Abstract
Continuous blood purification is now widely applied in many ICUs for continuous renal replacement therapy (CRRT) and its efficacy in the treatment of acute renal failure is now widely accepted. Of the various types of continuous blood purification methods available, such as continuous hemofiltration (CHF) and continuous hemodialysis (CHD), continuous hemodiafiltration (CHDF) has gained the popularity in critical care in Japan. However, the efficacy of CHDF in removing cytokines for non-renal indications, such as sepsis, severe acute pancreatitis and ARDS, remains controversial. We have reported that the clearance of various cytokines with CHDF positively and significantly correlates to pre-CHDF blood levels. The higher the cytokine blood level is, the larger its clearance with CHDF is. We also found that the blood level of cytokines significantly decreased with 3 days of CHDF in patients whose pre-CHDF blood levels were high, but that the blood level of cytokines did not decrease with 3 days of CHDF in patients whose pre-CHDF blood levels were low. We also found that the degree of the decrease in the blood level of cytokines was significantly correlated to the degree of improvement in organ dysfunction, indicating a clinical benefit of cytokine removal with CHDF. The removal of cytokines by CHDF seems to be not only through convection and diffusion which are the expected mechanisms of substance removal with CHDF, but also through the adsorption of cytokines to the hemofilter membrane. The polymethyl methacrylate membrane (PMMA) hemofilter is the best choice for CHDF in this regard since the PMMA hemofilter can adsorb cytokines better than hemofilters using other types of membranes.
In conclusion, CHDF is effective in removing cytokines from the bloodstream when the pre-CHDF cytokine blood levels of the patient are high and when CHDF is performed with a PMMA membrane hemofilter. Our results clearly indicate that CHDF can be applied for non-renal indications aimed at removing causative humoral mediators such as cytokines.
