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

Objective: This study evaluates the venous-arterial CO 2 difference (Pv-aCO 2 ) from peripheral venous blood (Pv-aCO 2 p) as a less invasive alternative to central venous Pv-aCO 2 for assessing tissue perfusion in septic shock.Methods: 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-aCO 2 p and central Pv-aCO 2 .Results: 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-aCO 2 p gap was 8 mmHg, whereas the central Pv-aCO 2 gap was 6 mmHg.A moderate correlation was found between Pv-aCO 2 p and central Pv-aCO 2 (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 pCO 2 .Conclusions: Peripheral Pv-aCO 2 p correlates well with central Pv-aCO 2 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.