Prediction of fluid responsiveness. What’s new?

Annals of Intensive Care

Table 1 Characteristics of tests assessing preload responsiveness by mimicking a classic fluid challenge

Test	Advantages	Limitations	Confounding factors	Criterion of judgement	Diagnostic threshold	Level of evidence*
Passive leg raising	→Reversible, no fluid infusion	→Requires a direct estimation of CO/SV	→Possible false negatives in case of intra-abdominal hypertension →False negatives in case of venous compression stockings	↗ CO	≥ 10%	++++
	→Works regardless of breathing activity, cardiac rhythm, Vt, lung compliance	→False negatives in case of IAH		↗ VTI	≥ 10%	++++
	→Very well validated			↗ end-tidal CO₂	≥ 5% ≥ 2 mmHg	++
				↗ perfusion index	≥ 9%	+
				↘ PPV/SVV	≥ − 1 to 4 points	+
				↘ capillary refill time	≥ − 27%	+
Mini-fluid challenge	→Easy to perform	→Requires a direct estimation of CO/SV	→Poor precision of the technique measuring cardiac output →Volume of fluid infused (minimum: 100 mL)	↗ CO	≥ 5%	++
	→Works regardless of breathing activity, cardiac rhythm, Vt, lung compliance, IAP	→Requires a precise estimation of CO/SV →Still requires fluid infusion		↗ VTI	≥ 10%	+
Trendelenburg manoeuvre	→Reversible, no fluid infusion →Possible even in prone position, on the operating table or under ECMO →Works regardless of breathing activity, cardiac rhythm, Vt, lung compliance	→Possible gastric reflux →Requires more validation	→Intra-abdominal hypertension?	↗ CO	≥ 8 to 10%	+

CO cardiac output, IAH intra-abdominal hypertension, ECMO extracorporeal membrane oxygenation, PPV pulse pressure variation, SV stroke volume, SVV stroke volume variation, Vt tidal volume under mechanical ventilation, VTI velocity-time integral in the left ventricular outflow tract
^*Takes into account the number of positive studies (confirming reliability) and of negative studies (denying reliability)