Reversible acute blindness in suspected metformin-associated lactic acidosis: a case report

BACKGROUND

Metformin is commonly used for the treatment of type 2 diabetes mellitus. Its multiple advantages include low risk of hypoglycemia, weight neutrality, low cost, and cardioprotective and anti-inflammatory effects. Renal insufficiency is one of the contraindications for its use. Inadvertent prescription in patients with renal insufficiency may lead to metformin-associated lactic acidosis, which brings a high risk of mortality. The early recognition and management of metformin-associated lactic acidosis are essential.

CASE REPORT

We present the case of a 58-year-old Hui woman with a history of type 2 diabetes mellitus with nephropathy and heart disease for which she was treated with metformin, insulin, and heart medications. She developed nausea, vomiting, anion gap metabolic acidosis due to hyperlactatemia, and acute kidney injury. She was hospitalized to receive intravenous hydration and correction of metabolic acidosis after she suddenly developed blindness. The diagnostic workup ruled out central causes and her symptoms resolved briefly after continuous venovenous hemodialysis was initiated, confirming the diagnosis of metformin-associated lactic acidosis.

CONCLUSIONS

Metabolic disruption can cause acute blindness. Metabolic acidosis in a patient with a history of metformin intake should suggest the possibility of metformin-associated lactic acidosis, which must be treated immediately, without waiting for the results of other examinations, especially in patients with sudden blindness. Further study of reversible blindness-associated severe metabolic acidosis is needed.

Severe lactic acidosis during tenofovir disoproxil fumarate and cobicistat combination for HIV patient

Lactic acidosis is a rare but serious side effect in individuals receiving nucleoside reverse transcriptase inhibitors. An underweight woman with HIV was admitted to our hospital because of nausea and diffuse myalgia. Her antiretroviral regimen had been changed to tenofovir disoproxil fumarate (TDF)/emtricitabine and darunavir/cobicistat 3 months prior, after which her renal function had gradually declined. After admission, she was diagnosed with lactic acidosis, and a liver biopsy suggested mitochondrial damage. Her plasma tenofovir levels were elevated at the onset of lactic acidosis. We hypothesise that the patient's low body weight, combined with the addition of cobicistat, induced renal dysfunction and led to elevated plasma tenofovir concentrations, resulting in mitochondrial damage and lactic acidosis. Careful monitoring of renal function and lactic acidosis is required during use of TDF-containing regimens for underweight HIV patients, particularly when combined with cobicistat.

Lactic acidosis in a patient with cancer

Lactic acidosis is commonly associated with tissue hypoperfusion and gives rise to concern regarding hypoxia or underlying hypotension. In the cancer patient, especially one undergoing chemotherapy, there is always concern for sepsis; however, in the otherwise clincially stable patient with cancer, type B lactic acidosis can also be related to their underlying malignancy. It is considered a haematological emergency given its high mortality rate. However, despite the urgency to treat type B lactic acidosis in these circumstances, treatment options beyond treatment of the malignancy are limited, and its presence portends a poor prognosis. This case highlights our current understanding of type B lactic acidosis and an approach to lactic acidosis evaluation in the cancer patient.

Treatment of severe metformin-associated lactic acidosis with renal replacement therapy and tris-hydroxymethyl aminomethane: a case report

BACKGROUND

Type B lactic acidosis is a rare but serious side effect of metformin use. The risk of metformin-associated lactic acidosis is elevated in renal or liver impairment, heart failure and in metformin overdose. Metformin-associated lactic acidosis is treated with renal replacement therapy although this can be limited by metformin's large volume of distribution and a patient's hemodynamic instability. Tris-hydroxymethyl aminomethane is a buffer that rapidly equilibrates in liver cells and increases the intracellular pH of hepatocytes. Intracellular alkalosis increases lactate uptake by the liver and can promote gluconeogenesis which results in increased lactate metabolism and decreased lactate production. Unlike intravenous bicarbonate which can worsen acidosis due to carbon dioxide retention and hypocalcemia, tris-hydroxymethyl aminomethane does not generate large amounts of carbon dioxide and can improve cardiac contractility in experimental models.

CASE PRESENTATION

We present a case of a 43-year-old African American male who intentionally ingested 480,000 g of metformin. He developed severe metformin-associated lactic acidosis that was refractory to 21 hours of high flux hemodialysis. This was followed by an additional 12 hours of high flux hemodialysis augmented by continuous intravenous infusion of tris-hydroxymethyl aminomethane. After initiating tris-hydroxymethyl aminomethane, the patient had rapid reversal of lactic acidosis and was weaned off vasopressors and mechanical ventilation.

CONCLUSIONS

While metformin-associated lactic acidosis can be treated with renal replacement therapy, severe cases of lactic acidosis may not be amenable to renal replacement therapy alone. Through its unique buffer mechanisms, tris-hydroxymethyl aminomethane can be used in conjunction with dialysis to rapidly improve acidosis associated with metformin.

Metformin as an emerging concern in wastewater: Occurrence, analysis and treatment methods

Metformin is a wonder drug used as an anti-hypoglycemic medication; it is also used as a cancer suppression medicament. Metformin is a first line of drug choice used by doctors for patients with type 2 diabetes. It is used worldwide where the drug's application varies from an anti-hypoglycemic medication to cancer oppression and as a weight loss treatment drug. Due to its wide range of usage, metformin and its byproducts are found in waste water and receiving aquatic environment. This leads to the accumulation of metformin in living beings and the environment where excess concentration levels can lead to ailments such as lactic acidosis or vitamin B12 deficiency. This drug could become of future water treatment concerns with its tons of production per year and vast usage. As a result of continuous occurrence of metformin has demanded the need of implementing and adopting different strategies to save the aquatic systems and the exposure to metformin. This review discuss the various methods for the elimination of metformin from wastewater. Along with that, the properties, occurrence, and health and environmental impacts of metformin are addressed. The different analytical methods for the detection of metformin are also explained. The main findings are discussed with respect to the management of metformin as an emerging contaminants and the major recommendations are discussed to understand the major research gaps.

Metformin: When Should We Fear Lactic Acidosis?

Metformin, a molecule belonging to the biguanide family, represents one of the most commonly prescribed medications for the treatment of diabetes mellitus in the world. Over the sixty years during which it has been used, many benefits have been described, which are not limited to the treatment of diabetes mellitus. However, since metformin is similar to other members of the same drug family, there is still much concern regarding the risk of lactic acidosis. This article aims to highlight the correlation between the use of metformin and the onset of renal damage or lactic acidosis. Metformin-associated lactic acidosis exists; however, it is rare. The appropriate use of the drug, under safe conditions, induces benefits without risks.

