[The effect of nifedipine on hemodynamics and gas exchange in dogs with experimental acute respiratory insufficiency].
OBJECTIVE
Evaluate the action of nifedipine, a calcium channel blocking agent, on the hemodynamics and gas exchange experimental acute respiratory failure.


METHODS
Lung injury was provoked in sixteen mongrel dogs with intratracheal instillation of hydrochloric acid (HC1) (0.1N; pH = 2.0; 2.0 ml/kg body weight). As steady state was achieved after HC1 instillation (maintenance of a stable arterial PO2), saline 1 ml (six dogs) or nifedipine (ten dogs) 30 micrograms/kg for body weight were intravenously injected. The hemodynamic variables and gas exchange parameters were analyzed before HC1, after HC1 and 10 and 30 minutes after nifedipine or saline.


RESULTS
The intratracheal instillation of HC1 provoked significant drop of PaO2, of systemic oxygen transport index (ITO2S), and increase of venous admixture (QVA/Q). Nifedipine provoked significant reduction of the mean systemic arterial pressure (Pas), and of the systemic (IRVS) and pulmonary vascular resistance index (IRVP), with significant increase of cardiac (IC) and systolic index (IS), with no changes ot the mean arterial pulmonary (Pap) and capillary pressures (Pcap). After nifedipine there was a significant increase of PaO2, PvO2, and ITO2S, with no significant variations of QVA/Q and alveolar arterial O2 difference (P(A-a)O2).


CONCLUSIONS
Nifedipine promoted systemic vasodilation, and probably by increasing the venous return and/or by a reflex mechanism, the cardiac output increased, augmenting the ITO2S. The IRVP decreased in the nifedipine group, with no significant alterations of Pap and Pcap, probably consequent to the systemic vasodilation provoked by the drug. The arterial PO2 augmented in the nifedipine group, as a consequence of mixed venous PO2 increase, since no changes occurred in QVA/Q, P(A-a)O2, inspired fraction of O2 and alveolar ventilation.
Feder
D
D
Escola Paulista de Medicina, São Paulo.
Romaldini
H
H
Silva
C O
CO
dos Santos
M L
ML
D000208:Acute Disease; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D004285:Dogs; D006439:Hemodynamics / Q000187:drug effects*; D006851:Hydrochloric Acid; D007275:Injections, Intravenous; D009543:Nifedipine / Q000008:administration & dosage / Q000494:pharmacology*; D011659:Pulmonary Gas Exchange / Q000187:drug effects*; D012131:Respiratory Insufficiency / Q000139:chemically induced / Q000473:pathology / Q000503:physiopathology*; D014690:Venous Pressure / Q000187:drug effects
D009543:Nifedipine; D006851:Hydrochloric Acid
Ação da nifedipina na hemodinâmica e nas trocas gasosas em cães com insuficiência respiratória aguda experimental.