Homogeneous water nucleation in argon, nitrogen, and nitrous oxide as carrier gases.

Experimental results for homogeneous nucleation of water droplets in the presence of argon, nitrogen, and, for the first time, nitrous oxide as carrier gases are reported. The main objective of the study was to investigate the effects of different carrier gases on the nucleation rate. These gases differ in the number of atoms comprising the molecule, which affects the expansion ratio required to reach the target nucleation temperature. The experiments cover nucleation temperatures from 220 to 260 K, nucleation pressures from 40 to 73 kPa, supersaturations of 6.5-20, and nucleation rates ranging from about 4 × 105 to 4 × 109 cm-3 s-1. The new data obtained with a modernized expansion chamber utilizing the nucleation pulse method show good agreement with the available literature data. Another important point of our work is the application of real gas corrections to calculate the nucleation temperature and supersaturation. The results show that the influence of carrier gases on nucleation rate in the investigated pressure range is modest (less than a factor of 7), while without the real gas correction, the apparent effect of carrier gas is significant, with differences as high as a factor of 90.

Insight into the formation of N-nitrosodimethylamine in metformin products.

An effective analytical method for the quantification of N-nitrosodimethylamine (NDMA) using a liquid chromatography coupled with tandem mass spectrometry was developed and applied to a process optimization study of the production of metformin film coated tablets in order to identify the key factors behind the NDMA formation in metformin products. The method uses a linear gradient elution with mobile phases 0.1 % formic acid in water for chromatography and methanol for chromatography and a column Acquity UPLC HSS T3 1.8 µm. The use of the tandem mass spectrometry in a positive ion mode with an atmospheric pressure chemical ionization allows for the use of an isotopically labelled internal standard and an external calibration standard. The method was validated according to the guidelines of International Council for Harmonization in terms of limit of detection and quantification, linearity, precision, accuracy and method selectivity. To further justify the effectiveness of the method, a comparison between two laboratories was performed using a linear regression testing. Both methods give comparable results. 469 samples of both metformin active pharmaceutical ingredient and film coated tablets were analysed and the key factors behind NDMA formation were identified. Hypotheses explaining the mechanism were formulated and confronted with measurements and scientific literature. Protective measures to prevent NDMA contamination in metformin products were drawn.

Possible Anomaly in the Surface Tension of Supercooled Water: New Experiments at Extreme Supercooling down to -31.4 °C.

The surface tension of water is suspected to show a substantial increase at low temperatures, which is considered to be one of the many anomalies of water. The second inflection point (SIP) anomaly, originally claimed to be at around -8 °C, was experimentally refuted down to -25 °C by Hrubý et al. (J. Phys. Chem. Lett. 2014, 5, 425-428). Recent molecular simulations predict the SIP anomaly near or even below the homogeneous freezing limit of around -38 °C. To contribute to an ongoing discussion about the SIP anomaly, new experiments focused on extreme levels of supercooling were carried out in this study. Unique experimental data down to -31.4 °C were collected using two measuring techniques based on the capillary rise method. A significant deviation from the extrapolated IAPWS formulation R1-76(2014) for surface tension of ordinary water was detected below -20 °C. Contrary to previous data, new experiments provide room for an anomaly in the course of surface tension in the deeply supercooled region.

Influence of the new standardized clinical cryopreservation/slow thawing protocol on immunogenicity of arterial allografts in rats.

