Does altitude affect blood gases in hemodialysis patients

INTRODUCTION This study aimed to determine whether predialysis blood gases is affected by altitude differences in hemodialysis patients with arteriovenous fistulas living in Turkey at three different altitudes. METHODS Patients' predialysis blood gases were compared by standardizing both arterial blood gases collections and working methods for patients undergoing hemodialysis using a dialysate with the same properties at altitudes of 30 m (sea level), 1020 m (moderate altitude), and 1951 m (high altitude). FINDINGS Blood gases disorders were detected in 32 (82.1%) high altitude group patients, whereas 49 (74.2%) sea level group patients had no blood gases disorders (P < 0.001). pH values in the high altitude group were significantly lower than those in the other groups, and the pH increased as altitude decreased (P < 0.001). The partial pressure of carbon dioxide (PaCO2 ) values was higher in the sea level group than in the other groups and increased at lower sea levels (P < 0.001). Bicarbonate values were significantly higher in the sea level group than in the other groups and increased at lower sea levels, similar to PaCO2 values (P < 0.001). The partial pressure of oxygen (PaO2 ) values in the high altitude and sea level groups were significantly higher and increased at lower sea levels (P < 0.001). The oxygen saturation (SaO2 ) values were significantly lower in the high altitude group than in the other groups and increased gradually at lower sea levels (P < 0.001). DISCUSSION Predialysis metabolic acidosis was more pronounced in patients undergoing hemodialysis at high altitudes, whereas PaCO2 , PaO2 , and SaO2 values were lower.