Effects of a dopamine-1 (DA-1) receptor agonist on systemic and intestinal oxygen delivery (D˙o 2)-uptake relationships were studied in anesthetized dogs during sequential hemorrhage. Control ( group 1) and experimental animals ( group 2) were treated similarly except for the addition of fenoldopam (1.0 μg · kg−1 · min−1) in group 2. Both groups had comparable systemic criticalD˙o 2(D˙o 2crit), but animals in group 2 had a higher gut D˙o 2crit(1.12 ± 1.13 vs. 0.80 ± 0.09 ml · kg−1 · min−1, P < 0.05). At the mucosal level, a clear biphasic delivery-uptake relationship was not observed in group 1; thus oxygen consumption by the mucosa may be supply dependent under physiological conditions. Group 2 demonstrated higher peak mucosal blood flow and lack of supply dependency at higher mucosalD˙o 2 levels. Fenoldopam resulted in a more conspicuous biphasic relationship at the mucosa and a rightward shift of overall splanchnic D˙o 2crit despite increased splanchnic blood flow. These findings suggest that DA-1 receptor stimulation results in increased gut perfusion heterogeneity and maldistribution of perfusion, resulting in increased susceptibility to ischemia.
Colon mucosal blood flow in early colon cancer.