Influence of continuous venovenous hemofiltration on transpulmonary thermodilution-derived parameters

Introduction

We studied the effects of continuous venovenous hemofiltration (CVVH) on transpulmonary hemodynamic parameters in nine ventilated patients [1, 2].

Methods

All together 32 calibrations were performed with and without CVVH treatment. For each calibration three consecutive injections of 20 ml cold saline were done via the central venous line (CVL), giving a total of 186 thermodilutions.

Results

Patient age was 72.3 ± 14, BMI 24.7 ± 3.8, SAPS II 56.2 ± 15.7. Regardless of the catheter position, CVVH increased the extravascular lung water index (EVLWi) from 11.3 ± 5 to 12.4 ± 6.3 (P = NS), while the cardiac index (CI) and global end-diastolic volume index (GEDVi) decreased from 5.1 ± 1.8 to 4.2 ± 1.3 (P = 0.03) and from 1036 ± 298 to 885 ± 185 (P = 0.02), respectively. The results of a subanalysis comparing correct catheter position (CVL placed in jugular or subclavian vein and dialysis catheter placed femorally) and faulty position (dialysis catheter positioned between the thermodilution injection and detection sites) are summarized in Table 1. In two patients catheters were exchanged during the stay from the faulty to the correct position, and this resulted in a significant decrease in all parameters: CI dropped from 6.1 ± 0.9 to 5 ± 0.3 (P = 0.014), GEDVi from 1253 ± 165 to 829 ± 161 (P = 0.001) and EVLWi from 16.1 ± 7.1 to 8.7 ± 1.2 (P = 0.03).

Table 1 Effect of CVVH on hemodynamic parameters in correct and faulty catheter positions

Conclusion

In critically ill patients treated with CVVH, the hemodynamic parameters obtained by PiCCO transpulmonary thermodilution can be influenced: EVLWi increases while CI and GEDVi drop. We hypothesize that this may be due to the position of the CVL and dialysis catheters.