End-tidal carbon dioxide after sodium bicarbonate infusion during mechanical ventilation or ongoing cardiopulmonary resuscitation.

PURPOSE: End-tidal CO2 is used to monitor the ventilation status or hemodynamic efficacy during mechanical ventilation or cardiopulmonary resuscitation (CPR), and it may be affected by various factors including sodium bicarbonate administration. This study investigated changes in end-tidal CO2 after sodium bicarbonate administration. MATERIALS AND METHODS: This single-center, prospective observational study included adult patients who received sodium bicarbonate during mechanical ventilation or CPR. End-tidal CO2 elevation was defined as an increase of ≥20% from the baseline end-tidal CO2 value. The time to initial increase (lag time, Tlag), time to peak (Tpeak), and duration of the end-tidal CO2 rise (Tduration) were compared between the patients with spontaneous circulation (SC group) and those with ongoing resuscitation (CPR group). RESULTS: Thirty-three patients, (SC group, n = 25; CPR group, n = 8), were included. Compared with the baseline value, the median values of peak end-tidal CO2 after sodium bicarbonate injection increased by 100% (from 21 to 41 mmHg) in all patients, 89.5% (from 21 to 39 mmHg) in the SC group, and 160.2% (from 15 to 41 mmHg) in the CPR group. The median Tlag was 17 s (IQR: 12-21) and the median Tpeak was 35 s (IQR: 27-52). The median Tduration was 420 s (IQR: 90-639). The median Tlag, Tpeak, and Tduration were not significantly different between the groups. Tduration was associated with the amount of sodium bicarbonate for SC group (correlation coefficient: 0.531, p = 0.006). CONCLUSION: The administration of sodium bicarbonate may lead to a substantial increase in end-tidal CO2 for several minutes in patients with spontaneous circulation and in patients with ongoing CPR. After intravenous administration of sodium bicarbonate, the use of end-tidal CO2 pressure as a physiological indicator may be limited.

Evaluation of arterial blood gas parameters as prognostic markers in amyotrophic lateral sclerosis.

BACKGROUND: Forced vital capacity (FVC) remains difficult to determine for some patients suffering from amyotrophic lateral sclerosis (ALS) due to the rapid progression of the disease. Arterial blood gas (ABG) parameters could represent a valuable alternative. The aim of this study was therefore to evaluate the correlation between ABG parameters and FVC, along with the prognostic ability of ABG parameters, in a large cohort of ALS patients. METHODS: ALS patients (n=302) with FVC and ABG parameters available at diagnosis were included. Correlations between ABG parameters and FVC were evaluated. Cox regression was then carried out to determine the association of each parameter (ABG and clinical data) with survival. Finally, receiver operating characteristic (ROC) curves were built to predict the survival of ALS. RESULTS: Bicarbonates (HCO3 - ), oxygen partial pressure (pO2 ), carbon dioxide partial pressure (pCO2 ), base excess (BE), oxygen saturation and oxyhemoglobin were significantly correlated with FVC both in patients with spinal or bulbar onset. Univariate Cox regression showed that HCO3 - and BE were associated with survival but only in spinal forms. ABG parameters predicted the survival of ALS with a similar performance to FVC, HCO3 - being the parameter with the highest area under the curve. CONCLUSIONS: Our results suggest that there is an interest in conducting a longitudinal evaluation throughout disease progression to confirm the equal performances of FVC and ABG. This study highlights the benefits of performing ABG analysis that could be used as an interesting alternative to FVC when spirometry cannot be performed.

Serum bicarbonate stability study at room temperature - influence of time to centrifugation and air exposure on bicarbonate measurement reported according to the CRESS checklist.

