Relationship Between the Anion Gap and Serum Lactate in Hypovolemic Shock

Background and objectives: Previous studies evaluating patients in the Intensive Care Unit with established lactic acidosis determined that the anion gap is an insensitive screening tool for elevated blood lactate. No prior study has examined the relationship between anion gap and serum lactate within the first hours of the development of lactic acidosis. Design, setting, participants, & measurements: Data were obtained prospectively from a convenience sample of adult trauma patients at a single level 1 trauma center. Venous samples were drawn prior to initiation of intravenous fluid resuscitation. A linear regression model was constructed to assess the relationship between serum lactate and anion gap, and 95% prediction intervals were computed. Logistic regression models were constructed to determine the sensitivity and specificity for several different anion gap and lactate cutpoints. Results: 128 patients with elevated serum lactate levels (>2.1 mmol/L) and 63 patients with normal serum lactate levels (< 2.1 mmol/L) were included. The sensitivity of an elevated anion gap (> 10) to reveal hyperlactatemia was only 43% whereas specificity was 84%. Sensitivity improved if the upper limit of normal anion gap was lowered and with increasing levels of serum lactate. The coefficient of determination between serum lactate level and AG yielded an R2 of 0.30 (p < 0.001) and the slope of this relationship was 2.185 with a 95% confidence interval of 2.011-2.359. The mean 95% prediction interval was + 8.9. Conclusions: Within the first hour of the development of lactic acidosis due to hypovolemic shock, the anion gap was not a sensitive indicator of an elevated serum lactate level, but it was fairly specific. The anion gap increased to a greater extent than the serum lactate, the 95% mean prediction interval was wide and approximately 70% of the change in anion gap could not be explained by increases in serum lactate, suggesting that other anions contribute to the anion gap in lactic acidosis.

Lactic Acidosis in Patients with Solid Cancer

Significance: Cancer-associated tissue-specific lactic acidosis stimulates and mediates tumor invasion and metastasis and is druggable. Rarely, malignancy causes systemic lactic acidosis, the role of which is poorly understood. Recent Advances: The understanding of the role of lactate has shifted dramatically since its discovery. Long recognized as only a waste product, lactate has become known as an alternative metabolism substrate and a secreted nutrient that is exchanged between the tumor and the microenvironment. Tissue-specific lactic acidosis is targeted to improve the host body's anticancer defense and serves as a tool that allows the targeting of anticancer compounds. Systemic lactic acidosis is associated with poor survival. In patients with solid cancer, systemic lactic acidosis is associated with an extremely poor prognosis, as revealed by the analysis of 57 published cases in this study. Although it is considered a pathology worth treating, targeting systemic lactic acidosis in patients with solid cancer is usually inefficient. Critical Issues: Research gaps include simple questions, such as the unknown nuclear pH of the cancer cells and its effects on chemotherapy outcomes, pH sensitivity of glycosylation in cancer cells, in vivo mechanisms of response to acidosis in the absence of lactate, and overinterpretation of in vitro results that were obtained by using cells that were not preadapted to acidic environments. Future Directions: Numerous metabolism-targeting anticancer compounds induce lactatemia, lactic acidosis, or other types of acidosis. Their potential to induce acidic environments is largely overlooked, although the acidosis might contribute to a substantial portion of the observed clinical effects. Antioxid. Redox Signal. 37, 1130-1152.

Arginine for the Treatment of Mitochondrial Encephalopathy, Lactic Acidosis, and Stroke-Like Episodes: A Systematic Review

Mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) syndrome is a mitochondrial disease that lacks a definitive treatment. Lately, there has been an increased interest in the scientific community about the role of arginine in the short and long-term settings of the disease. We aim to conduct a systematic review of the clinical use of arginine in the management of MELAS and explore the role of arginine in the pathophysiology of the disease. We used PubMed advanced-strategy searches and only included full-text clinical trials on humans written in the English language. After applying the inclusion/exclusion criteria, four clinical trials were reviewed. We used the Meta-analysis of Observational Studies in Epidemiology (MOOSE) guidelines and Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) protocol for this systematic review. We used the Cochrane Collaboration risk-of-bias tool to assess the bias encountered in each study. Overall, IV arginine seems to be effective in improving symptoms during acute attacks of MELAS, while oral arginine supplementation increases endothelial function, preventing further stroke-like episodes.

