PURPOSE: Pulmonary gas exchange (PGE) during hemodialysis (HD) has been extensively studied. However, little is known about HD effect on PGE in subjects with COPD. The purpose of this study was to examine changes in blood gases (BG) and pH in COPD patients during HD with bicarbonate dialysate and to compare them with patients without COPD.
METHODS: We enrolled thirteen subjects with COPD and thirteen CON patients in this study. All were dialyzed for 4 hrs against a bicarbonate HD solution. BG were analyzed immediately before dialysis (t0) and, during HD, at 30 min (t0.5), 1 hr (t1) and 4 hrs (t4). Data were analyzed using two-way ANOVA, with time as a repeated measure and group (COPD and CON) as independently assorted. Independent variables were: PO2, Alveolar-arterial O2 gradient (ΔA-a), PCO2, HCO3- and pH.
RESULTS: At t0, a statistically significant difference was observed for PO2 (CON: 84.7±3.60, COPD: 72.19±4.92; p< 0.001). For the first hr, PO2 decreased significantly, and at t1, O2 therapy was required for 9 COPD subjects. By t4, there was no significant difference in PO2 between CON and COPD. The ΔA-a remained significantly different between CON and COPD (P< 0.001 for all time periods), with increasing ΔA-a for both groups up to t1 and decreasing over the remaining 3 hr. For both groups, at t4, ΔA-a was significantly higher than at t0 (p< 0.001). For PCO2, both groups demonstrated parallel increases from t0 to t1 (p=0.0004), with COPD PCO2 significantly higher than CON at t0.5 and t1 (p< 0.05 for both); by t4, PCO2 levels decreased to nearly the same as at t0. Over the 4 hr treatment, HCO3- and pH increased significantly for both groups; however no significant difference was observed between COPD and CON.
CONCLUSION: Markedly increased ΔA-a during HD necessitates O2 supplementation in some COPD patients. COPD patients retain more CO2, however the buffer effect of HCO3- -based HD leads to metabolic alkalosis (pH≈7.51) at t4.
CLINICAL IMPLICATIONS: Some Copd patients may require oxygen treatment during hemodialysis.
DISCLOSURE: Maria Alfakir, No Financial Disclosure Information; No Product/Research Disclosure Information