Granulocyte Elastase, β-Thromboglobulin, and C3D during Acetate or Bicarbonate Hemodialysis with Hemophan® Compared to a Cellulose Acetate Membrane

Twenty-two patients were dialysed in a cross-over design using Hemophan® or cellulose acetate membranes. The dialysate buffer was acetate (n = 12) or bicarbonate (n = 10). Blood was sampled at 0, 15, 60 and 180 min and mean values were adjusted for changes in total protein in each sample. At 15 min during dialysis a decrease in leukocytes and platelets occurred with both membranes, irrespective of the buffer (Wilcoxon, p < 0.006). During dialysis, increases were found in granulocyte elastase inhibitor complex (E-α1-PI), β-thromboglobulin and C3d. β2-microgrobulin was not significantly changed in blood after dialysis with Hemophan® or cellulose acetate membranes with bicarbonate buffer. Side effects were more pronounced at 180 min during dialysis with bicarbonate in patients using cellulose acetate than with Hemophan® (p = 0.021, n = 8). Hemophan® seemed to be more favourable than cellulose acetate membranes in regard to leukopenia and E- α1-PI. The dialysate buffer may also alter membrane biocompatibility.

Immune function and leukocyte sequestration under the influence of parenteral lipid emulsions in healthy humans: a placebo-controlled crossover study

BACKGROUND

It remains unclear whether immune modulation by lipids contributes to the high risk of infectious complications that is associated with the use of parenteral nutrition. Although mixed long- and medium-chain triacylglycerol (LCT-MCT)-containing emulsions, but not pure LCT emulsions, activate neutrophils and impair crucial leukocyte functions in vitro, in vivo studies have failed to corroborate these findings.

OBJECTIVES

The present investigation was conducted to evaluate the effects of LCT and LCT-MCT on immune function in healthy humans and to assess whether the lack of in vivo effects results from sampling errors due to extravascular sequestration of activated neutrophils.

DESIGN

Saline, LCT-MCT, and LCT emulsions were administered intravenously for 4.5 h to 12 healthy volunteers in a randomized crossover design. Plasma triacylglycerol concentrations were clamped at a clinically relevant concentration of 3-5 mmol/L. Leukocyte population counts and neutrophil activation were assessed before and after infusion. Leukocyte sequestration was evaluated by monitoring the distribution of Technetium-99m-labeled autologous leukocytes during infusions.

RESULTS

Whereas LCT exerted no greater effects than did saline, LCT-MCT significantly decreased lymphocyte counts. However, no evidence for neutrophil activation was found with either lipid. Moreover, the clearance of radiolabeled leukocytes from the liver, spleen, and lungs was not altered by any lipid, which suggested that lipid emulsions do not induce leukocyte sequestration.

CONCLUSIONS

Short-term infusion of LCT-MCT (but not LCT) to healthy humans modulates leukocyte population counts but, in clear contrast with the in vitro situation, does not induce neutrophil activation. These disparate findings cannot be explained by MCT-induced leukocyte sequestration.

Endothelium: the next frontier in biocompatibility

Vascular endothelium plays a central role in two specific functional systems. It controls vascular tone, hemostasis, and substance transport. The endothelium is the "docking station" for trapping, deactivation, and regeneration of activated blood compounds and provides the principal clearance mechanism for biologically active mediators released by different cell types. The second function is a regenerational one. During the period between insults (or between dialysis sessions), the endothelium has to restore the "first line of defense," that is, to regenerate the injured athrombogenic surface of the vessel wall and its antioxidative potential, defoliate damaged endothelial cells, and interpolated new ones. These two important endothelial activities are required over and above its basic functions. Future research in artificial organs must take into account that continuous or intermittent blood-membrane contact creates an altered endothelial response. These altered responses may result in adaptional reactions that may differ substantially in the acutely ill patient on continuous venovenous hemofiltration (CVVH) or in a stable patient on maintenance hemodialysis. By a reduction in such factors as immediate or delayed cell-cell interactions (direct or indirect), it may be possible to influence the long-term outcome of chronic hemodialysis patients. Other research should strive to enhance those factors of endothelial function that are essential in the defensive and restorative properties of endothelial tissue. This is especially important in such continuous therapies as CVVH, long-term membrane oxygenation, and artificial heart and blood vessels. Currently, there are more unanswered questions than possible answers concerning endothelial functions in long-term hemodialysis patients, but it is clear that excluding endothelial cell behavior from investigation of extracorporeal therapy in the future would be a substantial omission.

Gene expression of interleukin-1 beta during hemodialysis

It is still controversial whether the hemodialysis (HD) procedure is an inflammatory process in vivo. Therefore, we studied the gene expression of interleukin-1 beta (IL-1 beta) as a marker of inflammation in peripheral blood mononuclear cells (PBMC) of patients during HD by Northern blotting and polymerase chain reaction. Compared to PBMC separated pre-HD (1.0 densitometric units), the amount of IL-1 beta mRNA was increased in PBMC leaving the dialyzer (12.2 +/- 2 densitometric units, P < 0.01), but was not increased in PBMC re-entering the dialyzer from the systemic circulation (0.6 +/- 0.1 densitometric units) in all 12 patients studied. The maximal amount of IL-1 beta mRNA in PBMC was seen at five minutes after start of HD. There was a significant correlation between the increase in IL-1 beta mRNA and the increase in activated complement C5a (r = 0.71, P < 0.01). HD using less complement-activating membranes (hemophan, polysulfone, polyamide or polyacrylonitrile) resulted in no detectable IL-1 beta mRNA. Furthermore, a monoclonal antibody against human C5a reduced the increase in IL-1 beta mRNA by 83% (P < 0.05), indicating that C5a plays a major role for induction of IL-1 beta mRNA during HD. This study demonstrates that during HD with regenerated cellulose, gene expression for IL-1 beta takes place in PBMC.

Complement activation and cytokine production as consequences of immunological bioincompatibility of extracorporeal circuits

The use of devices which result in exposure of blood to artificial surface has gained increasing importance in routine medical and surgical practice. In the field of biocompatibility, attention has long been directed at the mechanisms of thrombus formation of surfaces. In recent years however, a special interest has emerged for the study of the immunological consequences of blood-artificial surface interactions, thus broadening the concept of hemocompatibility. The contact of blood with artificial devices results in the activation of a number of humoral and cellular processes involved in natural and in specific immunological recognition of foreign surfaces by the host, and in the secondary occurrence of acute and chronic adverse reactions in patients undergoing extracorporeal circulation. The purpose of this review is to discuss the mechanisms involved in immunological bioincompatibility of extracorporeal circuits, with particular emphasis on the molecular basis of the activation of the complement system, the role of endotoxins, and the induction of cytokine production by activated monocytes.