Tidal Volume Challenge to Assess Volume Responsiveness with Dynamic Preload Indices During Surgery: a Prospective Study

Intraoperative algorithms and protocols regarding fluid therapy are key factors to prevent perioperative hypovolaemia or hypervolaemia, which are both known to increase morbidity and length of hospital stay. Response to fluid therapy (increase in stroke volume, SV) after a bolus infusion should be based on predictors of fluid responsiveness. It has been shown previously that static indices, such as central venous pressure or pulmonary wedge pressure are unsuitable for this purpose. Conversely dynamic indices such as stroke volume variation (SVV) or pulse pressure variation (PPV), can reliably predict fluid responsiveness during mechanical ventilation with a tidal volume of at least 8 ml/kg.

In recent years, the use of lung-protective ventilation strategy with tidal volumes of less than 8 ml/kg (e.g. Vt = 6ml/kg of ideal body weight) has been associated with better outcome of patients9 and has been recommended as the standard intraoperative mechanical ventilation strategy.10 Reduced tidal volumes, however, limit the reliability of dynamic PPV and SVV indicators. In order to overcome this Vt-related limitation to PPV and SVV, functional hemodynamic tests should be applied,11 aimed at increasing right ventricle preload. For example, discontinuation of mechanical ventilation as in the end-expiratory occlusion test (EEOT) has been tested, in intensive care patients, as well as in a surgical polulation with conflicting results.15,16 Recently Myantra and coll tested the tidal volume challenge (VtC) in 20 severely ill patients with acute circulatory failure. They demonstrated that the response to fluid administration can be reliably predicted through changes in PPV and SVV after VtC, defined as an increase in Vt to 8 ml/kg for 1 minute.

Tidal volume challenge has also been successfully tested in surgical patients. In neurosurgical patients in both supine and prone position. Messina and coll demonstrated that VtC can predict the response to fluid administration through a change in PPV and SVV with high sensitivity and specificity. In robotic laparoscopic procedures in the Trendelenburg position, Jun and coll20 showed PPV changes after a VtC were more sensitive and specific in predicting fluid responsiveness than SVV changes.

The purpose of this study is to investigate the ability of changes in PPV and SVV after VtC to predict fluid responsiveness in patients undergoing general anesthesia with protective mechanical ventilation.

Patient population / study design