OBJECTIVES: The aim was to evaluate the stability of serum bicarbonate at room temperature, depending on time to centrifugation and air exposure. METHODS: Stability study was conducted in the laboratory of Clinical Hospital Centre Rijeka, Croatia in January-February 2022. Nine samples from 10 volunteers were collected in clot activator gel tubes (Greiner Bio-One). Bicarbonate was measured on Beckman Coulter AU480 (Beckman Coulter, Brea, USA). Three tubes were left at room temperature for 30 min, three tubes for 2 h, three tubes for 4 h until centrifugation. First tube from first group (baseline) was measured immediately after centrifugation. Other measurements were expressed as percentage deviation (PD%) from baseline. First tube was remeasured after 1 and 2 h (OT_0h_1h; OT_0h_2h). Second and third tubes were opened 1 and 2 h after centrifugation (C_0h_1h; C_0h_2h). Second group of tubes was processed the same way with 2-hour centrifugation delay (WB_2h; OT_2h_1h; OT_2h_2h; C_2h_1h; C_2h_2h), and third group with 4-hour delay (WB_4h; OT_4h_1h; OT_4h_2h; C_4h_1h; C_4h_2h). PD% was compared to Maximum Permissible Difference (MPD=5.69%). MedCalc statistical software was used (MedCalc, Ostend, Belgium). RESULTS: Bicarbonate baseline mean value (range) was 27.3 (23.4-29.6) mmol/L. Obtained PD% (95%CI) were: C_0h_1h 0.46 (-1.21, 2.12); C_0h_2h 0.18 (-2.22, 2.57); OT_0h_1h -6.46 (-7.57, -5.36); OT_0h_2h -10.67 (-12.13, -9.21); WB_2h -0.15 (-2.04, 1.74); C_2h_1h 0.01 (-1.52, 1.54); C_2h_2h -0.40 (-2.65, 1.85); OT_2h_1h -5.43 (-7.30, -3.55); OT_2h_2h -11.32 (-13.57, -9.07); WB_4h -0.85 (-3.28, 1.58); C_4h_1h -2.52 (-4.93, 0.11); C_4h_2h -3.02 (-5.62, 0.43); OT_4h_1h -7.34 (-9.64, -5.05); OT_4h_2h -11.85 (-14.38, -9.33). CONCLUSIONS: Serum bicarbonate is stable for 4 h in closed uncentrifuged tubes, another 2 h in closed tubes after centrifugation, and is unstable within 1 h in opened tube.

El regulador de transmembrana de fibrosis quística (CFTR) disfuncional y sus efectos extrapulmonares / The dysfunction of transmembrane regulator in cystic fibrosis (CFTR) and its extrapulmonary effects

El daño del regulador de transmembrana de fibrosis quística (CFTR) puede causar una enfermedad grave fuera de los pulmones. El canal de cloruro (Cl-) ha sido el más estudiado, sin embargo, el bicarbonato (HCO3 -) tiene un rol muy importante en el comportamiento de las secreciones y la inflamación secundaria. El hecho de que CFTR funcione no sólo como un canal de Cl- sino también de HCO3- es un campo para la investigación y el desarrollo de fármacos para pacientes con daño genético o adquirido, este último frecuente en la población general. Algunos moduladores de CFTR pueden tener un beneficio terapéutico en el tratamiento de pancreatitis en ambas situaciones. La disfunción del CFTR a nivel renal puede resultar excepcionalmente en alcalosis metabólica y reducción del impulso ventilatorio. Hasta la fecha no está claro cuales serian sus efectos en los sistemas gastrointestinal y hepatobiliar.

Transmembrane regulator in cystic fibrosis (CFTR) can cause severe disease outside of the lungs. The chloride channel (Cl-) has been the most studied, however bicarbonate (HCO3 -) has a very important role in the behavior of secretions and secondary inflammation. The fact that CFTR works not only as a Cl- channel but also as an HCO3- channel is a field for research and development of drugs for patients with genetic or acquired damage, the latter frequent in the general population. Some CFTR modulators may have a therapeutic benefit in the treatment of pancreatitis in both situations. CFTR dysfunction at the renal level can exceptionally result in metabolic alkalosis and reduced ventilatory drive. To date it is not clear what its effects on the gastrointestinal and hepatobiliary systems would be.

Bicarbonato de sodio intravenoso ¿Cuándo, cómo y por qué utilizarlo? / Intravenous sodium bicarbonate. When, how and why to use it?

