Assessment of the human splanchnic venous volume-pressure relation using radionuclide plethysmography. Effect of nitroglycerin.

BACKGROUNDNo method exists to assess human splanchnic venous function, the most important region in terms of vascular capacity.METHODS AND RESULTSWe studied 25 stable patients without heart failure or hypertension to develop a method to assess the splanchnic venous volume-pressure (V-P) relation and to determine the effect of nitroglycerin (GTN). We used blood pool scintigraphy to assess changes in regional splanchnic vascular volume (SVV) and low levels of continuous positive airway pressure (CPAP) to passively alter venous pressure and thus, SVV. We postulated that the relation between SVV and the CPAP used would reflect the capacitance of the splanchnic venous bed and that changes in the position of this relation would provide a relative measurement of any change in capacitance. In 12 patients (group 1), the splanchnic vascular V-P curves were recorded before and 2, 9, and 20 minutes after 0.6 mg sublingual GTN; in eight patients (group 2), recordings were made at similar times before and after subling...