Abstract
Impedance cardiograph is an useful, noninvasive technique for the determination of cardiac output value and for the continuous monitoring of stroke volume following open heart surgery. Since April 1973, the measurements of cardiac output by this method have been carried out in 56 cases (520 occasions) after open heart surgery in our institution. A comparative study of cardiac output values by the simultaneous impedance cardiograph and dye dilution techniques in 35 cases revealed a close relationship between the two.
The coefficient of correlation was 0.83. The measurement of low cardiac index such as under 1.5 l/min/m2 is inaccurate with dye dilution methods, but this seems to be more accurate with impedance technique.
Isoproterenol is often used for the treatment of LOS following open heart surgery. Cardiac index measurement in cases treated with isopreterenol for LOS following artificial valve replacement disclosed CI often drop more than the value before isoproterenol administration even with elevated blood pressure when pulse rate exceeded 100/min. On the contrary, digitalis was very effective to increase cardiac output in those patients with valve replacement. This suggest that when isoproterenol used for LOS in patients after valve replacement, pulse rate must be controlled not to exceed 100/min to obtain increased cardiac output and digitalis should be started after 24 hrs postoperatively when arrhythmia is more unlikely to occur.
Impedance cardiograph proved also its availableness for the determination of optimum pulse rate of cardiac pacing, determination of appropriate pressure for positive endexpiratory pressure breathing, early recognition of pulmonary edema and observation of patients who received artificial valve replacement in the course of follow up by means of bycycle ergometer tests. Concerning these problems we would like to present in the near future.
