Improvement of gas exchange during inhibition of hypoxic pulmonary vasoconstriction by nitrendipine in piglets.
To determine how nitrendipine (N), a calcium antagonist, interferes with haemodynamics and gas exchange during hypoxia, we studied 12 piglets (4-6 weeks, 4.3-9.0 kg) anaesthetized with pentobarbital (20 mg.kg-1 i.p.). Haemodynamics, blood gases and multiple inert gas elimination were measured at the end of three consecutive 30 min periods of spontaneous breathing: room air (RA), 11-12% FIO2 (H) and 11-12% FIO2 with a randomly selected infusion of N (3 micrograms.kg-1.min-1) (HN) or the carrier solution (HP) (6 animals in each group). Pulmonary vascular resistance (Rpv) doubled from 8.7 +/- 2.8 mmHg.min-1.1-1 in RA to 19.5 +/- 10.0 (mean +/- SD) in H while PaO2 fell from 83 +/- 8.3 mmHg to 28.7 +/- 5.2. With N, Rpv fell back to room air value: 8.7 +/- 2.0 (p less than 0.02; comparison H and HN), while PaO2 rose from 29.3 +/- 6.3 mmHg in H to 46.1 +/- 6.1 HN (p less than 0.001) and PaCO2 fell from 33.8 +/- 10 to 23.9 +/- 3.7 mmHg. There was a small non-significant rise in VE. Haemodynamics and blood gases of the placebo group were not statistically different in H and HP. No extrapulmonary shunting was evidenced during any experimental period. The perfusion to lung zones with VA/Q lower than 0.005 rose from 1.1 +/- 2.1% in RA to 8.9 +/- 5.7% in H, but no further increase was obtained with N: 5.1 +/- 2.5%. Overall VA/Q matching did not deteriorate with N during hypoxia.(ABSTRACT TRUNCATED AT 250 WORDS)
D000818:Animals; D002302:Cardiac Output / Q000187:drug effects; D005260:Female; D006439:Hemodynamics / Q000187:drug effects; D000860:Hypoxia / Q000503:physiopathology*; D008297:Male; D009568:Nitrendipine / Q000494:pharmacology*; D010100:Oxygen / Q000097:blood; D011652:Pulmonary Circulation / Q000187:drug effects*; D011659:Pulmonary Gas Exchange / Q000187:drug effects*; D013552:Swine
D009568:Nitrendipine; D010100:Oxygen