In goal-directed fluid therapy (GDT) for major abdominal surgery, which haemodynamic variable is the most reliable dynamic predictor of fluid responsiveness in a mechanically ventilated patient?

• A Central venous pressure (CVP)
• B Pulmonary capillary wedge pressure (PCWP)
• C Pulse pressure variation (PPV) or stroke volume variation (SVV) ✓
• D Mean arterial pressure (MAP)

Explanation

Dynamic indices such as pulse pressure variation (PPV) and stroke volume variation (SVV) exploit the cardiorespiratory interaction during mechanical ventilation. A PPV or SVV >13% predicts that cardiac output will increase by >15% in response to a fluid bolus (fluid-responsive state). Static filling pressures (CVP, PCWP) are notoriously poor predictors of fluid responsiveness and should not guide fluid therapy in isolation. MAP is a downstream variable reflecting multiple factors. PPV/SVV are invalid in spontaneous breathing, arrhythmias, or open chest.

Reference: Morgan & Mikhail's Clinical Anesthesiology, 6th ed.

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Written and medically reviewed by the StethoPrep medical team.