| Objective:With the development of recent biomedical technologies, blood purification, which originally developed for the treatment of renal failure, had subsequently been applied to critical care. It had reported that various blood purification techniques had the effects to remove excess humoral mediators in excess inflammation which had been proved to play an important role in the pathogenesis of critical illnesses, such as severe sepsis and septic shock. While the cytokine-removing effects of blood purification therapies are still controversial. The clinical efficacy of high-volume hemofiltration (HVHF), a blood purification technique with improved cytokine removing capacity due to enhanced convection effect, has been reported in the treatment of septic shock. The techniques of Continuous Veno-Venous Hemofiltration (CVVH) effectively manage the removal of solutes and excessive fluid in the critically ill patient to achieve metabolic and fluid volume control. In CVVH, replacement solution may be infused before the filter, i.e. pre-dilution, or after the filter, i.e. post-dilution. The pre-dilution mode is defined as the blood is mixed with replacement solution before the filter and then the excess solute and water are removed. The post-dilution is defined as the blood flows to the filter and remove the solute and water directly and then the blood is mixed with replacement solution, which can be keep the balance of circulation. The two modes have different solute clearance. As for the the pre-dilution mode, it has been identified as a useful strategy which can delay clotting and improve the duration of circuit life. But the solute clearance was proved to be lower than the post-dilution mode due to blood mixing with replacement solution before the filter. Pre-dilution mode reduced small-molecule weight solute clearance significantly and can be compensated for by increasing the volume of ultrafiltration or blood flow rate. We conducted a prospective cross over study in a cohort of critically ill patients, to comparing plasma interleukin-6(IL-6) clearance, circuit life during pre-dilution 100% CVVH and pre-dilution 50% CVVH.Methods:We conducted a prospective cross over study in a cohort of critically ill patients from January 1,2009 to December 1,2009, to comparing plasma IL-6 sieving coefficient (SC), plasma IL-6 level(pre-filter and post filter), filter lifespan during pre-dilution 100% CVVH and pre-dilution 50% CVVH. Both modalities were administered based on a prescription of 35 ml/kg/h and using polyacrylonitrile filters.Results:During pre-dilution 50% CVVH, median plasma IL-6 SC was not significantly different at 2 hours (0.1017, interquartile range(IQR) 0.0794-0.1422) and 6 hours(0.0988, IQR 0.0667-0.1287), (p=0.278). Significant difference was found at 6 hours(0.0988, IQR 0.0667-0.1287) and 12 hours(0.0562, IQR 0.0277-0.0906), (p=0.009). During pre-dilution 100% CVVH, median plasma IL-6 SC was not significantly different at 2 hours(0.0724, IQR 0.0498-0.1140) and 6 hours(0.0647, IQR 0.0424-0.1128), (p=0.822). The median plasma IL-6 SC at 12 hours(0.0422, IQR 0.0240-0.0922) is lower than 6 hours(0.0647, IQR 0.0424-0.1128), nonetheless this difference did not reach statistical significance(p=0.136). There were not significant differences on plasma IL-6 SC at 2 hours(p=0.079), 6 hours(p=0.079) and 12 hours(p=0.308) between pre-dilution 100% CVVH and pre-dilution 50%. Surprisingly, the plasma IL-6 level show very significant difference between pre-filter and post-filter(159.5pg/ml, IQR99.0-238.0 vs 197.9pg/ml, IQR 121.4-278.7)(p=0.000).The median circuit life for pre-dilution 100% CVVH was 840min(95% confidence interval(CI) 687-993). The median circuit life for pre-dilution 50% CVVH was 840min(95%CI 581-1099). A Log Rank Test of the 16 paired comparisons showed the difference in circuit life between pre-dilution 100% and pre-dilution 50% CVVH was nothing statistically significant (log rank test:χ2=0.04, p=0.84) Conclusion:Pre-dilution 100% CVVH appears to warrant more plasma IL-6 convective clearances than pre-dilution 50%. Pre-dilution 50% don't decrease circuit life by limiting filtration fraction below 20%. |
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