Effect of age, feeding, and omeprazole administration on gastric tonometry in healthy neonatal foals

Gastric tonometry is commonly used in humans as an assessment of intestinal mucosal perfusion. Values in healthy foals are currently unknown.

Age, enteral feeding, and omeprazole administration would significantly alter gastric tonometry measurements in neonatal foals.

Nine clinically normal foals were used to assess the effect of age and feeding, and 8 similar foals were used to assess the effect of omeprazole.

At 1, 7, and 14 days of age, gastric intramucosal PCO2 (PgCO2) and arterial blood gas samples were obtained at baseline, immediately after feeding milk, and 1 and 2 hours after fasting for calculation of the intramucosal-arterial PCO2 difference (DeltaCO2). To evaluate the effect of omeprazole, foals were evaluated twice as above, 2 hours after fasting, comparing administration of omeprazole to no drug.

There was a significant effect of age and feeding on PgCO2 and DeltaCO2, whereas arterial PCO2 was not significantly affected by these factors. Postfeeding DeltaCO2 values were significantly lower than fasted values. Baseline and postfeeding DeltaCO2 increased with age. There was no significant effect of age on data collected after 1 or 2 hours of fasting. The 90% reference interval for DeltaCO2 data collected after fasting was 0-54 mmHg. Foals had a significantly higher mean gastric pH and significantly higher DeltaCO2 and PgCO2 following omeprazole relative to no treatment.

Because of the high and variable DeltaCO2, which is exacerbated by omeprazole administration, the reference interval in foals is extremely wide.