The acidosis-induced right shift of the HbO₂dissociation 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 eryfhrocytes 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 eryfhrocytes, a moderate pH decrease offsets the storage-induced increased HbO2 affinity.

Evaluation of Cerebral Oxygenation in Patients Undergoing Long-Term Hemodialysis

“…Second, changes in the pH of red blood cells influence the affinity between Hb and oxygen, which is known as the Bohr effect. Acidemia with arterial blood metabolic acidosis usually occurs in HD patients, which induces a rightward shift in the HbO 2 curve [23] that decreases affinity between Hb and oxygen, causing reduced microcirculatory oxygen saturation. In this study, the arterial blood pH values indicated slight acidemia, which might have influenced the rSO 2 values before HD via the decreased affinity between Hb and O 2 .…”

The involvement of cation leaks in the storage lesion of red blood cells

“…Molecules of 2,3-DPG modulate oxygen transport by preferentially binding to deoxyhemoglobin and thus facilitate the release of oxygen in the tissues. Loss of 2,3-DPG causes the oxygen dissociation curve of stored RBCs to shift to the left (Hamasaki and Yamamoto, 2000 ; Opdahl et al, 2011 ). Molecules of 2,3-DPG also modulate membrane stability and thus deformation properties of RBCs by interacting with band 3 (SLC4A1) and protein 4.1 (EPB41) and disrupting the link between the membrane and the cytoskeleton (Moriyama et al, 1993 ; Chang and Low, 2001 ).…”

Low preoperative regional cerebral oxygen saturation in hemodialysis patients

“…This means that HD patients had 20.4% lower rSO 2 values than non-HD patients after adjusting for these factors, indicating that low rSO 2 values in HD patients are, at least in part, because of factors other than age, anemia, or cardiac systolic function. Although it is not possible to determine the specific cause of low rSO 2 values in HD patients in our study, possible explanations are as follows: (1) metabolic acidosis frequently seen in HD patients decreases affinity between hemoglobin and oxygen [ 11 ] and decreases microcirculatory oxygen saturation. (2) The acute intravascular volume loss and fluid shifts that occur during dialysis induce cerebral edema and decrease intracerebral blood pressure, blood velocity, and cerebral perfusion [ 12 ].…”