Recommendations for diagnosis and treatment of methemoglobinemia

Blood Pressure Management for Hypotensive Patients in Intensive Care and Perioperative Cardiovascular Settings

Blood pressure is a critical physiological parameter, particularly in the context of cardiac intensive care and perioperative settings. As a primary indicator of organ perfusion, the maintenance of adequate blood pressure is imperative for the assurance of sufficient tissue oxygen delivery. Among critically ill and major surgery patients, the continuous monitoring of blood pressure is performed as a standard practice for patients. Nonetheless, uncertainties remain regarding blood pressure goals, and there is no consensus regarding blood pressure targets. This review describes the determinants of blood pressure, examine the influence of blood pressure on organ perfusion, and synthesize the current clinical evidence from various intensive care and perioperative settings to provide a concise guidance for daily clinical practice.

Concomitant oxidative haemolysis and methaemoglobinaemia following inhaled nitric oxide in a patient with G6PD deficiency

We report the case of a man in his 50s who developed acute respiratory distress syndrome and right heart failure, necessitating intubation and initiation of inhaled nitric oxide (iNO) to decrease right ventricular afterload and improve the right heart function. The course was complicated by acute anaemia, with a diagnostic workup revealing methaemoglobinaemia and evidence of oxidative haemolysis indicated by blister and bite cells on peripheral blood film. The patient received conservative management, including successive red blood cell transfusion and gradual iNO weaning due to suspected glucose-6-phosphate dehydrogenase (G6PD) deficiency. Discontinuation of iNO led to the resolution of both oxidative haemolysis and methaemoglobinaemia. Subsequent enzymatic assay, conducted 4 months later, confirmed G6PD deficiency. This case highlights a rare instance of concurrent methaemoglobinaemia and oxidative haemolytic anaemia following iNO in a patient with underlying G6PD deficiency.

Management of Congenital Methemoglobinemia in the Perioperative Setting: A Case Report and Review of Current Literature

Background

Methemoglobin is an altered state of hemoglobin where iron in hemoglobin is oxidized and incapable of binding oxygen; leading to complications such as cyanosis, dyspnea, headache, and heart failure. Methemoglobinemia can be congenital or acquired. Congenital methemoglobinemia is a rare disease and its worldwide incidence is unclear. We recently encountered the first documented case of congenital methemoglobinemia at our institution, necessitating perioperative care.

Case Presentation

In the present case, a 22-year-old man with congenital methemoglobinemia underwent general anesthesia for dental extraction. The surgeon was informed to avoid local anesthetics and oxygenation was performed with FiO2 of 1.0. Arterial blood gas analysis showed a PH of 7.337, PaO2 of 302 mm Hg, PaCO2 of 44 mm Hg, oxyhemoglobin level of 63.4%, and methemoglobin level of 37.8%. The patient had a stable course. No methylene blue therapy was required, although cyanosis was observed during surgery.

Conclusion

In summary, though rare, congenital methemoglobinemia poses fatal risks during surgery. Its management involves preoperative recognition and optimization, oxygenation status, multidisciplinary care, avoiding precipitating or oxidizing agents, discussing treatment options, maintaining cardiopulmonary stability, and ensuring perioperative safety measures with the medical team.

Hemoglobinopathy as a Rare Differential Disease for Low Oxygen Saturation by Pulse Oximetry: A Case Report and Literature Review

Pulse oximetry is used to screen for respiratory failure in dyspnea patients. However, pulse oximetry can yield false-positive results in certain situations. Unstable hemoglobinopathy is a disease in which mutations in the globin-encoding gene result in abnormal globin chain production, causing low percutaneous oxygen saturation (SpO2) levels due to changes in hemoglobin absorbance and oxygen affinity. We identified a new family lineage of Hb Hirosaki in an adult patient with chronic obstructive pulmonary disease, dyspnea, and low SpO2. According to our literature review, only a few cases of unstable hemoglobinopathy have been reported in adults. Most patients with unstable hemoglobinopathy are asymptomatic, and those with dyspnea often have respiratory diseases or severe anemia. To differentiate unstable hemoglobinopathy, an appropriate assessment of the discrepancy between SpO2 values and arterial blood gas analysis results is important.

A novel stoploss mutation CYB5R3 c.906A>G(p.*302Trpext*42) involved in the pathogenesis of hereditary methemoglobinemia

Recessive congenital methemoglobinemia (RCM) is a hereditary autosomal disorder with an extremely low incidence rate. Here, we report a case of methemoglobinemia type I in a patient with congenital persistent cyanosis. The condition was attributed to a novel compound heterozygous mutation in CYB5R3, characterized by elevated methemoglobin levels (13.4 % of total hemoglobin) and undetectable NADH cytochrome b5 reductase (CYB5R3) activity. Whole-exome sequencing (WES) revealed two heterozygous mutations in CYB5R3: a previously reported pathogenic missense mutation c.611G>A(p.Cys204Tyr) inherited from the father, and a novel stop codon mutation c.906A>G(p.*302Trpext*42) from the mother, the latter mutation assessed as likely pathogenic according to ACMG guidelines. In cells overexpressing the CYB5R3 c.906A>G mutant construct, the CYB5R3 mRNA level was significantly lower than in cells overexpressing the wild-type (WT) CYB5R3 construct. However, there was no significant difference in protein expression levels between the mutant and WT constructs. Notably, an additional protein band of approximately 55 kDa was detected in the mutant cells. Immunofluorescence localization showed that, compared to wild-type CYB5R3, the subcellular localization of the CYB5R3 p.*302Trpext*42 mutant protein did not show significant changes and remained distributed in the endoplasmic reticulum and mitochondria. However, the c.906A>G(p.*302Trpext*42) mutation resulted in increased intracellular reactive oxygen species (ROS) levels and decreased NAD+/NADH ratio, suggesting impaired CYB5R3 function and implicating this novel mutation as likely pathogenic.

