Metformin is the preferred medication for the initial management of type 2 diabetes mellitus (T2DM). Although its use is widely recommended, caution should be exercised when prescribing it to populations susceptible to systemic hypoperfusion conditions, as it can lead to accumulation in the body and metabolic disturbances that may result in metformin-associated lactic acidosis. This severe complication is often underdiagnosed. To promote a better understanding of this topic, the present review focuses on the analysis of the clinical, pathophysiological, diagnostic, and management aspects of metformin-associated lactic acidosis, with particular attention to management through renal replacement therapies. The analysis will be based on the experience of a series of cases of metformin-associated lactic acidosis treated at a hospital clinical center in Chile.

OBJECTIVE: The mitochondrial elongation factor Tu (EF-Tu), encoded by the TUFM gene, is a GTPase, which is part of the mitochondrial protein translation mechanism. If it is activated, it delivers the aminoacyl-tRNAs to the mitochondrial ribosome. Here, a patient was described with a homozygous missense variant in the TUFM [c.1016G>A (p.Arg339Gln)] gene. To date, only six patients have been reported with bi-allelic pathogenic variants in TUFM, leading to combined oxidative phosphorylation deficiency 4 (COXPD4) characterized by severe early-onset lactic acidosis, encephalopathy, and cardiomyopathy.
METHODS: The patient presented here had the phenotypic features of TUFM-related disease, lactic acidosis, hypotonia, liver dysfunction, optic atrophy, and mild encephalopathy.
CONCLUSIONS: We aimed to expand the clinical spectrum of pathogenic variants of TUFM.

Metformin intoxication causes lactic acidosis by inhibiting Krebs\' cycle and oxidative phosphorylation. Continuous renal replacement therapy (CRRT) is recommended for metformin removal in critically ill patients. According to current guidelines, regional citrate anticoagulation (RCA) is the first-line strategy. However, since metformin also inhibits citrate metabolism, a risk of citrate accumulation could be hypothesized. In the present study, we monitored the potential citrate accumulation in metformin-associated lactic acidosis (MALA) patients treated with CRRT and RCA using the physical-chemical approach to acid-base interpretation.
We collected a case series of 3 patients with MALA. Patients were treated with continuous venovenous hemofiltration (CVVH), and RCA was performed with diluted citrate solution. Citrate accumulation was monitored through two methods: the ratio between total and ionized plasma calcium concentrations (T/I calcium ratio) above 2.5 and the strong ion gap (SIG) to identify an increased concentration of unmeasured anions. Lastly, a mathematical model was developed to estimate the expected citrate accumulation during CVVH and RCA.
All 3 patients showed a resolution of MALA after the treatment with CVVH. The T/I calcium ratio was consistently below 2.5, and SIG decreased, reaching values lower than 6 mEq/L after 48 h of CVVH treatment. According to the mathematical model, the estimated SIG without citrate metabolism should have been around 21 mEq/L due to citrate accumulation.
In our clinical management, no signs of citrate accumulation were recorded in MALA patients during treatment with CVVH and RCA. Our data support the safe use of diluted citrate to perform RCA during metformin intoxication.

The use of sodium bicarbonate to treat metabolic acidosis is intuitive, yet data suggest that not all patients benefit from this therapy.
In this narrative review, we describe the physiology behind commonly encountered nontoxicologic causes of metabolic acidosis, highlight potential harm from the indiscriminate administration of sodium bicarbonate in certain scenarios, and provide evidence-based recommendations to assist emergency physicians in the rational use of sodium bicarbonate.
Sodium bicarbonate can be administered as a hypertonic push, as a resuscitation fluid, or as an infusion. Lactic acidosis and cardiac arrest are two common scenarios where there is limited benefit to routine use of sodium bicarbonate, although certain circumstances, such as patients with concomitant acute kidney injury and lactic acidosis may benefit from sodium bicarbonate. Patients with cardiac arrest secondary to sodium channel blockade or hyperkalemia also benefit from sodium bicarbonate therapy. Recent data suggest that the use of sodium bicarbonate in diabetic ketoacidosis does not confer improved patient outcomes and may cause harm in pediatric patients. Available evidence suggests that alkalinization of urine in rhabdomyolysis does not improve patient-centered outcomes. Finally, patients with a nongap acidosis benefit from sodium bicarbonate supplementation.
Empiric use of sodium bicarbonate in patients with nontoxicologic causes of metabolic acidosis is not warranted and likely does not improve patient-centered outcomes, except in select scenarios. Emergency physicians should reserve use of this medication to conditions with clear benefit to patients.

