Cardiac output (CO) monitoring is an integral part of management of patients during cardiac surgery, supramajor surgeries with large fluid shifts and critically ill patients in the ICU. It helps in early identification of insufficient tissue oxygenation and appropriate treatment can be instituted early. Traditionally, CO monitoring is done by thermodilution technique using pulmonary artery catheter. However, it is an invasive modality and several studies criticised and linked it to the increased mortality. This has lead into the development of newer minimally invasive methods most noticeably arterial pressure waveform derived cardiac output (APCO) monitoring system. It is an exciting technology based on normal population arterial waveform algorithm without any need of external calibration and can be attached to the pre­existing arterial line. However, thermodilution is still considered as a gold standard method of cardiac output monitoring. This article intends to highlight the pro and cons of these two techniques as well as other methods of CO monitoring. 

Keywords: Cardiac Output Monitor; Thermodilution; Pulmonary Artery Catheter; Flotrac; LiDCO; Echocardiograhy