Tidal Volume Challenge and Lung Recruitment Maneuver (TIDALREC): the Reliability of Pulse Pression Variation or Stroke Volume Variation on Fluid Responsiveness.

The LRM is performed first for 30 seconds (an insufflation pressure of 30 cmH2O for 30 seconds is applied). After a free interval of 3 minutes, the VtC is done during 1 minute. For VtC, tidal volume is increased from 6 to 8 ml.kg-1 of predicted body weight. Finally, after a new free interval of 3 minutes, the fluid challenge (consisting in fluid administration of 250 ml of Ringer Lactate) is started for 10 minutes (in aim to determine which patients are responders). This sequence is repeated every 30 minutes (maximum four times).

The VtC is performed first for 1 minute. After a free interval of 3 minutes, the LRM is done for 30 seconds. Finally, after another free interval of 3 minutes, the fluid challenge is started for 10 minutes. This sequence is repe-tead every 30 minutes (maximum four times).