Measurement of cardiac output and central volume by a modified decholin test of circulation time.

A technic is described for determining mean circulation time, cardiac output, and central blood volume by use of graded dosages of sodium dehydrocholate (Decholin) administered into a peripheral vein. The indicator-dilution curves derived by the technic were compared with radiopotas-sium-dilution curves obtained simultaneously in 12 patients. The results showed a surprisingly good agreement between the 2 methods and indicate that the traditional Decholin test of circulation time can be modified to provide much more information than it has in the past. T HE determination of arm-to-tongue circulation times by the sodium dehydrocholate (Decholin) method has a long history of clinical use. Still it has provided only limited quantitative or diagnostic information about the circulation and, for this reason, has been supplanted to a considerable extent by more complex methods. However, during the course of simultaneous radiopotassium-dilution curve and angiocardiographic studies in patients with rheumatic heart disease, we employed the times of appearance and disappearance of the Decholin taste to decide the timing of film exposures. It soon became apparent that we could frequently differentiate between mitral stenosis and insufficiency as well from the "Decholin" times as we could from the subsequently obtained dilution curves or Diodrast opacification patterns. This finding led us to appreciate that the Decholin test is fundamentally an application of the indicator-dilution principle in which Decholin serves as an indicator providing 2 subjective end points, the times of appearance and disappearance of the characteristic bitter taste. Therefore, we considered that these end points might be related to determinable, relatively constant blood concentrations of Decho-lin; if so, we might obtain multiple onset and offset times from multiple injections of graded doses of Decholin. These various times might then be appropriately related to the proper concentration coordinates so as to give adequate data for complete construction of an indicator-dilution curve. Such a curve would of course provide the same quantitative information on cardiac output and central blood volume as are provided by conventional dye and isotope-dilution technics. These concepts were tested experimentally by (1) determination indirectly of the blood concentrations of Decholin associated with the appearance and disappearance of the bitter taste, (2) determination of these times of onset and offset of taste following injections of 3 graded doses of Decholin, (3) construction of Decholin-dilution curves from the data on circulation times and blood concentrations at taste threshold, and finally (4) comparison of the results obtained from these curves …