OBJECTIVES AND DESIGN: At the present time there are two waiting list for patients with vascular prosthetic infection indicated for arterial transplantation in the Czech Republic. The inclusion of each patient for cold-stored or cryopreserved arterial transplantation is the preference of indicating surgeon. In this experimental work we studied the immunogenicity of rat aortal allografts treated by our new clinical cryopreservation/slow thawing protocol. MATERIAL AND METHODS: Brown-Norway (BN) (N = 6, 203-217 g) or Lewis (LEW) (N = 6, 248-254 g) abdominal aortal grafts treated in accordance with our new clinical cryopreservation/slow thawing protocol were orthotopically transplanted to Lewis recipients (N = 12, 191-245 g). Aortal wall histology and infiltration by recipient immune cells, as well as donor specific anti MHC class I and II antibodies in recipient serum were studied in both isografts and allografts on day 30 postransplant. Core data of cryopreserved allografts were compared to our previous data of cold-stored aortal allografts treated in accordance with our clinical cold-storage protocol. RESULTS: Cryopreserved allografts showed regular morphology of aortal wall with clear differentiation of all three basic anatomical layers on day 30 postransplant. Intimal layer showed no hyperplasia, luminal surface was covered by endothelial cells. No statistical difference was observed in tunica media thickness between isografts and allografts. The medial layer showed no necrosis, shrinkage or immunoglobuline G deposition in any experimental group. The adventitial infiltration by immune cells was significantly higher (P<0.05) in allografts. Cryopreserved allografts showed significant lower activation of both cell- and antibody mediated immunity compared to historical data of cold-stored allografts. CONCLUSION: Aortal wall histology of rat allografts treated by our new standardized clinical cryopreservation/slow thawing protocol was comparable to that of the cryopreserved isografts on day 30 posttranspant. The immunogenicity of cryopreserved aortal allografts was significantly lower compared to that of cold-stored aortal allografts.

Comparison of Different Thawing Protocols in Human Cryopreserved Venous Grafts.

BACKGROUND: The aim of our study was to assess the impact of different thawing protocols on morphological changes arising in cryopreserved human saphenous vein grafts. METHODS: The study was performed in 12 saphenous vein grafts harvested in brain death donors. Storage in the vapor phase of liquid nitrogen for 3 or 5 years followed. Two thawing protocols were tested: slow thawing in a refrigerator at temperature +4°C for 2 hr and rapid thawing-in a water bath at +37°C. Grafts were processed for scanning electron microscopy. Comparisons of continuous parameters under study between experimental groups were performed using the t-test (age, cold ischemia time, exposure to cryoprotectant, time of storage, total thawing time, mean thawing rate, morphology scoring of thawed HSVG) and the median test (HSVG length). Categorical parameters (sex and blood group) were formally tested using the chi-square test. RESULTS: All samples were evaluated according to morphological changes and scored in terms of morphologically intact endothelium, confluent endothelium with structural inhomogeneity, disruption of the intercellular contacts, separation of the endothelial cells, complete loss of the endothelium, and damage of the subendothelial layers. There is no statistically significant difference between the sample sets at the significance level of 0.05. There was no association with donors' age, sex, and time of storage. CONCLUSIONS: Human cryopreserved saphenous vein grafts in our experimental work showed no difference in terms of structural deterioration of the endothelial surface and basal membrane depending on different thawing protocols used.

The role of intraperitoneal ropivacaine in laparoscopic appendicectomy: a prospective, double-blinded randomized control Australian study.

BACKGROUND: Currently, intraoperative use of local anaesthetic is not routinely given in all laparoscopic appendicectomies. Although its use has been widely studied in laparoscopic hernia repairs, gynaecological laparoscopy and laparoscopic cholecystectomies, there are no published trials of the use of intraperitoneal local anaesthetic during laparoscopic appendicectomy in the Australasian setting. The aim of this study was to determine whether the use of intraperitoneal ropivacaine during laparoscopic appendicectomy will reduce the amount of post-operative opiate analgesia used, abdominal pain, post-operative nausea or vomiting, shoulder tip pain and length of hospital stay. METHODS: A randomized double-blinded placebo versus control trial was conducted with patients with clinically diagnosed appendicitis undergoing laparoscopic appendicectomy. Primary outcomes measured were the number of times the patient-controlled analgesia (PCA) button was pressed post-operatively and the average and total amount of fentanyl from PCA consumed during the post-operative period from 0 to 6 h and from 6 to 16 h. RESULTS: A total of 86 patients with 43 patients in the placebo normal saline group and 43 patients in the treatment ropivacaine group were included in the study. During the immediate post-operative period (0-6 h), there was a statistically significant reduction in the number of times the PCA button was pressed in the ropivacaine group compared to the normal saline group (16 versus 24 times, P = 0.02). CONCLUSION: Intraperitoneal ropivacaine has an analgesic effect for patients up to 6 h following emergency laparoscopic appendicectomy.

