Simplified Citrate Anticoagulation for CRRT Without Calcium Replacement.

Since 2012, citrate anticoagulation is the recommended anticoagulation strategy for continuous renal replacement therapy (CRRT). The main drawback using citrate as anticoagulant compared with heparin is the need for calcium replacement and the rigorous control of calcium levels. This study investigated the possibility to achieve anticoagulation while eliminating the need for calcium replacement. This was successfully achieved by including citrate and calcium in all CRRT solutions. Thereby the total calcium concentration was kept constant throughout the extracorporeal circuit, whereas the ionized calcium was kept at low levels enough to avoid clotting. Being a completely new concept, only five patients with acute renal failure were included in a short, prospective, intensely supervised nonrandomized pilot study. Systemic electrolyte levels and acid-base parameters were stable and remained within physiologic levels. Ionized calcium levels declined slightly initially but stabilized at 1.1 mmol/L. Plasma citrate concentrations stabilized at approximately 0.6 mmol/L. All postfilter ionized calcium levels were <0.5 mmol/L, that is, an anticoagulation effect was reached. All filter pressures were normal indicating no clotting problems, and no visible clotting was observed. No calcium replacement was needed. This pilot study suggests that it is possible to perform regional citrate anticoagulation without the need for separate calcium infusion during CRRT.

Formation of carbonated apatite particles from a supersaturated inorganic blood serum model.

Pathological calcification is common among for instance dialysis patients, and this causes an increase in mortality risk. An elevated serum phosphate concentration among those patients strongly correlates to this increase. In this work investigations of the conditions, composition, crystallinity and morphology of in vitro calcification are performed and related to results from in vivo studies. The study was performed under conditions mimicking physiological ones, i.e. a pH around 7.40, a temperature of 37 degrees C, an ionic strength of 150 mM and ion concentrations close to those in human serum including the effects of elevated phosphate concentrations. The course of precipitation involves an initial precipitate that subsequently re-dissolves to give another precipitate, in accordance with the well-known Ostwald ripening theory. The final bulk precipitate consists of a macroscopically amorphous carbonated apatite. The amorphous apatite is formed from assemblies of spherical particles in the mum range, in turn composed of nano-crystalline needles of about 10 x 100 nm. Even the initially formed precipitate, as well as a small amount of precipitate that occurs on the liquid surface, consist of a carbonated calcium phosphate. The in vitro observed carbonated apatite bears strong resemblance to in vivo cardiovascular calcification known from literature.

The observation of nano-crystalline calcium phosphate precipitate in a simple supersaturated inorganic blood serum model - composition and morphology.

Aim. Calcium phosphate deposition in blood vessels is correlated to increased mortality risk. In this study, the formation of solid calcium phosphate in an in vitro solution mimicking the inorganic part of blood serum was studied. Methods. The precipitates formed were analyzed using several experimental techniques, including infrared spectroscopy, Raman spectroscopy, X-ray energy dispersive spectroscopy, chemical analysis of combustion gases, thermogravimetric analysis, as well as transmission electron microscopy and scanning electron microscopy. Results. The results indicate a microscopically amorphous but nano-crystalline material with an overall apatite structure. A plausible stoichiometry was determined to Ca5(PO4)3(HCO3).4H2O with an estimated solubility constant of 6.10-39 (mol/L)9. Bicarbonate in the water solution was shown to be essential for the precipitation, giving implications for in vitro studies. Conclusions. The calcium phosphate formed in this study shows many similarities to pathological calcium phosphates regarding composition, morphology and crystallinity.