Thermodilution catheters are specialized medical devices used to measure cardiac output and hemodynamic pressures, primarily in critically ill patients. They are commonly used in conjunction with the thermodilution technique, which involves injecting a cold or room temperature solution into the right atrium and measuring the resulting temperature change in the pulmonary artery to determine cardiac output. These catheters also allow for the measurement of right atrial pressure, right ventricular pressure, pulmonary artery pressure, and pulmonary capillary wedge pressure.