Oxygen Transport in Children on Maintenance Haemodialysis

Abstract

1. Adaptive mechanisms of oxygen transport by blood have been studied in severely anaemic young patients on maintenance haemodialysis, in conditions of hyperphosphataemia (Pi greater than or equal to 2.2 mmol/l) or normophosphataemia. 2. In hyperphosphataemia whole-blood affinity for oxygen was slightly decreased, as measured by an increase in P50 (the partial pressure of oxygen necessary to half saturate haemoglobin). 2,3-Diphosphoglycerate was increased by 10% (P less than 0.10) whereas Pi, total erythrocyte phosphate and ATP were increased by 100%, 47% and 36% respectively, compared with control values. 3. After correction of hyperphosphataemia a small but significant decrease in P50 and 2,3-diphosphoglycerate, to normal values, was observed whereas the other variables, although significantly lowered, remained above control values. 4. In these severely anaemic and hyperphosphataemic patients P50 and 2,3-diphosphoglycerate are only slightly increased. ATP synthesis appears to be favoured over that of 2,3-diphosphoglycerate. This is possibly due to alterations in the erythrocyte membrane elicited by bi-weekly extracorporeal circulation. Adequate oxygen transport can be achieved only through a drastic increase in blood flow. Correction of hyperphosphataemia adds further to the abnormality. It is concluded that this condition could induce a long-term myocardial fatigue, which might be prevented with occasional small blood transfusions.

Erythrocyte organic phosphates and whole blood oxygen affinity in patients on continuous ambulatory peritoneal dialysis

“…Normal or low DPG values in uraemic patients with a significantly higher P50 in vivo and a moderate increase of ATP levels is a paradoxical situation [8, 131. Similar results were reported in severely anaemic children in the immediate post-haemodialysis period when Pi levels and venous and erythrocyte pH were normal [5]. Erythrocyte membrane alteration by extracorporeal circulation was considered as a possible contributing factor.…”

“…Another tentative explanation may be that of the inhibition of phosphofructokinase as recently reported in CAPD treated patients [22]. Other investigations are required to determine the various factors involved in the enhancement in uraemic patients of erythrocytic glycolysis with the production of ATP being favoured over that of DPG [5] even when anaemia is moderate and PI levels around the upper limit of the normal range.…”

“…Such a mechanism was absent in our patients treated by CAPD. Other investigations are required to determine the various factors involved in the enhancement in uraemic patients of erythrocytic glycolysis with the production of ATP being favoured over that of DPG [5] even when anaemia is moderate and PI levels around the upper limit of the normal range. The steady mild acidosis observed in patients on CAPD when using standard commercial dialysates with an acetate or lactate concentration of 35 mmol 1-' [I, 3,20,21] can contribute to prevent the expected increase of DPG.…”

Aluminium-Induced Anaemia in Haemodialysis Patients

“…In severely anaemic maintenance haemodialysis pa tients hyperphosphataemia causes an increase in diphosphoglycerate and a slight decrease in whole blood affin ity for oxygen as measured by an increase in P50 (the partial pressure of oxygen necessary to half saturate haemoglobin) [91]. Correction of hyperphosphataemia with aluminium hydroxide in these patients may de crease 2,3-diphosphoglycerate, cancelling the rightwards shift in the oxygen dissociation curve.…”