Pharmacokinetic and Biochemical Profiling of Sodium Dichloroacetate in Pregnant Ewes and Fetuses

Sodium dichloroacetate (DCA) is an investigational drug that shows promise in the treatment of acquired and congenital mitochondrial diseases, including myocardial ischemia and failure. DCA increases glucose utilization and decreases lactate production, so it may also have clinical utility in reducing lactic acidosis during labor. In the current study, we tested the ability of DCA to cross the placenta and be measured in fetal blood after intravenous administration to pregnant ewes during late gestation and labor. Sustained administration of DCA to the mother over 72 hours achieved pharmacologically active levels of DCA in the fetus and decreased fetal plasma lactate concentrations. Multicompartmental pharmacokinetics modeling indicated that drug metabolism in the fetal and maternal compartments is best described by the DCA inhibiting lactate production in both compartments, consistent with our finding that the hepatic expression of the DCA-metabolizing enzyme glutathione transferase zeta1 was decreased in the ewes and their fetuses exposed to the drug. We provide the first evidence that DCA can cross the placental compartment to enter the fetal circulation and inhibit its own hepatic metabolism in the fetus, leading to increased DCA concentrations and decreased fetal plasma lactate concentrations during its parenteral administration to the mother. SIGNIFICANCE STATEMENT: This study was the first to administer sodium dichloroacetate (DCA) to pregnant animals (sheep). It showed that DCA administered to the mother can cross the placental barrier and achieve concentrations in fetus sufficient to decrease fetal lactate concentrations. Consistent with findings reported in other species, DCA-mediated inhibition of glutathione transferase zeta1 was also observed in ewes, resulting in reduced metabolism of DCA after prolonged administration.

Lactic acidosis induces resistance to the pan-Akt inhibitor uprosertib in colon cancer cells

BACKGROUND

Akt signalling regulates glycolysis and drives the Warburg effect in cancer, thus decreased glucose utilisation is a pharmacodynamic marker of Akt inhibition. However, cancer cells can utilise alternative nutrients to glucose for energy such as lactate, which is often elevated in tumours together with increased acidity. We therefore hypothesised that lactic acidosis may confer resistance to Akt inhibition.

METHODS

The effect of the pan-Akt inhibitor uprosertib (GSK2141795), on HCT116 and LS174T colon cancer cells was evaluated in the presence and absence of lactic acid in vitro. Expression of downstream Akt signalling proteins was determined using a phosphokinase array and immunoblotting. Metabolism was assessed using 1H nuclear magnetic resonance spectroscopy, stable isotope labelling and gas chromatography-mass spectrometry.

RESULTS

Lactic acid-induced resistance to uprosertib was characterised by increased cell survival and reduced apoptosis. Uprosertib treatment reduced Akt signalling and glucose uptake irrespective of lactic acid supplementation. However, incorporation of lactate carbon and enhanced respiration was maintained in the presence of uprosertib and lactic acid. Inhibiting lactate transport or oxidative phosphorylation was sufficient to potentiate apoptosis in the presence of uprosertib.

CONCLUSIONS

Lactic acidosis confers resistance to uprosertib, which can be reversed by inhibiting lactate transport or oxidative metabolism.

The Association of Hypophosphatemia With Resistant Lactic Acidosis in Critical Care Illness

Critically ill patients are known to have a variety of electrolyte abnormalities. Lactic acidosis can frequently be seen secondary to shock states and is usually treated with aggressive volume resuscitation. Interestingly, hypophosphatemia is a potential cause of resistant lactic acidosis, which may not be as commonly identified or considered. We present a case of a 42-year-old man admitted twice over a span of 6 months with an elevated lactate level that did not resolve with volume resuscitation. It was ultimately determined that his lactic acidosis was due to hypophosphatemia after ruling out other potential causes. Phosphate replacement therapy resulted in the normalization of his lactate. In the literature, multiple theories have indicated the association of hypophosphatemia with lactic acidosis though no prior cases exist supporting a direct relationship. In this case, we set forth to evaluate the complicated relationship between all of these factors and to highlight the importance of early detection and treatment of hypophosphatemia, which may be beneficial in treating lactic acidosis.

A Case of Renal Involvement in B Lymphoblastic Lymphoma Leukemia

BACKGROUND

Renal involvement is rare in B lymphoblastic lymphoma (B-LBL). The authors describe a rare case of renal involvement in a 21-year-old male patient with B lymphoblastic lymphoma leukemia, presenting with severe lactic acidosis.

METHODS

Hematologic investigation, bone marrow aspirate and biopsy, cytogenetic analysis and renal biopsy were performed.

RESULTS

The patient achieved complete hematological remission (CHR) after induction therapy with the regimen of VDCP and received consolidation chemotherapy regularly. He remained CHR until now.

CONCLUSIONS

Renal biopsy, bone marrow aspirate, and biopsy are important to confirm a correct diagnosis. Renal involvement in B-LBL as a prognostic factor needs further studies.

[A case of severe metformin-associated lactic acidosis treated with CVVHDF and regional anticoagulation with sodium citrate]

Metformin is an antidiabetic drug; used to treat type II diabetes mellitus, metformin associated lactic acidosis has an incidence of 2-9 cases / 100,000 patients / year with high mortality (30%). We have had the case of a 75-year-old woman with metabolic acidosis as a result of metformin assumption, treated by renal replacement therapy (CRRT) with continuous veno-venous hemodiafiltration (CVVHDF).

RESULTS

after a short treatment period there was a reduction in Lactates (from 16.8 mmol/L to 12.6 mmol/L) and a progressive improvement of acidosis. In 72 hours the recovery of diuresis and subsequent suspension of CRRT was achieved.

CONCLUSION

CRRT, in addition to ensuring support for renal failure and volume correction, allowed a rapid recovery from metformin-associated lactic acidosis.

The Dramatic Recovery of a Patient with Biguanide-associated Severe Lactic Acidosis Following Thiamine Supplementation

Biguanides are a drug of choice for the treatment of type 2 diabetes mellitus. Although they can cause lactic acidosis in susceptible patients with predisposing risk factors, the incidence of lactic acidosis is reported to be very low when they are used properly. We herein present a case of biguanide-associated severe lactic acidosis complicated with thiamine deficiency that was provoked without predisposing factors for thiamine deficiency. Diabetic patients taking biguanide may be predisposed to thiamine deficiency, even when there is no evidence of risk factors, and the high-dose administration of thiamine may be essential in the treatment of this otherwise under-recognized disorder.

