Prognostic value of venous-arterial carbon dioxide difference in critically ill children with circulatory failure

Introduction: Circulatory failure is disturbance in tissue perfusion and when it is not recognized and treated early in the course, it may result in end organ damage, shock and even death. Macrohemodynamic signs fall short on reflecting microcirculation disturbances therefore indicators that show tissue perfusion are needed. Venous-arterial carbon dioxide difference (delta pCO2) is one of those indicators that are being discussed for this purpose. Aim: This study investigates the significance of delta pCO2 as a prognostic factor in critically ill children with circulatory failure in pediatric intensive care unit (PICU). Materials and Method: Our study included 30 patients from 1 months to 18 years, who are admitted to Istanbul University Faculty of Medicine Pediatric Intensive Care Unit (PICU) with circulatory failure between January -November 2020 who have central venous and peripheral arterial catheter and who are monitored with blood gases drawn tandemly and simultaneously both from arterial and venous catheter. Death, PRISM-Ⅲ, PELOD-2, pSOFA, VIS scores, total leukocyte and thrombocyte counts, PT, aPTT and supportive care recorded for each patient. Both venous and arterial blood gases are drawn at 0, 4 th,12th and 24th hours, and checked for pCO2, ScvO2 and lactate values. Delta pCO2 value (mmHg) is calculated as the difference between central venous pCO2 and arterial pCO2. Subgroups are defined according to cut off values as for lactate 2 mmol/L, for delta pCO2 6 mmHg, and for ScvO2 65%. Results: Thirty percent (n:9) of 30 patients died. Twenty forth hour PRISM-Ⅲ, PELOD-2,pSOFA, VIS scores and the number of organ failure were higher for the patients who died (respectively p:0,0001, p:0,0002, p:0,0001, p:0,00, p: 0,006). Presence of thrombocytopenia,prolonged PT and aPTT, mechanical ventilation and vasoactive support at 24th hour or renal replacement therapy need are found to be related to mortality (respectively p:0.035, p:0.026,p:0.019, p:0.019 p:0.031, p:0.013). There was a relationship between mortality and delta pCO2 ≥6 mmHg at admission (T0), lactate level ≥ 2 mmol/L in the first 24 hours and ScvO2 <%65 at T24 (respectively p:0.039, p<0.05, p:0.035). All the patients with central venous lactate level <2 mmol/L and delta pCO2 <6 mmHg survived. Lactate levels were significantly higher in patients whose delta pCO2 values ≥ 6 mmHg at admission (p<0,05). Conclusion: High delta pCO2 level is associated with increased mortality and higher lactate levels. Blood lactate level is the best marker for circulatory failure. For the patients with normal lactate levels delta pCO2 provided additional prognostic information, and there were no deaths among the patients whom the both are normal. Detailed cardiac function evaluation may be advised for the patients with normal lactate levels and high delta pCO2 levels.