Assessment of the splanchnic vascular capacity and capacitance using quantitative equilibrium blood-pool scintigraphy

A series of human and animal experiments were carried out to assess the usefulness of equilibrium blood pool scintigraphy (EBPS) to study acute changes of the splanchnic vascular capacity and the splanchnic vascular pressure-volume (P-V) relationship. Corrected regional abdominal count rate changes, before and after various pharmacologic interventions, were used to assess regional splanchnic vascular volume changes. Animals were instrumented to manipulate and record splanchnic venous pressures. In patients, splanchnic vascular capacity increased by 5.2 ± 6.9% (p < 0.001) after 0.6 mg sublingual nitroglycerin while no significant change was noted after sugar pills (0.9 ± 5.2%, p > 0.3). In dogs, splanchnic vascular capacity decreased by a mean of 16% during infusion of angiotensin (p < 0.001) and increased by a mean of 32% during infusion of nitroprusside (p < 0.001). The splanchnic vascular P-V curve was shifted rightwards during nitroglycerin administration. Thus, using the radionuclide technique we detected the expected qualitative and quantitative shifts in splanchnic capacity and capacitance. We conclude that EBPS is a useful method to assess acute changes of 1) the splanchnic vascular P-V relationship, in invasive animal studies, and 2) the splanchnic vascular capacity in noninvasive human and animal studies.