Conundrum in an asthma exacerbation

A 66-year-old man, an asthmatic, presented with symptoms suggestive of an acute exacerbation of asthma. His arterial blood gas revealed type 1 respiratory failure (PaO2 <8 kPa or 60 mm Hg with normal or low PaCO2) with a compensated lactic acidosis. He was treated for an asthma exacerbation and sepsis. Despite treatment, his respiratory rate remained elevated although his hypoxaemia improved. There was progressive worsening of the lactic acidosis. Treatment for sepsis was augmented. Peak flow measurements were not used to assess the severity of his exacerbation nor his response to treatment. An alternate diagnosis of acute coronary syndrome with acute pulmonary oedema was made and his asthma treatment was stopped. This coincided with a decline in his serum lactate. A diagnosis of salbutamol-induced lactic acidosis (SILA) was made. SILA is a relatively common complication of salbutamol therapy in moderate/severe asthma exacerbations. It is caused by a mechanism different from the lactataemia that is associated with septic shock and life-threatening asthma.

Lactate Clearance and Vasopressor Seem to Be Predictors for Mortality in Severe Sepsis Patients with Lactic Acidosis Supplementing Sodium Bicarbonate: A Retrospective Analysis

INTRODUCTION

Initial lactate level, lactate clearance, C-reactive protein, and procalcitonin in critically ill patients with sepsis are associated with hospital mortality. However, no study has yet discovered which factor is most important for mortality in severe sepsis patients with lactic acidosis. We sought to clarify this issue in patients with lactic acidosis who were supplementing with sodium bicarbonate.

MATERIALS AND METHODS

Data were collected from a single center between May 2011 and April 2014. One hundred nine patients with severe sepsis and lactic acidosis who were supplementing with sodium bicarbonate were included.

RESULTS

The 7-day mortality rate was 71.6%. The survivors had higher albumin levels and lower SOFA, APACHE II scores, vasopressor use, and follow-up lactate levels at an elapsed time after their initial lactate levels were checked. In particular, a decrement in lactate clearance of at least 10% for the first 6 hours, 24 hours, and 48 hours of treatment was more dominant among survivors than non-survivors. Although the patients who were treated with broad-spectrum antibiotics showed higher illness severity than those who received conventional antibiotics, there was no significant mortality difference. 6-hour, 24-hour, and 48-hour lactate clearance (HR: 4.000, 95% CI: 1.309-12.219, P = 0.015) and vasopressor use (HR: 4.156, 95% CI: 1.461-11.824, P = 0.008) were significantly associated with mortality after adjusting for confounding variables.

CONCLUSIONS

Lactate clearance at a discrete time point seems to be a more reliable prognostic index than initial lactate value in severe sepsis patients with lactic acidosis who were supplementing with sodium bicarbonate. Careful consideration of vasopressor use and the initial application of broad-spectrum antibiotics within the first 48 hours may be helpful for improving survival, and further study is warranted.

Treatment options for lactic acidosis and metabolic crisis in children with mitochondrial disease

The mitochondrial pyruvate oxidation route is a tightly regulated process, which is essential for aerobic cellular energy production. Disruption of this pathway may lead to severe neurometabolic disorders with onset in early childhood. A frequent finding in these patients is acute and chronic lactic acidemia, which is caused by increased conversion of pyruvate via the enzyme lactate dehydrogenase. Under stable clinical conditions, this process may remain well compensated and does not require specific therapy. However, especially in situations with altered energy demands, such as febrile infections or longer periods of fasting, children with mitochondrial disorders have a high risk of metabolic decompensation with exacerbation of hyperlactatemia and severe metabolic acidosis. Unfortunately, no controlled studies regarding therapy of this critical condition are available and clinical outcome is often unfavorable. Therefore, the aim of this review was to formulate expert-based suggestions for treatment of these patients, including dietary recommendations, buffering strategies and specific drug therapy. However, it is important to keep in mind that a specific therapy for the underlying metabolic cause in children with mitochondrial diseases is usually not available and symptomatic therapy especially of severe lactic acidosis has its ethical limitations.

Effect of sodium bicarbonate administration on mortality in patients with lactic acidosis: a retrospective analysis

Background

Lactic acidosis is a common cause of high anion gap metabolic acidosis. Sodium bicarbonate may be considered for an arterial pH <7.15 but paradoxically depresses cardiac performance and exacerbates acidosis by enhancing lactate production. This study aimed to evaluate the cause and mortality rate of lactic acidosis and to investigate the effect of factors, including sodium bicarbonate use, on death.

Methods

We conducted a single center analysis from May 2011 through April 2012. We retrospectively analyzed 103 patients with lactic acidosis among 207 patients with metabolic acidosis. We used SOFA and APACHE II as severity scores to estimate illness severity. Multivariate logistic regression analysis and Cox regression analysis models were used to identify factors that affect mortality.

Results

Of the 103 patients with a mean age of 66.1±11.4 years, eighty-three patients (80.6%) died from sepsis (61.4%), hepatic failure, cardiogenic shock and other causes. The percentage of sodium bicarbonate administration (p = 0.006), catecholamine use, ventilator care and male gender were higher in the non-survival group than the survival group. The non-survival group had significantly higher initial and follow-up lactic acid levels, lower initial albumin, higher SOFA scores and APACHE II scores than the survival group. The mortality rate was significantly higher in patients who received sodium bicarbonate. Sodium bicarbonate administration (p = 0.016) was associated with higher mortality. Independent factors that affected mortality were SOFA score (Exp (B) = 1.72, 95% CI = 1.12–2.63, p = 0.013) and sodium bicarbonate administration (Exp (B) = 6.27, 95% CI = 1.10–35.78, p = 0.039).

Conclusions

Lactic acidosis, which has a high mortality rate, should be evaluated in patients with metabolic acidosis. In addition, sodium bicarbonate should be prescribed with caution in the case of lactic acidosis because sodium bicarbonate administration may affect mortality.