Lactic acidosis is a potential adverse event related to metformin therapy. Although metformin-associated lactic acidosis (MALA) is a rare condition (about 10 cases / 100,000 patients / year), new cases continue to be reported, with a mortality of 40-50%. We describe two clinical cases characterized by severe metabolic acidosis, hyperlactacidemia, and acute renal injury. The first also with NSTEMI, successfully treated.

Objective: To investigate the clinical features and genetic features of combined oxidative phosphorylation deficiency 32 (COXPD32) caused by MRPS34 gene variation. Methods: The clinical data and genetic test of a child with COXPD32 hospitalized in the Department of Neurology, Children\'s Hospital, Capital Institute of Pediatrics in March 2021 were extracted and analyzed. A literature search was implemented using Wanfang, China biology medicine disc, China national knowledge infrastructure, ClinVar, human gene mutation database (HGMD) and Pubmed databases with the key words \"MRPS34\" \"MRPS34 gene\" and \"combined oxidative phosphorylation deficiency 32\" (up to February 2023). Clinical and genetic features of COXPD32 were summarized. Results: A boy aged 1 year and 9 months was admitted due to developmental delay. He showed mental and motor retardation, and was below the 3rd percentile for height, weight, and head circumference of children of the same age and gender. He had poor eye contact, esotropia, flat nasal bridge, limbs hypotonia, holding instability and tremors. In addition, Grade Ⅲ/6 systolic murmur were heard at left sternal border. Arterial blood gases suggested that severe metabolic acidosis with lactic acidosis. Brain magnetic resonance imaging (MRI) showed multiple symmetrical abnormal signals in the bilateral thalamus, midbrain, pons and medulla oblongata. Echocardiography showed atrial septal defect. Genetic testing identified the patient as a compound heterozygous variation of MRPS34 gene, c.580C>T (p.Gln194Ter) and c.94C>T (p.Gln32Ter), with c.580C>T being the first report and a diagnosis of COXPD32. His parents carried a heterozygous variant, respectively. The child improved after treatment with energy support, acidosis correction, and \"cocktail\" therapy (vitaminB1, vitaminB2, vitaminB6, vitaminC and coenzyme Q10). A total of 8 cases with COXPD32 were collected through 2 English literature reviews and this study. Among the 8 patients, 7 cases had onset during infancy and 1 was unknown, all had developmental delay or regression, 7 cases had feeding difficulty or dysphagia, followed by dystonia, lactic acidosis, ocular symptoms, microcephaly, constipation and dysmorphic facies(mild coarsening of facial features, small forehead, anterior