Methemoglobin Levels Research Articles

Bellastesin-Associated Methemoglobinemia in a Patient with Liver Alveococcosis

The presented clinical observation and analysis of the literature data draws an attention on the possibility of developing a life-threatening condition such as methemoglobinemia due to the use of the benzocaine preparation. The latter is part of the preparation bellastesin for the treatment of gastroenterological diseases. This drug is often taken by patients at their own at discretion and with no proper control and consideration of existing co-morbidities. In addition, one needs to pay attention on the indicators of oximetry, including the level of methemoglobin, when diagnosing diseases accompanied by cyanosis and respiratory insufficiency.

Assessment of Methemoglobin, Hemoglobin, Ferritin and Lactate dehydrogenase in COVID-19 Patients

Today world is trying to cope with the biggest pandemic caused by Coronavirus disease 2019 (COVID-19). The disease is graded as mild, moderate, serious and critical illness. Very few studies are done with methemoglobin along with other parameters for the assessment of the severity of COVID-19 disease. The objectives of the study were to estimate methemoglobin (Met-Hb), hemoglobin (Hb), ferritin and lactate dehydrogenase (LDH) levels in patients with COVID-19 disease and to investigate the interaction between these parameters and the severity of the disease. This observational study was conducted in three groups of COVID-19 patients- moderate, severe and critical, each group containing 30 patients, between June 2021 and September 2021 in the biochemistry department of a tertiary care hospital. For all patients, Met-Hb, Hb, ferritin, and LDH levels were estimated on the 2nd-3rd day of hospital admission. Patients in the critical group were older and had significantly high values of Met-Hb, ferritin and LDH and significantly low values of Hb (P<0.05). In multivariate ordinal regression analysis, older age (OR-3.08; 95%CI:1.19-7.19;P-0.019), higher values of LDH (OR-8.66; 95%CI:2.53-29.5; P-0.001) and ferritin (OR-3.08; 95%CI:1.09-8.7;P-0.033) were independently associated with severity of the disease. A cut-off value of 410.50 U/L for LDH predicted the severity of the disease with 90% sensitivity and 88.3% specificity. In conclusion, higher levels of LDH and ferritin were related to the severity of the disease in COVID-19 cases. Although Met-Hb showed a minimal increase without any association with severity, it may be an underlying cause of hypoxia that may go unnoticed. So, monitoring of all these parameters should be done at intervals.

The emerging trend of suicide using nitrite/nitrate in Victoria, Australia

Over the last 18 months the ingestion of nitrite/nitrate salts as a method of suicide has drastically increased, with a single case identified in 2017 and eight in 2019. Inorganic salts can be difficult to detect using standard instrumental methods regularly used in a forensic toxicology laboratory. Ingestion of nitrite/nitrate salts can directly oxidise haemoglobin to methaemoglobin (MetHb) and lead to methemoglobinemia (elevated met-haemoglobin). Methaemoglobinemia occurs within 1 h of consumption leading to severe tissue hypoxia. MetHb is subject to significant changes postmortem and testing of a blood sample in suspected cases must be conducted promptly. Detection of raised MetHb is non-specific but can be an indicator of nitrate/nitrite consumption. This study reviewed cases suspected of nitrite/nitrate poisoning in an attempt to identify common characteristics that can assist in identifying the cause of death in other suspected cases. Cases were initially identified from Police reports where either sodium nitrite or sodium nitrate salt was present at the scene of the incident. These cases were referred for testing in a specialised laboratory able to conduct nitrite/nitrate analysis in blood and when available urine and stomach contents. Briefly, samples were diluted with deionised water and analysed using flow injection analysis/ion chromatography on a Metrohm Compact IC comparing nitrate/nitrite levels. Blood methaemoglobin levels were measured using co-oximetry in all cases with a suitable postmortem blood sample. The concentrations of nitrite and nitrate in blood, urine or stomach contents were significantly higher in cases suspected of nitrite/nitrate consumption when compared to endogenous baseline levels. Blood concentrations for nitrite ranged from 135–230 mg/L (normal range < 0.2–10.9 mg/L) and for nitrate, 180 to 750 mg/L (normal range 14–115 mg/L). While nitrate is naturally converted to nitrate endogenously, cases involving sodium nitrate ingestion showed a higher proportion of nitrate in stomach contents. Only 5 of the 14 cases had a blood sample suitable for MetHb analysis, with results ranging from 8 to 14% (baseline level < 1.5%). Timely information provided in case circumstances is critical in enabling the collection and testing of samples in suspected nitrite/nitrate poisonings where these cases may otherwise be overlooked and remain undetected. The presence of nitrite/nitrate at elevated concentrations and in addition to raised MetHb may indicate a likely cause of death in the absence of other possible factors.

