Fluid responsiveness — dynamic > static
Predict who will respond to fluid bolus
Mnemonic device
PPV / SVV / PLR
Mapping
PPV
Pulse pressure variation >12-13% on positive pressure ventilation = fluid responsive
SVV
Stroke volume variation >10-12% (FloTrac/LiDCO) = fluid responsive
PLR
Passive leg raise — auto-bolus 250-300 mL; if SV ↑ >10% = fluid responsive (works with spontaneous breathing)
Static
CVP, PAOP, IVC diameter — POOR predictors of fluid responsiveness; abandoned in modern critical care
Caveats
PPV/SVV require: full mechanical ventilation TV ≥8 mL/kg, sinus rhythm, no spontaneous effort, no severe RV dysfunction
Clinical note: Half of hemodynamically unstable patients are NOT fluid-responsive. Knowing who needs fluid vs pressor changes management. PLR is the Swiss-army-knife test.