Detection of hypovolemia by non-invasive hemodynamic monitoring during major surgery using Ringer´s solution, 5% albumin, or 20% albumin as infusion fluid: a post-hoc analysis of a randomized clinical trial.

Background Fluid loading with crystalloids is the conventional treatment of major hemorrhage but might tend to create fluid overload. We studied hemodynamic profiles of fluid replacement therapies during major surgical hemorrhage and compared the ability of pulse pressure variation (PPV), plethysmographic variation index (PVI), cardiac output (CO) and Guyton´s approach to detect hypovolemia.Methods In this single center randomized controlled trial, fluid replacement therapy to treat hemorrhage in 42 patients was randomized to consist of either 5% albumin (12 mL/kg) or 20% albumin (3 mL/kg) over 30 min, both completed by Ringer lactate replacing blood loss in a 1:1 ratio, or Ringer solution alone in a 3:1 ratio. Measurements included CO, PPV, PVI, arterial and central venous pressures, heart rate (HR) and subsequent calculation of Guyton´s physiological parameters. CO was measured by an esophageal Doppler probe.Results The Ringer-only fluid program resulted in slight hypovolemia (mean, 313 mL), decreased mean arterial pressure (MAP), increased HR, PPV values and vasopressor requirement. The 5% and 20% albumin programs were more effective in filling the vascular system, as evidenced by higher mean circulatory filling pressure and unchanged or decreased PPV over the 5 h observation period. The 20% albumin increased the systemic vascular resistance and the resistance to venous return. Receiver operating characteristics curves indicated that hypovolemia > 500 mL could only be accurately detected by PPV when 5% albumin was used, that PVI was reliable when Ringer was infused, and that CO indicated the hypovolemia when 20% albumin was administered.Conclusions The trends in PPV, PVI, and CO reflected the changes in intravascular volume, but how well they indicated hypovolemia > 500 mL may differ depending on the choice of infusion fluid. Identifying hypovolemia using non-invasive hemodynamic monitors remains challenging and associated with low predictive values.Trial Registration Number NCT05391607, May 26, 2022.