Effect of Chronic Furosemide Administration on Acid-base Balance in Patients with Chronic Hypercapnic Respiratory Failure

We quantitatively analyzed the effect of long-term administration of oral furosemide on the PaCO2 -H+ relationship in patients with chronic hypercapnic respiratory failure. In this study we measured arterial blood gases of eighteen outpatients (mean duration of visits, 7.6 years; mean rise of PaCO2, 15.4 mmHg). We obtained linear regression lines for PaCO2 -H+ and determined their V-axis intercepts and slopes. The results indicated that an increase in the administered dose of furosemide decreased linearly the V-axis intercept of the regression line [(V-intercept) = -6.9(dose of furosemide) + 30.9, r = 0.81], and increased linearly the slope of the regression line [(slope) = 0. 094(dose of furosemide) +0.22, r= 0.74]. Thus, the regression line of the PaCO2 - H+ relationship moved downward and became steeper at higher doses of furosemide. The regression lines for each dose of furosemide crossed at a PaCO2 of 75 mmHg. We concluded that there is a mutual interaction between the renal and respiratory mechanisms for acid-hase balance in chronic hypercapnia and the effect of furosemide on the PaCO2- H+ relationship is negligible in severe hypercapnia.