Severe metabolic acidosis is defined by a pH < 7.2 with HCO3− < 8 mE- q/L in plasma. Its best treatment is to correct the underlying cause. However, acidemia produces multiple complications such as resistance to the action of catecholamines, pulmonary vasoconstriction, impaired cardiovascular function, hyperkalemia, immunological dysregulation, respiratory muscle fatigue, neurological impairment, cellular dysfunction, and finally, it contributes to multisystemic failure. Intravenous NaHCO3 buffers severe acidemia, preventing the associated damage and gains time while the causal disease is corrected. Its indication requires a risk-benefit assessment, considering its complications. These are hypernatremia, hypokalemia, ionic hypocalcemia, rebound alkalosis, and intracellular acidosis. For this reason, therapy must be "adapted" and administered judiciously. The patient will require monitoring with serial evaluation of the internal environment, especially arterial blood gases, plasma electrolytes, and ionized calcium. Isotonic solutions should be preferred instead of hypertonic bicarbonate. The development of hypernatremia must be prevented, calcium must be provided for hypocalcemia to improve cardiovascular function. Furthermore, in mechanically ventilated patients, a respiratory response similar to the one that would develop physiologically, must be established to be able to extract excess CO2 and thus avoid intracellular acidosis. It is possible to estimate the bicarbonate deficit, speed, and volume of its infusion. However, the calculations are only for reference. More important is to start intravenous NaHCO3 when needed, administer it judiciously, manage its side effects, and continue it to a safe goal. In this review we address all the necessary elements to consider in the administration of intravenous NaHCO3, highlighting why it is the best buffer for the management of severe metabolic acidosis.

Acid-base balance in hemodialysis patients in everyday practice.

INTRODUCTION: Abnormalities in blood bicarbonates (HCO3-) concentration are a common finding in patients with chronic kidney disease, especially at the end-stage renal failure. Initiating of hemodialysis does not completely solve this problem. The recommendations only formulate the target concentration of ≥22 mmol/L before hemodialysis but do not guide how to achieve it. The aim of the study was to assess the acid-base balance in everyday practice, the effect of hemodialysis session and possible correlations with clinical and biochemical parameters in stable hemodialysis patients. MATERIAL AND METHODS: We enrolled 75 stable hemodialysis patients (mean age 65.5 years, 34 women), from a single Department of Nephrology. We assessed blood pressure, and acid-base balance parameters before and after mid-week hemodialysis session. RESULTS: We found significant differences in pH, HCO3- pCO2, lactate before and after HD session in whole group (p < 0.001; p < 0.001; p < 0.001; p = 0.001, respectively). Buffer bicarbonate concentration had only statistically significant effect on the bicarbonate concentration after dialysis (p < 0.001). Both pre-HD acid-base parameters and post-HD pH were independent from buffer bicarbonate content. We observed significant inverse correlations between change in the serum bicarbonates and only two parameters: pH and HCO3- before hemodialysis (p = 0.013; p < 0.001, respectively). CONCLUSIONS: Despite the improvement in hemodialysis techniques, acid-base balance still remains a challenge. The individual selection of bicarbonate in bath, based on previous single tests, does not improve permanently the acid-base balance in the population of hemodialysis patients. New guidelines how to correct acid-base disorders in hemodialysis patients are needed to have less 'acidotic' patients before hemodialysis and less 'alkalotic' patients after the session.

Effects of different electrolyte solutions on blood washing in cardiac surgery with cardiopulmonary bypass / 中华麻醉学杂志