Ascorbic Acid for Methemoglobinemia Treatment: A Case Report and Literature Review

Purpose: Ascorbic acid has been proposed as an alternative treatment for methemoglobinemia in patients with glucose-6-phosphate dehydrogenase (G6PD) deficiency. However, its efficacy has never been compared to that of methylene blue given the inability of patients with G6PD deficiency to receive methylene blue. We present a case of methemoglobinemia treated with ascorbic acid in a patient without G6PD deficiency who had previously received methylene blue. Summary: A 66-year-old male was treated for methemoglobinemia deemed to be secondary to benzocaine throat spray. He received intravenous (IV) methylene blue but had a severe reaction: diaphoresis, lightheadedness, and hypotension. The infusion was stopped prior to completion. Approximately 6 days later he presented with methemoglobinemia following an additional overconsumption of benzocaine and was treated with ascorbic acid. In both instances his methemoglobin levels were >30% on arterial blood gas on admission and decreased to 6.5% and 7.8%, respectively, after administration of methylene blue and ascorbic acid. Conclusion: Ascorbic acid had a similar effect on decreasing the concentration of methemoglobin compared to methylene blue. Further research into use of ascorbic acid as a recommended agent for treatment of methemoglobinemia is warranted.

A safety evaluation of intermittent high-dose inhaled nitric oxide in viral pneumonia due to COVID-19: a randomised clinical study

High-dose inhaled Nitric Oxide (iNO) has been shown to have anti-inflammatory, vasodilator, and antimicrobial properties, resulting in improved arterial oxygenation as well as a beneficial therapeutic effect on lower respiratory tract infections. This study evaluated the safety and efficacy of 150-ppm intermittent iNO administered with a novel iNO-generator, for treating adults hospitalised for viral pneumonia. In this prospective, open-label, multicenter study, subjects aged 18-80, diagnosed with viral pneumonia received either standard supportive treatment alone (Control-Group) or combined with iNO for 40 min, 4 times per day up to 7 days (Treatment-Group). Out of 40 recruited subjects, 35 were included in the intention-to-treat population (34 with COVID-19). Adverse Events rate was similar between the groups (56.3% vs. 42.1%; respectively). No treatment-related adverse events were reported, while 2 serious adverse events were accounted for by underlying pre-existing conditions. Among the Treatment-Group, oxygen support duration was reduced by 2.7 days (Hazard Ratio = 2.8; p = 0.0339), a greater number of subjects reached oxygen saturation ≥ 93% within hospitalisation period (Hazard Ratio = 5.4; p = 0.049), and a trend for earlier discharge was demonstrated. Intermittent 150-ppm iNO-treatment is well-tolerated, safe, and beneficial compared to usual care for spontaneously breathing hospitalised adults diagnosed with COVID-19 viral pneumonia.

A Case study of polypharmacy-induced serotonin syndrome in a cancer patient

ABSTRACT

Polypharmacy in cancer care can be complex and detrimental, particularly among younger patients, who can be easily overlooked. This report showcases a 54-year-old woman with cancer, treated for dapsone-induced methemoglobinemia with methylene blue (MB), subsequently developing serotonin syndrome (SS) due to concurrent serotonin-active medications. This case highlights the critical impact of polypharmacy, emphasizing the necessity for acute care providers to diligently assess medication interactions, especially in emergencies. It underscores the importance of considering alternative treatments and the vigilant monitoring of symptoms indicative of adverse drug interactions to ensure patient safety and optimize outcomes in complex therapeutic scenarios.

Management of isopropyl nitrate-induced methaemoglobinaemia in pregnancy

A pregnant female in her early 30s presented with cyanosis and oxygen saturation of 78%. She ingested isopropyl nitrate mistaking it for cannabidiol. Her arterial blood gas showed a methaemoglobin of >30% (outside the measuring range). She was treated with 120 mg of methylthioninium chloride (2 mg/kg) and symptoms improved. Her pregnancy progressed but was induced at 36 weeks because her child was small for gestational age. Methaemoglobinaemia is a rare presentation in pregnancy. There have been no reported cases of isopropyl nitrate-induced methaemoglobinaemia in pregnancy. Historically, intra-amniotic methylthioninium chloride was used in amniocentesis but use stopped after links to fetal malformations and neonatal death were made. There is no evidence outlining the risks of isopropyl nitrate in pregnancy and limited data on fetal effects from maternal exposure to intravenous methylthioninium chloride. This case adds to the evidence that treating methaemoglobinaemia may outweigh the risks of maternal exposure to methylthioninium chloride.

A Comparative Investigation of the Pulmonary Vasodilating Effects of Inhaled NO Gas Therapy and Inhalation of a New Drug Formulation Containing a NO Donor Metabolite (SIN-1A)

Numerous research projects focused on the management of acute pulmonary hypertension as Coronavirus Disease 2019 (COVID-19) might lead to hypoxia-induced pulmonary vasoconstriction related to acute respiratory distress syndrome. For that reason, inhalative therapeutic options have been the subject of several clinical trials. In this experimental study, we aimed to examine the hemodynamic impact of the inhalation of the SIN-1A formulation (N-nitroso-N-morpholino-amino-acetonitrile, the unstable active metabolite of molsidomine, stabilized by a cyclodextrin derivative) in a porcine model of acute pulmonary hypertension. Landrace pigs were divided into the following experimental groups: iNO (inhaled nitric oxide, n = 3), SIN-1A-5 (5 mg, n = 3), and SIN-1A-10 (10 mg, n = 3). Parallel insertion of a PiCCO system and a pulmonary artery catheter (Swan-Ganz) was performed for continuous hemodynamic monitoring. The impact of iNO (15 min) and SIN-1A inhalation (30 min) was investigated under physiologic conditions and U46619-induced acute pulmonary hypertension. Mean pulmonary arterial pressure (PAP) was reduced transiently by both substances. SIN-1A-10 had a comparable impact compared to iNO after U46619-induced pulmonary hypertension. PAP and PVR decreased significantly (changes in PAP: -30.1% iNO, -22.1% SIN-1A-5, -31.2% SIN-1A-10). While iNO therapy did not alter the mean arterial pressure (MAP) and systemic vascular resistance (SVR), SIN-1A administration resulted in decreased MAP and SVR values. Consequently, the PVR/SVR ratio was markedly reduced in the iNO group, while SIN-1A did not alter this parameter. The pulmonary vasodilatory impact of inhaled SIN-1A was shown to be dose-dependent. A larger dose of SIN-1A (10 mg) resulted in decreased PAP and PVR in a similar manner to the gold standard iNO therapy. Inhalation of the nebulized solution of the new SIN-1A formulation (stabilized by a cyclodextrin derivative) might be a valuable, effective option where iNO therapy is not available due to dosing difficulties or availability.

