Pulse pressure variation (PPV) and stroke volume variation (SVV) do not predict fluid responsiveness when using a protective ventilation strategy: the use of functional haemodynamic tests can be useful to overcome this limitation.
We tested the use of a tidal volume challenge (VT
C), during 6 ml kg−1
[predicted body weight (PBW)] ventilation, and the end-expiratory occlusion test (EEOT) for prediction of fluid responsiveness.
An interventional prospective study.
Supine elective neurosurgical patients.
The study protocol was, first, the initial EEOT test was performed during baseline 6 ml kg−1
PBW ventilation; second, VT
C was performed by increasing the VT
up to 8 ml kg−1
PBW and PPV and SVV changes were recorded after 1 min; third, a second EEOT was performed during 8 ml kg−1
PBW ventilation; and VT
was reduced back to 6 ml kg−1
PBW and a third EEOT was performed. Finally, a 250 ml fluid challenge was administered over 10 min to identify fluid responders (increase in stroke volume index ≥10%).
In the 40 patients analysed, PPV and SVV values at baseline and EEOT performed at 6 ml kg−1
PBW did not predict fluid responsiveness. A 13.3% increase in PPV after VT
C predicted fluid responsiveness with a sensitivity of 94.7% and a specificity of 76.1%, while a 12.1% increase in SVV after VT
C predicted fluid responsiveness with a sensitivity of 78.9% and a specificity of 95.2%. After EEOT performed at 8 ml kg−1
PBW, a 3.6% increase in cardiac index predicted fluid responsiveness with a sensitivity of 89.4% and a specificity of 85.7%, while a 4.7% increase in stroke volume index (SVI) with a sensitivity of 89.4% and a specificity of 85.7%.
The changes in PPV and SVV obtained after VT
C are reliable and comparable to the changes in CI and SVI obtained after EEOT performed at 8 ml kg−1
PBW in predicting fluid responsiveness in neurosurgical patients.