Lactic Acidosis Related to Pharmacotherapy and Human Diseases

Lactic acidosis represents one of the most common conditions that can compromise the health of intensive care unit (ICU) patients, increasing the mortality of patients with high levels of Lactate who do not receive a proper treatment within the first 6 h of hospitalization. There are two enantiomers of lactic acid: L-lactic acid (when the concentration increases, it can lead to a state of severe acidemia risking cardiovascular collapse, causing an increase in mortality in ICU patients) and D lactic acid (produced in the human organism by microbiota and its production increases during some pathological status). Generally, increased levels of serum lactic acid could be due to numerous factors, including hypoxia (caused for example by septic/cardiogenic/hypovolemic or obstructive shock), specific pathologies (e.g., liver disease), use of some drugs (e.g., metformin), presence of toxins, and trauma. Since the underlying cause could be fatal for the ICU patient, it is important to understand the root of this clinical status with a view to correct it and prevent the risk of a poor clinical outcome. Prevention and early treatment are the keys to control the negative clinical consequences. The aim of this review is to revise the scientific literature for further confirmation about the importance of early identification of acidotic statuses and to underline how an early diagnosis can prevent the worst clinical outcome, especially for ICU patients who are more fragile compared to the general population.

Mitochondrial Effects of Common Cardiovascular Medications: The Good, the Bad and the Mixed

Mitochondria are central organelles in the homeostasis of the cardiovascular system via the integration of several physiological processes, such as ATP generation via oxidative phosphorylation, synthesis/exchange of metabolites, calcium sequestration, reactive oxygen species (ROS) production/buffering and control of cellular survival/death. Mitochondrial impairment has been widely recognized as a central pathomechanism of almost all cardiovascular diseases, rendering these organelles important therapeutic targets. Mitochondrial dysfunction has been reported to occur in the setting of drug-induced toxicity in several tissues and organs, including the heart. Members of the drug classes currently used in the therapeutics of cardiovascular pathologies have been reported to both support and undermine mitochondrial function. For the latter case, mitochondrial toxicity is the consequence of drug interference (direct or off-target effects) with mitochondrial respiration/energy conversion, DNA replication, ROS production and detoxification, cell death signaling and mitochondrial dynamics. The present narrative review aims to summarize the beneficial and deleterious mitochondrial effects of common cardiovascular medications as described in various experimental models and identify those for which evidence for both types of effects is available in the literature.

Tipping the balance between erythroid cell differentiation and induction of anemia in response to the inflammatory pathology associated with chronic trypanosome infections

Infection caused by extracellular single-celled trypanosomes triggers a lethal chronic wasting disease in livestock and game animals. Through screening of 10 Trypanosoma evansi field isolates, exhibiting different levels of virulence in mice, the current study identifies an experimental disease model in which infection can last well over 100 days, mimicking the major features of chronic animal trypanosomosis. In this model, despite the well-controlled parasitemia, infection is hallmarked by severe trypanosomosis-associated pathology. An in-depth scRNA-seq analysis of the latter revealed the complexity of the spleen macrophage activation status, highlighting the crucial role of tissue resident macrophages (TRMs) in regulating splenic extramedullary erythropoiesis. These new data show that in the field of experimental trypanosomosis, macrophage activation profiles have so far been oversimplified into a bi-polar paradigm (M1 vs M2). Interestingly, TRMs exert a double-sided effect on erythroid cells. On one hand, these cells express an erythrophagocytosis associated signature. On another hand, TRMs show high levels of Vcam1 expression, known to support their interaction with hematopoietic stem and progenitor cells (HSPCs). During chronic infection, the latter exhibit upregulated expression of Klf1, E2f8, and Gfi1b genes, involved in erythroid differentiation and extramedullary erythropoiesis. This process gives rise to differentiation of stem cells to BFU-e/CFU-e, Pro E, and Baso E subpopulations. However, infection truncates progressing differentiation at the orthochromatic erythrocytes level, as demonstrated by scRNAseq and flow cytometry. As such, these cells are unable to pass to the reticulocyte stage, resulting in reduced number of mature circulating RBCs and the occurrence of chronic anemia. The physiological consequence of these events is the prolonged poor delivery of oxygen to various tissues, triggering lactic acid acidosis and the catabolic breakdown of muscle tissue, reminiscent of the wasting syndrome that is characteristic for the lethal stage of animal trypanosomosis.

