Background: Venous-to-arterial carbon dioxide difference (PvaCO2) the Pcv-aCO2/arterial-to-venous oxygen content difference (Ca-cvO2) ratio may reflect the adequacy of blood flow during shock states. We sought to test whether the development of Pv-aCO2 PcvaCO2/ arterial-to-venous oxygen content difference ratio during the very early phases of resuscitation is related to multi-organ dysfunction and outcomes in a population of septic patients resuscitated targeting the usual oxygen-derived and hemodynamic parameters. Aim of the Work: To evaluate the changes in central venous-toarterial carbon dioxide difference (Pcv-aCO2 gap) and in PcvaCO2/ arterial-to-venous oxygen content difference (Ca-cvO2) ratio [Pcv-aCO2/Ca-cvO2 ratio] during the early resuscitation in sepsis and septic shock as a predictor for development of multi-organ dysfunction and mortality. Patients and Methods: This prospective observational study was
performed in a 24-bed mixed ICU in a university-affiliated hospital. We examined all septic patients with a new episode admitted to the emergency room or proceeding from clinical wards during a 24-month period. After approval by Ethical Medical Committee and obtaining informed consent, simultaneous blood samples were collected from the central venous line and the arterial catheter for obtaining venous and arterial gases respectively at T0, and 6 hours (T6), 12 hours (T12) and 24 hours (T24) later. Patients were classified twice; the first one into groups (A and B) according to PcvO2 gap and the second one into groups (C and D) according to Pcv-aCO2/Ca-cvO2 ratio. Group (A) Decreasing PcvaCO2 (high at T0, declining at T6), Group (B) Persistently high PcvaCO2 (high at T0 and T6), Group (C) Decreasing Pcv-aCO2/Ca-cvO2
ratio (high at T0, declining at T6), Group (D) Persistently high PcvaCO2/ Ca-cvO2 ratio (high at T0 and T6).
Results: During the 24-month period, 58 septic patients older than 18 years with a new episode were screened. Patients with advanced cirrhosis (n = 4), patients with severe chronic obstructive pulmonary disease (n = 8) and pregnant women (n = 4) were not included for analysis; additionally, two patients refused the procedure. The final sample was therefore 40 patients. Our recent study found that patients with persistently high Pcv-aCO2 gradient at T6 [8.64 ± 1.66] developed more organ dysfunction and have had a higher mortality rate (61.1%). This study showed that the persistently elevated Pcv-aCO2/Pa-vO2 ratio at time 6 was associated with a mortality rate of 73.7% of the patients. While decreasing of PcvaCO2/ Pa-vO2 ratio within the first 6 hours of resuscitation was associated with a survival rate of 90.5%. Conclusion: Data support the hypothesis that persistence of high PCO2 Gap and high Pcv-aCO2/ Pa-vO2 ratio during the early resuscitation of patients in sepsis is associated with significant higher multi-organ dysfunction and poor outcomes in critically-ill patients.