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Oxygen transport in children on maintenance haemodialysis
Insights
In anemic patients on hemodialysis, hyperphosphatemia slightly reduces blood oxygen affinity. Correcting phosphate levels improves oxygen transport but may still lead to myocardial fatigue, potentially preventable with transfusions.
Area of Science:
- Physiology
- Nephrology
- Biochemistry
Background:
- Severely anemic patients on maintenance hemodialysis often experience hyperphosphatemia.
- Oxygen transport adaptation in these patients is crucial for maintaining tissue oxygenation.
- Understanding the interplay between anemia, hyperphosphatemia, and erythrocyte function is vital.
Purpose of the Study:
- To investigate the adaptive mechanisms of oxygen transport in anemic patients undergoing hemodialysis.
- To compare oxygen transport in conditions of hyperphosphatemia versus normophosphatemia.
- To assess the impact of hyperphosphatemia correction on blood oxygen affinity and erythrocyte metabolism.
Main Methods:
- Studied oxygen transport in young, severely anemic patients on maintenance hemodialysis.
- Measured blood oxygen affinity using P50 (partial pressure of oxygen for 50% hemoglobin saturation).
- Analyzed levels of 2,3-diphosphoglycerate, inorganic phosphate (Pi), total erythrocyte phosphate, and ATP.
Main Results:
- Hyperphosphatemia was associated with decreased whole-blood oxygen affinity (increased P50) and elevated erythrocyte 2,3-diphosphoglycerate, Pi, and ATP.
- Correction of hyperphosphatemia led to a decrease in P50 and 2,3-diphosphoglycerate towards normal values.
- Despite correction, other variables remained elevated, suggesting altered erythrocyte membrane function possibly due to extracorporeal circulation.
Conclusions:
- In anemic, hyperphosphatemic patients, P50 and 2,3-diphosphoglycerate increases are modest, with ATP synthesis favored over 2,3-DPG.
- Adequate oxygen transport relies heavily on increased blood flow, and hyperphosphatemia correction further complicates this.
- Sustained hyperphosphatemia may induce long-term myocardial fatigue, potentially mitigated by occasional blood transfusions.
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.