Mutant TP53 driving the Warburg Effect in Mantle Cell lymphoma

The p53 mutation R273H in tumor cells leads to increased glucose uptake, lactic acidosis, and accelerated tumor growth, as was previously shown in mice. We here present a patient with mantle cell lymphoma harboring this p53_R273H mutation, whose clinical course is characterized by severe lactic acidosis, hypoglycemia, and aggressive disease.

Blue-green neutrophilic inclusion bodies with concurrent liver failure as a predictor of imminent death

Objectives

Blue-green, birefractory, poorly-defined, cytoplasmic inclusions in some types of leukocytes are an underdiagnosed finding, which composition and clinical significance is not well understood. Inclusions are only found on peripheral blood smear (PBS).

Case presentation

We report the case of a male with a history of chronic disease (hypertension, obesity, dyslipidemia, and kidney failure) admitted to the emergency room (ER) with shortness of breath, who was later transferred to the intensive care unit (ICU). The patient had a torpid disease course and ultimately died of multiorgan failure, including severe liver failure. When his status exacerbated, these inclusions were observed on PBS in conjunction with liver enzyme abnormalities.

Conclusions

This case confirms that blue-green inclusions on PBS in cases of acute severe liver failure with concurrent lactic acidosis should be immediately reported to the medical team, since it is suggestive of critical status and poor prognosis.

Cardiac Dysfunction Due to Thiamine Deficiency after Hemodialysis for Biguanide-related Lactic Acidosis

Biguanide is an ideal drug for the treatment of type 2 diabetes mellitus. When used appropriately, the incidence of lactic acidosis is reported to be very low. Risk factors associated with biguanide-related lactic acidosis include chronic kidney disease, congestive heart failure, alcohol use, severe dehydration, shock, hypoxic states, sepsis, and advanced age. We herein report a case of cardiac dysfunction due to thiamine deficiency after hemodialysis in a patient with suspected biguanide-related lactic acidosis. Patients who develop severe lactic acidosis while taking biguanides should be given a large dose of thiamine without delay, given the possibility of thiamine deficiency as a complication.

Entering the sugar rush era: revisiting the antihyperglycemic activities of biguanides after a century of metformin discovery

The development of clinically viable metformin analogs is a challenge largely to be overcome. Despite being an extremely efficient drug for the treatment of type 2 diabetes mellitus, multiple studies were conducted seeking to improve its hypoglycemic activity or to ameliorate aspects such as the low oral absorption and the incidence of gastrointestinal side effects. Furthermore, efforts have been made to attribute new activities, or even to expand the pre-existing ones, that could enhance its effects in the diabetes, such as pancreas-protective, antioxidant, and anti-inflammatory activities. In this manuscript, we describe the analogs of metformin developed in the last three decades, highlighting the lack of computationally based rational approaches to guide their development. We also discuss this is probably a consequence of how unclear the mechanism of action of the parent drug is and highlight the recent advances towards establishment of the main molecular target(s) for metformin. We also explored the binding of metformin, buformin and phenformin to the mitochondrial respiratory chain complex I through molecular docking analyses and reviewed the prospects of applying computational tools to improve the success in the development of such analogs. Therefore, it becomes evident the wide range of molecular targets, as well as the multiple activities displayed by metformin, make this drug a promising prototype for the development of novel entities, particularly for the treatment of type 2 diabetes mellitus.

