Establishing goals of volume management in critically ill patients with renal failure

Volume management remains a challenging component of caring for the critically ill. Renal failure complicates fluid management. We sought to identify relationships between delta blood volume and physiology-based targets for both the adequacy of left ventricular filling (stroke volume index [SVI]) and preload dependency (stroke volume variability [SVV]) in patients undergoing dialysis in the intensive care unit.

Patients undergoing dialysis with an arterial line in place were eligible. Delta blood volume was measured during dialysis along with simultaneous SVI and SVV via an arterial pressure cardiac output monitor. Patients were dichotomized as "negative" fluid strategy if fluid was removed, or "positive" fluid strategy if fluid was added during renal replacement therapy. Delta blood volume's association with SVI and SVV was examined separately by fluid strategy group.

A total of 26 patients (11 continuous and 15 intermittent dialysis) were investigated. Compared with that in patients with negative fluid strategy, SVV was significantly higher at baseline in patients with positive fluid strategy, while baseline SVI was significantly lower. Fluid removal was associated with significant increases to SVV in both strategy groups. Fluid removal was associated with significant decreases to SVI, and this effect was similar regardless of fluid strategy.

Physiologic variables assessing cardiac performance (SVI) and preload responsiveness (SVV) provide simple yet meaningful targets when one is determining the best approach for volume management in critically ill patients undergoing dialysis.