Mario Seoane

Effect of hydralazine on intrapulmonary shunt

We compared the acute effects of bilateral arteriovenous fistulas to those of hydralazine infusion on hemodynamics and pulmonary gas exchange in dogs with pulmonary edema induced by administration of oleic acid. Oleic acid significantly (p < .01) increased intrapulmonary shunt (Qsp/Qt) and pulmonary and systemic vascular resistance, and reduced cardiac output. Once the lesion stabilized, both opening the fistula and infusing hydralazine produced a similar and significant (p < .01) increase in cardiac output, and a significant (p < .05) decrease in resistance. Mixed venous oxygen tension (Pvch) closely followed the changes in cardiac output; however, Pao2 did not change. Qsp/Qt significantly (p < .01) increased with the fistulas open and with hydralazine infusion. Closure of the fistulas or bleeding the animal at the end of the experiment reversed the changes in cardiac output and Qsp/Qt. The comparable increases in cardiac output and Qsp/Qt produced by opening the fistulas or infusing hydralazine may be related to levels of Pvo2. The hydralazine-associated Pvo2 increase indicates that this drug increased oxygen transport to the tissues even as Qsp/Qt became larger.

PaO2 increases with coughing in patients with chronic lung disease.

We considered if the cyanosis frequently observed during a cough attack in patients with chronic lung disease was due to worsening hypoxemia. To investigate the effects of cough on PaO2, we measured arterial blood gases before and after a voluntary coughing period of 45 sec, in 11 patients with Interstitial Lung Disease (ILD) and 14 patients with Chronic Obstructive Lung Disease (COPD). All patients significantly increased (p < 0.05) their PaO2 (COPD: from 49 ± 2 to 60 ± 2 mmHg; ILD from 44 ± 2 to 51 ± 3 mmHg, mean ± SD) and decreased their PaCO2. We conclude that stable patients with COPD and ILD increase their PaO2 with coughing most likely due to hyperventilation. The cyanosis observed could be due to peripheral circulatory effects of coughing.