Metformin-associated Lactic Acidosis with Hypoglycemia during the COVID-19 Pandemic

Metformin-associated lactic acidosis (MALA) is an extremely rare but life-threatening adverse effect of metformin treatment. The lifestyle changes associated with the coronavirus disease 2019 (COVID-19) pandemic may increase the potential risk of MALA development in patients with diabetes. We herein report a 64-year-old Japanese man taking a small dose of metformin who presented with MALA accompanied by hypoglycemia secondary to increased alcohol consumption triggered by lifestyle changes during the pandemic. Physicians should prescribe metformin judiciously to prevent MALA development and pay close attention to lifestyle changes in patients at risk for MALA during the COVID-19 pandemic.

METHEMOGLOBINEMIA - A CASE REPORT AND LITERATURE REVIEW

The objective of this case report is to present a patient with acquired methemoglobinemia due to poisoning of an unknown cause. A 55-year-old man was brought to the Emergency Department, University Hospital Center Zagreb, with an unwell appearance, cyanotic, restless, and presented with a quantitative consciousness disorder. An initial assessment showed decreased oxygen saturation (SpO2 85 [%]), while point-of-care arterial blood gas (ABG) analysis assessed normal partial pressure of oxygen (pO2). Severe lactic acidosis with a compensatory drop in partial pressure of carbon dioxide (pCO2) and high rates of methemoglobin were found. Supportive oxygen therapy and crystalloid solutions were administered, which resulted in rapid clinical recovery within 40 minutes of the initial assessment. Clinical recovery was accompanied by normalized ABG test results taken serially. Typical antidotes, methylene blue and vitamin C, were not administered due to rapid clinical improvement. Methemoglobinemia can be congenital (hereditary) or acquired (toxic). Both conditions are rarely seen in emergency departments, nevertheless, they should be approached properly since methemoglobinemia can be a severe, and fatal, condition. Methemoglobinemia symptoms are the results of inadequate oxygen transport. The diagnosis was confirmed by co-oximetry, while three clinical entities suspected methemoglobinemia: refractory hypoxia, “cyanosis-saturation gap“ and dark brown blood. This paper reports our patient’s clinical presentation, discusses the causes and mechanisms of possible poisoning, and reviews recent guidelines for methemoglobinemia management.

Potential cyanide poisoning reported to the UK national poisons information service: 2008-2019

INTRODUCTION

Cyanide is a prevalent, lethal chemical. Possible sources of exposure include products of combustion, plant material, industry, chemical warfare and terrorism.

METHODS

Retrospective review of UK Poisons Information Database of telephone enquiries to the National Poisons Information Service between 1^st January 2008 and 31^st December 2019 where cyanide poisoning was considered a possibility. Data extracted included demographics, exposure source, clinical features, Poisoning Severity Score, lactate concentration and antidotes given.

RESULTS

A total of 1,252 cases of suspected cyanide poisoning were identified, 239 (19%) involved children under 10 years. The commonest sources of exposure were ingestion of plant material (437 cases; 35%) and smoke inhalation (399; 32%). Smoke inhalation caused the majority of severe and fatal cases (139; 71%). Clinical features associated with fatal outcomes were cardiac arrest (OR 36.4; 95% CI 14.4-92.2), hypotension (15.8; 7.0-35.9), coma (10.8; 5.6-21.0) and lactic acidosis (7.8; 4.1-14.8). 110 patients (9%) were given an antidote and 40 patients (3%) died.Lactate concentrations correlate with Poisoning Severity Score category (r = 0.6, p < 0.0001). Serum lactate <2.0 mmol/L was associated with Poisoning Severity Score None or Minor (sensitivity 76%; specificity 86%) and >11.0 mmol/L was associated with fatal outcome (sensitivity 74%; specificity 80%). 61 cases (5%) had severe carboxyhaemoglobin toxicity (COHb >30%). This was associated with a fatal outcome (OR 7.0; 95% CI 1.5-33.7) and there was positive correlation between carboxyhaemoglobin and Poisoning Severity Score, r = 0.57, p < 0.0001.

