Introduction: Tonometry is a validated non-invasive method for calculating intramucosal pH (pHim) in a hollow viscus and has been used in predicting mortality in adult critical care. This technique has never been used in the human neonate. We hypothesized that gastric pHim would correlate with intestinal blood flow in a neonatal animal neonate.

Methods: Fourteen 1 - 3 day old piglets were anesthetized and ventilated, an extraluminal flow probe was placed around the superior mesenteric artery (SMA) to measure blood flow. After stabilization a tonometer was placed intragastrically, the balloon filled with phosphate buffered saline. Seven piglets were randomized to control group and 7 to study group which received epinephrine in doses of 0, 1, 2 and 4 mcg/kg/min. to promote splanchnic vasoconstriction. Arterial blood gases, serum lactate and tonometer CO2 were measured q60 min. for 4 hours. pHim and ratio of tonometer versus arterial CO2 (rCO2) were calculated.

Results: Intramucosal pHim decreased over time in both study and control groups. There was a significant difference in pHim between the study and control groups. Using linear regression, pHim was positively correlated with% decrease in SMA flow (p=0.0002;r=0.43) and lactate (p=0.0007;r=0.4).

Conclusions: Gastric tonometry is a valid method to indirectly assess intestinal perfusion in neonatal piglets. In the human neonate this technique may prove valuable in identifying the optimal time to introduce enteral nutrition in infants vulnerable to gut ischemia.Table

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