Effect of continuous hemofiltration (CVVHF) on inflammatory parameters

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Introduction

Hemofiltration and hemodialysis are very important life saving procedures in the management of critically ill patients. The ability of these techniques to remove low molecular weight toxic substances from the circulation is very well documented, but little is known about their influence on inflammatory or lipid peroxidation parameters. Procalcitonin, PMN-elastase and Neopterin can be used as diagnostic and prognostic parameters to monitor critically ill patients and to control therapeutic interventions. For these reasons the aim of this preliminary investigation was to evaluate the effect of continuous veno-venous hemofiltration (CVVHF) versus intermittent hemodialysis (IHD) on plasma concentrations of inflammatory (Neopterin, PMN-elastase, Procalcitonin) and lipid peroxidation parameters (Malonic dialdehyde, Peroxides, Antibodies to oxidised LDL).

Patients and methods

We investigated 20 consecutive mechanically-ventilated critically ill patients (n=12, 25-86 years, 7 male, 5 female) under CVVHF (blood flow 100-150 ml/min, ultrafiltrate 1-2 l/h). Cellulose triacetate membranes (FB-21U Biorena) (n=3) and polyacrilonitrile membranes (AN69 Hospal) (n=9) were used in this group. In the IHD group (n=8, 31-86 years, 5 male, 3 female) (blood flow 200-250 ml/min, dialysate flow 500 ml/min) polysulfone membranes (F8HPS Fresenius) were applied. Blood samples were drawn at 0, 10, 60 and 240 min after starting the procedure from before and after the membrane. Serum and plasma samples were drawn at 0, 10, 60 and 240 min after the onset of CVVHF or IHD. After 30 min at 4°C, the blood samples were centrifuged at 3000 × g.

Malonic dialdehyde (MDA) determination was done by HPLC according to the method of Wong et al Neopterin (NPT), Elastase, Procalcitonin (PCT) and antibodies to oxidised LDL (oLAb) were determined by commercially available ELISA methods. Determination of peroxides was performed by an enzymatic method based on the peroxidase reaction with tetramethylbenzidine as a chromogenic substrate.

Statistical analysis

In the case of a Gaussian distribution the statistical analysis was done by the t-test. Other distributions were assayed by the χ² test.

Results

PCT and oLAb remained more or less constant in all observations. No statistically significant differences were observed before and after membrane passage or between the CVVHF and the IHD group. PMN-elastase concentrations increased constantly from start to the end of CVVHF and IHD. MDA levels reached the maximum 10 min after the onset of CVVHF and IHD. Again lower concentrations were observed in the IHD group compared with CVVHF. Peroxides were not detectable in most of the samples of the CVVHF group. In the IHD group, there were statistically significant differences in peroxide concentrations before and after the membrane passage. Neopterin concentrations decreased significantly after membrane passage in both CVVHF and IHD group. The decrease was more pronounced in the IHD group. Details in data for all parameters in both groups are presented in Table 1.

Discussion

For inflammation parameters (oLAb, NPT, PCT) no significant increases in concentrations could be observed. This indicates that no pronounced inflammatory reactions arise due to the dialysis procedure. The decrease in Neopterin concentrations after membrane passage shows efficient clearance of low molecular weight substances during CVVHF and IHD. In contrast, PMN-elastase concentrations increased from start to the end of CVVHF and IHD thus indicating PMN activation rather than activation of macrophages. In case of lipid peroxidation parameters, we found a peak in MDA concentrations 10 min after onset of CVVHF and IHD, which might be a consequence of PMN activation after contact with the membranes. In conclusion, our data suggest that even beneficial procedures like CVVHF or IHD may activate inflammatory and lipid peroxidation processes.

Table 1 Concentrations of inflammatory and lipid peroxidation parameters in CVVHF and IHD patients