CONCLUSIONS

Most cases of ingestion of plant material involved children under five years and resulted in no or mild symptoms. In adults smoke inhalation was associated with the most severe poisoning. The lactate cut-off values associated with each severity score calculated in this study are lower than the values used by NPIS on TOXBASE. Analytical conformation of cyanide exposure was unavailable in the majority of case, limiting the strength of these conclusions.

Linezolid Intoxication with Extreme Lactate Blood Levels Successfully Treated with Dialytic Treatment in ICU: A Case Report

INTRODUCTION

Lactic acidosis is a rare but life-threatening complication associated with prolonged linezolid therapy. No specific treatment is suggested, except for antibiotic therapy interruption.

CASE REPORT

A 70-years-old woman faced severe linezolid intoxication after antibiotics therapy initiation for infection of a surgical sternal wound. The patient suffered from a severe increment of blood lactate and thrombocytopenia. She was admitted to ICU twice, and due to dialytic treatment, linezolid and lactate serum levels came back to normality.

CONCLUSION

More studies should be conducted to evaluate the human tissue storage sites of linezolid and the influence of various factors on its clearance and plasma concentrations in critically ill patients.

Molecular and neurological features of MELAS syndrome in paediatric patients: A case series and review of the literature

Background

Mitochondrial encephalomyopathy, lactic acidosis and stroke‐like episodes (MELAS) syndrome is one of the most well‐known mitochondrial diseases, with most cases attributed to m.3243A>G. MELAS syndrome patients typically present in the first two decades of life with a broad, multi‐systemic phenotype that predominantly features neurological manifestations––stroke‐like episodes. However, marked phenotypic variability has been observed among paediatric patients, creating a clinical challenge and delaying diagnoses.

Methods

A literature review of paediatric MELAS syndrome patients and a retrospective analysis in a UK tertiary paediatric neurology centre were performed.

Results

Three children were included in this case series. All patients presented with seizures and had MRI changes not confined to a single vascular territory. Blood heteroplasmy varied considerably, and one patient required a muscle biopsy. Based on a literature review of 114 patients, the mean age of presentation is 8.1 years and seizures are the most prevalent manifestation of stroke‐like episodes. Heteroplasmy is higher in a tissue other than blood in most cases.

Conclusion

The threshold for investigating MELAS syndrome in children with suspicious neurological symptoms should be low. If blood m.3243A>G analysis is negative, yet clinical suspicion remains high, invasive testing or further interrogation of the mitochondrial genome should be considered.

Myoglobin Interaction with Lactate Rapidly Releases Oxygen: Studies on Binding Thermodynamics, Spectroscopy, and Oxygen Kinetics

Myoglobin (Mb)-mediated oxygen (O₂) delivery and dissolved O₂ in the cytosol are two major sources that support oxidative phosphorylation. During intense exercise, lactate (LAC) production is elevated in skeletal muscles as a consequence of insufficient intracellular O₂ supply. The latter results in diminished mitochondrial oxidative metabolism and an increased reliance on nonoxidative pathways to generate ATP. Whether or not metabolites from these pathways impact Mb-O₂ associations remains to be established. In the present study, we employed isothermal titration calorimetry, O₂ kinetic studies, and UV-Vis spectroscopy to evaluate the LAC affinity toward Mb (oxy- and deoxy-Mb) and the effect of LAC on O₂ release from oxy-Mb in varying pH conditions (pH 6.0–7.0). Our results show that LAC avidly binds to both oxy- and deoxy-Mb (only at acidic pH for the latter). Similarly, in the presence of LAC, increased release of O₂ from oxy-Mb was detected. This suggests that with LAC binding to Mb, the structural conformation of the protein (near the heme center) might be altered, which concomitantly triggers the release of O₂. Taken together, these novel findings support a mechanism where LAC acts as a regulator of O₂ management in Mb-rich tissues and/or influences the putative signaling roles for oxy- and deoxy-Mb, especially under conditions of LAC accumulation and lactic acidosis.

