New insights regarding rationale, therapeutic target and dose of hemofiltration and hybrid therapies in septic acute kidney injury

Mediator removal from tissue (capillary blood compartment, CABC) and transport to the central circulation (central blood compartment, CEBC) must be effective. Effectiveness through a passive mechanism seems unlikely as the surface of CEBC (30 m(2)) is smaller than CABC (300 m(2)) whereby the former will be a limiting factor in passive transport. According to studies, a high exchange volume can induce an 80-fold increase in lymphatic flow. This results in displacement (active transport) of mediators to CEBC. Recent studies have shown that the delivered dose constitutes the mainstay of continuous renal replacement therapy. However, these results are not likely to change the recommendation: 35 ml/kg/h, adjusted for predilution, in septic acute kidney injury (AKI). Recently, studies were focusing on global intensive care unit AKI. In non-septic AKI, those studies show that 20-25 ml/kg/h was optimal. The DO-RE-MI trial underscored the importance of delivery which could be obtained by targeting doses between 5 and 10 ml/kg/h higher than prescribed. Until the IVOIRE trial becomes available, septic AKI should be treated by continuous veno-venous hemofiltration at 35 ml/kg/h. In non-septic AKI, 25 ml/kg/h remains optimal.

Septic acute kidney injury: the culprit is inflammatory apoptosis rather than ischemic necrosis

For a long time, acute kidney injury (AKI) was considered to be a primarily hemodynamic condition characterized by a reduction of renal blood flow, induced by either cardiogenic or distributive (septic) shock. Consequently, all efforts to treat AKI were essentially concentrated on increasing renal flow by enhancing cardiac flow output and perfusion pressure. At the beginning of this decade, Bellomo and co-workers produced new and intriguing data in an animal model of septic AKI that undermined existing concepts. They observed that medullar and cortical renal blood flow were both maintained and even increased in septic shock, underscoring that septic AKI was a totally different physiological phenomenon than nonseptic AKI. Also, apoptosis was found to play a more important role in sepsis and septic shock than pure necrosis. Despite these findings, the role of apoptosis as a main mechanism of organ dysfunction remains topic of debate.

Continuous hemofiltration in 2009: what is new for clinicians regarding pathophysiology, preferred technique and recommended dose?

In the last years, publications have questioned the classical dose of 35 ml/kg, but are those studies strong enough in terms of scientific power in order to change our practice? We will try to settle some recommendations for clinicians. Manipulation of dose, porosity, and combinations have yielded promising findings. However, conclusive evidence based on randomized trials remains scarce, limiting the practical implementation in daily practice. From the few designed studies, it is safe to say that optimization of delivered dose has a proven positive effect. An ultrafiltration rate of around 35 ml/kg/h, with adjustment for predilution, can be recommended for the septic patient. Recent studies do not have enough power to change this recommendation in view of its shortcomings. Finally the recommendation is to keep going with a continuous technique, a pure continuous veno-venous hemofiltration mode, and at a dose of 35 ml/kg/h while waiting for other studies to be published.

[High-volume hemofiltrations]

Almost 10 years ago, standard hemofiltration (HF) was carried out at an ultrafiltration (UF) rate of not more than 2 1/hour and only a predilution variant was usually used. However, after Ronco published the results of his study early in the 20th century the situation changed as this study provided evidence that increasing an UF rate up to 35 ml/kg/hr had a positive effect in patients with acute renal failure (ARF). At the same time, there was a new standard for the determination of high-volume HF (HVHF) and new concepts generalized in this paper have emerged. Moreover, two different procedures of HVHF: (1) a continuous high-volume technique providing a rate of 50-70 ml/kg/hr during 24 hours; (2) an intermittent high-volume technique, the so-called HVHF with short courses of treatment, a very high volume at a rate of 100-120 ml/kg/hr during 4-8 hours. Later on this technique came to be called pulse HVHF. Both methods are designated by the abbreviation HVHF, but their concepts and results are slightly different, as will be discussed below. As for the higher doses of plasma replacement therapy, it is necessary to put the results of two recently published studies into routine clinical practice of continuous vein-venous HF (CVVHF) as soon as possible just in 2008. The performed studies suggest the most important role of adequate dosage of CVVHF and show that the use of a dose of 35 ml/kg/hr in critically ill patients with ARF increased survival by almost 20%. These two studies contain today's most vivid evidence, but one awaits the results of other studies that confirm (or do not confirm) these conclusions. In the world where more importance is attached to evidence-based medicine, two first-level studies will yield Stage A recommendations that may be guided by any intensive care specialist using CVVHF in expectation of the results of on-going investigations. Nevertheless, many difficulties are to be surmounted while introducing new procedures into routine intensive care practice. The most cardinal problems are those associated with requirements for blood flow via vascular access with pre- and postdilution procedures, with the type of employed membranes and substituting liquids, and with a possible need for concomitant dialysis. From the strictly practical standpoint, introduction of these changes into routine intensive care practice may be extremely difficult. This will undoubtedly require that physicians and nurses should make joint effects.