hairline extending onto forehead,high and narrow palate, thick gums, short columella, and synophrys), 2 cases died of respiratory and circulatory failure, and 6 were still alive at the time of reporting, with an age range of 2 to 34 years. Blood and (or) cerebrospinal fluid lactate were elevated in all 8 patients. MRI in 7 cases manifested symmetrical abnormal signals in the brainstem, thalamus, and (or) basal ganglia. Urine organic acid test were all normal but 1 patient had alanine elevation. Five patients underwent respiratory chain enzyme activity testing, and all had varying degrees of enzyme activity reduction. Six variants were identified, 6 patients were homozygous variants, with c.322-10G>A was present in 4 patients from 2 families and 2 compound heterozygous variants. Conclusions: The clinical phenotype of COXPD32 is highly heterogenous and the severity of the disease varies from development delay, feeding difficulty, dystonia, high lactic acid, ocular symptoms and reduced mitochondrial respiratory chain enzyme activity in mild cases, which may survive into adulthood, to rapid death due to respiratory and circulatory failure in severe cases. COXPD32 needs to be considered in cases of unexplained acidosis, hyperlactatemia, feeding difficulties, development delay or regression, ocular symptoms, respiratory and circulatory failure, and symmetrical abnormal signals in the brainstem, thalamus, and (or) basal ganglia, and genetic testing can clarify the diagnosis.
目的： 总结MRPS34基因变异致联合氧化磷酸化缺陷症32型（COXPD32）的临床表型及基因型特点。 方法： 回顾性分析2021年3月首都儿科研究所附属儿童医院收治的1例MRPS34基因变异致COXPD32患儿的临床资料及遗传学检测结果，并以“联合氧化磷酸化缺陷症32型”“MRPS34基因”或“combined oxidative phosphorylation deficiency 32”“MRPS34 gene”为关键词分别检索中国知网、万方和中国生物医学文献数据库或ClinVar、人类基因组突变数据库（HGMD）和PubMed数据库建库至2023年2月的文献。总结COXPD32的临床表型及基因型特点。 结果： 患儿，男，1岁9月龄，因“发育迟滞”入院。患儿语言及运动发育落后，眼神接触差，身高、体重及头围均低于同年龄同性别儿童P3。双眼内斜视，鼻梁低平，胸骨左缘闻及Ⅲ/6级收缩期杂音，四肢肌张力减低，持物不稳，存在意向性及静止性震颤。血气分析示重度代谢性酸中毒并乳酸酸中毒；头颅磁共振成像示双侧丘脑、中脑、脑桥及延髓多发对称性异常信号；心脏多普勒超声示房间隔缺损；基因检测示MRPS34基因c.580C>T（p.Gln194Ter）和c.94C>T（p.Gln32Ter）复合杂合变异，分别遗传自其父母，c.580C>T（p.Gln194Ter）为首次报道，诊断为COXPD32。予保证能量、纠正酸中毒、左卡尼汀口服液改善能量代谢及维生素B1、维生素B2、维生素B6、维生素C、辅酶Q10“鸡尾酒”疗法等治疗后患儿病情好转。文献检索到中文文献0篇，英文文献2篇，结合本例共8例患者。7例患者婴儿期内起病，1例不详。8例患者均存在生长发育迟滞或倒退，7例有喂养困难或吞咽困难，其余症状为肌张力障碍、眼部症状、小头畸形、便秘及特殊面容（皮肤粗糙、前额小、发际线低至前额、眉毛粗重、上腭高窄呈“V”形、牙龈厚、鼻小柱短及连眉）等；2例死于呼吸循环衰竭，6例报道时仍存活，年龄范围为2~34岁。8例患者均有血和（或）脑脊液乳酸升高。7例头颅磁共振成像示双侧脑干、丘脑和（或）基底节等大脑深部灰质核团对称性异常信号；尿液有机酸检测仅1例有丙氨酸升高。5例患者行组织呼吸链酶活性检测，均有不同程度的酶活性降低。检索到6个变异位点，6例为纯合变异，2例为复合杂合变异，其中c.322-10G>A在2个家系的4例患者中出现。 结论： MRPS34基因变异所致COXPD32临床表型多样，疾病严重程度轻重不一，轻者表现为生长发育迟缓、喂养困难、肌张力障碍、高乳酸、眼部症状及线粒体呼吸链酶活性降低等，或可存活至成年，重者可因呼吸循环衰竭致死。对于不明原因酸中毒、高乳酸血症、喂养困难、生长发育迟滞或倒退、眼部症状、呼吸循环衰竭及脑干、丘脑和（或）基底节对称性异常信号者，需考虑COXPD32，基因检测可明确诊断。.