Optimizing pediatric periprocedural pain management part I-Evolving ethics and topical anesthetics

Pediatric procedure-related pain management is often incompletely understood, inadequately addressed, and critical in influencing a child's lifelong relationship with the larger health care community. We highlight the evolution of ethics and expectations around optimizing periprocedural pain management as a fundamental human right. We investigate the state-of-the-art of topical anesthetics, reviewing their mechanisms of action and providing comparisons of their relative safety and efficacy data to help guide clinical selection. In total, this two-part review offers a combination of conventional approaches and innovative techniques that should be used multimodally-in series and in parallel-to help optimize pain management and provide alternatives to sedation medication and general anesthesia.

Extracorporeal Membrane Oxygenation in Intoxication and Overdoses: A Systematic Review

Extracorporeal membrane oxygenation (ECMO) has been increasingly applied over recent decades to treat severe cardiogenic shock and acute lung failure and cardiac arrest of various causes. Acute intoxication with therapeutic substances or other chemical substances can cause severe cardiogenic shock or even cardiac arrest. The purpose of this study was to conduct a qualitative systematic review of ECMO use in intoxication and poisoning. We searched the PubMed, Medline, and Web of Science databases from January 1971 to December 2021 and selected appropriate studies according to our inclusion and exclusion criteria to evaluate the role of ECMO in intoxication and poisoning systematically. Survival at hospital discharge was examined to describe the outcome. The search resulted in 365 publications after removing duplicates. In total, 190 full-text articles were assessed for eligibility. A total of 145 articles from 1985 to 2021 were examined in our final qualitative analysis. A total of 539 (100%) patients were included (mean age: 30.9 ± 16.6 years), with a distribution of n = 64 (11.9%) cases with venovenous (vv) ECMO, n = 218 (40.4%) cases with venoarterial (va) ECMO, and n = 257 (47.7%) cases with cardiac arrest and extracorporeal cardiopulmonary resuscitation. Survival at hospital discharge was 61.0% for all patients, 68.8% for vaECMO, 75% for vvECMO, and 50.9% for extracorporeal cardiopulmonary resuscitation. When used and reported, ECMO seems to be a valid tool for adult and pediatric patients suffering intoxication from various pharmaceutical and nonpharmaceutical substances due to a high survival rate at hospital discharge.

Anesthetic Management of a Patient With Hemoglobin M Disease Undergoing Laparoscopic Uterine Myomectomy: A Case Report

Hemoglobin M (Hb M) is a group of abnormal Hb variants that form methemoglobin, which leads to cyanosis. Patients with Hb M appear cyanotic but are usually asymptomatic. Cyanosis with low peripheral oxygen saturation is unresponsive to oxygen therapy despite normal partial pressure of oxygen. As such, close attention should be paid during anesthesia. We report the first case of a Hb M patient undergoing laparoscopic uterine myomectomy under general anesthesia.

Dapsone-Induced Methemoglobinemia in a Woman With Multiple Myeloma Without Glucose-6-Phosphate Dehydrogenase (G6PD) Deficiency

Methemoglobinemia is a condition characterized by the presence of abnormal hemoglobin, known as methemoglobin, in the blood, which impairs the ability of red blood cells to carry oxygen effectively. Symptoms include cyanosis, shortness of breath, fatigue, and in severe cases, organ damage or death. We presented a case of a 49-year-old female with multiple myeloma who developed drug-induced methemoglobinemia while on dapsone prophylaxis for Pneumocystis carinii pneumonia (PCP). Despite normal glucose-6-phosphate dehydrogenase (G6PD) levels, the patient exhibited cyanosis and shortness of breath. The case underscores the importance of considering methemoglobinemia in patients with unexplained hypoxemia, especially when associated with medication use. Diagnosis relies on clinical assessment, arterial or venous blood gas analysis with co-oximetry, and a thorough medication history. Methemoglobinemia poses a diagnostic challenge due to its varied presentations and requires a high index of suspicion, particularly in patients with multiple myeloma receiving potentially causative medications such as dapsone. Thorough evaluation, interdisciplinary collaboration, and prompt treatment are essential for favorable outcomes in these complex cases.

Hemoglobin Binding to the Red Blood Cell (RBC) Membrane Is Associated with Decreased Cell Deformability

The deformability of red blood cells (RBCs), expressing their ability to change their shape as a function of flow-induced shear stress, allows them to optimize oxygen delivery to the tissues and minimize their resistance to flow, especially in microcirculation. During physiological aging and blood storage, or under external stimulations, RBCs undergo metabolic and structural alterations, one of which is hemoglobin (Hb) redistribution between the cytosol and the membrane. Consequently, part of the Hb may attach to the cell membrane, and although this process is reversible, the increase in membrane-bound Hb (MBHb) can affect the cell's mechanical properties and deformability in particular. In the present study, we examined the correlation between the MBHb levels, determined by mass spectroscopy, and the cell deformability, determined by image analysis. Six hemoglobin subunits were found attached to the RBC membranes. The cell deformability was negatively correlated with the level of four subunits, with a highly significant inter-correlation between them. These data suggest that the decrease in RBC deformability results from Hb redistribution between the cytosol and the cell membrane and the respective Hb interaction with the cell membrane.

[Methemoglobinemia]

Methemoglobinemia (MetHb) refers to the state of oxidation of the iron ion "ferrous" (Fe2+) to iron "ferric" (Fe3+) within the heme molecule that makes up hemoglobin (Hb). This state is physiological if its level remains controlled. The ferrous state of the heme molecule occurs in the event of significant oxidative stress. The pathophysiology of MetHb involves NADH, NADPH and glucose cycle enzymes such as cytochrome-b5-reductase. MetHb can be acquired or more rarely, congenital. Acquired causes include drug-induced effects such as topical anesthetics, or toxic effects such as nitrites. Primary causes are linked to enzyme deficiencies or constitutional Hb abnormalities. Excessively high MetHb causes symptoms of varying intensity, depending on the level of MetHb and associated comorbidities. Clinical signs are dominated by cyanosis, indicative of tissue hypoxia, which can be complicated by severe metabolic disorders leading to death. Diagnosis can be complex, as the resulting biological abnormalities may go undetected. Treatment is mainly based on identifying the etiology and restoring the heme molecule to its physiological state. Methylene blue is the main antidote in cases of elevated MetHb, but precautions must be taken in its use, and its physico-chemical effects must be understood. We provide an update on methemoglobinemia, summarizing its pathophysiology and clinical presentations, complementary tests and therapeutic principles.

