REPRODUCIBILITY OF DOUBLE INDICATOR DILUTION MEASUREMENTS OF INTRATHORACIC BLOOD-VOLUME COMPARTMENTS, EXTRAVASCULAR LUNG WATER, AND LIVER-FUNCTION

Study objective: Arterial thermal dye dilution (TDDart) with the COLD system (Munich, Germany) allows measurement of cardiac index (CI), par tial blood volumes, lung water, and liver function. The aim of the stu dy was to determine agreement of TDDart measurements with pulmonary ar tery thermal dilution measurements (TDpa) and to assess the reproducib ility of TDDart parameters. Design: Prospective study. Setting: ICU of a university hospital department of cardiac surgery. Patients: Thirty consecutive patients after coronary artery bypass grafting. measureme nts and results: Triplicate measurements of TDDart parameters were per formed 1, 3, 6, 12, and 24 h postoperatively and coefficients of varia tion (CVs) were computed. At the 3-h point, additional fivefold TDDart measurements were done and compared with TDpa measurements. The coeff icient of correlation for Ct from TDDart vs TDpa was 0.96 (p<0.001), a nd the mean difference was 0.16 L/min/m(2) (2.4%). The CVs of the TDDa rt and TDpa CI measurement were 7.2% and 5.9%; the CVs of other TDDart parameters were 4.6% (cardiac function index), 8.3% (global end-diast olic volume), 7.0% (intrathoracic blood volume), 7.6% (total blood vol ume), 7.4% (right ventricular end-diastolic volume), 7.4% (right heart end-diastolic volume), 11.3% (left heart end-diastolic volume [LHEDV] ), 12.0% (right to left heart volume proportion [R/LHV]), 8.8% (pulmon ary blood volume), 10.8% (extravascular lung water), 16.4% (plasma dis appearance rate of dye), and 19.8% (dye clearance). The CV did not dep end on Glasgow coma scale or on body temperature. Conclusion: The CVs of LHEDV and R/LHV are influenced by asynchronous TDDart and TDpa vari ation. The CVs of plasma disappearance and dye clearance are increased as the half-life of the dye is longer than the measurement sequence. All other parameters derived from TDDart and TDpa show a clinically su fficient reproducibility.