Objective:To evaluate the effects of different electrolyte solutions on blood washing in cardiac surgery with cardiopulmonary bypass (CPB).Methods:Sixty patients, aged 18-80 yr, weighing 50-100 kg, undergoing cardiac surgery with CPB with expected banked blood transfusion 4-6 U in our hospital, were divided into 3 groups ( n=20 each) by a random number table method: compound electrolyte injection group (group A), sodium bicarbonate Ringer′s solution group (group B) and normal saline group (group C). Banked blood and salvaged autologous blood were washed with compound electrolyte injection, sodium bicarbonate Ringer′s solution and normal saline.Banked and autologous blood was collected before washing and immediately after washing for blood gas analysis.The osmotic fragility of red blood cells was measured by colorimetry, and the concentration of 2, 3-diphosphoglycerate (2, 3-DPG) was determined by enzyme-linked immunosorbent assay. Results:Compared with the baseline before washing, the concentrations of K +, Glu and Lac in banked blood were significantly decreased, the concentrations of K + in banked blood were increased, and the concentrations of Glu and Lac in autologous blood were decreased, the osmotic fragility of erythrocytes was increased, and the concentrations of 2, 3-DPG in banked and autologous blood were increased after washing in the three groups ( P<0.05). Compared with group C, the concentrations of Na + and Cl - in banked and autologous blood were significantly decreased, the concentrations of K + in banked and autologous blood were increased, the osmotic fragility of erythrocytes in banked and autologous blood was decreased, and the concentrations of 2, 3-DPG in banked and autologous blood were increased in A and B groups ( P<0.05). Compared with A and C groups, BE in banked and autologous blood were significantly increased after washing in group B than in A and C groups ( P<0.05). After washing, Ca 2+ was detected in banked and autologous blood in group B, however, Ca 2+ was not detected in banked and autologous blood in group A and group C. Conclusions:Compound electrolyte solution and sodium bicarbonate Ringer′s solution provide better efficacy when used for blood washing in cardiac surgery with CPB, and sodium bicarbonate Ringer′s solution can also improve the acidic and calcium-free internal environment of blood.

The Δ Anion Gap/Δ Bicarbonate Ratio in Early Lactic Acidosis: Time for Another Delta?

Background: The ratio of Δ anion gap and Δ bicarbonate (ΔAG/ΔHCO3) is used to detect coexisting acid-base disorders in patients with high anion gap metabolic acidosis. Classic teaching holds that, in lactic acidosis, the ΔAG/ΔHCO3 is 1:1 within the first few hours of onset and subsequently rises to 1.8:1. However, this classic 1:1 stoichiometry in early lactic acidosis was derived primarily from animal models and only limited human data. The objective of this study was to examine the ΔAG/ΔHCO3 within the first hours of the development of lactic acidosis. Methods: Data were obtained prospectively from a convenience sample of adult (age >18 years) trauma-designated patients at a single level-1 trauma center. Venous samples, including a chemistry panel and serum lactate, were drawn before initiation of intravenous fluid resuscitation. Results: A total of 108 patients were included. Of these, 63 patients had normal serum lactate levels (≤2.1 mmol/L) with a mean AG of 7.1 mEq/L, the value used to calculate subsequent ΔAG values. ΔAG/ΔHCO3 was calculated for 45 patients who had elevated serum lactate levels (>2.1 mmol/L). The mean ΔAG/ΔHCO3 for all patients with elevated serum lactate levels was 1.86 (SD, 1.40). Conclusions: The mean ΔAG/ΔHCO3 was 1.86 within the first hours of the development of lactic acidosis due to hypovolemic shock, confirming a small prior human study. This contradicts the traditional belief that, in lactic acidosis, the ΔAG/ΔHCO3 is 1:1 within the first several hours. The classic 1:1 stoichiometry was determined on the basis of animal models in which lactic acid is infused into the extracellular space, facilitating extracellular buffering of protons by bicarbonate. In contrast, our results demonstrate a higher initial ΔAG/ΔHCO3 ratio in early endogenous lactic acidosis in humans. Our analysis indicates this is likely due to unmeasured anions contributing to an elevation in AG.

Role of HCO3- umbrella in the pathogenesis of primary biliary cholangitis / 临床肝胆病杂志

Primary biliary cholangitis (PBC) is an autoimmune disease. Although PBC has the features of autoimmune disease, it has poor response to immunosuppressants and good response to the drugs participating in bile acid metabolism, such as ursodeoxycholic acid. Studies have shown that the bicarbonate secretion of biliary epithelial cells is impaired in PBC patients, and bile acid not blocked by HCO3- umbrella enters biliary epithelial cells and mediates their damage and apoptosis, leading to the expression of autoantibodies in apoptotic cells and immunologic injury. In order to explore the role of HCO3- umbrella secreted by biliary epithelial cells in the pathogenesis of PBC, this article briefly introduces the physiological function and production mechanism of HCO3- umbrella and the influencing factors for HCO3- secretion, and it is pointed out that reduced HCO3- secretion may be a key link in the pathogenesis of PBC and a potential therapeutic target.