Thambiah S, Masiman AD, Samsudin IN, Lai YY. Refractory hypoxia and saturation gap in a COVID-19 patient

Acquired methemoglobinemia, predominantly due to oxidizing medications occurs when heme iron in hemoglobin is oxidized from ferrous to ferric ion and binds oxygen irreversibly leading to functional anemia, cyanosis, and tissue hypoxia. We report a case of a 60-year-old man with multiple comorbidities who was diagnosed with coronavirus disease 2019 (COVID-19) and developed methemoglobinemia after consumption of prescribed supplements. He presented with dyspnea and cyanosis. An oxygen saturation gap with characteristic chocolate-brown arterial blood indicated methemoglobinemia. Outsourced methemoglobin (MetHb) was increased at 9.0%. Despite aggressive intervention, he succumbed to his illness. In this case, we discuss the pathophysiology of why some individuals, especially the elderly with COVID-19 are more susceptible to develop methemoglobinemia after possibly being exposed to oxidizing agents. Laboratory methods for assessing oxygen saturation, including pulse oximetry, arterial blood gas and co-oximetry are examined in relation to this case. The importance of considering a diagnosis of methemoglobinemia based on clinical and biochemical findings although MetHb assay or co-oximetry are not readily available is also emphasized.

Shades of Blue: A Case Series of Acquired Methemoglobinemia

Acquired methemoglobinemia (MetHb) is a rare but potentially life-threatening condition that has varied etiology, usually toxin- or drug-induced. We had five cases of acquired methemoglobinemia during six months. Their presentation varied from an asymptomatic state to respiratory distress. The presence of cyanosis and low oxygen saturation (SpO2), despite normal partial pressure of oxygen (PaO2) and chocolate brown-colored blood, were diagnostic clues present in all cases. A high level of methemoglobinemia was detected on arterial blood gas (ABG), confirming the diagnosis. Methylene blue was used as an antidote along with supportive care in symptomatic cases. All these cases of methemoglobinemia recovered completely. A high index of suspicion for methemoglobinemia should be maintained in cases presenting with persistent hypoxia or cyanosis despite normal PaO2.

A Rare Case of Methemoglobinemia after Ifosfamide Infusion in a 3-Year-Old Patient Treated for T-ALL

Methemoglobinemia is a potentially life-threatening, rare condition in which the oxygen-carrying capacity of hemoglobin is diminished. We present the case of a 3-year-old boy treated for T-cell acute lymphoblastic leukemia (T-ALL) who developed methemoglobinemia (MetHb 57.1%) as a side effect of ifosfamide administration. Due to his critical condition, the patient was transferred to the intensive care unit (ICU). The therapy included methylene blue administration, an exchange transfusion, catecholamine infusion, and steroids. Improving the general condition allowed for continuing chemotherapy without ifosfamide and completion of the HR2 block. Vigilance for methemoglobinemia as a very rare side effect should be widespread when using ifosfamide in the treatment protocols.

Novel mutation in alpha-spectrin gene in Saudi patients with hereditary spherocytosis

Hereditary spherocytosis (HS) is the most common hereditary hemolytic disorder induced by red blood cell (RBC) membrane defect. This study was undertaken to determine mutations in genes associated with RBC membrane defect in patients with HS such as α-spectrin gene (SPTA1), β-spectrin gene (SPTB), ankyrin gene (ANK1), band 3 anion transport gene (SLC4A1) and erythrocyte membrane protein band 4.1 gene (EPB41). Blood samples were collected from 23 unrelated patients with HS. Patients were diagnosed according to the guidelines from the British Society for Hematology. All hematological examinations for the determination of RBC abnormalities and osmotic fragility tests were conducted. Genomic DNA were extracted from peripheral blood cells and coding exons of known genes for hereditary spherocytosis were enriched using Roche/KAPA sequence capture technology and sequenced on an Illumina system via next-generation sequencing (NGS). The data showed that most of the HS patients confirmed splenomegaly and showed elevated reticulocytes and abnormal bilirubin values. NGS analysis identified the heterozygous variant c.5501G > A in the exon 39 of SPTA1 gene, resulted in a Trp1834*, which leads to a premature stop codon and subsequent mRNA degradation (nonsense- mediated decay) or truncation in α spectrin. Moreover, our data also revealed conventional mutations in genes SPTB, ANK, SLC4A1 and EBP41 in severe patients of HS. In short, this is the first report that determined a novel mutation c.5501G > A in SPTA1 gene in the Saudi population. To the best of our knowledge, this variant c.5501G > A has not been described in global literature so far. This novel mutation in SPTA1 gene is unique in the Saudi population.

Familial Psychomotor Delay of an Uncommon Cause: Type II Congenital Methemoglobinemia

Methemoglobinemia is due to oxidization of divalent ferro-iron of hemoglobin to ferri-iron of methemoglobin (MetHb) which is incapable of transferring oxygen to tissues. This disease may be acquired by intoxication with oxidizing agents or inherited with a mutation of CYB5R3, the gene coding for the methemoglobin reductase or cytochrome B5 reductase 3 responsible for the reduction of MetHb to hemoglobin. We report the case of 2 sisters aged respectively of 15 and 8 months. They were born to a second-degree consanguineous marriage with a history of precocious and unexplained deaths in 3 relatives. Both sisters presented neurological features including psychomotor retardation, microcephaly, and axial hypotonia. Cerebral magnetic resonance imaging revealed cerebral atrophy in both cases associated with hypoplasia of the corpus callosum in the younger child. The association of neurological disability, cyanosis, and hypoxemia prompted a search for methemoglobinemia, with MetHB levels respectively of 26% and 15.8%in the 2 sisters. Initial treatment was based on methylene blue, then ascorbic acid. The genetic study revealed a c.463+8G>C mutation of CYB5R3 confirming the diagnosis of methemoglobinemia type II. The diagnosis of methemoglobinemia, although rare, should be considered in the presence of psychomotor retardation with cyanosis and subacute onset hypoxemia, especially in the presence of a family history.

