MEASUREMENT OF INTESTINAL VASCULAR CAPACITANCE IN DOGS - AN APPLICATION OF BLOOD-POOL SCINTIGRAPHY

To define relative changes in intestinal vascular capacitance, we deve loped a model that allowed us to construct intestinal vascular pressur e-volume relationships (PVR). Thirteen a:chloralose-anesthetized and s plenectomized dogs were studied using a pneumatic constrictor and a sm all catheter to change and measure portal venous pressure. A small lea d sheet was placed beneath the abdominal wall. Relative changes in int estinal blood volume (IBV) were determined by in vivo blood pool scint igraphy with Tc-99m-labeled erythrocytes and were expressed as percent ages corrected for specific activity and abdominal wall radioactivity. PVRs were constructed using data recorded during graded inflations of the portal venous constrictor. The abdominal wall contributed 32.4 +/ - 7.7% (SD) of the total counts. During a 4-h control period, PVRs var ied by no more than 6% (of IBV). In the isolated intestinal circulatio n, the change in IBV was precisely proportional to the volume of blood added, indicating that this method can detect very small changes in v olume (less than or equal to 5 mi). Nitroglycerin (25 mu g . kg(-1) . min(-1)) increased capacitance by 20%. Although it measures only relat ive changes, the model is stable and sensitive, provides reproducible measurement of intestinal PVRs, and, with adaptation, may prove useful in patient studies.