The acidosis-induced right shift of the HbO₂ dissociation curve is maintained during erythrocyte storage

Abstract

Background and objectives. In fresh blood, tissue hypoxia increases microcirculatory acidosis, which enhances erythrocyte O₂ unloading and increases the amount of available O₂. Storage of erythrocytes increases the HbO₂ affinity and reduces O₂ unloading. We examined the development of the affinity change during a period of 5 weeks of storage by present blood bank standards, and investigated to what extent acidosis offsets the affinity change. Materials and methods. Blood from volunteer donors was processed and stored as erythrocyte concentrates (EC). At 2–5 day intervals, EC were drawn from the bags and suspended in plasma and crystalloids to an Hb ≈ 10 g/dL. The suspensions were adjusted to give a pH of 7.40, 7.10, 6.80 or 6.30 and equilibrated with different gas mixtures to SO₂ 0, 25, 50, 75 and 100%. Measurements of the PO₂/SO₂ pairs at each pH were used to calculate the position of the HbO₂ curve and its P₅₀ value. Results. A significant leftward shift in the HbO₂ curve was established after 1 week of storage; after 2.5 weeks only minor further changes were observed. Acidification right-shifted the HbO₂ curve, after 2.5 weeks of storage the curve at pH 7.10 was similar to that for fresh blood at pH 7.40. Calculations of extractable O₂ showed that the left-shifted HbO₂ curve of stored EC could be advantageous at a low arterial PO₂. Conclusions. The rightward shift of the HbO₂ curve due to acidosis is well maintained in stored erythrocytes, a moderate pH decrease offsets the storage-induced increased HbO₂ affinity.

Key Words::

• Acidosis
• blood gas analysis
• blood preservation
• erythrocytes
• haemoglobin
• human
• oxyhaemoglobin

Acknowledgements

This work was supported in part by a grant from the Health Trust South-East, Norway.

The assistance and advice of Professor Emeritus Harald Refsum, MD, PhD, during the initial phase of this study is greatly appreciated, as is the statistical assistance of Professor Leiv Sandvik, PhD.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.