Detection of methaemoglobinaemia in a COVID-19 patient on dapsone

Methaemoglobinaemia occurs when iron in haemoglobin is oxidised into a form that cannot transport oxygen. At low levels, it is asymptomatic, though at rising levels symptoms arise from impaired oxygenation, and it can ultimately be fatal. While uncommon, it is important to consider in hypoxaemic COVID-19 patients, especially if they are not clinically improving on standard treatments and workup for other causes does not explain the ongoing hypoxaemia. It is often diagnosed through a mismatch in peripheral and arterial oxygen, with the former typically less than the latter. We present the case of a COVID-19 patient who was found to have methaemoglobinaemia due to dapsone use for Pneumocystic jirovecii pneumonia (PJP) prophylaxis while on chemotherapy. Dapsone was stopped and supplemental high-flow nasal cannula was provided, and methaemoglobin levels improved over a 5-day period. She was discharged to follow-up with her haematologist in the clinic.

Methaemoglobinaemia Associated With Mixed Cocaine and Amphetamine Overdose: A Case Report

Methaemoglobinaemia is a rare disorder characterized by increased levels of methaemoglobin, a form of haemoglobin with oxidized iron that cannot efficiently bind oxygen. This leads to inadequate oxygen delivery to tissues with various clinical manifestations from asymptomatic to severe persistent hypoxia, CNS symptoms, and cardiovascular collapse. Acquired methaemoglobinaemia is typically a sudden condition, often resulting from poisoning by specific drugs and compounds, which can potentially have fatal consequences. We present a case of a patient who came with severe methaemoglobinaemia due to intoxication with cocaine and amphetamine.

The role of carbon monoxide in aerotoxic syndrome

Chronic low-level exposure to toxic compounds in airplane cabin air may result in Aerotoxic Syndrome (AS). Aetiologic agents are organophosphates and numerous volatile organic hydrocarbons originating from leaks of engine oil and hydraulic fluids. Despite a documented history spanning decades, the role of carbon monoxide remains controversial. What evidence exists that carbon monoxide (CO), present in the cocktail of toxic compounds in bleed air, contributes to the AS? We selected 22 publications encompassing 888 flights with 18 different aircraft types. In one study of 100 flights, fume events were confirmed in 38. Four studies were initialized after air quality incidents. The cabin CO concentrations could be categorized in three levels, 1) low (<5 ppm), without health implications, 2) moderate (5-10 ppm) with probably health implications in case of chronic exposure, and 3) high > 10 ppm, with health effects in case of acute and chronic exposure. These levels were recorded in 12, 6 and 4 studies respectively. In the six studies in category 2, max CO concentrations ranged from 5.8-9.4 ppm. The four studies with CO > 10 ppm comprised 376 of the 888 flights (42%) with six aircraft types. Toxic CO levels ranging between 13-60 ppm were identified in at least 129 of 888 (14.5%) flights. In one study with high CO levels four flight attendants were diagnosed with CO poisoning with elevated HbCO levels. Max CO levels in aviation are either the same or higher than current occupational exposure limits (OEL) for ground-based workplace exposures or levels for urban street transport environments. Specific aspects of aviation should be taken into consideration: the effect of low(er) air pressure at high altitudes increasing the toxicity of CO, and the binding of CO to CYP enzymes, leading to impaired organophosphate detoxification. We conclude that CO must be considered an important factor in the lubrication derived cocktail of airborne toxic compounds causing AS. In line with the WHO advice, a reduction of the OEL to 5 ppm over 8 hr time weighted average (TWA) for aircrew is strongly recommended. And we advocate continuous monitoring during all phases of flight and installation of CO detectors in the air supply ducts to the aircraft cabin.

Dapsone-Induced Methemoglobinemia Presenting Concomitantly With COVID-19 Pneumonia and Pulmonary Embolism: A Case Report

Acquired methemoglobinemia is a treatable condition that is often clinically subtle and can be missed on routine clinical assessment. We present a 73-year-old male who was evaluated in the emergency department with worsening respiratory symptoms requiring oxygen. He tested COVID-19 positive and had new pulmonary emboli evident on his CT chest. The patient was on dapsone therapy as a treatment for bullous pemphigoid. The discrepancy between his oxygen levels on the pulse oximeter and blood gas was noted and was treated with 3% methylene blue for dapsone-induced methemoglobinemia. The patient received treatment for COVID-19 pneumonia and pulmonary emboli. Our case demonstrates that dapsone-induced methemoglobinemia can present concomitantly with other more common causes of acute hypoxic respiratory failure. It is noteworthy for physicians to maintain a high index of suspicion for oxygen level discrepancy in hypoxic patients and consider the possibility of acquired methemoglobinemia. Hence, earlier detection and treatment of the etiology of tissue hypoxia.

The first Chinese with Hb Chile leading to chronic anemia and methemoglobinemia: a case report

BACKGROUND

Hemoglobin (Hb) Chile [β28(B10) Leu > Met; HBB: c.85 C > A] is a rare hemoglobin variant caused by a missense mutation in the HBB gene. Only one case of Hb Chile has been reported worldwide so far. It is an unstable hemoglobin, characterized by cyanosis associated with chronic methemoglobinemia and hemolytic anemia induced by sulfonamides or methylene blue.

CASE PRESENTATION

A 9-year-3-month-old girl had mild anemia of unknown etiology for more than 6 years. She had a slight pallor without other symptoms or signs. The complete blood count revealed normocytic normochromic anemia with a sometimes-elevated reticulocyte count, and the bone marrow cytology showed marked erythroid hyperplasia, but the tests related to hemolysis were normal. Therefore, the whole exome sequencing was performed and showed a heterozygous mutation for HBB: c.85 C > A. With asymptomatic methemoglobinemia confirmed later, she was eventually diagnosed with Hb Chile.

CONCLUSIONS

This is the first report of Hb Chile in China and the second worldwide. This case shows that Hb Chile is clinically heterogeneous and difficult to diagnose and expands our understanding on the clinical and hematological traits of the disease.