Long-term safety of dichloroacetate in congenital lactic acidosis

We followed 8 patients (4 males) with biochemically and/or molecular genetically proven deficiencies of the E1α subunit of the pyruvate dehydrogenase complex (PDC; 3 patients) or respiratory chain complexes I (1 patient), IV (3 patients) or I+IV (1 patient) who received oral dichloroacetate (DCA; 12.5 mg/kg/12 h) for 9.7 to 16.5 years. All subjects originally participated in randomized controlled trials of DCA and were continued on an open-label chronic safety study. Patients (1 adult) ranged in age from 3.5 to 40.2 years at the start of DCA administration and are currently aged 16.9 to 49.9 years (mean ± SD: 23.5 ± 10.9 years). Subjects were either normal or below normal body weight for age and gender. The 3 PDC deficient patients did not consume high fat (ketogenic) diets. DCA maintained normal blood lactate concentrations, even in PDC deficient children on essentially unrestricted diets. Hematological, electrolyte, renal and hepatic status remained stable. Nerve conduction either did not change or decreased modestly and led to reduction or temporary discontinuation of DCA in 3 patients, although symptomatic worsening of peripheral neuropathy did not occur. We conclude that chronic DCA administration is generally well-tolerated in patients with congenital causes of lactic acidosis and is effective in maintaining normal blood lactate levels, even in PDC-deficient children not consuming strict ketogenic diets.

[Lactic acidosis in a patient with exercabation of asthma receiving inhalation therapy]

We present a case of severe lactic acidosis due to exacerbation of asthma in presence of normal tissue perfusion and oxygenation in a 35-year-old woman with poorly controlled asthma. After admission, she was treated continuously with inhalation of salbutamol (a beta-agonist) resulting in lactic acidosis, which was misinterpreted as treatment failure. The lactic acidosis reversed on discontinuation of the inhalation therapy. Although lactic acidosis is a rare complication to inhalation of beta-agonists, it is important for the clinicians to recognize this.

Sodium bicarbonate treatment during transient or sustained lactic acidemia in normoxic and normotensive rats

Introduction

Lactic acidosis is a frequent cause of poor outcome in the intensive care settings. We set up an experimental model of lactic acid infusion in normoxic and normotensive rats to investigate the systemic effects of lactic acidemia per se without the confounding factor of an underlying organic cause of acidosis.

Methodology

Sprague Dawley rats underwent a primed endovenous infusion of L(+) lactic acid during general anesthesia. Normoxic and normotensive animals were then randomized to the following study groups (n = 8 per group): S) sustained infusion of lactic acid, S+B) sustained infusion+sodium bicarbonate, T) transient infusion, T+B transient infusion+sodium bicarbonate. Hemodynamic, respiratory and acid-base parameters were measured over time. Lactate pharmacokinetics and muscle phosphofructokinase enzyme's activity were also measured.

Principal Findings

Following lactic acid infusion blood lactate rose (P<0.05), pH (P<0.05) and strong ion difference (P<0.05) drop. Some rats developed hemodynamic instability during the primed infusion of lactic acid. In the normoxic and normotensive animals bicarbonate treatment normalized pH during sustained infusion of lactic acid (from 7.22±0.02 to 7.36±0.04, P<0.05) while overshoot to alkalemic values when the infusion was transient (from 7.24±0.01 to 7.53±0.03, P<0.05). When acid load was interrupted bicarbonate infusion affected lactate wash-out kinetics (P<0.05) so that blood lactate was higher (2.9±1 mmol/l vs. 1.0±0.2, P<0.05, group T vs. T+B respectively). The activity of phosphofructokinase enzyme was correlated with blood pH (R2 = 0.475, P<0.05).

Conclusions

pH decreased with acid infusion and rose with bicarbonate administration but the effects of bicarbonate infusion on pH differed under a persistent or transient acid load. Alkalization affected the rate of lactate disposal during the transient acid load.

Treating acute asthma--salbutamol may not always be the right answer

β2 agonists are used as first-line treatment in acute asthma. However, they may paradoxically worsen respiratory failure through development of lactic acidosis

A rare metabolic complication of acute lymphoblastic leukemia in childhood: lactic acidosis

A 13-year-old boy presented with nausea, fatigue, weight loss, and bone pain for two months. Complete blood count and serum renal and liver function tests were all normal. Blood gas analysis revealed severe metabolic acidosis with high anion gap. Lactate level was 61.2 mmol/L. Abdominal ultrasonography yielded bilateral nephromegaly and hepatomegaly with increased echogenicity. Peripheral blood smear revealed 2% blasts. Bone marrow aspiration showed 'Common ALL Antigen'-negative acute lymphoblastic leukemia by flow cytometric analysis. Metabolic acidosis dissolved as soon as chemotherapy was begun. Lactic acidosis at the presentation of acute lymphoblastic leukemia--especially with low tumor burden--is a very rare and almost always fatal complication. Our patient is still alive and in remission, which is a point of interest in this child.

Thiamine supplementation in the critically ill

PURPOSE OF REVIEW

To summarize the properties of thiamine and evaluate current evidence on thiamine status and supplementation, for different populations of critically ill patients.

RECENT FINDINGS

Thiamine, in the form of thiamine pyrophosphate, is a critical co-factor in the glyocolysis and oxidative decarboxylation of carbohydrates for energy production. Different studies have shown that critical illness in adults and children is characterized by absolute or relative thiamine depletion, which is associated with an almost 50% increase in mortality. Thiamine deficiency should be suspected in different clinical scenarios such as severe sepsis, burns, unexplained heart failure or lactic acidosis, neurological disorder in patients with previous history of alcoholism, starvation, chronic malnutrition, long-term parenteral feeding, hyperemesis gravidarum, or bariatric surgery. Nonetheless, thiamine supplements are not routinely given to critically ill patients. Clinicians should be able to suspect and recognize risk factors for the occurrence of severe neurological disorders secondary to thiamine deficiency, as early treatment can prevent the appearance of permanent neurological damage.

SUMMARY

Symptoms and signs associated with thiamine deficiency lack sensitivity and specificity in critically ill patients. Consequently, depletion is frequently unrecognized and underdiagnosed by clinicians. Potentially deleterious consequences of thiamine depletion should be avoided by early and appropriate supplementation.

