Monitoring: Equipment and Computers
Background and Goal of Study: It has been shown that the increase in lactate and the reduction of inramucosal pH during cardiac surgery are due to hemodynamic instability which induces splanchnic and peripheral hypoperfusion (1,2). This study evaluated the change in transcutaneous PCO2 (tcPCO2) on the earlobe to test whether tcPCO2 reflects the peripheral hypoperfusion during cardiopulmonary bypass (CPB).
Materials and Methods: 20 adult patients undergoing cardiac surgery using CPB were enrolled. Plasma lactate concentration and PaCO2 were measured before and after CPB, along with tcPCO2 on an earlobe (TOSCA, Linde, Switzerland). Peripheral blood flow on the earlobe was also measured using laser Doppler method. Relationship between lactate and PCO2 difference (dCO2 = tcPCO2 − PaCO2) was evaluated by using Chi square and ROC analysis, where p value and AUC were calculated.
Results and Discussions: 138 measurements were evaluated in 20 patients. Lactate > 2 mmol/L was significantly associated with dCO2 > 5mmHg (p < 0.01, AUC 0.634). The significant relationship between lactate and dCO2 indicates that tcPCO2 at the earlobe represents the systemic hypoperfusion which sacrifices peripheral circulation.
Conclusion(s): tcCO2 at the earlobe could represent such hypoperfusion that induced systemic increase in lactate during CPB.
1 Eur J Cardiothorac Surg. 2003; 23: 917-24.
2 Paediatr Anaesth. 2003; 13: 777-84.