Central Venous Blood Composition and the Pulmonary Ventilation during Hemodialysis

Abstract

The elimination of CO₂ across the dialyzer has been reported as the cause of the pulmonary hypoventilation during hemodialysis. There are some evidences that the venous line blood composition could influence the central venous blood and this one the pulmonary ventilation. Our purpose was to analyze (1) the influence of the changes in composition of the venous line blood on the central venous blood and (2) the possible role of the central venous blood composition on the pulmonary ventilation of 10 chronic renal failure patients during hemodialysis performed twice in the same patients in two different conditions: acetate dialysate without (condition I) and with (condition II) constant addition of 100% CO₂ bubbling into the dialysis bath. During condition I the venous line blood pH was kept in a normal range, and the PCO₂ was low, whereas during condition II the pH was very low and the PCO₂ extremely high. The patients during condition I decreased their pulmonary ventilation and lost CO₂ across the dialyzer as the central venous blood pH and HCO^-₃ increased, and PCO₂ did not change. The same patients during condition II increased their pulmonary ventilation and absorbed CO₂ across the dialyser as the central venous blood pH decreased and PCO₂ increased. Thus, the venous line blood has influence on the central venous blood composition, and this plays a role on the control of pulmonary ventilation of these patients.

Hypoventilation during Hemodialysis

“…The results in the article by Faro et al [1], regarding acetate dialysis without addition of C 0 2 into the dialysis bath, are confirmed in our study, measuring true mixed venous blood. However, we disagree with their conclu sion that venous line blood plays a role in the control of pulmonary ventilation during routine hemodialysis.…”

“…In a recent article in this journal [1], Faroet al studied the influence of C 0 2 changes, due to Co2 extraction during acetate dialysis, on the central venous blood com position and their effect on the pulmonary ventilation. They postulated that the decrease in C 0 2 in the venous line blood has influence on the central venous blood composition, and that this plays a role in the control of the pulmonary ventilation in these patients.…”

Influence of different dialysis modalities in the measurement of resting energy expenditure in patients with acute kidney injury in ICU

“…The change in VO2 during dialysis is a matter of controversy. VO2 was decreased [19,20], unchanged [21e23] or increased [24e26] during HD and PD [27]. Discrepancies also exist regarding to VCO2 [21,25,26,28].…”

Disorders of Respiration and Sleep-Disordered Breathing in Patients with Chronic Renal Failure

“…When this RQ is used in the alveolar gas equation, the A-aO 2 gradient remains unchanged, suggesting that alveolar hypoventilation is a sufficient explanation for observed hypoxemia [54,67,[72][73][74]. Several investigators report that if the CO 2 removal in the dialysate can be prevented hypoxemia can be avoided [54,[67][68][69][70]78,79] or greatly ameliorated [71]. Additionally, exercise during the dialytic session has been shown to decrease the fall in PaO 2 by increasing ventilation [80].…”