Chlorpromazine attenuates the pulmonary vascular response to isocapneic alveolar hypoxia in piglets.

We investigated the cardiovascular effects of chlorpromazine (CPZ) during normoxia and during alveolar hypoxia (HYP) in 9 chronically instrumented piglets aged 10-14 days. Each animal was instrumented for measurements of pulmonary and systemic arterial and left atrial pressures and pulmonary blood flow. Each piglet was studied three times: once during normoxia following infusions of normal saline (NS) and CPZ (1 mg/kg), once during established HYP (10% O2-2.5% CO2) following the infusion of NS and a third time during established HYP following the infusion of CPZ (1 mg/kg). CPZ did not alter any of the cardiovascular variables during normoxia but decreased the pulmonary arterial pressure and pulmonary vascular resistance during HYP. Thus, CPZ is a vasodilator in the pulmonary vascular bed of piglets, preconstricted by HYP.