Kidney Week

Abstract: SA-PO418

Effect of Hemodialysis on Hemoglobin Oxygen Affinity

Session Information

• Hemodialysis and Frequent Dialysis - 2
  October 26, 2024 | Location: Exhibit Hall, Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: Dialysis

• 801 Dialysis: Hemodialysis and Frequent Dialysis

Authors

• Sharma, Shilpa, University of California Los Angeles David Geffen School of Medicine, Los Angeles, California, United States

Shilpa Sharma, MD, MPH

• Salusky, Isidro B., University of California Los Angeles David Geffen School of Medicine, Los Angeles, California, United States

Isidro B. Salusky, MD, FASN

• Ganz, Tomas, University of California Los Angeles David Geffen School of Medicine, Los Angeles, California, United States

Tomas Ganz, MD, PhD

• Ix, Joachim H., University of California San Diego, La Jolla, California, United States

Joachim H. Ix, MD, FASN

Background

Hemoglobin (Hg) changes its affinity for oxygen (O₂) binding depending on ambient O₂ tension, acid/base status, 2,3 diphosphoglycerate (2,3 DPG) and other factors. 2,3 DPG is a key regulator of O₂ affinity within red blood cells and its levels are affected by blood phosphate. P50 is a marker of O₂ availability in tissues- A P50 reduction indicates increased Hg:O₂ affinity, decreased O₂ release and worsening tissue hypoxia. We measured P50 changes during hemodialysis (HD) and explored their predictors.

Methods

Venous blood gas, and other laboratory parameters were measured pre and post HD in 18 stable maintenance HD patients. We analyzed patients with tunneled dialysis catheters to avoid arterio-venous mixing. Associations of P50 with laboratory parameters and demographics were examined using linear regression models.

Results

Mean age was 72, 89% were male, and median dialysis vintage was 2.5 (IQR 0.9, 3.5) years. P50 levels decreased from a mean (±SD) of 27.1±0.9 mmHg to 26.2±0.7 mmHg during HD (Figure; P<0.001). Among 12 predictors evaluated, only higher baseline serum phosphate, and greater reductions in phosphate during HD were the predictors of P50 change (Table).

Conclusion

The HD procedure induces consistent reductions in P50, increasing Hg:O₂ affinity. The magnitude of mean P50 change was large – similar to that observed among Mt. Everest climbers (1). This observation provides a new potential mechanism leading to tissue hypoxia during HD. P50 changes were strongly associated with phosphate changes. Future studies should determine if intra-dialytic phosphate repletion may ameliorate tissue hypoxia and its adverse cardiac consequences in HD patients.

Reference
(1) Red cell function at extreme altitude on Mount Everest. J Appl Physiol 56: 109–116, 198 PMID: 6693310

Funding

• Veterans Affairs Support