Concordance analysis between dosed serum bicarbonate and that calculated by gas analysis in chronic renal patients / Análise de concordância entre o bicarbonato sérico dosado e o calculado pela gasometria em pacientes renais crônicos

Abstract Introduction: The control of metabolic acidosis in dialysis patients focuses on the supply of bicarbonate during the dialysis session, and it is not standard in all hemodialysis to assess serum bicarbonate concentrations. Bicarbonate expressed in blood gas analysis is the most sensitive standard of analysis and it is measured indirectly, using the Henderson-Hasselbalch equation. There are no studies in this population evaluating the concordance between the calculated bicarbonate with the direct method of biochemical analysis. The aim of this study was to analyze the concordance between the measured and calculated serum bicarbonate levels using blood gas analysis. Methods: We analyzed blood samples from chronic kidney patients undergoing hemodialysis, using the same sample of bicarbonate analysis by biochemistry and gasometry. The concordance was assessed using the Bland-Altman method. Results: 51 samples were analyzed. The analysis revealed a high correlation (r = 0.73) and a mean difference (bias) of 1.15 ± 3 mmol/L. The median time between collection and examination was 241 minutes. Discussion: We can conclude that the biochemical bicarbonate analysis compared to that calculated from blood gas analysis in chronic renal patients was consistent. For greater concordance between the data, it is important that the time between the collection of the samples and the referral to the laboratory for carrying out the dosages does not exceed four hours. The serum bicarbonate dosage can result in cost savings when compared to that of bicarbonate in blood gas analysis.

Resumo Introdução: O controle da acidose metabólica em pacientes dialíticos está voltado, principalmente, para o suprimento de bicarbonato durante a sessão de diálise, não sendo padrão em todas as hemodiálises avaliar as concentrações séricas do bicarbonato. O bicarbonato expresso na gasometria é considerado o padrão mais sensível de análise e é medido indiretamente por meio da equação de Henderson-Hasselbalch. Não há estudos nessa população avaliando a concordância do bicarbonato calculado com o método direto de análise bioquímica. O objetivo deste estudo é analisar a concordância entre o bicarbonato sérico medido e o calculado por meio da gasometria. Métodos: Foram analisadas amostras de sangue de pacientes renais crônicos em hemodiálise sendo feito na mesma amostra de análise do bicarbonato pela bioquímica e análise pela gasometria. A concordância foi avaliada pelo método de Bland-Altman. Resultados: Foram analisados um total de 51 amostras. A análise de correlação revelou alta correlação (r = 0.73) e a diferença média (bias) de 1.15 ± 3 mmol/L. O tempo mediano entre a realização da coleta e do exame foi de 241 minutos. Discussão: Podemos concluir que a realização da dosagem bioquímica do bicarbonato comparada com a calculada a partir da gasometria em pacientes renais crônicos foi concordante. Para maior concordância entre os dados, é importante que o tempo entre a coleta das amostras e o encaminhamento ao laboratório para a realização das dosagens não exceda quatro horas. A dosagem do bicarbonato sérico pode resultar numa economia de custos comparada à do bicarbonato da gasometria.

Role of Bicarbonates and Mannitol in Rhabdomyolysis: A Comprehensive Review.

Rhabdomyolysis is characterized by rapid muscle breakdown and release of intracellular muscle components into the circulation. Acute renal injury is the most common and fatal complication of rhabdomyolysis. The current literature emphasizes the importance of preventing rhabdomyolysis and finding the benefits of sodium bicarbonates and mannitol in its prevention. A PubMed database search for the keywords "Rhabdomyolysis," "Sodium bicarbonate use in rhabdomyolysis," "Mannitol use in rhabdomyolysis," and a Medical Subject Headings (MeSH) search using the keyword "Rhabdomyolysis; Acute Kidney Injury (Subheading-Prevention and control)" generated 10,005 articles overall. After a thorough application of inclusion/exclusion criteria, 37 relevant studies were selected for this literature study. This analysis demonstrates that aggressive early volume resuscitation with normal saline should continue being the principal focus of therapy, and the use of sodium bicarbonate and mannitol in practical situations is not entirely justified. This article also emphasizes the need for future research on this topic and provides recommendations for future research.

