Intradialytic Hypoxemia in Chronic Hemodialysis Patients

When kidney failure occurs, patients are at risk for fluid overload states, which can cause pulmonary edema, pleural effusions, and upper airway obstruction. Kidney disease is also associated with impaired respiratory function, as in central sleep apnea or chronic obstructive pulmonary disease. Hence, respiratory and renal diseases are frequently coexisting. Hypoxemia is the terminal pathway of a multitude of respiratory pathologies. The measurement of oxygen saturation (SO₂) is a basic and commonly used tool in clinical practice. Both arterial oxygen saturation (SaO₂) and central venous oxygen saturation (ScvO₂) can be easily obtained in hemodialysis (HD) patients, SaO₂ from an arteriovenous access and ScvO₂ from a central catheter. Here, we give a brief overview of the anatomy and physiology of the respiratory system, and the different technologies that are currently available to measure oxygen status in dialysis patients. We then focus on literature regarding intradialytic SaO₂ and ScvO₂. Lastly, we present clinical vignettes of intradialytic drops in SaO₂ and ScvO₂ in association with different symptoms and clinical scenarios with an emphasis on the pathophysiology of these cases. Given the fact that in the general population hypoxemia is associated with adverse outcomes, including increased mortality, cardiac arrhythmias and cardiovascular events, we posit that intradialytic SO₂ may serve as a potential marker to identify HD patients at increased risk for morbidity and mortality.