Measuring Cardiac Output: Intermittent Bolus Thermodilution Method

Abstract

cialist in the cardiac care unit and cardiac observation unit at UCLA Medical Center and is an assistant professor of nursing at the UCLA School of Nursing, Los Angeles, Calif. by a computer and converted into a measurement of cardiac output. Cardiac output is inversely proportional to the area under the curve. The normal cardiac output curve has a rapid smooth upstroke and a gradual downstroke (Figure 1). A small area under the curve indicates a high cardiac output. The faster blood flows through the heart, the earlier the peak and sharper the drop, because the catheter senses temperature change over a short period. A low cardiac output results in a larger area under the curve. When blood flows slowly (low cardiac output), the area under the curve (temperature change over time) is greater because the catheter senses changes in temperature over a longer period. The curves vary according to the patient’s clinical condition and according to deviations in technique (Figure 2). Concerns about contamination of prefilled syringes of injectate and proximal port of a pulmonary artery catheter located in the right atrium. In the atrium, the injectate mixes with the blood and passes through the tricuspid valve into the right ventricle. A thermistor within the catheter senses the change in blood temperature as the blood passes the catheter tip located in the pulmonary artery. A curve that shows the change in temperature over time is calculated ProtocolsforPractice