Introduction Profound haemodynamic changes are invariably seen in ALF and resemble those found in later stages of septic shock. Vasopressor support is frequently required and in discriminatory fluid resuscitation can worsen intracranial hypertension (ICH) and lung injury. Markers of preload dependency have thus far not been studied in this patient group and response to dynamic manoeuvres such as passive leg raising or end expiratory hold cannot be considered safe in this population due to the high incidence of ICH.
Method Patients admitted to a tertiary referral specialist ICU with ALF. All patients were in vasoplegic shock, requiring multiorgan support including controlled mechanical ventilation. Cardiac output monitoring via transpulmonary thermodilution (TPTD) and pulse contour analysis (PiCCO_, Pulsion Munich) was performed. Markers of fluid responsiveness were compared between responders (CI≥15%) and non-responders to a colloid fluid challenge (5 ml/kg IBW). All patients had a transthoracic echocardiogram (TTE) performed before and after fluid administration. The predictive capacity of stroke volume—pulse pressure variation (SVV, PPV) and respiratory change in peak aortic velocity (DV peak) for preload dependency was analysed.
Results 26 patients (mean age 40 (13), 15 M: 11 F,) with mixed aetiology ALF were assessed. The mean APACHE II score was 23 (4) and mean SOFA 15 (2). Change in CI and SVI were closely correlated (R=0.726, p<0.001). There was no difference between those defined as responders using a cut-off of CI or SVI of 10%. When using 15%, 7 patients would have been classified differently. Intraclass correlation coefficient (ICC) for CI and SVI change was 0.83 (0.62–0.92), confirmed using Pasing & Blakock regression (A= −0.278, −0.88 to 0.16, B=1.26, 0.88 to 1.72) suggesting haemodynamic changes in both measures are interchangeable. Using a cut-off of a change in CI of 15% only PPV predicted fluid responsiveness (AUROC 0.79, 0.58–0.93, p=0.005, cut-off >9%, sensitivity 75%, specificity 62%). SVV weakly predicted fluid responsiveness in this cohort (AUROC 0.73, 0.52–0.87, p=0.005, cut-off >11%), While there was a trend towards reduction in DV peak (mean difference −3%, p=0.080) this was not different between those defined as fluid responders by CI (Repeated measures ANOVA p=0.124) and AVV prior to fluid bolus did not predict a CI response (AUROC 0.637, 0.413–825, p=0.322).
Conclusion Baseline PiCCO parameters predict fluid responsiveness but the respiratory variability in DV peak did not predict a CI response to fluid bolus in this cohort of ALF patients. PPV may be a more suitable PiCCO index for assessing fluid requirements in patients with ALF than SVV.
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