Immunosuppressive protocols with tacrolimus after cryopreserved aortal allotransplantation in rats.

OBJECTIVES AND DESIGN: The aim of our study was to simulate in rats all aspects and techniques used in our new clinical program of cryopreserved alloarterial transplantation and investigate the influence of two immunosuppressive protocols with tacrolimus on acute rejection of these allografts. MATERIALS AND METHODS: Cryopreserved abdominal aortic grafts were transplanted between Brown-Norway and Lewis rats. Tacrolimus (0.2 mg/kg daily) was administered from day 1 to day 30 (TAC1) or from day 7 to day 30 (TAC7), respectively. No immunosuppressed isogeneic (ISO) and allogeneic (ALO) rats combination served as control. Aortal wall infiltration by immunocompetent cells (MHC II+ cells of recipient origin) was studied on day 30 after transplantation. Flow cytometry was used for the analysis of day 30 sera for the presence of donor specific anti-MHC class I and II antibodies. RESULTS: The aortal allografts in both immunosuppressed groups showed regular morphology of aortal wall with no depositions of immunoglobulin G on day 30. The adventitial infiltration of non-immunosuppressed aortal allografts by MHC class II positive cells of recipient origin was significantly higher (ALO 20.7±6.7 cells, P<0.001) compared to both immunosuppressed groups (TAC1 5.9±5.5 cells, TAC7 6.1±5.1 cells). Day 30 sera from the allogeneic non-immunosuppressed animals decreased significantly the binding of fluorescence-labelled MHC class I (46.9±19.4%) and class II (65.8±11.9%) antibody to donors spleen cells compared with day 30 sera from both immunosuppressed groups (TAC1, anti-MHC class I 102.4±4.2%, p < 0.001, anti-MHC class II 102.6±6.0%), (TAC7, anti-MHC class I 79.9±3.3%, p < 0.001, anti-MHC class II 80.9±2.7%). CONCLUSION: Both immunosuppressed protocols with tacrolimus (administration from day 1 or from day 7 following transplantation) were able to suppress acute cell- and antibody-mediated rejection of cryopreserved abdominal aortic allografts processed in accordance with our new standardized clinical protocol.

Predictions of homogeneous nucleation rates for n-alkanes accounting for the diffuse phase interface and capillary waves.

Homogeneous droplet nucleation has been studied for almost a century but has not yet been fully understood. In this work, we used the density gradient theory (DGT) and considered the influence of capillary waves (CWs) on the predicted size-dependent surface tensions and nucleation rates for selected n-alkanes. The DGT model was completed by an equation of state (EoS) based on the perturbed-chain statistical associating fluid theory and compared to the classical nucleation theory and the Peng-Robinson EoS. It was found that the critical clusters are practically free of CWs because they are so small that even the smallest wavelengths of CWs do not fit into their finite dimensions. The CWs contribute to the entropy of the system and thus decrease the surface tension. A correction for the effect of CWs on the surface tension is presented. The effect of the different EoSs is relatively small because by a fortuitous coincidence their predictions are similar in the relevant range of critical cluster sizes. The difference of the DGT predictions to the classical nucleation theory computations is important but not decisive. Of the effects investigated, the most pronounced is the suppression of CWs which causes a sizable decrease of the predicted nucleation rates. The major difference between experimental nucleation rate data and theoretical predictions remains in the temperature dependence. For normal alkanes, this discrepancy is much stronger than observed, e.g., for water. Theoretical corrections developed here have a minor influence on the temperature dependency. We provide empirical equations correcting the predicted nucleation rates to values comparable with experiments.