Dihydrolipoamide dehydrogenase (DLD) deficiency in a Spanish patient with myopathic presentation due to a new mutation in the interface domain

We present a 32-year-old patient who, from age 7 months, developed photophobia, left-eye ptosis and progressive muscular weakness. At age 7 years, she showed normal psychomotor development, bilateral ptosis and exercise-induced weakness with severe acidosis. Basal blood and urine lactate were normal, increasing dramatically after effort. PDHc deficiency was demonstrated in muscle and fibroblasts without detectable PDHA1 mutations. Ketogenic diet was ineffective, however thiamine gave good response although bilateral ptosis and weakness with acidosis on exercise persisted. Recently, DLD gene analysis revealed a homozygous missense mutation, c.1440 A>G (p.I480M), in the interface domain. Both parents are heterozygous and DLD activity in the patient's fibroblasts is undetectable. The five patients that have been reported with DLD-interface mutations suffered fatal deteriorations. Our patient's disease is milder, only myopathic, more similar to that due to mutation p.G229C in the NAD(+)-binding domain. Two of the five patients presented mutations (p.D479V and p.R482G) very close to the present case (p.I480M). Despite differing degrees of clinical severity, all three had minimal clues to DLD deficiency, with occasional minor increases in α-ketoglutarate and branched-chain amino acids. In the two other patients, hypertrophic cardiomyopathy was a significant feature that has been attributed to moonlighting proteolytic activity of monomeric DLD, which can degrade other mitochondrial proteins, such as frataxin. Our patient does not have cardiomyopathy, suggesting that p.I480M may not affect the DLD ability to dimerize to the same extent as p.D479V and p.R482G. Our patient, with a novel mutation in the DLD interface and mild clinical symptoms, further broadens the spectrum of this enzyme defect.

Reality of severe metformin-induced lactic acidosis in the absence of chronic renal impairment

BACKGROUND

Lactic acidosis in metformin use is a widely recognised but rare side effect. Case reports usually describe elderly patients with conditions which in themselves can cause lactic acidosis or with known contraindications to metformin. We present cases of an elderly woman, a younger woman and a man who developed serious metformin-induced lactic acidosis in the absence of chronic renal impairment.

RESULTS

Laboratory results showed acute renal failure in all patients. The pH was 6.77, 6.98 and 6.7, respectively, and lactate levels were 18.2, 18.4 and 11.7 mmol/l, respectively. Metformin plasma levels were 58, 57 and 39 mg/l. All patients received continuous veno-venous haemofiltration (CVVH), using bicarbonate as a buffer solution shortly after arrival on our ICU. In the subsequent hours, a steep decline in the plasma levels was observed, with a concomitant increase in pH. No other diagnoses were made, so we concluded that all patients were suffering from metformin-induced lactic acidosis. Despite the severity of the metabolic acidosis, both female patients survived. Our male patient died after a prolonged stay in the ICU, but this was not related to metformin.

CONCLUSION

Metformin-induced lactic acidosis does exist. Metformin-induced lactic acidosis may occur in patients with previously normal renal function, even in young patients. Patients with extreme (lactic) metabolic acidosis caused by metformin can survive when CVVH treatment is initiated rapidly. Intercurrent symptoms or diseases that affect renal perfusion can precipitate lactic acidosis.

[Clinical implications of lactic acidosis in purulent meningitis]

Lactic acidosis is an integral index of metabolic disturbances and severity of inflammation processes. This study was designed to measure lactate levels in blood and cerebrospinal fluid (CSF), CSF/blood lactate ratio, correlation coefficient between CSF lactate and other CSF parameters in patients with purulent meningitis of different etiology. The study included 112 patients (62 men and 50 women aged 18-70 years) admitted to No2 City Hospital, Moscow, for the treatment of meningococcal and pneumococcal meningitis (40 and 23 respectively), purulent meningitis of unknown etiology (22), staphylococcal sepsis with secondary purulent meningitis (11), serous viral meningitis (9), and non-inflammatory lesions of central nervous system (control group of 7patients). Blood and CSF lactate levels were measured on admittance, days 3- 7and 8-18 after the initiation of therapy. CSF lactate was especially high in patients with primary purulent meningitis having lower blood lactate levels. Patients with sepsis and secondary purulent meningitis had higher lactate levels in plasma than in CSF on admittance and days 8-18 after the onset of therapy; this situation reflects a generalized infectious process. CSF lactate positively correlated with protein content and pleocytosis intensity in the liquor and negatively with the glucose level. Prognosis of the disease depended on the efficiency of antibacterial therapy.

Effects of hypertonic sodium bicarbonate solution on electrolyte concentrations and enzyme activities in newborn calves with respiratory and metabolic acidosis

OBJECTIVE

To determine concentrations of electrolytes, total bilirubin, urea, creatinine, and hemoglobin; activities of some enzymes; and Hct and number of leukocytes and erythrocytes of newborn calves in relation to the degree of acidosis and treatment with a hypertonic sodium bicarbonate (NaHCO(3)) solution.

ANIMALS

20 acidotic newborn calves with a blood pH < 7.2 and 22 newborn control calves with a blood pH > or = 7.2.

PROCEDURES

Approximately 10 minutes after birth, acidotic calves were treated by IV administration of 5% NaHCO(3) solution. The amount of hypertonic solution infused was dependent on the severity of the acidosis.

RESULTS

Treatment resulted in a significant increase in the mean +/- SEM base excess from -8.4 +/- 1.2 mmol/L immediately after birth to 0.3 +/- 1.1 mmol/L 120 minutes later. During the same period, sodium concentration significantly increased from 145.3 +/- 0.8 mmol/L to 147.8 +/- 0.7 mmol/L. Mean chloride concentration before NaHCO(3) administration was significantly lower in the acidotic calves (99.6 +/- 1.1 mmol/L) than in the control calves (104.1 +/- 0.9 mmol/L). Calcium concentration in acidotic calves decreased significantly from before to after treatment. Concentrations of potassium, magnesium, and inorganic phosphorus were not affected by treatment.

CONCLUSIONS AND CLINICAL RELEVANCE

Administration of hypertonic NaHCO(3) solution to acidotic neonatal calves did not have any adverse effects on plasma concentrations of several commonly measured electrolytes or enzyme activities. The treatment volume used was smaller, compared with that for an isotonic solution, which makes it more practical for use in field settings.

Investigations on the association of D-lactate blood concentrations with the outcome of therapy of acidosis, and with posture and demeanour in young calves with diarrhoea

The objective of this prospective study was to elucidate whether amounts of bicarbonate needed for correction of acidosis and normalization of clinical signs are influenced by blood D-lactate concentrations in calves with diarrhoea. In 73 calves up to 3 weeks old with acute diarrhoea and base excess values below -10 mmol/l correction of acidosis was carried out within 3.5-h by intravenous administration of an amount of sodium bicarbonate which was calculated using the formula: HCO (mmol) = body mass (kg) x base deficit (mmol/l) x 0.6 (l/kg). Clinical signs, venous base excess, and plasma D-lactate concentrations were monitored immediately following admission, following correction of acidosis at 4 h and 24 h after admission. The base excess and plasma D-lactate concentrations throughout the study were -17.8 +/- 4.0, -0.4 +/- 0.4, -3.0 +/- 5.5 mmol/l (base excess), and 10.0 +/- 4.9, 9.8 +/- 4.8, 5.4 +/- 3.4 mmol/l (D-lactate) for the three times of examination. Metabolic acidosis was not corrected in more than half of the calves (n = 43) by the calculated amount of bicarbonate, whereas the risk of failure to correct acidosis increases with D-lactate concentrations. The study shows that calves with elevated D-lactate concentrations do not need additional specific therapy, as D-lactate concentrations regularly fall following correction of acidosis and restitution of body fluid volume, for reasons that remain unclear. However, calves with distinct changes in posture and demeanour need higher doses of bicarbonate than calculated with the factor of 0.6 in the formula mentioned above probably because of D-hyperlactataemia.

