Can venous blood gas values be used instead of arterial blood gas values in respiratory alkalosis

Objective: The increase in alveolar ventilation causes disposal of large amounts of carbon dioxide from the respiratory system resulting in hypocapnia and respiratory alkalosis. Hypocapnia reduces cerebral blood flow, alkalosis leads to a leftward shift in oxygen- hemoglobin dissociation curve causing reduced oxygen delivery to tissues. Therefore, immediate diagnosis and close monitoring of respiratory alkalosis is necessary in emergency situations. In this study, the comparison of arterial and venous blood gas parameters of patients with respiratory alkalosis, and the evaluation of the usability of venous blood gas instead of arterial blood gas in patients with respiratory alkalosis were aimed. Methods: Ninety patients with respiratory alkalosis were enrolled in this study prospectively. Arterial and venous blood gas samples of patients enrolled in the study were drawn simultaneously in room air without administering any treatment after admitting to the emergency department. Results: The correlation between the results of pH, partial pressure of carbon dioxide (pCO2), bicarbonate (HCO 3 ) and base excess (BE) (respectively, r= 0.764, r= 0.839, r= 0.843, r= 0.883) in arterial and venous blood gas samples were statistically significant (p 80 mmHg in 23 patients (25.6%), between 60-80 mmHg in 29 (32.2%) patients and <60 mmHg in 38 (42.2%) patients. A statistically significant correlation (r= 0.540, p<0.001) detected only between arterial and venous blood gas samples of patients with PaO 2 <60mmHg and O 2 saturation <90% among these three groups. Conclusion: In the follow-up of patients with respiratory alkalosis, if O2 saturation is ≥90%; pH, pCO 2 and HCO 3 of venous blood gas samples can be used instead of arterial blood gas samples. If patient's O2 saturation <90%; pH, pCO2, HCO3 and also pO2 values in venous blood gas sample can be used instead of arterial blood gas samples.