Abstract
Conventional indices of tissue perfusion after surgery involving cardiopulmonary bypass (CPB) may not accurately reflect disordered cell metabolism. Venous hypercarbia leading to an increased veno-arterial difference in CO2 tensions (V-aCO2 gradient) has been shown to reflect critical reductions in systemic and pulmonary blood flow that occur during cardiorespiratory arrest and septic shock. We therefore measured plasma lactate levels and V-aCO2 gradients in 10 patients (mean age 57.2 years) following CPB and compared them with conventional indices of tissue perfusion. Plasma lactate levels, cardiac index (CI) and oxygen uptake\((\dot VO_2 )\) all increased significantly (p<0.05 vs baseline levels) up to 3h following surgery. Oxygen delivery\((\dot DO_2 )\) did not change. Plasma lactate levels correlated significantly with CI (r=0.47,p<0.01). V-aCO2 fell significantly with time (p<0.01 vs baseline). There was an inverse relationship between V-aCO2 and cardiac index and V-aCO2 and lactate (r=−0.37,p<0.05;r=−0.3,p<0.05 respectively). We conclude that blood lactate, CI and\(\dot VO_2 \) increase progressively following CPB. An increase in lactate was associated with a decrease in V-aCO2. An increase in V-aCO2 was not therefore associated with evidence of inadequate tissue perfusion as indicated by an increased blood lactate concentration.
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Ariza, M., Gothard, J.W.W., Macnaughton, P. et al. Blood lactate and mixed venous-arterial PCO2 gradient as indices of poor peripheral perfusion following cardiopulmonary bypass surgry. Intensive Care Med 17, 320–324 (1991). https://doi.org/10.1007/BF01716189
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DOI: https://doi.org/10.1007/BF01716189