Sodium nitrite suicide and social media influence

ABSTRACT

This article addresses the increase in suicide rates in the US, emphasizing the emergence of sodium nitrite ingestion as a method of self-harm, particularly among adolescents and young adults influenced by social media. Given the rising incidence of sodium nitrite-related suicide attempts, healthcare providers must remain vigilant and prepared to respond effectively.

[Methemoglobinemia Induced by Sildenafil Tablets Ordered in the Darknet - Importance of Syncopes' Causes]

Drug-induced methemoglobinemia is a well-known phenomenon as well as induction by poppers (alcylnitrites substance group). Usually, suspicion is thrown in the right direction by a thorough medical history and environmental survey. But if intoxication is unintended and happens within the very private environment diagnosis might be very tricky. We report on an unusual case of accidental intoxication with probably contaminated tablets which were bought in the darknet. Finally, diagnosis was made by blood gas analysis' methemoglobine values.

N-acetylcysteine: a novel approach to methaemoglobinaemia in normothermic liver machine perfusion

Extended duration of normothermic machine perfusion (NMP) provides opportunities to resuscitate suboptimal donor livers. This intervention requires adequate oxygen delivery typically provided by a blood-based perfusion solution. Methaemoglobin (MetHb) results from the oxidation of iron within haemoglobin and represents a serious problem in perfusions lasting > 24 h. We explored the effects of anti-oxidant, N-acetylcysteine (NAC) on the accumulation of methaemoglobin. NMP was performed on nine human donor livers declined for transplantation: three were perfused without NAC (no-NAC group), and six organs perfused with an initial NAC bolus, followed by continuous infusion (NAC group), with hourly methaemoglobin perfusate measurements. In-vitro experiments examined the impact of NAC (3 mg) on red cells (30 ml) in the absence of liver tissue. The no-NAC group sustained perfusions for an average of 96 (range 87-102) h, universally developing methaemoglobinaemia (≥ 2%) observed after an average of 45 h, with subsequent steep rise. The NAC group was perfused for an average of 148 (range 90-184) h. Only 2 livers developed methaemoglobinaemia (peak MetHb of 6%), with an average onset of 116.5 h. Addition of NAC efficiently limits formation and accumulation of methaemoglobin during NMP, and allows the significant extension of perfusion duration.

Methemoglobinemia in Hemodialysis Patients due to Acute Chlorine Intoxication: A Case Series Calling Attention on an Old Problem

INTRODUCTION

Hemodialysis uses municipal water that must be strictly purified and sterilized to be used for that procedure. Large amounts of decontaminants are often used, such as chlorine, and if these compounds are not subsequently removed they can be transferred to the blood of patients causing complications including methemoglobinemia.

METHODS

In this case series study, dialysis patients in one unit were evaluated. We reviewed clinical characteristics and laboratory findings obtained on the day when the water supply was disinfected with chlorine, with the aim to quantify methemoglobin concentrations. Our objective was to characterize the clinical presentation and management of patients who presented with methemoglobinemia on a specific index day. We also reviewed reported cases in the literature regarding this underreported complication.

RESULTS

Eight patients who presented with chlorine intoxication were evaluated. The methemoglobin concentrations were between 1.3% and 7.9% (reference value 0-1%). We believe this to be caused by water containing 0.78 mg/L of total chlorine. Seven patients presented with cyanosis, 4 with dizziness, 6 with dark brown blood, 4 with dyspnea, and 4 with headache and hemolytic anemia. Subjects were treated with supplemental oxygen, methylene blue, intravenous vitamin C, blood transfusions, and increased doses of erythropoietin. No patient died, and all continued with their usual hemodialysis sessions.

CONCLUSION

Acute chlorine intoxication transferred by the water used during hemodialysis sessions can present with methemoglobinemia accompanied by cyanosis, oxygen desaturation, and hemolytic anemia. Chlorine levels should be carefully monitored in the water used for hemodialysis treatment.

Multicomponent-Loaded Vesosomal Drug Carrier for Controlled and Sustained Compound Release

Liposomes have been extensively adopted in drug delivery systems with clinically approved formulations. However, hurdles remain in terms of loading multiple components and precisely controlling their release. Herein, we report a vesosomal carrier composed of liposomes encapsulated inside the core of another liposome for the controlled and sustained release of multiple contents. The inner liposomes are made of lipids with different compositions and are co-encapsulated with a photosensitizer. Upon induction of reactive oxygen species (ROS), the contents of the liposomes are released, with each type of liposome displaying distinct kinetics due to the variance in lipid peroxidation for differential structural deformation. In vitro experiments demonstrated immediate content release from ROS-vulnerable liposomes, followed by sustained release from ROS-nonvulnerable liposomes. Moreover, the release trigger was validated at the organismal level using Caenorhabditis elegans. This study demonstrates a promising platform for more precisely controlling the release of multiple components.

A fatal suicidal sodium nitrite ingestion determined six days after death

Sodium nitrite (SN) is an inorganic salt that appears as a slightly yellowish crystalline solid, odorless, and highly soluble in water at room temperature. It is highly toxic to humans at specific doses because it can oxidize hemoglobin to methemoglobin, causing severe tissue hypoxia. A 20-year-old woman was unconscious in her bedroom and died shortly after that. Two days later, following the discovery of a jar of SN and a paper in which were written instructions on how to take it (and the website from which the procedure was learned) in the same room were death occurred, the Judicial Authority ordered the execution of the autopsy on the exhumed body of the young woman. The autopsy procedure was performed ∼ 2h after exhumation. It showed greyish-purple hypostasis, labial cyanosis, stomach distension and greenish color but empty, subpleural petechiae, brownish fluid in the pleural cavities (∼300 ml), congested and edematous lungs and diffuse visceral congestion. At autopsy, foamy liquid was observed at the lung section and subsequent squeezing. In addition, the autopsy showed edema and hemorrhagic petechiae of the laryngeal, glottal, and tracheal submucosa and green-brownish foamy liquid in the tracheal lumen. The cause of death was attributed tocardiac arrest induced by anoxia resulting from acute methemoglobinemia caused by sodium nitrite poisoning, intensified by severe malnutrition. Manner of death was suicidal.

