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Dynamic indices do not predict volume responsiveness in routine clinical practice.
B Lansdorp1, J Lemson, M J A M van Putten
1MIRA--Institute for Biomedical Technology and Technical Medicine, University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands. b.lansdorp@utwente.nl
Dynamic indices like pulse pressure variation (PPV) predict fluid responsiveness but require strict conditions. Routine use with low tidal volumes or arrhythmias significantly reduces their accuracy.
Area of Science:
- Critical Care Medicine
- Cardiovascular Physiology
- Mechanical Ventilation
Background:
- Dynamic indices (PPV, SPV, SVV) predict fluid responsiveness under controlled ventilation without arrhythmias.
- Clinical practice often deviates from these strict conditions.
- The impact of common variations on predictive accuracy is unclear.
Purpose of the Study:
- To evaluate the effect of ventilator settings, calculation methods, and arrhythmias on dynamic indices' predictive value for fluid responsiveness.
- To determine optimal conditions for using dynamic indices in sedated, mechanically ventilated patients.
Main Methods:
- Prospective evaluation of 47 fluid challenges in 29 cardiac surgery patients.
- Patients grouped by tidal volume (TV).
- Dynamic indices calculated using various methods (30s, breath-by-breath, TV correction, arrhythmia exclusion).
Main Results:
- Optimal prediction achieved with TV >7 ml/kg, breath-by-breath calculation, TV correction, and arrhythmia exclusion (AUC 0.90-0.95).
- Lower TVs decreased predictive value.
- Calculation over 30s and exclusion of arrhythmias reduced AUC significantly (0.51-0.63).
Conclusions:
- Dynamic indices (PPV, SPV, SVV) are reliable predictors only under strict conditions.
- Low tidal volume, cardiac arrhythmias, and specific calculation methods substantially reduce predictive value in routine practice.