Fructose 1,6 bisphosphatase deficiency: outcomes of patients in a single center in Turkey and identification of novel splice site and indel mutations in FBP1

OBJECTIVES

Fructose 1,6 bisphosphatase (FBPase) deficiency is a rare autosomal recessively inherited metabolic disease. It is encoded by FBP1, and the enzyme catalyzes the hydrolysis of fructose-1,6-bisphosphate to fructose 6-phosphate. Patients with recurrent episodes of metabolic acidosis, hypoglycemia, hypertriglyceridemia, and hyperketonemia are present.

METHODS

In this study, we describe the clinical, biochemical, and molecular genetic features of six unrelated Turkish patients from six different families who were genetically diagnosed with FBPase deficiency in our clinic between 2008 and 2020. Their clinical and laboratory data were collected retrospectively. Next-generation sequencing (NGS) was performed for the molecular genetic analysis.

RESULTS

All patients were hospitalized with recurrent hypoglycemia and metabolic acidosis episodes. Three out of six patients were presented in the neonatal period. The mean age at diagnosis was 26 months. NGS revealed a known homozygous gross deletion including exon 2 in three patients (50%), a known homozygous c.910_911dupTT pathogenic variant in one patient (16%), a novel homozygous c.651_653delCAGinsTAA likely pathogenic variant, and another novel homozygous c.705+5G>A splice site variant. Leukocyte FBPase analysis detected no enzyme activity in the patient with homozygous c.705+5G>A splice site variant.

CONCLUSIONS

We identified two novel mutations in this study. One of them is a splice site mutation which is five bases downstream of the exon, and the other one is an indel mutation. Both of the splice site and indel mutations are exceedingly rare in FBP1, and to the best of our knowledge, there are second splice site and indel variants reported in the literature. Exon 2 deletion is the most common mutation consistent with the previous reports in Turkish patients. FBPase is a frequent cause of hypoglycemia and metabolic acidosis, and the widespread use of molecular genetic analysis would contribute to the enlightenment of advanced genetic factors and possible genotype/phenotype correlation.

Reduced lactic acidosis risk with Imeglimin: Comparison with Metformin

The global prevalence of type 2 diabetes (T2D) is expected to exceed 642 million people by 2040. Metformin is a widely used biguanide T2D therapy, associated with rare but serious events of lactic acidosis, in particular with predisposing conditions (e.g., renal failure or major surgery). Imeglimin, a recently approved drug, is the first in a new class (novel mode of action) of T2D medicines. Although not a biguanide, Imeglimin shares a chemical moiety with Metformin and also modulates mitochondrial complex I activity, a potential mechanism for Metformin‐mediated lactate accumulation. We interrogated the potential for Imeglimin to induce lacticacidosis in relevant animal models and further assessed differences in key mechanisms known for Metformin's effects. In a dog model of major surgery, Metformin or Imeglimin (30–1000 mg/kg) was acutely administered, only Metformin‐induced lactate accumulation and pH decrease leading to lactic acidosis with fatality at the highest dose. Rats with gentamycin‐induced renal insufficiency received Metformin or Imeglimin (50–100 mg/kg/h), only Metformin increased lactatemia and H⁺ concentrations with mortality at higher doses. Plasma levels of Metformin and Imeglimin were similar in both models. Mice were chronically treated with Metformin or Imeglimin 200 mg/kg bid. Only Metformin produced hyperlactatemia after acute intraperitoneal glucose loading. Ex vivo measurements revealed higher mitochondrial complex I inhibition with Metformin versus slight effects with Imeglimin. Another mechanism implicated in Metformin's effects on lactate production was assessed: in isolated rat, liver mitochondria exposed to Imeglimin or Metformin, only Metformin (50–250 µM) inhibited the mitochondrial glycerol‐3‐phosphate dehydrogenase (mGPDH). In liver samples from chronically treated mice, measured mGPDH activity was lower with Metformin versus Imeglimin. These data indicate that the risk of lactic acidosis with Imeglimin treatment may be lower than with Metformin and confirm that the underlying mechanisms of action are distinct, supporting its potential utility for patients with predisposing conditions.

