Hypoxic pulmonary vasoconstriction(HPV) is an intrapulmonary adaptation mechanism that diverts blood away from hypoxic regions of the lung. There are controversial reports regarding the effects of metabolic acidosis on HPV. Metabolic acidosis
induced by
acid infusion has been observed either not to affect, to increase, or to decrease hypoxia-induced increased in pulmonary arterial pressure(PAP) or pulmonary vascular resistance(PVR). But Some have suggested that hypoxia and acidosis are major
determinants, and that, although they may function as independent stimuli. They also manifest a complex interdependence. Experiments were designed to measure cardiopulmonary hemodynamic parameters during normal oxygenation by controlled
mechanical
respiration and exposures to metabolic acidosis around of arterial pH up to 7.19 unit by intravenous infusion of 2 M CHl in the rare of 2 mmol/kg/min.
the authors conducted experiments in intact dogs to reevaluated the effects of metabolic acidosis by infusion of HCl on HPV with normoxemia.
Cardiopulmonary vascular paramenters were measured at several pH levels (range of 7.38±7.19).
@ES The results were as follows:
@EN 1. Arterial pH was changed from7.38±0.01 unit to 7.30±0.02 unit and 7.19±0.04 unit at 30 and 60 minutes respectively, after intravenous infusion of HCl
2. At 10 and 60 minutes after intravenous infusion of HCl, mean PaP was significantly increased 96.34±16.935 and 109.12.00%(P=0.0000) respectively, from basic value of 13.14±0.74 mmHg.
3. Mean PVR was also significantly increased 167.14±19.56% and 215.00±33.91% at 30 and 60 minutes rexspectively(p=0.0000), after intravenous infusion of HCl from basic value of 361.78±23.94 yne. Sec. cm.-5.
4. Cardiac output had slowly decreased from 1.83±0.07 to 1.53±0.18 L/min (up to about 16.4% after 60 mintes) after intravenous infusion of HCl(P<0.05).
5. there were no significant changes of central venous pressure, pulmonary capillary wedge pressure, mean arterial blood pressure, and hear rate throughout the experiment.
With above results the author concluded that metabolic acidosis by infusion of HCl increased PAP and PVR markedly, but decreased cardiac output slowly, This suggested that metabolic acidosis was one of major determinants to increase HPV.
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