Pulmonary hemodynamics in newborn piglets during hypoxemia and reoxygenation: Blocking of the endothelin-1 receptors

The effects of blocking endothelin (ET) receptors in pulmonary circulation during hypoxemia and reoxygenation were studied in five groups of piglets. Ten minutes before hypoxemia, the Hyp group (n = 10) was given saline and t he l-mg (n = 9) and 5-mg group (n = 9), respectively, were given 1 and 5 mg /kg i.v. SE 217242 (an ET receptor antagonist). Two groups served as normox ic controls. The piglets were ventilated with 8% O-2 until base excess was <-20 mmol/L or mean arterial blood pressure was <20 mm Hg. Reoxygenation wa s performed with air. The increase of mean pulmonary artery pressure was si gnificantly attenuated during hypoxemia and reoxygenation in the l-mg group (p = 0.006). The pulmonary vascular resistance index increased significant ly at the end of hypoxemia in the Hyp and 5-mg groups but was comparable to baseline in the 1-mg group. During the study period, the changes in pulmon ary vascular resistance index were significantly attenuated in the l-mg gro up compared with the 5-mg group. Stroke volume index was significantly atte nuated compared with baseline in the 5-mg group during both hypoxemia and r eoxygenation, whereas, in the Hyp and 1-mg group, stroke volume index was a ttenuated only at the end of hypoxemia. During hypoxemia, plasma ET-1 decre ased from 1.9 +/- 0.2 to 1.3 +/- 0.3 ng/L (p = 0.008) in the Hyp group, rem ained unchanged in the I-mg group, and increased from 1.6 +/- 0.2 to 6.6 +/ - 1.6 ng/L (p = 0.008) in the 5-mg group. We conclude that blocking ET rece ptors attenuates pulmonary vasoconstriction during hypoxemia and reoxygenat ion in piglets.