In recent years, after all the attention has been focused on the dose for continuous renal replacement therapy (CRRT) in sepsis and systemic inflammation response syndrome (SIRS), the relatively negative results of all those studies did urge our expectations on new approaches regarding CRRT in sepsis and SIRS. So far, after the failure of the major randomized studies on dose, attention is now drawn to new membranes that could better eliminate massive amounts of unbound mediators in wider spectrum and also in greater magnitude Nevertheless, for septic acute kidney injury, the recommended dose will remain 35 ml/kg/h until the IVOIRE (hIgh VOlume in Intensive Care) study will be published. In this new armamentarium, we have distinguished the first tools that can still be called membranes ranging from AN69 Surface Treated (ST), SEPTEX, polymethylmetacrylate, to Oxiris that can still run with a CRRT device. Polymyxin B is still a kind of membrane although it has a larger surface, but it can run in a hemoperfusion system and is also much more selective. Adsorptive columns and sorbents are not anymore membranes but are seen as cartridges as the surface is extremely huge when compared with that of membranes (more than 500 m). They can still run in a hemoperfusion device. At the very end, we do have apheresis or selective plasma exchange (also very close to sorbents and columns) but we have very few data up to now regarding sepsis. Regarding spectrum, CytoSorb seems to be very promising although it is not able to capture endotoxin and IL-10. Oxiris is also promising as it can capture endotoxin and cytokines. AN69 ST is very powerful to capture numerous cytokines and especially high-mobility group box 1 protein (a very upstream cytokine). Polymethylmetacrylate has also the power to capture endotoxin and numerous other cytokines probably with a larger magnitude than Oxiris although this is not proven. Lastly, high-porosity membranes (Septex) may play a role especially when used in continuous venovenous hemodialysis mode. At the end, if we look for a more enlarged spectrum and a higher magnitude, CytoSorb might be seen as the most promising although not having the ability to fix endotoxin. Future studies will tell us which membrane or sorbent will be most useful in the adjunctive treatment for sepsis.
Adequate feeding of critically ill patients under continuous renal replacement therapy (CRRT) remains a challenging issue. We performed a systematic search of the literature published between 1992 and 2012 using the quorum guidelines regarding nutrition in intensive care unit patients treated with CRRT. Daily recommended energy requirements during CRRT are between 25 and 35 kcal/kg with carbohydrates and lipids accounting for 60-70% and 30-40% of calorie intake, respectively. Daily protein needs range from 1.5 to 1.8 g/kg. Indirect calorimetry corrected for CRRT-induced CO2 diversion should be used to more correctly match calorie intake to the real needs. This type of tool is not yet available but hopefully soon. Electrolyte deficit as well as overload have been described during CRRT but, in general, can be easily controlled. Although not strongly evidenced, consensus exists to supplement important micronutrients such as amino acids (glutamine), water-soluble vitamins and trace elements.
This study confirms in humans an age-related increase in plasma urea levels (r ؍ 0.62; P < 0.001; y ؍ 0.229x ؉ 18.26) and no correlation between plasma creatinine and age (r ؍ 0.06; NS). Fractional urea excretion (FE urea) decreases with age (r ؍ ؊0.41; P < 0.001; y ؍ ؊0.226x ؉ 55). Comparing urea and creatinine clearances, measured in 19 young and in 15 old women, a larger decrease of urea clearance (؊56%) compared with the creatinine clearance (؊43%) was observed as expected, explaining the lower FE urea in the elderly. In old women, the daily urea excretion was 27% and the daily creatinine excretion was 42% lower than in young women. An age-related decrease of same magnitude in both creatinine production and creatinine clearance explains why plasma creatinine remains stable with increasing age. The observation of a more important decrease in urea clearance (56%) than in urea production (27%) in older women led to an expected increase in plasma urea of 29%. These observations incited a comparison of biochemical profiles from younger and older patients with the syndrome of inappropriate secretion of antidiuretic hormone (SIADH). Young patients with SIADH present lower mean plasma urea (18 ؎ 8 mg/dl) and higher mean FE urea (58 ؎ 14%), compared with both young control subjects (mean plasma urea 27 ؎ 7 mg/dl; mean FE urea 46 ؎ 10%) and old patients with SIADH (mean plasma urea 29 ؎ 8 mg/dl; mean FE urea 44 ؎ 15%). Physicians must realize that frankly low plasma urea values and high FE urea values can be expected only in young patients with SIADH, whereas old patients with SIADH will present values of plasma urea and FE urea in the same range than young control subjects. However, old patients with SIADH show still lower mean plasma urea values and higher mean FE urea values, compared with old control subjects (mean plasma urea 39 ؎ 8 mg/dl; mean FE urea 36 ؎ 9%), in whom plasma urea values between 40 and 50 mg/dl must be considered as usual.Clin J Am Soc Nephrol 1: 909 -914, 2006. doi: 10.2215/CJN.00320106 B oth plasma urea and fractional urea excretion (FE urea) are considered as useful biochemical parameters in the differential diagnosis of salt-depleted hyponatremic and patients with the syndrome of inappropriate secretion of antidiuretic hormone (SIADH) (1-3). Hyponatremia in SIADH is usually associated with a low plasma urea as a result of a high FE urea (4), whereas in hyponatremia that is caused by salt depletion (SD), plasma urea usually is increased as a result of an abnormal low FE urea (5) (prerenal uremia). Unfortunately, the usefulness of plasma urea and FE urea in discriminating SIADH and SD is limited by an important degree of "overlapping" values. In earlier work (6), we noted that plasma urea values Ͼ30 mg/dl were observed in 82% of patients with SD, whereas plasma urea values Ͻ30 mg/dl were seen in 79% of patients with SIADH. Eighty-two percent of the patients with salt-depleted hyponatremic presented FE urea values Ͻ50%, but only 52% of the patients with SIADH showed FE urea values Ͼ50...
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