Correlation between Peripheral and Central Venous Blood Partial Pressure of Carbon Dioxide in Critically Ill Patients with Shock

Objective: To determine the correlation and relationship between upper extremity peripheral and central venous blood partial pressure of carbon dioxide (PcvCO₂) in critically ill patients with shock. Materials and Methods: The present study was a single center, observational study. A paired sample of upper extremity peripheral and central venous blood was taken from critically ill adult patients receiving vasopressor or inotropic drug for blood gas analysis. Correlation of carbon dioxide tension of venous blood from the two sites were determined. Results: Thirty paired samples were obtained from 12 patients, by two medical and one surgical intensive care units, aged between 53 and 90 years who received norepinephrine infusion that ranged from 0.01 to 0.95 mcg/kg/minute actual body weight. The intraclass correlation revealed that peripheral venous carbon dioxide tension (PpvCO₂) was excellently correlated with PcvCO₂ (ICC 0.98, 95% CI 0.96 to 0.99, p<0.001). The Bland-Altman plot demonstrated mean bias of 0.2 with the limits of agreement of –5.3 to 5.8. Conclusion: The present study revealed excellent correlation between PpvCO₂ and PcvCO₂ in critically ill patients with shock. Clinical implications of the findings require further study.