Reference sample microsphere method to measure blood flow effects on small intestinal perfusion in the rat.

To evaluate whether the microsphere method, including the necessary surgical procedures, for blood flow determination creates hemodynamic stress and a secondary reduction in small intestinal perfusion, we monitored the small intestinal perfusion with laser Doppler (LD) fluxmetry in 3 groups of Sprague-Dawley rats. Group I was studied during two microsphere injections without manipulation, group II was subjected to mesenterial-root occlusion during the second injection, and for group III, vasodilatation with papaverine preceded the second injection. While cardiac output and kidney blood flow were constant at the two microsphere injections, mean blood pressure (p < 0.05) and hematocrit (p < 0.01) significantly decreased in all 3 groups. Blood glucose increased significantly (p < 0.01). LD values also declined significantly (p < 0.05) between the start and end of experiments. In group I, the initial values of 9.5 perfusion units (PU) (5-23) decreased to 6.5 PU (3-12), in group II, 10.5 PU (5-24) decreased to 7.0 PU (4-15) and in group III, 9.0 PU (5-13) decreased to 5.5 PU (4-12). In conclusion, these findings suggest that the microsphere technique with two injections of spheres and reference sample withdrawals may affect the perfusion of the small intestine in the Sprague-Dawley rat.