In vitro exposure of whole blood to a cannabinoid mixture impairs the quality of red blood cells and platelets.

In a recent study, 13.8% of blood donors had reported cannabis use in the 72 hours preceding their donation, and these donors are not deferred under existing criteria in Canada. This high prevalence raises concerns about the potential impact of cannabis use on the quality of blood products. The current study assessed the impact of a cannabinoid mixture on the quality of red blood cells and platelets, from the time of collection and processing to their storage. To mimic pre-donation cannabis use, whole blood was collected and exposed (in vitro) to varying concentrations (range: 1-24 μg/mL) of a cannabinoid mixture (CM) overnight. Whole blood was then separated into red blood cells (RBCs) and platelets-rich plasma (PRP), which were stored at 4°C (for RBCs) or at room temperature (for PRP). Flow cytometry analyses, hemolysis measurements and biochemical analyses were performed during the processing stage and throughout storage. In the RBC fraction, free hemoglobin levels were increased in a dose-dependent manner after the addition of a cannabinoid mixture to whole blood. Hemolysis and methemoglobin levels were significantly higher in CM-exposed RBCs than CM-free controls, after processing and throughout storage. Furthermore, platelet counts and CD62P expression (on day 7 post-separation) were significantly lower in CM-exposed PRP than cannabinoid-free PRP controls. The aggregation potential of CM-exposed platelets was significantly lower than that of cannabinoid-free controls, after the processing and throughout storage. An in vitro exposure to a cannabinoid mixture hemolyzed RBCs, impaired oxygen transport by RBCs, reduced platelet counts, and impaired platelet function. These results suggest that pre-donation cannabis use might impair the quality of blood products.

A Case of Suspected Cocaine Adulterant-Associated Methemoglobinemia in the United States

A 30-year-old male with a past history of polysubstance use presents to a drug rehabilitation facility after cocaine and heroin use just prior to arrival. While drinking at a water fountain at the facility, he became unresponsive. He was discovered to have an oxygen saturation of 50% on room air with an improvement to 87% on non-rebreather masks. Arterial blood gas revealed a methemoglobin level of 45.8%. The patient was given methylene blue with a repeat methemoglobin level of 0.00% within six hours. We attribute this presentation to local anesthetic-adulterated cocaine, a well-documented cause of methemoglobinemia in the United Kingdom rarely described in the United States.

Scalable production and complete biophysical characterization of poly(ethylene glycol) surface conjugated liposome encapsulated hemoglobin (PEG-LEH).

Particle encapsulated hemoglobin (Hb)-based oxygen (O2) carriers (HBOCs) have clear advantages over their acellular counterparts because of their larger molecular diameter and lack of vasoactivity upon transfusion. Poly(ethylene glycol) surface conjugated liposome encapsulated Hb (PEG-LEH) nanoparticles are considered a promising class of HBOC for use as a red blood cell (RBC) substitute. However, their widespread usage is limited by manufacturing processes which prevent material scale up. In this study, PEG-LEH nanoparticles were produced via a scalable and robust process using a high-pressure cell disruptor, and their biophysical properties were thoroughly characterized. Hb encapsulation, methemoglobin (metHb) level, O2-PEG-LEH equilibria, PEG-LEH gaseous (oxygen, carbon monoxide, nitric oxide) ligand binding/release kinetics, lipocrit, and long-term storage stability allowed us to examine their potential suitability and efficacy as an RBC replacement. Our results demonstrate that PEG-LEH nanoparticle suspensions manufactured via a high-pressure cell disruptor have Hb concentrations comparable to whole blood (~12 g/dL) and possess other desirable characteristics, which may permit their use as potential lifesaving O2 therapeutics.

Methemoglobinemia due to use of poppers: a case report

BackgroundMethemoglobinemia is an excess of oxidized hemoglobin in the blood, affecting oxygen transportation. It is characterized by central cyanosis that does not respond to oxygen therapy. Prognosis is excellent when treated adequately and rapidly. We present a case report of a 38-year-old Caucasian man suffering from methemoglobinemia due to the use of poppers.Case presentationA 38-year-old Caucasian man known as a smoker and addicted to cocaine was admitted to the emergency department with dyspnea, agitation, and central cyanosis that started approximately 3 hours before admission. The persistent hypoxia despite high-flow oxygen therapy and a history of poppers use helped to reveal a condition known as methemoglobinemia.ConclusionsOur case highlighted a typical clinical presentation of methemoglobinemia. This possible life-threatening condition can occur after ingestion or inhalation of poppers, commonly sold in sex shops for recreational purposes. This can be easily confirmed by the methemoglobin level of the blood gases, provided the emergency physician considers this diagnosis. Rapid treatment with intravenous methylene blue is effective and leads to a favorable prognosis.