Bedside lung ultrasound, mobile radiography and physical examination: a comparative analysis of diagnostic tools in the critically ill.

OBJECTIVE: To compare lung ultrasonography (LUS), chest xray (CXR) and physical examination (Ex) for the detection of pathological abnormalities in the lungs of critically ill patients. DESIGN, SETTING AND PARTICIPANTS: A prospective cohort study of 145 patients in the intensive care unit of a tertiary teaching hospital who were undergoing echocardiography for a clinical indication. MAIN OUTCOME MEASURES: Each patient was independently assessed by Ex, CXR and LUS on the same day. Examiners were asked to comment on the presence or absence and severity of pleural effusion, lung consolidation and alveolar interstitial syndrome (AIS). Independent expert examiners performed the LUS and an independent radiologist reported on the CXR. RESULTS: Ex, CXR and LUS were in fair agreement with each other in detecting a pulmonary abnormality (CXR v LUS, κ = 0.31; CXR v Ex, κ = 0.29; LUS v Ex, κ = 0.22). LUS detected more abnormalities than did CXR (16.2%; χ(2) = 64.1; P < 0.001) or Ex (23.5%; χ(2) = 121.9; P < 0.001). CXR detected more pleural effusions than LUS (9.3%; χ(2) = 7.6; κ = 0.39), but LUS detected more pleural effusions than Ex (22.8%; χ(2) = 36.4; κ = 0.18). There was no significant difference in the performance of LUS and CXR in quantifying the size of a pleural effusion (Z = -1.2; P = 0.23). Ex underestimated size compared with CXR or LUS. LUS detected more consolidation than CXR (17%; χ(2) = 115.9; P < 0.001) and Ex (16.2%; χ(2) = 90.3; P < 0.001). We saw no difference in performance between CXR and Ex in detecting lung consolidation (0.9%; χ(2) = 0.51; P < 0.48). LUS detected more cases of AIS than CXR (5.5%; χ(2) = 7.9; P = 0.005) and Ex (13%; χ(2) = 25.8; P < 0.001). CONCLUSIONS: There was only fair-to-moderate agreement between LUS, CXR and Ex in detecting pulmonary abnormalities, including pleural effusion, lung consolidation and AIS. The higher rate of detection from LUS, combined with its ease of use and increasing accessibility, makes for a powerful diagnostic tool in the ICU.

[A rare case of mobile atherosclerotic plaque with a high embolic potential in the femoral artery]. / Vzácný prípad mobilního aterosklerotického plátu ve femorální tepne s vysokým embolizacním potenciálem.

Atherosclerosis is a diffuse disease which may lead to the development of unstable atherosclerotic plaque. Its rupture can result in acute ischemic event. The atherosclerotic plaques with a mobile component are typical presentations of such instability and patients with these plaques are at high risk of acute ischemic events. In the current literature, substantial data regarding the mobile atherosclerotic plaques in carotid arteries and thoracic aorta is published. However there are almost no data concerning the mobile plaques in the peripheral arteries of the lower limbs. We present a rare case of a patient with generalized atherosclerosis, in whom an asymptomatic mobile atherosclerotic plaque in the common femoral artery with a high embolic potential was diagnosed. This plaque was successfully removed by femoral endarterectomy. On the basis of this case, we review the possibilities and limitations of the current imaging methods in detection of mobile plaques in the peripheral arteries. Moreover optimal therapeutic approaches in such patients are discussed.

Juxtarenal Modular Aortic Stent Graft Infection Caused by Staphylococcus aureus.

