[Intraoperative and postoperative microdialysis measurement of the human heart--feasibility and initial results]

Microdialysis measurements of human cardiac metabolism during and after cardiac operations have not been published up to now. The goal of this study was to evaluate feasibility of the method in a clinical setting and to interpret first results.

In 5 patients microdialysis measurements were made in regular intervals during aortocoronary bypass surgery. Analysis of dialysate was done by high performance liquid chromatography or enzymatic fluorometry. In the last 2 patients measurements were also taken during the postoperative course up to the time of extubation.

During aortic cross clamping a mean 7-fold rise of the radical scavenger glutathione was observed (range 0.9-15.4; p = 0.06). During reperfusion the glucose/lactate(Glc/Lac)-rate rose from 0.4 to 3.1 (p = 0.02). Concentrations of ascorbic acid, cysteine and uric acid remained neutral or showed no regular changes. In the 2 patients who were also observed postoperatively, lactate rose significantly at 190 min and 340 min postoperatively (decrease in Glc/Lac-ratio from 2.5 to 0.4 and 2.0 to 0.4 respectively).

Microdialytic measurements of metabolic parameters can be performed on the human heart in a clinical setting. So far no complications have been observed and the microdialysis probe can be installed in such a fashion, that it can be easily removed transcutaneously during the postoperative course. Substances that are important in ischemia and reperfusion can be measured and their concentrations show changes that are not just artefacts. Postoperatively, metabolic alterations may be observed in the myocardial septum that are not recordable with conventional techniques (i.e., pressure measurements, cardiac output, ECG).