Slow continuous ultrafiltration: how many fluids must be taken out?

Introduction

Ultrafiltration (UF) is effective and safe in treating volume-overloaded patients with acute decompensated heart failure (ADHF) and diuretic resistance [1]. Accurate determination of the amount of fluid to be removed and maintenance of the circulating blood volume are critically important [2]. The inferior vena cava diameter (IVCD) and its collapsibility index (IVCCI) are compromised in ADHF patients due to high right atrial pressure [3]. We hypothesized that monitoring of IVCCI could be used to optimize fluid removal rate during UF.

Methods

Twenty patients (nine male, 11 female; age 76 ± 4, New York Heart Association classes III to IV) admitted to our medical ICU for ADHF were treated with UF (Aquadex System 100; CHF Solutions, Minneapolis, MN, USA). The heart rate (HR), mean arterial pressure (MAP) and IVCD with M-mode subcostal echocardiography during spontaneous breathing were evaluated before UF (T0), at 12 hours (T1) and at 24 hours (T2). The IVCCI was calculated as follows: [(IVCD_max – IVCD_min)/IVCD_max] × 100.

Results

The mean UF time was 25.5 ± 5 hours with a mean volume of 259 ml/hour and a total ultrafiltrate production of 6.6 ± 2 l. Differences between the T0 and T2 parameters are presented in Table 1. Hypotension was observed only in those patients (2/20) who reached IVCCI >35%. In all the other patients a significant increase in IVCCI was obtained without any hemodynamic instability.

Table 1 (abstract P277)

Conclusion

Inferior vena cava ultrasound is a rapid, simple and noninvasive means for bedside monitoring of the intravascular volume during UF.