Dopamine, dobutamine, and phentolamine effects on pulmonary vascular mechanics

Abstract

The pressure-flow (P-Q) relationship of the pulmonary vasculature, in an isolated canine lobe perfused under classical zone II conditions, can be characterized by a rectilinear segment at high flow, a curvilinear segment at low flow, and a pulmonary arterial pressure (Ppa) that exceeds alveolar pressure at zero flow. This demonstrates the presence of critical closure in the pulmonary vascular bed. Effects of drugs on pulmonary vascular resistance (PVR) must take the normal P-Q relationship into account. We examined the effect of dopamine (D) and dobutamine (DB), alone and in combination with phentolamine (P), on the slope of the rectilinear segment of the P-Q curve (equivalent to vascular conductance), the extrapolated Ppa intercept (Ppai), and the Ppa at zero flow (Ppaz). Low-dose D (0.4-0.8 mg) and DB (1.0-5.0 mg) did not significantly alter any parameter from control. Higher-dose D (1.2-6.8 mg) and DB (13-38 mg) decreased vascular conductance 32.3 +/- 12.1 (SE) to 50.45 +/- 5.6% (P less than 0.05), and P alone increased conductance 12.0 +/- 2.6% (P less than 0.01) from control with no significant effect on Ppai or Ppaz. The change in conductance with D and DB alone was abolished when either drug was given in combination with P. Ppaz and Ppai decreased significantly from control with DB in combination with P when no significant effect on vascular conductance was noted. The results suggest that lung vessels determining changes in flow resistance are pharmacologically distinct from those subserving critical closure in the pulmonary vascular bed.

Hydrodynamics of the Spinal Epidural Space in Pigs Determined by Constant-Flow Methods

“…This phenomenon is well described for the pulmonary circulation, 15 in which additional flow units open to accommodate increases in cardiac output, leaving the pulmonary artery pressure relatively unaffected.…”

“…The situation may be similar to capillary recruitment in the lung. 15 Recruitment of exit pathways could well explain the apparent impunity with which large volumes of fluid are infused during epiduroscopy and spinal-cord cooling. The objective of this study was to use hydrodynamics to study how fluid leaves the epidural space.…”

A Novel In Vivo Approach to Assess Radial and Axial Distensibility of Large and Intermediate Pulmonary Artery Branches

“…In future clinical applications of our method, an acute increase in PA pressure can be obtained via physical exercise, taking advantage of the positive relationship between cardiac output and PA pressure [30]. Alternatively, PA pressure can be temporarily increased via dobutamine infusion, which is often done clinically for stress testing [31,32].…”

PEEP-induced pulmonary vasoconstriction in neonatal piglets: Analysis by pressure-flow curves

“…3,5 An increase in the slope of the Pa/Q plot is seen with an increase in pulmonary vascular tone, vessel stiffness, or a reduction in the surface area of the vasculature. [15][16][17][18][19][20] In adult lungs, static lung inflation and PEEP applied during positive pressure ventilation, under Zone 2 conditions, increased Pi and caused a parallel shift of the slope of the Pa/Q plot. 6,8,18,21 In our study, on the other hand, PEEP increased both the Pi and the slope of the Pa/Q plot.…”