Transcutaneous oxygen tension monitoring in critically ill patients receiving packed red blood cells

Abstract

PurposeWhether transfusions of packed red blood cells (PRBCs) affect tissue oxygenation in stable critically ill patients is still matter of discussion. The microvascular capacity for tissue oxygenation can be determined noninvasively by measuring transcutaneous oxygen tension (tcpO2). The aim of this study was to assess tissue oxygenation by measuring tcpO2 in stable critically ill patients receiving PRBC transfusions. MethodsNineteen stable critically ill patients, who received 2 units of PRBC, were prospectively included into this pilot study. Transcutaneous oxygen tension was measured continuously during PRBC transfusions using Clark's electrodes. In addition, whole blood viscosity and global hemodynamics were determined. ResultsReliable measurement signals during continuous tcpO2 monitoring were observed in 17 of 19 included patients. Transcutaneous oxygen tension was related to the global oxygen consumption (r = −0.78; P = .003), the arterio-venous oxygen content difference (r = −0.65; P = .005), and the extraction rate (r = −0.71; P = .02). The transfusion-induced increase of the hemoglobin concentration was paralleled by an increase of the whole blood viscosity (P < .001). Microvascular tissue oxygenation by means of tcpO2 was not affected by PRBC transfusions (P = .46). Packed red blood cell transfusions resulted in an increase of global oxygen delivery (P = .02) and central venous oxygen saturation (P = .01), whereas oxygen consumption remained unchanged (P = .72). ConclusionsIn stable critically ill patients, microvascular tissue oxygenation can be continuously monitored by Clark's tcpO2 electrodes. According to continuous tcpO2 measurements, the microvascular tissue oxygenation is not affected by PRBC transfusions.