Objective: Metformin, commonly prescribed in diabetic patients, can cause lactic acidosis. Although generally rare, this side effect remains a source of concern in procedures requiring contrast media, due to the risk of contrast-induced nephropathy. Temporarily withdrawing metformin during the peri-procedural period is often practiced, but clinical decisions are difficult in emergency situations, such as acute coronary syndromes. In this systematic review with meta-analysis, we aimed to further investigate the safety of percutaneous coronary interventions in patients on concurrent metformin therapy.Design, Setting and Participants: We analyzed studies in patients undergoing (elective or emergency) percutaneous coronary interventions with or without concurrent metformin administration, reporting on the incidence of metformin-associated lactic acidosis and peri-procedural renal function.Methods: PubMed, ClinicalTrials.gov, Cochrane Library, and Scopus were systematically searched without language restrictions throughout August 2022. Randomized clinical trials and observational studies were assessed with the Revised Cochrane Collaboration Risk of Bias tool and the Newcastle-Ottawa quality scale, respectively. Data synthesis addressed the mean drop in estimated glomerular filtration rate (eGFR) and the incidence of contrast-induced nephropathy, in addition to lactic acidosis.Results: Nine studies were included, totaling 2235 patients (1076 continuing metformin during the peri-procedural period), mostly with eGFR above 30 mL/min/1.73m2 No cases of lactic acidosis were reported. The mean post-procedural drop in eGFR was 6.81mL/min/1.73m2 (95% confidence interval [CI]: 3.41 to 10.21) in the presence of metformin and 5.34 mL/min/1.73m2 (95% CI: 2.98 to 7.70) in its absence. The incidence of contrast-induced nephropathy was not affected by concurrent metformin, as shown by a (between-groups) standardized mean difference of 0.0007 (95% CI: -0.1007 to 0.1022).Conclusion: Concurrent metformin during percutaneous coronary interventions in patients with relatively preserved renal function is safe, without added risk of lactic acidosis or contrast-induced nephropathy. Thus, emergency revascularization in the context of acute coronary syndromes should not be deferred. More data from clinical trials in patients with severe renal disease are needed.

BACKGROUND: Thyrotoxic periodic paralysis (TPP) is a rare and most often acquired subtype of hypokalemic periodic paralysis. The association of varying degrees of muscle weakness, hyperthyroidism and hypokalemia characterizes it. The treatment requires potassium supplementation, control of hyperthyroidism and prevention measures. It is a frequent disease in Asian men, but much rare in Caucasian or African populations. This is the first report of TPP associated with lactic metabolic acidosis in an African man.
METHODS: A 23 year-old African man, native from Morocco, with recurrent episodes of tetraparesis for eleven months, and abdominal pain, was referred for evaluation. Biochemical investigations showed severe hypokalemia associated with hyperthyroidism and lactic metabolic acidosis. His EKG showed signs of hypokalemia such as sinus tachycardia and U waves. After potassium supplementation, neurological recuperation was quick and complete. Thyroid ultrasound identified a hypoechogenic and hypervascularized goiter, associated with high levels of thyroid antibodies, in favor of Grave\'s disease. With antithyroid drugs and life-style changes, the patient did not have any other attack.
METHODS: In addition to the case report, this article presents an extended review of literature, from the first large study reporting the diagnosis and incidence of TPP in 1957 to nowadays. Are reported here the latest information concerning epidemiology, clinical manifestations, complementary examinations, management and genetic finding. The lactic acidosis observed initially is exceptional, never described in TPP. TPP is a diagnostic and therapeutic emergency, requiring careful potassium supplementation, in order to avoid the risk of the onset of rebound hyperkalemia, to be maintained until the etiological treatment is effective. Paraclinical assessment with emergency EKG and electromyogram are essential to assess the impact.
CONCLUSIONS: It is essential in the face of any hypokalaemic periodic paralysis, including in non-Asian subjects, to search hyperthyroidism.
CONCLUSIONS: This report demonstrates the importance of thyroid testing in case of acute muscle weakness, even in non-Asian patients in order to diagnose TPP. This is a rare but possible etiology, to be distinguished from the familial form of hypokalemic periodic paralysis. It also questions on the impact of TPP on energetic metabolism, in particular on lactic metabolism.