Abstract No.: ABS0288: Comparison of the effect of two balanced crystalloid intraoperative (intravenous) solutions (PlasmalyteTM versus Sterofundin TM) on lactate levels during major cancer surgeries

Background &Aims:

Use of balanced fluids as intra-operative fluids substantially decrease the incidence of lactic acidosis; especially after major cancer surgeries. Aim of present study was to compare the effects of two acetate based balanced solutions, PlasmalyteTM and SterofundinTM on lactate, pH, electrolytes and haemodynamics after major onco-surgery.

Methods:

In this prospective randomised parallel group study, 60 patients undergoing major onco surgeries were randomised in one o fthe two groups to receive either PlasmalyteTM (PL) (30 patients) or SterofundinTM (SF) (30 patients) as an intra-operative fluid. Arterial Blood Gas analysis (ABG) was sampled before surgery (Baseline) and at the time of haemostasis (Post surgery). Heart rate and mean blood pressure were noted every 30 minutes. Blood loss during surgery was replaced with either colloid or blood. Descriptive statistical analyses, including mean and standard deviation for continuous variables, and count and percentage for categorical variables was performed. Student t-test was used to compare continuous variables and Fisher’s exact test was used for categorical variables. p <0.05 was considered to indicate statistical significance. Analysis was performed using SPSS Version 23.0 software.

Results:

The patient’s age was found to be comparable in both the groups (p=0.19). There was not any statistically significant difference seen in lactate (p=0.085) or pH (p=0.89) values between the two groups. Electrolyte levels were well maintained within normal limits in both PL and SF groups except calcium which was significantly higher in SF group post surgery(p<0.001). Difference in heart rate and mean blood pressure was found to be insignificant at all time points. Blood loss during the surgery was also similar in both the groups (p=0.937).

Conclusion:

Both PL and SF balanced crystalloid solutions can be safely recommended as an intraoperative fluid in major oncological surgeries. Both the fluids effectively maintain the pH and significantly decrease the incidence of lactic acidosis during cancer surgeries. Calcium levels are better maintained with the infusion of Sterofundin solution.

Expanding the phenotypic and molecular spectrum of NFS1-related disorders that cause functional deficiencies in mitochondrial and cytosolic iron-sulfur cluster containing enzymes

Iron-sulfur cluster proteins are involved in critical functions for gene expression regulation and mitochondrial bioenergetics including the oxidative phosphorylation system. The c.215G>A p.(Arg72Gln) variant in NFS1 has been previously reported to cause infantile mitochondrial complex II and III deficiency. We describe three additional unrelated patients with the same missense variant. Two infants with the same homozygous variant presented with hypotonia, weakness and lactic acidosis, and one patient with compound heterozygous p.(Arg72Gln) and p.(Arg412His) variants presented as a young adult with gastrointestinal symptoms and fatigue. Skeletal muscle biopsy from patients 1 and 3 showed abnormal mitochondrial morphology, and functional analyses demonstrated decreased activity in respiratory chain complex II and variably in complexes I and III. We found decreased mitochondrial and cytosolic aconitase activities but only mildly affected lipoylation of pyruvate dehydrogenase and 2-oxoglutarate dehydrogenase enzymes. Our studies expand the phenotypic spectrum and provide further evidence for the pathogenicity and functional sequelae of NFS1-related disorders with disturbances in both mitochondrial and cytosolic iron-sulfur cluster containing enzymes.

Emergent Hemodialysis Followed by Continuous Renal Replacement Therapy: A Management Challenge in a Patient With Life-Threatening Metabolic Acidosis of Multifactorial Etiology

Metabolic acidosis is a frequently encountered laboratory finding in daily clinical practice. Rapid pH correction is almost always preferred and necessary while performing workup to identify the causative factors. We present the case of a 73-year-old male presenting with progressive dyspnea and severe metabolic acidosis. He had a pH of 6.6, bicarbonate of 1.8 mg/dL, lactic acid of 18.1 mg/dL, and pCO2 of 14.1 mmHg. The intensivist and nephrologist made a joint decision to rapidly correct the pH using bicarbonate and emergent hemodialysis. Subsequently, continuous renal replacement therapy (CRRT) was started, leading to a favorable outcome. Our patient's most likely etiology of lactic acidosis was metformin because he had a very high lactic acid, high anion gap metabolic acidosis, and acute renal failure on presentation. From our case and literature review, we suggest using hemodialysis, CRRT, and bicarbonate replacement for a better prognosis in patients with critical acidosis in view of frank renal failure and concurrent metformin use.