Suicidal sodium nitrite intoxication: a case report focusing on the postmortem findings and toxicological analyses-review of the literature

Sodium nitrite (NaNO₂) is an inorganic compound that is commonly used as a preservative (E250) in the fish and meat industry. When ingested, sodium nitrite will lead to methemoglobinemia, hypotension, and arrhythmias. An increasing trend in the use of sodium nitrite as a suicide agent has been reported. In Belgium however it remains a rare phenomenon. The ingestion of sodium nitrite is not always apparent from the death scene investigation, especially in cases of covert administration or accidental ingestion. Hence, the forensic pathologist must be aware of this trend and the postmortem changes related to the ingestion of sodium nitrite to effectively identify these cases and determine the cause and manner of death. We describe a case of fatal self-poisoning following the oral ingestion of sodium nitrite with suicidal intent. Postmortem investigations showed signs of methemoglobinemia, such as a gray-brown discoloration of lividity and a chocolate brown discoloration of the blood. Postmortem toxicological investigation revealed methemoglobinemia (35%) in cardiac blood, hypernatremia (159.6 mmol/L) in vitreous humor, and the presence of nitrite in gastric contents (1.15 g/L) and, for the first time in a forensic case, in serum (38 µg/mL). A review of the existing literature regarding cases of sodium nitrite intoxications was performed to correlate these findings.

Amiodarone-induced blue man syndrome: a case report

BACKGROUND

Amiodarone is one of the most commonly used and effective antiarrhythmic drugs to treat ventricular and supraventricular arrhythmias. Besides its advantages, this drug has side effects like liver, digestive, pulmonary, thyroid, neural, skin, optical, hematologic, psychiatric, and cardiac complications. Blue-gray cutaneous discoloration, also known as blue man syndrome, is an undesirable and unusual side-effect of chronic amiodarone therapy in less than 3% of patients.

CASE PRESENTATION

This report presents a 51-year-old Caucasian man treated for the past 3 years with amiodarone and implantable cardioverter defibrillators due to his ventricular arrhythmia and cardiomyopathy, without any follow-up visit to his doctor. He was referred to the medical center for blue-gray discoloration on his nose and cheeks, which had started to appear in the last 3 weeks.

CONCLUSION

Considering the findings obtained in this report and the numerous side effects of amiodarone, the blue-man syndrome is a rare yet important finding of this drug which may influence the patient's daily life. It is recommended that all patients under treatment with this drug be notified about its side effects and visit their doctors regularly. Regarding the high therapeutic value of this drug, the lack of any association between blue man syndrome and other complications, and the related aesthetic problems, the role of the caregiver becomes much more critical in the prescription of amiodarone.

Out of the Blue: Methemoglobinemia Associated With the Use of Amyl Nitrite in Rush Poppers for Erectile Stimulation

We report a clinical scenario involving a 51-year-old male patient with a history of prediabetes and gastritis who exhibited altered mental status following the consumption of poppers, a supplement containing nitrites, which is used for erectile stimulation. Shortly after the ingestion, the patient experienced convulsions, foaming at the mouth, and subsequently developed altered mental status and severe respiratory distress. The diagnosis of methemoglobinemia was confirmed based on elevated methemoglobin levels on venous blood gas analysis. Notably, the patient's blood had a chocolate-colored appearance upon admission, which is a characteristic finding in methemoglobinemia. Prompt recognition and management, including the administration of methylene blue, led to the resolution of symptoms. This case highlights the potential complications associated with the consumption of poppers and emphasizes the importance of early intervention.

Facile synthesis of Ag@Fe3O4/ZnO nanomaterial for label-free electrochemical detection of methemoglobin in anemic patients

Methemoglobinemia (MetHb, Fe³⁺) is a chronic disease arising from the unequal distribution of oxyhemoglobin (HbFe²⁺, OHb) in the blood circulatory system. The oxidation of standard oxyhemoglobin forms methemoglobin, causing cyanosis (skin bluish staining). Methemoglobin cannot bind the pulmonary gaseous ligands such as oxygen (O₂) and carbon monoxide (CO). As an oxidizing agent, the biochemical approach (MetHb, Fe³⁺) is modified in vitro by sodium nitrite (NaNO₂). The silver-doped iron zinc oxide (Ag@Fe₃O₄/ZnO) is hydrothermally synthesized and characterized by analytical and spectroscopic techniques for the electrochemical sensing of methemoglobin via cyclic voltammetry (CV). Detection parameters such as concentration, pH, scan rate, electrochemical active surface area (ECSA), and electrochemical impedance spectroscopy (EIS) are optimized. The linear limit of detection for Ag@Fe₃O₄/ZnO is 0.17 µM. The stability is determined by 100 cycles of CV and chronoamperometry for 40 h. The serum samples of anemia patients with different hemoglobin levels (Hb) are analyzed using Ag@Fe₃O₄/ZnO modified biosensor. The sensor's stability, selectivity, and response suggest its use in methemoglobinemia monitoring.

Phenazopyridine-Induced Methemoglobinemia in a Jehovah's Witness Treated with High-Dose Ascorbic Acid Due to Methylene Blue Contradictions: A Case Report and Review of the Literature

Methemoglobinemia is an acute medical emergency that requires prompt correction. Physicians should have a high degree of suspicion of methemoglobinemia in cases that present with hypoxemia that does not resolve with supplemental oxygenation, and they should confirm this suspicion with a positive methemoglobin concentration on arterial blood gas. There are multiple medications that can induce methemoglobinemia, such as local anesthetics, antimalarials, and dapsone. Phenazopyridine is an azo dye used over-the-counter as a urinary analgesic for women with urinary tract infections, and it has also been implicated in causing methemoglobinemia. The preferred treatment of methemoglobinemia is methylene blue, but its use is contraindicated for patients with glucose-6-phosphatase deficiency or those who take serotonergic drugs. Alternative treatments include high-dose ascorbic acid, exchange transfusion therapy, and hyperbaric oxygenation. The authors report a case of a 39-year-old female who took phenazopyridine for 2 weeks to treat dysuria from a urinary tract infection and subsequently developed methemoglobinemia. The patient had contraindications for the use of methylene blue and was therefore treated with high-dose ascorbic acid. The authors hope that this interesting case promotes further research into the utilization of high-dose ascorbic acid for managing methemoglobinemia in patients who are unable to receive methylene blue.