Metabolic Alkalosis: A Brief Pathophysiologic Review.

Metabolic alkalosis is a very commonly encountered acid-base disorder that may be generated by a variety of exogenous and/or endogenous, pathophysiologic mechanisms. Multiple mechanisms are also responsible for the persistence, or maintenance, of metabolic alkalosis. Understanding these generation and maintenance mechanisms helps direct appropriate intervention and correction of this disorder. The framework utilized in this review is based on the ECF volume-centered approach popularized by Donald Seldin and Floyd Rector in the 1970s.  Although many subsequent scientific discoveries have advanced our understanding of the pathophysiology of metabolic alkalosis, that framework continues to be a valuable and relatively straightforward diagnostic and therapeutic model.

Low Serum Bicarbonate and CKD Progression in Children.

BACKGROUND AND OBJECTIVES: Studies of adults have demonstrated an association between metabolic acidosis, as measured by low serum bicarbonate levels, and CKD progression. We evaluated this relationship in children using data from the Chronic Kidney Disease in Children study. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: The relationship between serum bicarbonate and a composite end point, defined as 50% decline in eGFR or KRT, was described using parametric and semiparametric survival methods. Analyses were stratified by underlying nonglomerular and glomerular diagnoses, and adjusted for demographic characteristics, eGFR, proteinuria, anemia, phosphate, hypertension, and alkali therapy. RESULTS: Six hundred and three participants with nonglomerular disease contributed 2673 person-years of follow-up, and 255 with a glomerular diagnosis contributed 808 person-years of follow-up. At baseline, 39% (237 of 603) of participants with nonglomerular disease had a bicarbonate level of ≤22 meq/L and 36% (85 of 237) of those participants reported alkali therapy treatment. In participants with glomerular disease, 31% (79 of 255) had a bicarbonate of ≤22 meq/L, 18% (14 of 79) of those participants reported alkali therapy treatment. In adjusted longitudinal analyses, compared with participants with a bicarbonate level >22 meq/L, hazard ratios associated with a bicarbonate level of <18 meq/L and 19-22 meq/L were 1.28 [95% confidence interval (95% CI), 0.84 to 1.94] and 0.91 (95% CI, 0.65 to 1.26), respectively, in children with nonglomerular disease. In children with glomerular disease, adjusted hazard ratios associated with bicarbonate level ≤18 meq/L and bicarbonate 19-22 meq/L were 2.16 (95% CI, 1.05 to 4.44) and 1.74 (95% CI, 1.07 to 2.85), respectively. Resolution of low bicarbonate was associated with a lower risk of CKD progression compared with persistently low bicarbonate (≤22 meq/L). CONCLUSIONS: In children with glomerular disease, low bicarbonate was linked to a higher risk of CKD progression. Resolution of low bicarbonate was associated with a lower risk of CKD progression. Fewer than one half of all children with low bicarbonate reported treatment with alkali therapy. Long-term studies of alkali therapy's effect in patients with pediatric CKD are needed.

[Flecainid intoxication: Evolution, complications and care of]. / Intoxication volontaire à la flecaïnide : évolution, complications et prise en charge.

This report presents the case of a young man of 24 years old with Asperger syndrome who ingest quantities of medication whose flecainide. Resume of his stay in intensive care unit, notably serious adverse effect which ventricular tachycardia with membrane stabilizing effect and lengthening of stay in intensive care unit. Study of literature of different take care already published, with notion of mid-term leaching of flecainide which were ingest days before, at different levels all over the world.

Microbial electrosynthesis feasibility evaluation at high bicarbonate concentrations with enriched homoacetogenic biocathode.

