ERAS: Goal Directed Fluid Therapy

Goal Directed Fluid Therapy (GDT) is a tenant of ERAS protocols, utilizing an intra-arterial waveform for automated measurements of pulse pressure variations (PPV) or stroke volume variation (SVV) in order to determine response to fluid boluses. Essentially, if the respiratory variations in the arterial waveform exceed 10-15%, the patient is assumed to be fluid responsive and would likely benefit from a bolus (typically 250 mL) of a balanced crystalloid solution. Fluid resuscitation should be held once the parameter has fallen to <10% to avoid hypervolemia.

Measurements of pulse variation may be used as a surrogate for pre-load dependence or responsiveness. If the patient is “dry”, the positive intra-thoracic pressure created during the inspiratory loop of mechanical ventilation impairs venous return to the heart. This decrease in the right ventricular stroke volume leads to a decreased left ventricular stroke volume and is reflected by a change in the arterial pressure curve. Conversely, when the patient is optimally hydrated, their preload should be close to or at the plateau of the Frank-Starling curve (see image below), greatly reducing the above phenomenon. 1 PPV is less reliable in the setting of spontaneous breathing or cardiac arrhythmias.

Studies indicate this method is a superior deviation from the historical “fixed-volume” or liberal fluid approach. In a meta-analysis published by Chong et al, GDT was associated with lower risk of mortality, pneumonia, acute kidney injury, and wound infection as well as portended a shorter length of hospital stay.2 GDT appears to be most effective in the context of ERAS protocols, which implement multiple processes reducing fluid imbalances throughout the perioperative period, including avoidance of pre-operative dehydration and encouraging early post-operative alimentation and ambulation.