the addition of reflux, leads to overdistension and rupture of the stomach. Colonic rupture is a potential complication of enteral fluid therapy in man. Administration of fluid into the stomach leads to increased colonic motility through the gastro‐colic reflex. In cases of severe impaction, this could lead to a colonic rupture. However, this has not been reported in horses [54, 55]. Cecal ruptures after enteral fluid therapy for cecal impaction have rarely been reported [56].

Prevention

Enteral fluids can be administered as a bolus or as a continuous rate of infusion. If a bolus infusion is used, the maximum amount to be administered has to be taken into account. The volume of the stomach of a 450 kg horse is approx. 8–15 L. Administration of more than 8 L is not recommended. Amounts have to be adjusted to body weight. If continuous rate infusion is chosen, the rate should be gradually increased from 5 ml/kg/h initially, to a maximum of 15 ml/kg/h, to avoid signs of abdominal discomfort. The stomach needs to be assessed for reflux before administration. The horse’s reaction and vital parameters should be checked during administration to avoid over distention of the stomach.

Diagnosis and clinical signs

If tachycardia, tachypnea or signs of colic occur, administration should be discontinued. If signs persist, a large bore nasogastric tube should be placed to check for reflux.

Treatment

Discontinue enteral fluid therapy and empty the stomach by nasogastric intubation.

Expected outcome

If gastric distension is relieved on time, the prognosis is good. If the stomach ruptures due to volume overload, the prognosis is grave.