Correlation between Arterial and Central Venous Blood Gas Values in Critically Ill Patients

Arterial blood gas (ABG) analysis is a commonly and golden standard performed procedure that is often used to assess the acid-base status along with adequacy of ventilation and oxygenation among predominantly critically/acutely ill patients. Unfortunately, prolonged arterial catheterization or repeated direct blood sampling from the artery is associated with rare, but serious, complications to the patient as well as the health care providers. Patients who require frequent blood gas testing often have indwelling central venous catheters for the administration of intravenous medications or the monitoring of central vascular pressures, allowing for repeated central venous blood gas (VBG) analysis. Venous blood gas analysis requires fewer punctures, is a relatively safer procedure for both the patient and health care provider, and may be alternative to ABG analysis.^(1–4)

The current study aimed to determine the correlation between arterial and central venous blood gas measurements for monitoring of acid-base balance & oxygenation in the critically ill patients.

Prospective comparative study of 90 samples from 45 patients with diverse medical & surgical conditions was conducted.

Identity plot was used to check the perfect agreement between the paired measurements. The strength of the relationship between the arterial and venous gas values was assessed with the Pearson product–moment correlation coefficient test. Arterial pH and venous pH, PCO₂and HCO₃ were found to be correlated significantly, while the correlation between the arterial and venous PO₂ and SO₂ were not statistically significant.

as a result of perfect correlation between the arterial and central venous measurements of acid – base (pH, PCO₂, HCO₃⁻) levels in the critically ill patients, VBG can accurately replace the ABG, obviate the need for continues arterial sampling and reduce the risk of arterial puncture and arterial cannulation complications