A somatostatin analog improves tilt table tolerance by decreasing splanchnic vascular conductance

Splanchnic hemodynamics and tilt table tolerance were assessed after an infusion of placebo or octreotide acetate, a somatostatin analog whose vascular effects are largely confined to the splanchnic circulation. We hypothesized that reductions in splanchnic blood flow (SpBF) and splanchnic vascular conductance (SpVC) would be related to improvements in tilt table tolerance. In randomized, double-blind, crossover trials, hemodynamic variables were collected in 14 women and 16 men during baseline, 70° head-up tilt (HUT), and recovery. A repeated-measures analysis of variance was used to compare changes from baseline with respect to sex and condition. HUT elicited an increase in heart rate and decreases in mean arterial pressure, cardiac index, stroke index, and systemic vascular conductance. Additionally, SpVC and non-SpVC were lower during HUT. Octreotide reduced SpBF and SpVC and increased systemic vascular conductance and non-SpVC. Changes in SpBF and SpVC between supine and HUT were smaller in women (P < 0.05). Tilt table tolerance was increased after administration of octreotide [median tilt time: 15.7 vs. 37.0 min (P < 0.05) and 21.8 vs. 45.0 min (P < 0.05) for women and men, respectively]. A significant relationship existed between change (Δ) in SpBF (placebo-octreotide) and Δtilt time in women (Δtilt time = 2.5-0.0083 ΔSpBF, P < 0.01), but not men (Δtilt time = 3.41-0.0008 ΔSpBF, P = 0.59). In conclusion, administration of octreotide acetate improved tilt table tolerance, which was associated with a decrease in SpVC. In women, but not men, the magnitude of reduction in SpBF was positively associated with improvements in tilt tolerance.