Partial Pressure of Oxygen-Guided Adrenal Venous Sampling in Primary Aldosteronism

[Background]Primary aldosteronism (PA) is a leading cause of endocrine hypertension, characterized by the increased cardiovascular risks. Adrenal venous sampling (AVS) plays a pivotal role in optimization of treatment strategy for PA. However, technical challenges, such as anatomical variations and the small sizes of target vessels, often preclude us from appropriate cannulation to the adrenal veins. This study aimed to explore the distribution of partial pressure of oxygen (pO2) in the adrenal and their neighboring veins, inspired by our awareness of lighter red color of adrenal venous blood than the others. [Methods]We enrolled 168 PA patients who underwent AVS at our center from 2021 to 2024. During AVS, we collected residual blood samples (0.2 mL for each) from bilateral adrenal, hepatic, inferior phrenic and external iliac veins both at baseline and under cosyntropin stimulation to perform blood gas analysis. Statistical analysis was conducted to evaluate the pO2 distributions and its associations with clinical parameters. [Results]The pO2 levels were significantly higher in bilateral adrenal veins than in their counterparts. The pO2 levels tended to remain the same even after cosyntropin initiation, with its decrement only detected in the adrenal veins. In addition, the levels of partial pressure of carbon dioxide were lower in the adrenal veins than in the others. Of note, in the adrenal veins, pO2 levels were significantly negatively correlated with ipsilateral levels of both aldosterone and cortisol. Finally, results of our present study firstly demonstrated the significance of evaluating pO2 in identifying adrenal veins compatible to the selectivity index of cortisol, a standard criterion for successful cannulation. [Conclusion]This is the first study to examine the pO2 dynamics in the human adrenal and non-adrenal veins, demonstrating its potential as a reliable tool for improving AVS cannulation success rates. Our findings also presented the oxygen consumption in the adrenal glands for steroidogenesis during cosyntropin stimulation. The pO2 measurement is a faster, easier and less-expensive tool enhancing AVS techniques. Our findings could improve clinical practice and research towards the next stage of adrenocortical endocrinology. Clinical PerspectiveO_ST_ABSWhat is new?C_ST_ABS-The adrenal venous specimens appear lighter red than those from non-adrenal veins, which is considered to be due to significantly higher partial pressure of oxygen in the adrenal veins. -Cosyntropin stimulation results in decreased partial pressure of oxygen in the adrenal veins, indicating increased adrenal consumption of oxygen due to ACTH-driven steroid synthesis. What are the clinical implications?-Measurement of partial pressure of oxygen has a high ability for identifying adrenal veins compatible to the selectivity index of cortisol, a standard criterion for successful adrenal vein cannulation. -Venous blood gas analysis is a faster, easier and less-expensive tool for confirmation of successful cannulation to the adrenal veins when performing adrenal venous sampling.