Clinical application of the ultrasound velocity dilution method for cardiac output (CO) measurement in the absence of arteriovenous circuit in ICU patients

Background Ultrasound velocity indicator dilution method of cardiac output (CO) determination has been proposed as an alternative to thermodilution me thod in the treatment of patients during extracorporeal detoxification proc edures. Recently, a modification of the method that does not require extrac orporeal circuit existence has been used in experimental studies and has be en reported. The aim. The aim of the study was to evaluate the possibility of the clinic al application of the ultrasound velocity dilution method in the absence of the extracorporeal circuit. Method. The Transonic Systems Inc. flow-dilution sensor was clipped onto a tube connecting arterial and venous lines routinely used in critically ill patients. The calibration injection of I mi of 0.9% saline solution (Vcal) at body temperature was made into the arterial site of the system followed by the indicator dilution calibration curve registration (Scal). Then a bol us of 10-20 mi of the same indicator (Vinj) was injected into the central V ein with the subsequent recording of the first passage curve (Sinj). The ar eas under the dilution curves with known blood flow and known volumes of in jection were used for cardiac output calculation according to the following formula: CO = Q x (Vinj/Vcal) x (Scal/Sinj). Results. A comparative study of CO determination with thermodilution method was made in II patients in the early postoperative period after open heart surgery In 26 measurements, mean values for CO were 5.9 +/- 1.6 For the ul trasound method and 5.85 +/- 1.7 l/min for the thermodilution method. The d ifference between the two methods was less than 10% in 5 (19.3%) cases and less than 16% in 3 (11.5%) cases. The correlation coefficient was 0.97 and the linear regression equation: COtherm. = -0.1 + 1.01 x COus. Conclusions. In clinical practice the modification of the ultrasound veloci ty dilution method, that did not require continuous arteriovenous shunt or extracorporeal circuit existence, was developed and approved. The method is reliable, and, in the presence of arterial and venous lines in critically ill patients, does not require cardiac catherization for CO measurement.