thermodilution

The technique also measures cardiac output by analysis of the femoral artery thermodilution curve.

Cardiac output was measured in triplicate by thermodilution technique using 10 ml saline solution at room temperature.

By attaching both the injector site and the ventricular thermistor to a small computer, the thermodilution curve can be plotted.

In the case of PiCCO, transpulmonary thermodilution is used as the calibrating technique.

Mean systemic, right atrial, and pulmonary artery pressures and thermodilution cardiac outputs were measured every 4 h in all patients.

Modern catheters are fitted with a heating filament which intermittently heats and measures the thermodilution curve providing serial Q measurement.

The Q derived from this cold-saline thermodilution is used to calibrate the arterial PP contour, which can then provide continuous Q monitoring.

Pulmonary Artery Thermodilution (Trans-right-heart Thermodilution)

The historically significant Swan-Ganz multi-lumen catheter allows reproducible calculation of Cardiac Output from a measured time/temperature curve (The "thermodilution curve").

Transpulmonary thermodilution uses the Stewart-Hamilton principle, but measures temperatures changes from central venous line to a central arterial line (i.e. femoral or axillary) arterial line.

MRI flow measurements have been shown to be highly accurate compared to measurements with a beaker and timer and less variable than both the Fick principle and thermodilution.

The concept of using thermodilution to measure cardiac output was originally the idea of Arnost Fronek MD, PhD of the Cardiovascular Institute in Prague.

The pulmonary artery catheter (PAC), also known as the Swan-Ganz catheter, was introduced to clinical practice in 1970 and provides direct access to the right heart for thermodilution measurements.

All patients were monitored using a fiberoptic thermodilution pulmonary artery catheter (Oximetrix Opticath Catheter, Abbot Critical Care System) and a radial or femoral arterial catheter.

Cardiac output was measured using the thermodilution technique and a bedside computer allowing the recording of each thermodilution curve (Oximetrix 3 SO 2 /CO Computer).

The indicator method was further developed with replacement of the indicator dye by heated or cooled fluid and temperature change measured at different sites in the circulation rather than dye concentration; this method is known as thermodilution.

While transpulmonary thermodilution allows for less invasive Q calibration, the method is also less accurate than PA thermodilution and still requires a central venous and arterial line with the attendant infection risks.

Transpulmonary thermodilution spans right heart, pulmonary circulation and left heart; this allows further mathematical analysis of the thermodilution curve, giving measurements of cardiac filling volumes (GEDV), intrathoracic blood volume, and extravascular lung water.

The PAC thermodilution method involves injection of a small amount (10ml) of cold glucose at a known temperature into the pulmonary artery and measuring the temperature a known distance away (6-10 cm) using the same catheter with temperature sensors set apart at a known distance.