Introduction. We are presenting a case report of an infected modular abdominal stent graft. Case Presentation. A 67-year-old male patient three years after Cook's modular abdominal aortic aneurysm (AAA) graft implantation for juxtarenal AAA with an implantation of a stent extension into the right common iliac artery for type Ib endoleak. The patient was admitted into our center in severe condition with suspected retroperitoneal bleeding. Computed tomography angiography (CTAG) confirmed retroperitoneal bleeding in the right common iliac artery. An urgent surgical revision was indicated; destructed arterial wall around the stent extension in the right common iliac artery was discovered. Due to the severe state of health of the patient, a resection of the infected stent and affected arterial wall was performed, followed by an iliac-femoral crossover bypass. The patient was transported to the intensive care unit with hepatic and renal failure, with maximal catecholamine support. Combined antibiotic treatment was started. The patient died five hours after the procedure. The cause of death was multiorgan failure caused by sepsis. Hemocultures and perioperative microbiological cultures showed the infection agent to be Staphylococcus aureus methicillin sensitive. Conclusion. Stent graft infection is a rare complication. Treatment is associated with high mortality and morbidity.

Basilic Vein Transposition Used as a Tertiary Vascular Access for Hemodialysis: 15 Years of Experience.

INTRODUCTION: The quality of the life in patients requiring long term hemodialysis is directly proportional to the long-term patency of their vascular access. Basilic vein transposition for vascular access (BAVA) represents a suitable option for creating a tertiary native vascular access for hemodialysis on the upper extremities for patients requiring long term hemodialysis. The purpose of the study is to compare BAVAs with arteriovenous grafts (AVG). METHOD: Data collection was based on selecting all of the patients with BAVA created in the time period in between January 1996 and August 2011. A questionnaire was created and sent to the selected hemodialysis centers. The resulting set of data was statistically analyzed and evaluated. RESULTS: In the time period between 1 January 1996 and August 2011, arteriovenous access for hemodialysis was created in 6754 patients (7203 procedures in total). Out of these patients, 175 BAVAs were created. Our patient database of those undergoing the BAVA procedure consisted of 98 females (56%) and 77 males (44%) with an average age of 64.5 years. The prevalence of diabetes mellitus was 60% (105 patients). Primary patency after 12 months was 68.8%, 24 months 59.7%, 36 months 53.8, 48 months 53.8%, and 60 months 50%. Primary assisted patency after 12 months was 89.9%, 24 months 84.6%, 36 months 77.8%, 48 months 77.9%, 60 months 70.8%. Secondary patency after 12 months was 89.4%, 24 months 86.9%, 36 months 81%, 48 months 78.9%, 60 months 75.7%. Twenty-nine BAVAs (16.5%) were obliterated. CONCLUSION: Patients benefit from this type of procedure due to the longer patency of a native arteriovenous access, as well as a lower incidence of infectious complications.

A sensing mechanism for the detection of carbon nanotubes using selective photoluminescent probes based on ionic complexes with organic dyes.

The multifunctional properties of carbon nanotubes (CNTs) make them a powerful platform for unprecedented innovations in a variety of practical applications. As a result of the surging growth of nanotechnology, nanotubes present a potential problem as an environmental pollutant, and as such, an efficient method for their rapid detection must be established. Here, we propose a novel type of ionic sensor complex for detecting CNTs - an organic dye that responds sensitively and selectively to CNTs with a photoluminescent signal. The complexes are formed through Coulomb attractions between dye molecules with uncompensated charges and CNTs covered with an ionic surfactant in water. We demonstrate that the photoluminescent excitation of the dye can be transferred to the nanotubes, resulting in selective and strong amplification (up to a factor of 6) of the light emission from the excitonic levels of CNTs in the near-infrared spectral range, as experimentally observed via excitation-emission photoluminescence (PL) mapping. The chirality of the nanotubes and the type of ionic surfactant used to disperse the nanotubes both strongly affect the amplification; thus, the complexation provides sensing selectivity towards specific CNTs. Additionally, neither similar uncharged dyes nor CNTs covered with neutral surfactant form such complexes. As model organic molecules, we use a family of polymethine dyes with an easily tailorable molecular structure and, consequently, tunable absorbance and PL characteristics. This provides us with a versatile tool for the controllable photonic and electronic engineering of an efficient probe for CNT detection.