Metabolic acidosis

Acute metabolic acidosis is frequently encountered in critically ill patients. Metabolic acidosis can occur as a result of either the accumulation of endogenous acids that consumes bicarbonate (high anion gap metabolic acidosis) or loss of bicarbonate from the gastrointestinal tract or the kidney (hyperchloremic or normal anion gap metabolic acidosis). The cause of high anion gap metabolic acidosis includes lactic acidosis, ketoacidosis, renal failure and intoxication with ethylene glycol, methanol, salicylate and less commonly with pyroglutamic acid (5-oxoproline), propylene glycole or djenkol bean (gjenkolism). The most common causes of hyperchloremic metabolic acidosis are gastrointestinal bicarbonate loss, renal tubular acidosis, drugs-induced hyperkalemia, early renal failure and administration of acids. The appropriate treatment of acute metabolic acidosis, in particular organic form of acidosis such as lactic acidosis, has been very controversial. The only effective treatment for organic acidosis is cessation of acid production via improvement of tissue oxygenation. Treatment of acute organic acidosis with sodium bicarbonate failed to reduce the morbidity and mortality despite improvement in acid-base parameters. Further studies are required to determine the optimal treatment strategies for acute metabolic acidosis.

Metabolic acidosis in childhood: why, when and how to treat

OBJECTIVES

To critically discuss the treatment of metabolic acidosis and the main mechanisms of disease associated with this disorder; and to describe controversial aspects related to the risks and benefits of using sodium bicarbonate and other therapies.

SOURCES

Review of PubMed/MEDLINE, LILACS and Cochrane Library databases for articles published between 1996 and 2006 using the following keywords: metabolic acidosis, lactic acidosis, ketoacidosis, diabetic ketoacidosis, cardiopulmonary resuscitation, sodium bicarbonate, treatment. Classical publications concerning the topic were also reviewed. The most recent and representative were selected, with emphasis on consensus statements and guidelines.

SUMMARY OF THE FINDINGS

There is no evidence of benefits resulting from the use of sodium bicarbonate for the hemodynamic status, clinical outcome, morbidity and mortality in high anion gap metabolic acidosis associated with lactic acidosis, diabetic ketoacidosis and cardiopulmonary resuscitation. Therefore, the routine use of sodium bicarbonate is not indicated. Potential side effects must be taken into consideration. Treating the underlying disease is essential to reverse the process. The efficacy of other alternative therapies has not been demonstrated in large-scale studies.

CONCLUSIONS

Despite the known effects of acidemia on the organism in critical situations, a protective role of acidemia in hypoxic cells and the risk of alkalemia secondary to drug interventions are being considered. There is consensus regarding the advantages of alkali and sodium bicarbonate therapy in cases with normal anion gap; however, in the presence of high anion gap acidosis, especially lactic acidosis, diabetic acidosis and cardiopulmonary resuscitation, the use of sodium bicarbonate is not beneficial and has potential adverse effects, limiting its indication. The only points of agreement in the literature refer to the early treatment of the underlying disease and the mechanisms generating metabolic acidemia. Other promising treatment alternatives have been proposed; however, the side effects and absence of controlled studies with pediatric populations translate into lack of evidence to support the routine use of such treatments.

Approaches to the treatment of mitochondrial diseases

Therapy for mitochondrial diseases is woefully inadequate. However, lack of a cure does not equate with lack of treatment. Palliative therapy is dictated by good medical practice and includes anticonvulsant medication, control of endocrine dysfunction, and surgical procedures. Removal of noxious metabolites is centered on combating lactic acidosis, but extends to other metabolites. Attempts to bypass blocks in the respiratory chain by administration of electron acceptors have not been successful, but this may be amenable to genetic engineering. Administration of metabolites and cofactors is the mainstay of real-life therapy and is especially important in disorders due to primary deficiencies of specific compounds, such as carnitine or coenzyme Q10 (CoQ10). There is increasing interest in the administration of reactive oxygen radicals (ROS) scavengers, both in primary mitochondrial diseases and in neurodegenerative diseases. Gene therapy is a challenge because of polyplasmy and heteroplasmy, but novel experimental approaches are being pursued. One important strategy is to decrease the ratio of mutant to wild-type mitochondrial genomes ("gene shifting") by different means: (1) converting mutated mitochondrial DNA (mtDNA) genes into normal nuclear DNA genes ("allotopic expression"); (2) importing cognate genes from other species ("xenotopic expression"); (3) correcting mtDNA mutations by importing specific restriction endonucleases; (4) selecting for respiratory function; and (5) inducing muscle regeneration. Germline therapy raises ethical problems but is being considered for prevention of maternal transmission of mtDNA mutations. Preventive therapy through genetic counseling and prenatal diagnosis is becoming increasingly important for nuclear DNA-related disorders.

Floppy kid syndrome caused by D-lactic acidosis in goat kids

BACKGROUND

Goat kids with floppy kid syndrome have metabolic acidosis, muscle weakness, and depression but no dehydration.

HYPOTHESIS

D-Lactate is the major component of acidemia in goat kids with floppy kid syndrome.

ANIMALS

Fifty-five goat kids with floppy kid syndrome (group F) and 35 clinically healthy goat kids (group C).

METHODS

Clinical, biochemical, microbiologic, virologic, parasitologic, and pathologic examinations.

