Major surgery is associated with significant trauma and is a potential cause of multiple system organ failure and death. Measurement of cardiac output using a variety of techniques during the perioperative period has enabled practitioners to proactively optimise stroke volume and cardiac output in an attempt to reduce postoperative complications. Although pulmonary artery catheter has been widely used and considered as the gold standard for measuring cardiac output, recent advancement of technology has seen the development of a number of less-invasive haemodynamic monitors. Oesophageal Doppler ultrasonography is a minimally invasive method for measuring stroke volume and cardiac output. It is user-friendly and is one of the few low-invasive technologies to date, which has been used successfully to guide intra-operative fluid administration, resulting in improvement in outcome and significant reduction in duration of hospital stay.