Renal Function Reserve in Chronic Obstructive Pulmonary Disease with Type II Respiratory Failure

Background and objective: increase in renal blood flow in response to certain stimuli such as dopamine infusion, oral protein load, and amino acid infusion. Reduced or absent renal functional reserve (RFR) is an early index of renal impairment. Our work studies the (RFR) in Chronic Obstructive Pulmonary Disease (COPD) patients with chronic compensated type II respiratory failure.  Methods: Our study included 15 COPD patients with compensated type II respiratory failure and 5 normal controls. The patient group had mean Pa O2 56.5±6.4 and Pa CO2 56.5±3.2, while in normal controls the mean Pa O2 was 97.4 ± o.3 and Pa CO2 was 42.3 ± 1.2. Hypoxic patients (Pa O2 or=60mmHgandSaO2 >or=90%withoutriseofPaCO2within2 hours before and during the study. The pulsatility index (PI), an index of reno-vascular resistance (RVR), was measured non invasively by Doppler Ultrasonograghy at baseline and 20 minutes after infusion of dopamine in diuretic dose.  Results: The baseline PI was nearly similar in the control group and in COPD patients (no significant difference), the PI fell significantly in the control group after dopamine infusion from 1.03 ± 0.14 to 0.83 ± 0.1(P< 0.05), but increased significantly in COPD patients from 1.02 ± 0.12 to1.18 ± 0.13 (P<0.05) after dopamine infusion.  Conclusion: Renal functional reserve is impaired in hypercapnic COPD patients and this may be a factor in the development of edema frequently seen in these patients.