RESULTS

The animals in group F had a blood pH of 7.13 +/- 0.11 and a base excess of -17.8 +/- 3.8 mM, which were both lower than the values in the control animals (pH, 7.32 +/- 0.31; base excess, -0.1 +/- 2.7 mM; P < .001). Floppy kids had a significantly larger anion gap than healthy kids (31.2 +/- 3.7 versus 21.5 +/- 8.5 mM; P < .001). The concentration of L-lactate was lower in floppy kids than in healthy kids (0.67 +/- 0.49 versus 1.60 +/- 1.02 mM), but the concentration of D-lactate was higher in floppy kids (7.43 +/- 2.71 versus 0.26 +/- 0.24 mM; P < .001). Intravenous and oral administration of sodium bicarbonate in floppy kids resulted in a significant increase in blood pH and base excess and a decrease in the anion gap (P < .001). In addition, the concentration of L-lactate increased (P = .039).

CONCLUSIONS AND CLINICAL IMPORTANCE

Metabolic acidosis in goat kids with floppy kid syndrome is caused by an increase in the plasma concentration of D-lactate.

[Experimental study of the efficacy of apovincaminic acid derivative on the model of reperfusive cerebral damage]

Neuroprotector properties of a new apovincaminic acid derivative (LHT 2 - 02) were studied on a model of acute brain ischemia in cats. LHT 2 - 02 has proved to be more effective than the reference drugs vinpocetin and glycine in preventing the reperfusive damage, which was manifested by decreased postishemic hyperglycemia and suppressed postishemic metabolic lactate acidosis.

Lactobacillus GG does not affect D-lactic acidosis in diarrheic calves, in a clinical setting

D-lactate, produced by gastrointestinal fermentation, is a major contributor to metabolic acidosis in diarrheic calves. Lactobacillus rhamnosus GG survives gastrointestinal transit in the neonatal calf and does not produce D-lactate. To determine whether this probiotic reduces gastrointestinal D-lactate production or severity of diarrhea or both, 48 calves (mean, 11 days old; range, 2-30 days) admitted to the clinic for treatment of diarrhea were randomly allocated to 2 groups. The experimental group was given Lactobacillus rhamnosus GG (1 x 10(11) cfu/d) PO, dissolved in milk or oral electrolyte solution, in addition to clinic treatment protocols; the other group served as a control. Serum and fecal samples were obtained at admission and at 24 and 48 hours after initial administration of Lactobacillus rhamnosus GG. All samples were analyzed for D- and L-lactate by using high-pressure liquid chromatography. Feces were also analyzed for pathogens, Lactobacillus rhamnosus GG recovery, and dry matter. D-lactic acidemia (>3 mmol/L) was present in 37/48 calves at admission. Lactobacillus rhamnosus GG was recovered in the feces of 13 experimental calves and 0 control calves 24 hours after administration. No difference in serum or fecal D- or L-lactate between the groups was detected at any time point. After therapy, D-lactic acidosis was absent at 48 hours in all but 1 calf. No relation between fecal pathogen (viral, bacterial, or protozoal) and degree of D-lactic acidosis was observed. The reduction in mortality and greater fecal dry matter in Lactobacillus rhamnosus GG-treated calves was not statistically significant.

Controlled clinical trial of dichloroacetate for treatment of congenital lactic acidosis in children

OBJECTIVE

Open-label studies indicate that oral dichloroacetate (DCA) may be effective in treating patients with congenital lactic acidosis. We tested this hypothesis by conducting the first double-blind, randomized, control trial of DCA in this disease.

METHODS

Forty-three patients who ranged in age from 0.9 to 19 years were enrolled. All patients had persistent or intermittent hyperlactatemia, and most had severe psychomotor delay. Eleven patients had pyruvate dehydrogenase deficiency, 25 patients had 1 or more defects in enzymes of the respiratory chain, and 7 patients had a mutation in mitochondrial DNA. Patients were preconditioned on placebo for 6 months and then were randomly assigned to receive an additional 6 months of placebo or DCA, at a dose of 12.5 mg/kg every 12 hours. The primary outcome results were (1) a Global Assessment of Treatment Efficacy, which incorporated tests of neuromuscular and behavioral function and quality of life; (2) linear growth; (3) blood lactate concentration in the fasted state and after a carbohydrate meal; (4) frequency and severity of intercurrent illnesses and hospitalizations; and (5) safety, including tests of liver and peripheral nerve function.

OUTCOME

There were no significant differences in Global Assessment of Treatment Efficacy scores, linear growth, or the frequency or severity of intercurrent illnesses. DCA significantly decreased the rise in blood lactate caused by carbohydrate feeding. Chronic DCA administration was associated with a fall in plasma clearance of the drug and with a rise in the urinary excretion of the tyrosine catabolite maleylacetone and the heme precursor delta-aminolevulinate.

CONCLUSIONS

In this highly heterogeneous population of children with congenital lactic acidosis, oral DCA for 6 months was well tolerated and blunted the postprandial increase in circulating lactate. However, it did not improve neurologic or other measures of clinical outcome.

Appendix to the German-Austrian HIV Therapeutic Guidelines: strategies for treating morphological and metabolic alterations under antiretroviral treatment (current as of December 2004)

The recommendations made in this review are based on the current clinical knowledge with regard to the origin and therapy of lipodystrophy. They should be regarded as provisional and will change with expanding knowledge. The recommendations for treating dyslipidaemia in particular are oriented closely on the American recommendations of the National Cholesterol Education Program (NCEP III), and may be regarded both by HIV practitioners and patients as excessive and too rigid. The therapeutic goals of the NCEP in the first intervention studies in HIV-positive individuals were only achieved for a small proportion of the HIV patients. In addition, preliminary results suggest a potentially higher risk of adverse events in HIV-patients under statins or fibrates. The clinical efficacy of interventions with lipid lowering drugs has not been validated in HIV-seropositive patients. However, therapeutic decisions so far have been based on data obtained in non-HIV cardiovascular intervention studies. With more and more results becoming available from the HIV patient population a revision of these recommendations will be required.

Malaria and fluids – balancing acts

Severe malaria has many manifestations, of which coma and lactic acidosis are the best independent predictors of a fatal outcome. Most deaths from malaria occur within the first 24 h of admission, despite appropriate antimalarial chemotherapy. Adjunctive therapy for severe malaria has been seen as a way to improve survival by 'buying time' until antimalarials can act. Several adjunctive therapies have undergone clinical trials in the past 25 years but all of these trials showed worsened outcome or no benefit to patients receiving adjuncts compared with those receiving placebo. Although metabolic acidosis occurs in both hypovolaemia and malaria, the contribution of the former to the pathophysiology of severe malaria is unclear. I suggest that lactic acidosis due to malaria can be explained primarily by factors that are independent of volume depletion. Lactic acidosis in malaria can be treated safely with dichloroacetate. This intervention could prove useful as an adjunctive therapy aimed at reducing mortality rates in severe malaria.

