Effects of catecholamines on the pulmonary venous bed in sheep

Objective: To assess the effects of various catecholaminergic agents on pulmonary venous tone. Design: Prospective, randomized, controlled, experimental study. Setting: Physiology laboratory of a university hospital. Subjects: Thirty anesthetized, mechanically ventilated adult sheep. Interventions: Four groups of six animals received I-hr infusions of norepinephrine (0.5 mu g/kg/min), epinephrine (0.5 mu g/kg/min), dopamine (10 mu g/kg/min), or dobutamine (10 mu g/kg/min). Measurements and Main Results: A 7-Fr pulmonary artery catheter was placed in a proximal location to measure cardiac output and pressure in a large pulmonary vein (Ppw) after balloon inflation. Another catheter wedged in a small pulmonary artery measured pressure in a small pulmonary vein (Pdw). A third catheter measured left atrial pressure (PLA). This method was able to detect the pulmonary venoconstrictive effects of histamine in a separate group of six animals. Pdw-PLa increased from a mean of 2.0 +/- 1.7 to 3.0 +/- 1.5 (so) cm H2O (p <.01), 2.3 +/- 1.6 to 4.4 +/- 1.3 cm H2O (p <.01), and 1.7 +/- 1.0 to 3.5 +/- 2.2 cm H2O (p <0.05) with norepinephrine, epinephrine, and dopamine, respectively. All of these drugs increased Pdw-Ppw, but only norepinephrine and epinephrine increased Ppw-PLA. No change in either pressure difference was observed with dobutamine. Elevation of cardiac output alone could not account for these findings since the increase in cardiac output induced by fluid infusion did not change the pressure differences. Conclusion: Norepinephrine, epinephrine, and dopamine at doses commonly used in humans increase pulmonary venous tone in sheep.