Surface tension of supercooled water determined by using a counterpressure capillary rise method.

Measurements of the surface tension of supercooled water down to -25 °C have been reported recently (Hrubý et al. J. Phys. Chem. Lett. 2014, 5, 425-428). These experiments did not show any anomalous temperature dependence of the surface tension of supercooled water reported by some earlier measurements and molecular simulations. In the present work, this finding is confirmed using a counterpressure capillary rise method (the counterpressure method) as well as through the use of the classical capillary rise method (the height method). In the counterpressure method, the liquid meniscus inside the vertical capillary tube was kept at a fixed position with an in-house developed helium distribution setup. A preset counterpressure was applied to the liquid meniscus when its temperature changed from a reference temperature (30 °C) to the temperature of interest. The magnitude of the counterpressure was adjusted such that the meniscus remained at the same height, thus compensating the change of the surface tension. One advantage of the counterpressure method over the height method consists of avoiding the uncertainty due to a possible variation of the capillary diameter along its length. A second advantage is that the equilibration time due to the capillary flow of the highly viscous supercooled water can be shortened. For both the counterpressure method and the height method, the actual results are relative values of surface tension with respect to the surface tension of water at the reference temperature. The combined relative standard uncertainty of the relative surface tensions is less than or equal to 0.18%. The new data between -26 and +30 °C lie close to the IAPWS correlation for the surface tension of ordinary water extrapolated below 0.01 °C and do not exhibit any anomalous features.

Surface Tension of Supercooled Water: No Inflection Point down to -25 °C.

A dramatic increase in the surface tension of water with decreasing temperature in the supercooled liquid region has appeared as one of the many anomalies of water. This claimed anomaly characterized by the second inflection point at about +1.5 °C was observed in older surface tension data and was partially supported by some molecular simulations and theoretical considerations. In this study, two independent sets of experimental data for the surface tension of water in the temperature range between +33 and -25 °C are reported. The two data sets are mutually consistent, and they lie on a line smoothly extrapolating from the stable region. No second inflection point and no other anomalies in the course of the surface tension were observed. The new data lies very close to the extrapolated IAPWS correlation for the surface tension of ordinary water, which hence can be recommended for use, e.g., in atmospheric modeling.

Prediction of compartment syndrome based on analysis of biochemical parameters.

BACKGROUND: The possibility of predicting severe compartment syndrome using simple biochemical parameters was evaluated in a single-center study of 55 patients who presented with acute femoral embolism and who were treated with open surgical embolectomy. METHODS: Parameters related to tissue damage and oxidative metabolism (i.e., lactate, bilirubin, myoglobin, uric acid, glucose, and fibrinogen) were monitored in ipsilateral femoral vein blood. RESULTS: Several statistically significant predictors of relevant compartment syndrome after surgical reperfusion were found, including lactate, uric acid, transcutaneous oxygen pressure, bilirubin, intrafascial pressure, and serum myoglobin. Glycemia and serum albumin did not significantly change over time. CONCLUSIONS: The lactate concentration in femoral vein blood sampled during surgical embolectomy can be used for the stratification of additional postoperative risk of clinically significant compartment syndrome complicating reperfusion after acute embolism of the femoral artery.

Surgical extirpation of glomus tumor from rare localization on the upper extremity.

