Arteriovenous carboxyhemoglobin difference is not correlated to TNF-alpha, IL-6, PCT, CRP and leukocytes in critically ill patients

BACKGROUND: It is still unclear as to whether the paradoxical arteriovenous carboxyhemoglobin (COHb) difference found in critical illness may represent a novel marker of the acute inflammatory response. We determined whether the arterial and central venous COHb concentration or their difference may be correlated to classical pro-inflammatory markers. METHODS: Arterial and matched central venous blood gases were obtained from non-smoking intensive care patients undergoing gastrointestinal surgery, and were correlated with plasma concentrations of tumor necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6), procalcitonin (PCT), C-reactive protein (CRP) and leukocytes. RESULTS: No correlation was found between arteriovenous COHb difference and the investigated pro-inflammatory mediators. While arterial and central venous COHb concentrations were positively correlated to plasma concentrations of TNF-alpha (P< or =0.01), IL-6 (P<0.05) and PCT (P< or =0.01), they were neither interrelated with PCT nor with leukocytes. CONCLUSIONS: Arteriovenous COHb difference does not appear to be a marker of the acute inflammatory response. Future studies are needed to investigate whether arterial and central venous COHb concentrations by themselves may serve as indicators of systemic inflammation.