Fructose-1,6-bisphosphatase deficiency causes fatty liver disease and requires long-term hepatic follow-up

Liver disease, occurring during pediatric or adult age, is often of undetermined cause. Some cases are probably related to undiagnosed inherited metabolic disorders. Hepatic disorders associated with fructose-1,6-bisphosphatase deficiency, a gluconeogenesis defect, are not reported in the literature. These symptoms are mainly described during acute crises, and many reports do not mention them because hypoglycemia and hyperlactatemia are more frequently in the forefront. Herein, the liver manifestations of 18 patients affected with fructose-1,6-bisphosphatase deficiency are described and the corresponding literature is reviewed. Interestingly, all 18 patients had liver abnormalities either during follow-up (hepatomegaly [n = 8/18], elevation of transaminases [n = 6/15], bright liver [n = 7/11]) or during acute crises (hepatomegaly [n = 10/17], elevation of transaminases [n = 13/16], acute liver failure [n = 6/14], bright liver [n = 4/14]). Initial reports described cases of liver steatosis, when liver biopsy was necessary to confirm the diagnosis by an enzymatic study. There is no clear pathophysiological basis for this fatty liver disease but we postulate that endoplasmic reticulum stress and de novo lipogenesis activation could be key factors, as observed in FBP1 knockout mice. Liver steatosis may expose patients to severe long-term liver complications. As hypoglycemia becomes less frequent with age, most adult patients are no longer monitored by hepatologist. Signs of fructose-1,6-bisphosphatase deficiency may be subtle and can be missed in childhood. We suggest that fructose-1,6-bisphosphatase deficiency should be considered as an etiology of hepatic steatosis, and a liver monitoring protocol should be set up for these patients, during lifelong follow-up.

Case report: Fatal outcome of pyridoxine-dependent epilepsy presenting as respiratory distress followed by a circulatory collapse

Pyridoxine-dependent epilepsy is a rare autosomal recessive disease usually associated with neonatal seizures that do not respond to common antiseizure medications but are controlled by pyridoxine administration. Because the symptoms can mimic common neonatal disorders, the diagnosis can be initially missed or delayed. We report a fatal case of a boy who was initially diagnosed with respiratory distress, birth asphyxia, and persistent pulmonary hypertension and whose condition rapidly deteriorated during the first day of life.

Murburn precepts for lactic-acidosis, Cori cycle, and Warburg effect: Interactive dynamics of dehydrogenases, protons, and oxygen

It is unresolved why lactate is transported to the liver for further utilization within the physiological purview of Cori cycle, when muscles have more lactate dehydrogenase (LDH) than liver. We point out that the answer lies in thermodynamics/equilibriums. While the utilization of NADH for the reduction of pyruvate to lactate can be mediated via the classical mechanism, the oxidation of lactate (with/without the uphill reduction of NAD⁺ ) necessitates alternative physiological approaches. The latter pathway occurs via interactive equilibriums involving the enzyme, protons and oxygen or diffusible reactive oxygen species (DROS). Since liver has high DROS, the murburn activity at LDH would enable the cellular system to tide over the unfavorable energy barriers of the forward reaction (~476 kJ/mol; earlier miscalculated as ~26 kJ/mole). Further, the new mechanism does not necessitate any "smart decision-making" or sophisticated control by/of proteins. The DROS-based murburn theory explains the invariant active-site structure of LDH isozymes and their multimeric nature. The theoretical insights, in silico evidence and analyses of literature herein also enrich our understanding of the underpinnings of "lactic acidosis" (lowering of physiological pH accompanied by lactate production), Warburg effect (increased lactate production at high pO₂ by cancer cells) and approach for cancer therapy.