Lactic acidosis. Lactic acidosis associated with metformin use in treatment of type 2 diabetes mellitus

Metformin, an antihyperglycemic, is widely used in the treatment of type 2 diabetes mellitus (DM). A rare, but important complication associated with this drug is the development of lactic acidosis: Overall mortality of lactic acidosis is approximately 50%. Certain subsets of patients taking metformin are at greater risk of developing lactic acidosis. This report discusses the development of metformin-associated lactic acidosis in four older adults admitted to an institution during a 2-month period, treatments, and outcomes. We recommend an aggressive treatment strategy of hemodialysis followed by peritoneal dialysis, continuous bicarbonate infusion, and tight glucose control. We review the cautions and contraindications of metformin use for the treatment of type 2 DM and report an educational plan for residents and staff instituted to improve drug complication awareness and reduce mortality.

Yeast mediates lactic acidosis suppression after antibiotic cocktail treatment in short small bowel?

During acidotic periods in a girl with a short small bowel, very high D-lactic acid concentrations were measured in blood and urine; the patient's characteristic faecal flora contained mainly lactobacilli, and during antibiotic cocktail treatment also many yeasts. In this case report we sought to understand the beneficial effect of the antibiotic cocktail. Microbiological analysis was performed in faecal samples. Total lactic acid in serum and urine was studied using capillary gas chromatography-mass spectrometry, and D- and L-lactic acid in serum and urine by enzymatic assay. The results were coupled to patient's condition. Antibiotic cocktail therapy reduced the acidosis-associated symptoms, faecal lactobacilli and D-lactic acid production, but simultaneously the antibiotic therapy strongly increased the percentage of yeast in the faecal flora. Four to six weeks after each course of treatment the percentage of yeast decreased, whereas the percentage of intestinal lactobacilli increased; D-lactic acid also simultaneously increased in blood and urine. The patient felt well and showed a high percentage of intestinal yeast, but she often suffered from acidosis owing to a high percentage of lactobacilli. The yeast was identified as the pathogenic Candida glabrata. From the mentioned data together with data from the literature it was concluded that during several weeks the selected pathogenic yeast, C. glabrata, acted as a microbiological and metabolic buffer. Shortly after the course of antibiotic treatment this intestinal yeast strongly competed with the intestinal lactobacilli and thus prevented renewed rapid growth, massive D-lactic acid production from glucose and consequently also D-lactic acid-associated acidosis. The emergence of this yeast led us to consider probiotic lactobacilli or yeast for therapeutic use. The lack of knowledge regarding bile acid-deconjugating activity in both lactobacilli and probiotic yeast means that a final recommendation is not yet possible.

Thiamine-responsive congenital lactic acidosis: clinical and biochemical studies

We studied six infants with thiamine-responsive congenital lactic acidosis and normal pyruvate dehydrogenase complex activity in vitro, through clinical and biochemical analysis. In addition to elevated lactate and pyruvate levels, the data revealed increased urinary excretion of alpha-ketoglutarate, alpha-ketoadipate, and branched chain ketoacids, indicating functional impairment of thiamine-requiring enzymes, such as pyruvate dehydrogenase complex, alpha-ketoglutarate dehydrogenase complex, alpha-ketoadipate dehydrogenase, and branched chain amino acid dehydrogenase. The metabolism of thiamine has not been investigated in patients with thiamine-responsive congenital lactic acidosis. We evaluated two specific transport systems, THTR-1 (SLC19A2) and THTR-2 (SLC19A3), and a pyrophosphorylating enzyme of thiamine, thiamine pyrophosphokinase (hTPK 1), in addition to pyruvate dehydrogenase complex and alpha-ketoglutarate dehydrogenase complex activity; no abnormality was found. Although the clinical features of thiamine-responsive congenital lactic acidosis are heterogeneous and clinical responses to thiamine administration vary, we emphasize the importance of early diagnosis and initiation of thiamine therapy before the occurrence of permanent brain damage. Careful monitoring of lactate and pyruvate would be useful in determining thiamine dosage.

Therapeutic approach in a case of Pearson's syndrome

Mitochondrial cytopathy is a multisystemic disease that requires different pharmacological and specialist approaches; although most therapies are usually of scarce effectiveness. We describe a clinical management of a very young girl with Pearson's syndrome that developed the symptoms of Kearns-Sayre syndrome. Many of symptoms were temporarily improved by the replacement therapy with hydrocortisone introduced to treat the partial adrenal insufficiency. During her life, she showed an ample clinical spectrum of symptoms because of multiple organs involvements: firstly bone marrow and, thereafter, brain, retina, inner ear, and kidney. Partial adrenal insufficiency, rarely described in mitochondrial disorders, was a distinctive characteristic of this case. When our patient was treated with hydrocortisone, in addition to ubiquinone and carnitine, the episodes of decompensation regressed and an improvement of the adrenal insufficiency, but only temporary reversion of the weakness of muscle, ophthalmoplegia and of the fatigue, were testified. Nevertheless, after a brief period of recovery, she developed the de Toni-Debré-Fanconi syndrome and the reappearance of the neurological symptoms.

Pyruvate in the correction of intracellular acidosis: a metabolic basis as a novel superior buffer

The review focuses on biochemical metabolisms of conventional buffers and emphasizes advantages of sodium pyruvate (Pyr) in the correction of intracellular acidosis. Exogenous lactate (Lac) as an alternative of natural buffer, bicarbonate, consumes intracellular protons on an equimolar basis, regenerating bicarbonate anions in plasma while the completion of gluconeogenesis and/or oxidation occurs via tricarboxylic-acid cycle in mitochondria mainly in liver and kidney, or heart. The general assumption that Lac is 'metabolized to bicarbonate' in liver to serve as a buffer has been questioned. Pyr as a novel buffer would be superior to conventional ones in the correction of metabolic acidosis. Several likely biochemical mechanisms of Pyr action are discussed. Experimental evidence, in vivo, strongly suggested that Pyr would be particularly efficient in the correction of severe acidemia: type A lactic acidosis, hypercapnia with cardiac arrest, and diabetic and alcoholic ketoacidosis in animal experiments and clinic settings. Because of its multi-cytoprotection, Pyrs not only correct acidosis, but also benefit theunderlying dysfunction of vital organs. In addition, Pyr is also a potential buffer component of dialysis solutions. However, the instability of Pyr in aqueous solutions restricts its clinical applications as a therapeutic agent. Attempts to create a stable Pyr preparation are needed.