Hyperosmolal feedings and gastrointestinal blood flow and oxygenation in newborn lambs.

Hyperosmolal feedings have been implicated as a cause of potential disruption to the physiology of the neonatal intestinal tract. To evaluate this we studied eight awake lambs (11 +/- 2 days old) with chronically implanted catheters in the portal sinus, descending aorta, and left and right ventricles. Blood flow (Q) was calculated with the radionuclide-labeled microsphere technique and O2 delivery (DO2) and consumption (VO2) by the Fick principle using blood O2 contents. Lambs were studied initially after a 4-h fast and sequentially at 2, 3, and 4 h after eating a hyperosmolal (590 mOsmol) formula. Cardiac output (mean +/- SEM, 332 +/- 22 ml.min-1.kg-1) and whole animal VO2 (16.5 +/- 2.5 ml O2.min-1.kg-1) remained stable. Total gastrointestinal (GI) blood flow increased 28% by 3 h. Small intestine Q increased 21% 3 h after feeding and then returned to baseline. Similarly, large intestinal Q increased 77% after feeding and remained elevated. There was no effect on stomach Q. Total GI vascular resistance fell 28% 3 h after feeding then returned to baseline. DO2 to the GI tract increased at 3 h and returned to baseline. There was no change, though, in GI VO2 (3.9 +/- 0.4 ml O2.min-1.100 g-1) or in the extraction (VO2/DO2) of oxygen (21.2 +/- 1.8%) during the study. Furthermore, there was no evidence for GI tract acidosis at any time. Systemic organ blood flow (except hepatic arterial blood flow) remained unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)