Methaemalbumin: a diagnostic surrogate for methaemoglobinaemia and treatment with red cell exchange in a patient with thalassaemia

A man in his 30s with alpha thalassaemia (four-alpha globin gene deletion) presented with 1 week of shortness of breath and 1 month of general malaise. Pulse oximetry monitoring revealed low peripheral oxygen saturation of approximately 80% despite maximal high-flow nasal cannula oxygen (fractional inspired oxygen 1.0-60 L/min flow). Arterial blood gas samples were chocolate brown in colour, with a low arterial partial pressure of oxygen of 197 mm Hg. This large oxygen saturation gap raised suspicion for methaemoglobinaemia. However, the patient's co-oximetry results were suppressed by the blood gas analyser and delayed a definitive diagnosis. A methaemalbumin screen was sent instead, which was positive at 65 mg/L (reference interval: <3 mg/L). Treatment with methylene blue was initiated but did not result in complete resolution of cyanosis. This patient had been red cell exchange dependent since childhood for thalassaemia. Therefore, an urgent red cell exchange was initiated overnight, leading to an improvement in symptoms and interpretability of co-oximetry results. This resulted in rapid improvement without residual sequelae or complications. We conclude that a methaemalbumin screen can be used as a surrogate test for prompt confirmation of diagnosis in lieu of co-oximetry in cases of severe methaemoglobinaemia or in cases with underlying haemoglobinopathy. Red cell exchange can allow prompt methaemoglobinaemia reversal, especially if methylene blue is only partially effective.

Inflammatory phenotype, clinicopathologic variables, and effects of long-term methylene blue in dogs with hereditary methemoglobinemia caused by cytochrome b5 reductase deficiency

OBJECTIVE

To determine whether dogs with cytochrome b5 reductase (CYB5R) deficiency have a constitutive proinflammatory phenotype, characterize hematologic and serum chemistry results, and describe changes in methemoglobin (MetHb) levels and serum C-reactive protein (CRP) concentrations after long-term per os (PO) methylene blue (MB) therapy.

ANIMALS

21 client-owned dogs (CYB5R deficient, n = 10; healthy controls, 11).

PROCEDURES

In this prospective, case-control study, methemoglobin levels were measured using a blood gas analyzer with co-oximetry. Plasma tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and interleukin-10 (IL-10) concentrations were measured using a canine-specific multiplex bead-based assay. Serum CRP concentrations were measured with a canine-specific commercial ELISA kit. Serum CRP concentration and MetHb levels were measured in 6 dogs with CYB5R deficiency after ≥ 60 days of PO MB therapy.

RESULTS

As expected, MetHb levels were higher in dogs with CYB5R deficiency compared to controls (P < .001). Plasma TNF-α, IL-6, IL-10, and serum CRP concentrations were no different between CYB5R-deficient and control dogs. Dogs with CYB5R deficiency had lower absolute lymphocyte (P = .005) and eosinophil counts (P = .04) and higher alanine transaminase (P = .04) and alkaline phosphatase activity (P = .02) than controls, but these changes were not clinically relevant. Methemoglobin levels decreased after PO MB therapy (P = .03).

CLINICAL RELEVANCE

These results suggest that otherwise healthy dogs with CYB5R deficiency do not have a constitutive proinflammatory phenotype and clinically relevant abnormalities in hematologic and serum chemistry panels are not expected. Dogs with decreased quality of life attributed to methemoglobinemia from CYB5R deficiency might benefit from PO MB therapy.

Methemoglobinemia Secondary to Inhalation of Automobile Emissions with Suicide Motivations

BACKGROUND

Methemoglobinemia (MetHb) is a rare and potentially severe dyshemoglobinemia that can be induced by exposure to oxidizing agents, decreasing the functional capacity of the hemoglobin molecule to transport and release oxygen into the tissues. MetHb can originate from gases with oxidizing capacity generated by internal combustion engines, although since the universalization of catalyst converters in automobiles, a tiny proportion of MetHb poisoning is due to exposure to engine gases and fumes. Within this group, only two cases due to suicidal motivations have been reported in the last 30 years.

CASE PRESENTATION

Here, we expose the case of a patient with MetHb levels of 25.2% (normal 0-1.5%) who with suicidal motivations had attached and locked a hose to the exhaust pipe of her vehicle with electrical tape, becoming exposed to a sustained concentration of the vehicle's exhaust. Upon her arrival at the emergency department, the presence of generalized greyish cyanosis with alterations of the sensorium, dissociation between saturation measured by arterial blood gas analysis and pulse oximetry (98% vs. 85%), no response to high-flow oxygen therapy, and an excellent response to intravenous methylene blue treatment were highlighted.

CONCLUSIONS

This report illustrates an original case of acute toxic acquired MetHb due to inhalation of oxidizing substances originating from the bad ignition of an internal combustion engine. When evaluating a patient with suspected gas intoxication, we usually consider poisoning by the most common toxins, such as carbon monoxide or cyanide. In this context, we propose an algorithm to assist in the suspicion of this entity in patients with cyanosis in the emergency department. MetHb poisoning should be suspected, and urgent co-oximetry should be requested when there is no congruence between cyanosis intensity and oxygen saturation measured by pulse oximetry, if there is discordance between the results of oxygen saturation measured by arterial blood gas and pulse oximeter, and if there is no response to oxygen treatment. This algorithm could be useful to not delay diagnosis, improve prognosis, and limit potential sequelae.

Phenazopyridine-Induced Methemoglobinemia: A Case Report

Methemoglobinemia is a condition caused by increased methemoglobin, a reduced form of hemoglobin, in the blood. This causes the molecules to bind oxygen more tightly and decreases their ability to release that oxygen to tissue. Most cases of methemoglobinemia are acquired and occur either in pediatric populations or in individuals with predisposing conditions. This report illustrates a case of an otherwise healthy 31-year-old patient presenting to the emergency department with cyanosis of the hands and mouth and an O2 saturation of 78% after taking increased doses of the over-the-counter medication phenazopyridine. A "chocolate-brown" color of her arterial blood, and increased methemoglobin levels of 20.2%, confirmed the diagnosis of methemoglobinemia. She was treated with both methylene blue and ascorbic acid, and her oxygen saturation and serum chemistry returned to normal levels within a few hours. The case highlights the importance of discussing the dosage of all over-the-counter medications with patients and recognizing the signs and symptoms of methemoglobinemia.