Objective. To report on a very rare case of a glomus tumor manifested on the upper arm in a healthy young male patient. Case Presentation and Intervention. A 22-year-old male patient presented with bluish multifocal venous malformation on the left upper arm and was admitted for venous malformation excision. Pain, discomfort, and upper arm paraesthesia had been present for almost 6 years. Ultrasonography revealed septet tumor without blood flow in the subcutaneous region of anterior aspect of the upper arm. A multifocal venous malformation approximately 5-10 mm in diameter was excised. Histological examination showed dilated vascular area with proliferated glomus cells with round nucleus in the wall of dilated vascular structures. Based on histological examination, the final diagnosis was made as "glomangioma." Conclusion. Histological examination is the only method that can establish final diagnosis. Currently, the only available treatment for this type of tumor is surgical excision.

Bioenergetic gain of citrate anticoagulated continuous hemodiafiltration--a comparison between 2 citrate modalities and unfractionated heparin.

PURPOSE: To determine bioenergetic gain of 2 different citrate anticoagulated continuous hemodiafiltration (CVVHDF) modalities and a heparin modality. MATERIALS AND METHODS: We compared the bio-energetic gain of citrate, glucose and lactate between 29 patients receiving 2.2% acid-citrate-dextrose with calcium-containing lactate-buffered solutions (ACD/Ca(plus)/lactate), 34 on 4% trisodium citrate with calcium-free low-bicarbonate buffered fluids (TSC/Ca(min)/bicarbonate), and 18 on heparin with lactate buffering (Hep/lactate). RESULTS: While delivered CVVHDF dose was about 2000 mL/h, total bioenergetic gain was 262 kJ/h (IQR 230-284) with ACD/Ca(plus)/lactate, 20 kJ/h (8-25) with TSC/Ca(min)/bicarbonate (P < .01) and 60 kJ/h (52-76) with Hep/lactate. Median patient delivery of citrate was 31.2 mmol/h (25-34.7) in ACD/Ca(plus)/lactate versus 14.8 mmol/h (12.4-19.1) in TSC/Ca(min)/bicarbonate groups (P < .01). Median delivery of glucose was 36.8 mmol/h (29.9-43) in ACD/Ca(plus)/lactate, and of lactate 52.5 mmol/h (49.2-59.1) in ACD/Ca(plus)/lactate and 56.1 mmol/h (49.6-64.2) in Hep/lactate groups. The higher energy delivery with ACD/Ca(plus)/lactate was partially due to the higher blood flow used in this modality and the calcium-containing dialysate. CONCLUSIONS: The bioenergetic gain of CVVHDF comes from glucose (in ACD), lactate and citrate. The amount substantially differs between modalities despite a similar CVVHDF dose and is unacceptably high when using ACD with calcium-containing lactate-buffered solutions and a higher blood flow. When calculating nutritional needs, we should account for the energy delivered by CVVHDF.

Quantification of systemic delivery of substrates for intermediate metabolism during citrate anticoagulation of continuous renal replacement therapy.

BACKGROUND: There are limited data on systemic delivery of metabolic substrates during citrate anticoagulation. The direct citrate measurements are usually not available. METHODS: Patients on 2.2% acid-citrate-dextrose (ACD, n = 41) were compared to a control group on unfractionated heparin (n = 17). All were treated on 1.9-m(2) polysulfone filters. Samples were taken from the central venous catheter, ports pre- and post-filter and from effluent. RESULTS: The gain of citrate in CVVH (n = 18) was not different from CVVHDF (n = 23, p = 0.8). Mean gain of citrate was 25.4 ± 6.4 mmol/h. The systemic loads of lactate (p = 0.12) and glucose (p = 0.23) in CVVH were similar to CVVHDF. Mean inputs of lactate and glucose were 62.9 ± 21.1 and 26.6 ± 10.4 mmol/h, respectively. The mean difference between post- and prefilter unmeasured anions (d-UA) correlated with mean difference of citrate concentrations (p < 0.0001, r(2) = 0.66). The estimated caloric load of the citrate modalities was 5,536 ± 1,385 kJ/ 24 h. CONCLUSIONS: ACD might represent a significant load of metabolic substrates, particularly if used with lactate buffer. Systemic delivery of citrate can be predicted using d-UA in the extracorporeal circuit.