Concordance of CO2 gaps measured using peripheral and central venous blood in patients diagnosed with septic shock

This study evaluates the venous-arterial CO2 difference (Pv-aCO2) from peripheral venous blood (Pv-aCO2p) as a less invasive alternative to central venous Pv-aCO2 for assessing tissue perfusion in septic shock.

A prospective, single-center study included 54 septic shock patients with central venous catheters placed within 24 h of intensive care unit admission. Blood samples from arterial, central venous, and peripheral venous sources were analyzed. Correlation analyses and Bland-Altman plots were used to assess agreement between Pv-aCO2p and central Pv-aCO2.

Patients had a mean age of 70 years, and 51.9% were male. The median SOFA score was 8.5, and the mean APACHE-II score was 22.7. The Pv-aCO2p gap was 8 mmHg, whereas the central Pv-aCO2 gap was 6 mmHg. A moderate correlation was found between Pv-aCO2p and central Pv-aCO2 (r = 0.593, p < 0.001), with stronger correlations observed in patients with arterial lactate ≥2 mmol/L (r = 0.673) and hemoglobin <8 g/dL (r = 0.625). Bland-Altman analysis revealed a mean difference of 8.278 mmHg between arterial and peripheral pCO2.

Peripheral Pv-aCO2p correlates well with central Pv-aCO2 and can serve as a less invasive alternative for assessing tissue perfusion in septic shock patients. It offers practical utility when central venous access is not available, aiding in early clinical decisions.