THE USE OF THE ISTAT PORTABLE ANALYZER IN PATIENTS UNDERGOING CARDIOPULMONARY BYPASS

Objective. To evaluate the utility of the iSTAT blood analyzer, a beds ide device for hematocrit, sodium, potassium, and glucose measurement during cardiopulmonary bypass (CPB). Methods. Forty patients scheduled for elective CPB were evaluated prospectively. In addition to using t he iSTAT analyzer, blood samples were analyzed at four time points: fo llowing induction of anesthetic, 10 min. after initiation of CPB, 60 m in, after initiation of CPB, and following heparin neutralization by p rotamine. Blood glucose concentration was measured by the hospital lab oratory using a Kodak Analyzer and by a glucose meter, electrolytes we re evaluated by the Kodak Analyzer and BGE (a device which is commonly used for ''satellite laboratory'' determinations of electrolyte and b lood gas results), and hematocrit samples were measured by the hospita l laboratory using an NE 8,000 and a centrifuge. The means and standar d deviations of the differences between the methods were calculated. R esults. The hematocrit values determined by the iSTAT machine, when ad justed for the level of total protein (according to manufacturer's dir ections), differed from the laboratory values by 0.53 +/- 1.46 percent age points. An alternative to measuring total protein and making the a djustment is simply adding 1% to the hematocrit in the pre-CPB period and 3% on-CPB or post-CPB, which we found to yield values that differe d from the laboratory by 0.52 +/- 1.42 percentage points. For all four tests (hematocrit, sodium, potassium, and glucose) the iSTAT had a si milar relationship to the laboratory values as did the other commonly used means (centrifuge, BGE, and glucose meter) of clinical evaluation . Conclusion. In summary, we found that in patients undergoing CPB, th e iSTAT Values agreed sufficiently well with standard laboratory value s and that the iSTAT instrument can be relied upon for bedside measure ments.