An enrichment methodology was developed for a homoacetogenic biocathode that is able to function at high concentrations of bicarbonates for the microbial electrosynthesis (MES) of acetate from carbon dioxide. The study was performed in two stages; enrichment of consortia in serum bottles and the development of a biocathode in MES. A homoacetogenic consortium was sequentially grown under increasing concentrations of bicarbonate, in serum bottles, at room temperature. The acetate production rate was found to increase with the increase in the bicarbonate concentration and evidenced a maximum production rate of 260 mg/L d-1 (15 g HCO3-/L). On the contrary, carbon conversion efficiency decreased with the increase in the bicarbonate concentration, which evidenced a maximum at 2.5 g HCO3-/L (90.16%). Following a further increase in the bicarbonate concentration up to 20 g HCO3-/L, a visible inhibition was registered with respect to the acetate production rate and the carbon conversion efficiency. Well adapted biomass from 15 g HCO3-/L was used to develop biocathodic catalyst for MES. An effective biocathode was developed after 4 cycles of operation, during which acetate production was improved gradually, evidencing a maximum production rate of 24.53 mg acetate L-1 d-1 (carbon conversion efficiency, 47.72%). Compared to the enrichment stage, the carbon conversion efficiency and the rate of acetate production in MES were found to be low. The production of acetate induced a change in the catholyte pH, from neutral conditions towards acidic conditions.

Measuring pH and Buffer Capacity in Fluids Aspirated from the Fasted Upper Gastrointestinal Tract of Healthy Adults.

PURPOSE: The design of biorelevant conditions for in vitro evaluation of orally administered drug products is contingent on obtaining accurate values for physiologically relevant parameters such as pH, buffer capacity and bile salt concentrations in upper gastrointestinal fluids. METHODS: The impact of sample handling on the measurement of pH and buffer capacity of aspirates from the upper gastrointestinal tract was evaluated, with a focus on centrifugation and freeze-thaw cycling as factors that can influence results. Since bicarbonate is a key buffer system in the fasted state and is used to represent conditions in the upper intestine in vitro, variations on sample handling were also investigated for bicarbonate-based buffers prepared in the laboratory. RESULTS: Centrifugation and freezing significantly increase pH and decrease buffer capacity in samples obtained by aspiration from the upper gastrointestinal tract in the fasted state and in bicarbonate buffers prepared in vitro. Comparison of data suggested that the buffer system in the small intestine does not derive exclusively from bicarbonates. CONCLUSIONS: Measurement of both pH and buffer capacity immediately after aspiration are strongly recommended as "best practice" and should be adopted as the standard procedure for measuring pH and buffer capacity in aspirates from the gastrointestinal tract. Only data obtained in this way provide a valid basis for setting the physiological parameters in physiologically based pharmacokinetic models.

[Metabolic acidosis : Diagnosis and treatment]. / Metabolische Azidose : Diagnostik und Therapie.

Acid-base disorders and in particular metabolic acidosis are very common in critically ill patients and contribute significantly to morbidity and mortality. We shed light on the most common causes, the pathophysiology and treatments. Particular attention will be paid to the common practice of substituting sodium bicarbonate in the light of recent study results.

Biotic dissolution of autunite under anaerobic conditions: effect of bicarbonates and Shewanella oneidensis MR1 microbial activity.

Uranium is a contaminant of major concern across the US Department of Energy complex that served a leading role in nuclear weapon fabrication for half a century. In an effort to decrease the concentration of soluble uranium, tripolyphosphate injections were identified as a feasible remediation strategy for sequestering uranium in situ in contaminated groundwater at the Hanford Site. The introduction of sodium tripolyphosphate into uranium-bearing porous media results in the formation of uranyl phosphate minerals (autunite) of general formula {X1-2[(UO2)(PO4)]2-1·nH2O}, where X is a monovalent or divalent cation. The stability of the uranyl phosphate minerals is a critical factor that determines the long-term effectiveness of this remediation strategy that can be affected by biogeochemical factors such as the presence of bicarbonates and bacterial activity. The objective of this research was to investigate the effect of bicarbonate ions present in the aqueous phase on Ca-autunite dissolution under anaerobic conditions, as well as the role of metal-reducing facultative bacterium Shewanella oneidensis MR1. The concentration of total uranium determined in the aqueous phase was in direct correlation to the concentration of bicarbonate present in the solution, and the release of Ca, U and P into the aqueous phase was non-stoichiometric. Experiments revealed the absence of an extensive biofilm on autunite surface, while thermodynamic modeling predicted the presence of secondary minerals, which were identified through microscopy. In conclusion, the dissolution of autunite under the conditions studied is susceptible to bicarbonate concentration, as well as microbial presence.

