Goal Directed Therapy is changing the management of surgical patients. There is a growing body of evidence that patients undergoing major surgery (ASA III, IV, V) are going to experience significantly better clinical outcomes when their fluid status is monitored and acted upon in real time, as opposed to those whose fluid status is managed using traditional static parameters such as central venous pressure, arterial blood pressure, urine output or pulmonary capillary wedge pressure.
This approach, known as “Goal Directed Therapy”, is built upon the premise that maintaining the patient in a normovolemic state will ensure proper oxygenation of the internal organs. The “Goal” of “Goal Directed Therapy” is to make sure that oxygen demand is met by oxygen delivery. The challenge has been to manage the patient’s position on the Frank-Starling curve via a fluid challenge without inducing hypervolemia. While this can be done through the use of a thermal dilution catheter to calculate stroke volume, and hence the patient’s preload status, the risk of using this device has essentially restricted the use of these devices to only the highest-acuity cases (predominantly cardiac surgery patients). This has rendered the devices as “nice-to-have” as opposed to “must-have” for the majority of surgical cases.
During positive pressure ventilation, the decrease in inspiratory right ventricular stroke volume is proportional to the degree of hypovolemia. This decrease is transmitted to the left heart after about three beats (i.e., the pulmonary transit time). A new generation of hemodynamic monitoring devices - including ECOM - has reached the market in the past decade that allows for much less invasive assessment of preload status through the monitoring of variation in stroke volume (Stroke Volume Variation, or SVV) in these ventilated patients. By using these devices, the clinician can view “Cardiac Output” as a surrogate for “Oxygen Delivery”, and can manage the patient’s fluid status on a beat-to-beat basis.
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