Evaluation of an automated repetitive sequence-based PCR system for subtyping Enterobacter sakazakii

Enterobacter sakazakii is regarded as a ubiquitous organism that can be isolated from a wide range of foods and environments. Infection in at-risk infants has been epidemiologically linked to the consumption of contaminated powdered infant formula. Preventing the dissemination of this pathogen in a powdered infant formula manufacturing facility is an important step in ensuring consumer confidence in a given brand together with the protection of the health status of a vulnerable population. In this study we report the application of a repetitive sequence-based PCR typing method to subtype a previously well-characterized collection of E. sakazakii isolates of diverse origin. While both methods successfully discriminated between the collection of isolates, repetitive sequence-based PCR identified 65 types, whereas pulsed-field gel electrophoresis identified 110 types showing > or =95% similarity. The method was quick and easy to perform, and our data demonstrated the utility and value of this approach to monitor in-process contamination, which could potentially contribute to a reduction in the transmission of E. sakazakii.

Characterization of thioredoxin y, a new type of thioredoxin identified in the genome of Chlamydomonas reinhardtii

The sequencing of the Arabidopsis genome revealed a multiplicity of thioredoxins (TRX), ubiquitous protein disulfide oxido-reductases. We have analyzed the TRX family in the genome of the unicellular green alga Chlamydomonas reinhardtii and identified eight different thioredoxins for which we have cloned and sequenced the corresponding cDNAs. One of these TRXs represents a new type that we named TRX y. This most probably chloroplastic TRX is highly conserved in photosynthetic organisms. The biochemical characterization of the recombinant protein shows that it exhibits a thermal stability profile and specificity toward target enzymes completely different from those of TRXs characterized so far.

Murine dendritic cells derived from myeloid progenitors of the thymus are unable to produce bioactive IL-12p70

Dendritic cells (DC) are present at low density in the thymus where they mediate negative selection of self-reactive thymocytes. Previous reports suggest that thymic DC (TDC) are a single population of lymphoid-related DC. In this study, we documented the presence in the adult mouse thymus of an additional population of TDC exhibiting a myeloid phenotype (CD11c(+) CD8alpha(-) CD11b(+)). This population, which can be purified, represented approximately 20% of the total TDC and differs from the population of lymphoid TDC (CD11c(+) CD8(+) CD11b(-)) by its incapacity to produce IL-12p70 under double stimulation by LPS and anti-CD40. Furthermore, using an original culture system allowing expansion of DC from myeloid progenitors, we demonstrated that DC exhibiting a similar myeloid phenotype can be derived from a common DC/macrophage progenitor resident in the adult mouse thymus. We found that, in contrast with myeloid splenic DC expanded in the same conditions, these cultured TDC were unable to produce IL-12p70 under double stimulation by LPS and anti-CD40 or LPS and IFN-gamma. Thus, our results suggest that 1) adult mouse thymus contains at least two phenotypically and functionally distinct populations of DC; and 2) cultured myeloid DC derived from thymus and spleen differ by their ability to produce IL-12p70. The mechanisms underlying the differences in IL-12-secreting capacities of the cultured splenic and thymic DC are under current investigation.

Evaluation of acute normovolemic hemodilution for surgical repair of craniosynostosis

This clinical report investigated the potential benefit of acute normovolemic hemodilution (ANH) as a blood-saving technique in the surgical repair of craniosynostosis. Over a 4-year period, 34 healthy children undergoing surgical repair of scaphocephaly or pachycephaly were randomly assigned to two groups of 17 patients each. Patients of the first group (ANH group) were submitted to ANH (target Ht: 25%) immediately before surgery and patients of the second group (Control group) were not. During surgery, estimated blood loss was compensated with a 5% albumin solution and no autologous or homologous blood was transfused. At the end of surgery, intraoperative blood loss (mean +/- SD) calculated on the basis of the Ht value and the children weight was 21.3+/-8% of the estimated blood volume (EBV) in the ANH group and 24+/-6.6% in the Control group. Children of the ANH group received their autologous blood (18.9+/-3.3% of EBV) systematically at the end of surgery. In the postoperative period, homologous blood was transfused when the Ht value was equal or less than 21%. Both groups were comparable regarding age, weight, type of craniosynostosis, duration of surgery, EBV, and preoperative Ht value. No difference was observed between ANH and Control groups in the number of patients who received homologous blood (15/17 and 14/17, respectively), in the amount of homologous blood transfused (17+/-4.7% and 19.6+/-6.3% of the EBV, respectively), and in the Ht value before hospital discharge (29.4+/-5.0% and 30.7+/-4.9%, respectively). In conclusion, this report suggests that ANH reduces neither the incidence of homologous transfusion nor the amount of homologous blood transfused in this series of children undergoing surgical repair of craniosynostosis.