Approximation of bicarbonate concentration using serum total carbon dioxide concentration in patients with non-dialysis chronic kidney disease.

BACKGROUND: We investigated the relationship between serum total carbon dioxide (CO2) and bicarbonate ion (HCO3-) concentrations in pre-dialysis chronic kidney disease (CKD) patients and devised a formula for predicting low bicarbonate (HCO3- < 24 mmol/L) and high bicarbonate (HCO3- ≥ 24 mmol/L) using clinical parameters. METHODS: In total, 305 samples of venous blood collected from 207 pre-dialysis patients assessed by CKD stage (G1 + G2, 46; G3, 50; G4, 51; G5, 60) were investigated. The relationship between serum total CO2 and HCO3- concentrations was analyzed using Pearson's correlation coefficient. An approximation formula was developed using clinical parameters correlated independently with HCO3- concentration. Diagnostic accuracy of serum total CO2 and the approximation formula was evaluated by receiver operating characteristic curve analysis and a 2 × 2 table. RESULTS: Serum total CO2 correlated strongly with HCO3- concentration (r = 0.91; P < 0.001). The following approximation formula was obtained by a multiple linear regression analysis: HCO3- (mmol/L) = total CO2 - 0.5 × albumin - 0.1 × chloride - 0.01 × (estimated glomerular filtration rate + blood glucose) + 15. The areas under the curves of serum total CO2 and the approximation formula for detection of low bicarbonate and high bicarbonate were 0.981, 0.996, 0.993, and 1.000, respectively. This formula had superior diagnostic accuracy compared with that of serum total CO2 (86.6% vs. 81.3%). CONCLUSION: Serum total CO2 correlated strongly with HCO3- concentration in pre-dialysis CKD patients. An approximation formula including serum total CO2 showed superior diagnostic accuracy for low and high bicarbonate compared with serum total CO2.

Effects of Treatment of Metabolic Acidosis in CKD: A Systematic Review and Meta-Analysis.

BACKGROUND AND OBJECTIVES: Metabolic acidosis is associated with progression of CKD and has significant adverse effects on muscle and bone. A systematic review and meta-analysis was conducted to evaluate the benefits and risks of metabolic acidosis treatment with oral alkali supplementation or a reduction of dietary acid intake in those with CKD. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: MEDLINE, Embase, and Cochrane CENTRAL were searched for relevant trials in patients with stage 3-5 CKD and metabolic acidosis (<22 mEq/L) or low-normal serum bicarbonate (22-24 mEq/L). Data were pooled in a meta-analysis with results expressed as weighted mean difference for continuous outcomes and relative risk for categorical outcomes with 95% confidence intervals (95% CIs), using a random effects model. Study quality and strength of evidence were assessed using Cochrane risk of bias and the Grading of Recommendations Assessment, Development and Evaluation criteria. RESULTS: Fourteen clinical trials were included (n=1394 participants). Treatment of metabolic acidosis with oral alkali supplementation or a reduction of dietary acid intake increased serum bicarbonate levels (14 studies, 1378 patients, mean difference 3.33 mEq/L, 95% CI, 2.37 to 4.29) and resulted in a slower decline in eGFR (13 studies, 1329 patients, mean difference -3.28 ml/min per 1.73 m2, 95% CI, -4.42 to -2.14; moderate certainty) and a reduction in urinary albumin excretion (very-low certainty), along with a reduction in the risk of progression to ESKD (relative risk, 0.32; 95% CI, 0.18 to 0.56; low certainty). Oral alkali supplementation was associated with worsening hypertension or the requirement for increased antihypertensive therapy (very-low certainty). CONCLUSIONS: Low-to-moderate certainty evidence suggest that oral alkali supplementation or a reduction in dietary acid intake may slow the rate of kidney function decline and potentially reduce the risk of ESKD in patients with CKD and metabolic acidosis.