We studied the effects of the beta2-adrenoceptor and DA1-receptor agonist dopexamine on ventilation perfusion (V(A)/Q) distribution in anesthetized, paralyzed patients (n = 17) undergoing major abdominal surgery. Intrapulmonary shunt (Q(S)/Q(T)) (percentage of cardiac output [CO]), perfusion of low V(A)/Q areas (percentage of CO), ventilation of high V(A)/Q areas (percentage of total ventilation [V(E)]), and dead space ventilation [percentage of V(E)]) were calculated from the retention/excretion data of six inert gases. In the control state, Q(S)/Q(T) was 11% +/- 9% (mean +/- SD) and little perfusion of low V(A)/Q areas (3% +/- 4%) was observed. Infusion of 1.0 microg kg(-1) x min(-1) dopexamine had no effect on Q(S)/Q(T) and low V(A)/Q areas despite an increased CO (7.7 +/- 2.2 L/min versus 6.2 +/- 1.2 L/min; P < 0.01). Pao2 increased from 15.5 +/- 5.6 kPa (116 +/- 42 mm Hg) to 17.3 +/- 6.3 kPa (130 +/- 47 mm Hg) (P < 0.05). Infusion of 2.0 microg x kg(-1) x min(-1) dopexamine further increased CO to 8.4 +/- 2.7 L/min (P < 0.01) without alterations of Q(S)/Q(T), perfusion of low V(A)/Q areas, and Pao2. We concluded that dopexamine (1.0 microg x kg(-1) x min(-1) and 2.0 microg x kg(-1) x min(-1)) has no adverse effects on V(A)/Q relationships and Q(S)/Q(T) in anesthetized, paralyzed patients.
Implications: The I.V. administration of vasoactive drugs can improve oxygen delivery to different organ systems but may impair pulmonary gas exchange. In anesthetized, paralyzed patients, we studied the effects of beta2-adrenoceptor and DA1-receptor agonist dopexamine on ventilation perfusion distribution. Dopexamine (1.0 microg x kg(-1) x min(-1) and 2.0 microg x kg(-1) min(-1)) improved cardiac output and oxygenation without alterations of intrapulmonary shunt.