BACKGROUND: Metformin-treated patients may experience severe hyperlactatemia or lactic acidosis (LA). LA often requires intensive-care-unit (ICU) treatment, and mortality rates are high. Here, we investigate the impact of renal dysfunction and renal replacement therapy (RRT) on the outcomes of critically ill patients with metformin-associated LA (MALA). Furthermore, we assessed associations between mortality and metformin dose, metformin plasma/serum concentrations, lactate level, and arterial pH. Finally, we investigated whether the recommended classification in MALA, metformin-unrelated LA, metformin-induced LA, and LA in metformin therapy appears useful in this regard.
METHODS: We performed a retrospective analysis based on a systematic PubMed search for publications on hyperlactatemia/LA in metformin-treated ICU patients from January 1995 to February 2020. Case-level data including demographics and clinical conditions were extracted, and logistic regression analyses were performed.
RESULTS: A total of 92 ICU patients were reported. Two of these patients had no comorbidities interfering with lactate metabolism. In the overall group, arterial pH, lactate levels, and metformin plasma/serum concentrations were similar in survivors versus non-survivors. Ingested daily metformin doses and plasma/serum creatinine levels were significantly higher in survivors versus non-survivors (p = 0.007 vs. p = 0.024, respectively). Higher plasma/serum creatinine levels, higher lactate levels, and lower arterial pH were all associated with patients receiving RRT (all p < 0.05). Overall mortality was 22% (20 out of 92 patients) and did not differ between the RRT and non-RRT groups.
CONCLUSIONS: Mortality is high in ICU patients with metformin-associated hyperlactatemia/LA. Unexpectedly, higher ingested metformin dose and plasma/serum creatinine were associated with a better outcome. Survival was similar in patients with or without need for RRT.

Metformin poisoning with lactic acidosis is an uncommon yet clinically serious condition related to the inhibition of normal aerobic metabolism. Toxicity may occur after an acute overdose although it is much more common after a systemic insult, such as acute kidney injury, in the setting of chronic use. Hemodialysis is currently the preferred extracorporeal treatment modality (Grade 1D evidence) although some patients may be too hemodynamically unstable to tolerate it. Continuous renal replacement therapy is considered an alternative if hemodialysis is unavailable but an evaluation of survival amongst this specific treatment class is lacking.
To assess overall survival and provide an updated review of the toxicokinetic elimination parameters of patients receiving continuous renal replacement therapy for metformin poisoning.
A comprehensive search was performed using the EMBASE and MEDLINE libraries from inception until November 30, 2021. Data was extracted and findings were summarized. Toxicokinetic parameters were analyzed and confirmed for accuracy when data permitted.
Eighty-three reports met inclusion criteria. These consisted of only low-quality evidence including 75 case reports, four case series, and four descriptive retrospective reviews. Overall survival among patients suffering from metformin toxicity who received continuous extracorporeal treatment was 85.8%. When stratified between metformin-induced lactic acidosis and metformin-associated lactic acidosis, survival was 75.0% and 87.4%, respectively. Available continuous renal replacement therapy toxicokinetic parameters were quite heterogeneous. Errors in previously published toxicokinetic calculations were noted in only two instances. The overall average and median peak metformin concentrations were 70.5 mg/L and 41.9 mg/L, respectively. The average and median extracorporeal clearance rates were 39.0 mL/min and 42.1 mL/min (range 9.0-58.7 mL/min). The average and median elimination half-life parameters were 27.5 h and median 23.0 h. Elimination half-life ranged from seven to 74 h. There was no meaningful relationship between peak metformin concentration and continuous extracorporeal treatment half-life at lower concentrations, though at very high concentrations (over 200 mg/L), there was a trend towards a half-life below 20 h. There is insufficient data to robustly evaluate overall survival in relation to the extracorporeal clearance rate. Finally, there was no relevant relationship between maximal lactate concentration and survival, nor nadir pH and survival, for patients with either type of metformin toxicity.
This retrospective systematic analysis of published cases treating metformin related lactic acidosis with continuous renal replacement therapy notes an overall slightly greater survival percentage compared to previous publications of individuals requiring any modality of renal replacement therapy. Because of publication bias, these results should be interpreted with caution and serve as hypothesis generating for future research. Prospective study focusing on the most clinically meaningful endpoint - survival - will help elucidate if continuous modalities are non-inferior to intermittent hemodialysis in metformin toxicity.