Pharmacodynamic analysis of a fluid challenge with 4 ml kg−1 over 10 or 20 min: a multicenter cross-over randomized clinical trial

Abstract

Purpose A number of studies performed in the operating room evaluated the hemodynamic effects of the fluid challenge (FC), solely considering the effect before and after the infusion. Few studies have investigated the pharmacodynamic effect of the FC on hemodynamic flow and pressure variables. We designed this trial aiming at describing the pharmacodynamic profile of two different FC infusion times, of a fixed dose of 4 ml kg −1 . Methods Forty-nine elective neurosurgical patients received two consecutive FCs of 4 ml kg −1 of crystalloids in 10 (FC 10 ) or 20 (FC 20 ) minutes, in a random order. Fluid responsiveness was defined as stroke volume index increase ≥ 10%. We assessed the net area under the curve (AUC), the maximal percentage difference from baseline (d max ), time when the d max was observed (t max ), change from baseline at 1-min (d 1 ) and 5-min (d 5 ) after FC end. Results After FC 10 and FC 20, 25 (51%) and 14 (29%) of 49 patients were classified as fluid responders (p = 0.001). With the exception of the AUCs of SAP and MAP, the AUCs of all the considered hemodynamic variables were comparable. The d max and the t max were overall comparable. In both groups, the hemodynamic effects on flow variables were dissipated within 5 min after FC end. Conclusions The infusion time of FC administration affects fluid responsiveness, being higher for FC 10 as compared to FC 20 . The effect on flow variables of either FCs fades 5 min after the end of infusion. Supplementary Information The online version contains supplementary material available at 10.1007/s10877-021-00756-3.

How can assessing hemodynamics help to assess volume status?

“…Recent studies have helped to better delineate the way a fluid challenge should be assessed, and this has important consequences regarding the techniques used for hemodynamic monitoring. Regarding the volume that should be administered, evaluating the changes in CO after administration of 4 mL/kg of crystalloids over 10 min allows the identification of the maximal number of fluid responders [ 66 ], compared to slower rates or smaller amounts of fluids [ 66 , 67 ]. Ideally, the effects of a fluid bolus should be assessed on CO or surrogates.…”

Variations of pulse pressure and central venous pressure may predict fluid responsiveness in mechanically ventilated patients during lung recruitment manoeuvre: an ancillary study

“…Our analysis and conclusions on fluid responsiveness prediction focused on the STEP-UP phase with increasing levels of pressure from 20 to 45 cmH 2 O. The STEP-DOWN phase, by prolonging the delay between the STEP-UP phase and the VE may have biased the result of the fluid responsiveness [ 26 ]. Future studies should compare the performance of a LRM at 30 cmH 2 O versus a LRM up to 45 cmH 2 O without the STEP-DOWN phase to verify our results.…”

Pathophysiology of fluid administration in critically ill patients

“…Recently, all aspects related to FC administration were investigated, showing that the amount of fluid given, the rate of administration and the threshold adopted to define fluid responsiveness impact on the final outcome of an FC [57][58][59][60][61]. A RCT showed that the duration of the administration of an FC affected the rate of fluid responsiveness, shifting from 51.0% after a 4 ml/kg FC completed in 10 min to 28.5% after an FC completed in 20 min [57].…”

“…Recently, all aspects related to FC administration were investigated, showing that the amount of fluid given, the rate of administration and the threshold adopted to define fluid responsiveness impact on the final outcome of an FC [57][58][59][60][61]. A RCT showed that the duration of the administration of an FC affected the rate of fluid responsiveness, shifting from 51.0% after a 4 ml/kg FC completed in 10 min to 28.5% after an FC completed in 20 min [57]. However, this study was conducted in a limited sample of neurosurgical patients during a period of hemodynamic stability, which limits the external validity of the results in different surgical settings or in critically ill patients.…”