USE OF AN EXTRACORPOREAL ARTERIOVENOUS TUBING LOOP TO MEASURE CARDIAC-OUTPUT IN INTENSIVE-CARE UNIT PATIENTS BY ULTRASOUND VELOCITY DILUTION

Thermodilution cardiac output (CO) measurement requires heart catheter ization and is known as a risk factor. The existing cannula in the rad ial artery in intensive care unit (ICU) patients can be used to measur e CO by ultrasound dilution (COus). An arteriovenous shunt between the radial artery and cubital vein was created using a 25 cm tubing loop. An ultrasound flow dilution sensor was clamped on the tubing and conn ected to a modified HD01 monitor (Transonic Systems, Inc., Ithaca, NY) . Calibration injections of 1 ml 0.9% NaCl were injected into the tubi ng. An intravenous bolus injection consisted of 10-20 mi 0.9% NaCl. Si multaneously, CO was measured by thermal dilution (COth; MI 166A, Hewl ett Packard, Andover, MA). Each value for COth or COus was based on th e average of three to five injections. Blood flow through the shunt wa s 10 to 26 ml/min. The comparison was made on 14 patients. In 33 measu rements, the regression equation was COth = -0.08 + 1.02 COus (r = 0.9 7). In 22 cases, the difference between COth and COus was less than 5% , in 9 cases it was in the range of 5-10%, and in 2 cases it was in th e range of 10-20%. The presence of arterial and venous lines in an ICU setting obviates the need for cardiac catheterization for the determi nation of CO.