The oesophageal Doppler monitor

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Abstract
The oesophageal Doppler monitor, described in the early 1970s1 and subsequently refined by Singer,2 provides a safe and minimally invasive means of continuously monitoring the circulation. A paper in this week's issue describes using the oesophageal Doppler monitor to guide intraoperative fluid resuscitation in elderly patients undergoing repair of proximal femoral fractures (p 909).3 These patients are typically managed with only minimal intraoperative monitoring, and the paper thus raises questions about the role of invasive intraoperative monitoring. Similar questions have recently been raised about the role and use of pulmonary artery catheters.4 The oesophageal Doppler monitor measures blood flow velocity in the descending thoracic aorta using a flexible ultrasound probe about the size of a nasogastric tube. When combined with a nomogram based estimate of aortic cross sectional area (derived from the patient's age, height, and weight), it allows haemodynamic variables, including stroke volume and cardiac output, to be calculated. Despite several potential sources of error, there is good correlation, at least in adults, between measures of …