Predictors of fluid responsiveness in critically ill patients mechanically ventilated at low tidal volumes: systematic review and meta-analysis

Abstract

Introduction Dynamic predictors of fluid responsiveness have shown good performance in mechanically ventilated patients at tidal volumes (Vt) > 8 mL kg−1. Nevertheless, most critically ill conditions demand lower Vt. We sought to evaluate the operative performance of several predictors of fluid responsiveness at Vt ≤ 8 mL kg−1 by using meta-regression and subgroup analyses. Methods A sensitive search was conducted in the Embase and MEDLINE databases. We searched for studies prospectively assessing the operative performance of pulse pressure variation (PPV), stroke volume variation (SVV), end-expiratory occlusion test (EEOT), passive leg raising (PLR), inferior vena cava respiratory variability (Δ-IVC), mini-fluid challenge (m-FC), and tidal volume challenge (VtC), to predict fluid responsiveness in adult patients mechanically ventilated at Vt ≤ 8 ml kg−1, without respiratory effort and arrhythmias, published between 1999 and 2020. Operative performance was assessed using hierarchical and bivariate analyses, while subgroup analysis was used to evaluate variations in their operative performance and sources of heterogeneity. A sensitivity analysis based on the methodological quality of the studies included (QUADAS-2) was also performed. Results A total of 33 studies involving 1,352 patients were included for analysis. Areas under the curve (AUC) values for predictors of fluid responsiveness were: for PPV = 0.82, Δ-IVC = 0.86, SVV = 0.90, m-FC = 0.84, PLR = 0.84, EEOT = 0.92, and VtC = 0.92. According to subgroup analyses, variations in methods to measure cardiac output and in turn, to classify patients as responders or non-responders significantly influence the performance of PPV and SVV (p < 0.05). Operative performance of PPV was also significantly affected by the compliance of the respiratory system (p = 0.05), while type of patient (p < 0.01) and thresholds used to determine responsiveness significantly affected the predictability of SVV (p = 0.05). Similarly, volume of fluids infused to determine variation in cardiac output, significantly affected the performance of SVV (p = 0.01) and PLR (p < 0.01). Sensitivity analysis showed no variations in operative performance of PPV (p = 0.39), SVV (p = 0.23) and EEOT (p = 0.15). Conclusion Most predictors of fluid responsiveness reliably predict the response of cardiac output to volume expansion in adult patients mechanically ventilated at tidal volumes ≤ 8 ml kg−1. Nevertheless, technical and clinical variables might clearly influence on their operative performance

Changes in stroke volume induced by lung recruitment maneuver can predict fluid responsiveness during intraoperative lung-protective ventilation in prone position

“…In this study, the percentage of fluid responders was 43%, which is lower than that (approximately 50%) indicated in several systematic reviews about fluid responsiveness [ 40 , 41 ]. This difference may be due to the differences in the amount of fluid infused and the definition of fluid responders.…”

Prediction of fluid responsiveness. What’s new?

“…However, several studies which clearly demonstrated the validity of the EEO test had included ventilated patients with a Vt less than 8 mL/kg, and even less than 7 mL/kg [ 42 , 53 ]. This was even recently confirmed by a meta-analysis that only included studies performed under conditions of low Vt [ 54 ]. In addition, the EEO test has been shown to be reliable regardless of the level of respiratory driving pressure [ 55 ].…”

“…The Vt challenge has been validated by far fewer studies than the PLR test, for example, although its reliability has been confirmed in a recent meta-analysis [ 54 ]. Moreover, the diagnostic thresholds differ slightly between the few available studies (Table 2 ), which in addition expressed the change in PPV either as an absolute value [ 30 , 52 , 65 ]} or as a percent change [ 56 , 66 , 67 ], or both [ 29 ].…”

“…After relatively small studies, two recent meta-analyses confirmed the reliability of the mini-fluid challenge [ 45 , 54 ]. This has been confirmed by a multicentre study involving more than 100 patients in the operating theatre [ 81 ] so that one can now reasonably consider that this is a reliable way to detect preload responsiveness (Table 1 ).…”

Point-of-Care Ultrasound for the Trauma Anesthesiologist

“…As such, POCUS measurements of the IVC size and collapsibility index have been used to assess volume status [ 8 , 9 ] and have been studied extensively in ICU patients [ 10 ]. POCUS is clearly less invasive than traditional measurements of fluid status, such as central venous pressure or pulmonary arterial catheter measurements.…”