Assessment of Severity of Methaemoglobinemia Following Fibreoptic Bronchoscopy with Lidocaine

Lidocaine is commonly used for topical anaesthesia during fibreoptic bronchoscopy (FOB) and it can cause methaemoglobinemia. The present study was undertaken to evaluate the severity of post-bronchoscopy methaemoglobinemia while using lidocaine as a topical anaesthetic agent. We prospectively studied consecutive adult patients who underwent diagnostic FOB in our institution. Blood methaemoglobin levels were estimated by co-oximetry before bronchoscopy and one hour after first instillation of lidocaine. Occurrence of symptoms suggestive of mild methaemoglobinemia (i.e., fatigue, palpitation, dizziness, nausea and headache) were recorded in a severity scale before collection of post-bronchoscopy blood samples. A total of 48 adult patients were enrolled in this study. The mean amount of lidocaine used for bronchoscopy during this study was 7.4 +/- 1.4 mg/kg body weight. The mean pre- and post-bronchoscopy methaemoglobin levels were 0.44 mg/mL and 0.80 mg/mL, respectively. After bronchoscopy, severe and very severe symptoms were reported by 2.1% to 10.4% patients. However, severities of the symptoms were unrelated to post-bronchoscopy methaemoglobin level or the amount of lidocaine used during the FOB. Blood methaemoglobin levels following FOB remained within the physiological limits when British Thoracic Society recommended dose of lidocaine was used. However, few patients had symptoms similar to mild methaemoglobinemia after FOB.

Effect of Soot Inhalation on Methaemoglobin and Oxyhaemoglobin Levels of some Residents of Iwofe, Port Harcourt Rivers state, Nigeria.

Soot is a mass of impure particles of carbon obtained from incomplete hydrocarbon combustion. Soot is an ultrafine air-borne pollutant and enters into the body through ingestion, skin contact and inhalation causing devastating effects on the blood cells. The aim of the study was to determine the effect of soot inhalation on methaemoglobin and oxyhaemoglobin levels of individuals resident in both Iwofe, Port Harcourt (exposed subjects) and Ihiala, Anambra state (control subjects). The study is a case control study involving residents of Iwofe, Rumuolumeni, who have been exposed to soot pollution in the environment for an average period of one year. Iwofe is in Port Harcourt, the capital of Rivers State, Nigeria. A total of fifty (50) test samples were obtained. Thirty control samples were obtained from subjects in Ihiala a city located in the South of Anambra state where illegal oil refineries and other major means of soot generation are not as comparable to what is present in Port Harcourt and its environs. Methaemoglobin and Oxyhaemoglobin concentrations were analyzed using spectrophotometric method. The data obtained was analyzed using SPSS for descriptive statistics (mean and standard deviations) and inferential statistics (t-test). The student t-test was used to test for difference in the methaemoglobin and oxyhaemoglobin levels between the exposed subjects and non-exposed controls and based on age groups and gender. An error of probability (p ≤ 0.05) is considered levels of exposed subjects showing the effect of soot inhalation. Activities of illegal oil refineries (a major source of soot pollution in the city) should be stopped along with other activities like burning of tyres, indiscriminate burning of wastes and gas flaring etc.

SAFETY AND EFFICACY OF INHALED HIGH-DOSE NITRIC OXIDE IN NON-INTUBATED PATIENTS WITH COVID-19 PNEUMONIA

TYPE: Abstract TOPIC: Chest Infections PURPOSE: There are no proven pharmacologic interventions for COVID-19 that primarily target the respiratory system. This study evaluated the safety and the beneficial effects of high-dose inhaled nitric oxide (NO) in non-intubated patients with COVID-19. METHODS: In this interventional study, NO gas (160 parts-per-million [ppm]) was administered for thirty minutes twice daily in hospitalized, non-intubated COVID-19 patients. RESULTS: Between March and June 2020, twenty-nine COVID-19 patients received a total of 217 inhaled NO treatments. The maximum level of nitrogen dioxide was 1.5 ppm. The peak level of methemoglobin (MetHb) during the treatments was 4.7% and decreased in all patients 5 minutes after NO discontinuation. No adverse events, such as hypoxemia or hypotension, occurred during treatments, and none of the patients experienced acute kidney injury during hospitalization. Breathing NO acutely decreased the respiratory rate of tachypneic patients and improved oxygenation in hypoxemic patients [Figure 1]. One of the 29 patients studied required invasive mechanical ventilation and none of the patients died during the trial. The median hospital length of stay was 6 days [interquartile range 4-8]. Discharged patients did not require hospital readmission and did not develop sequelae of COVID-19 during 28 days of follow-up. CONCLUSIONS: In non-intubated COVID-19 patients, administration of inhaled NO at 160 ppm for 30 minutes twice daily decreased the respiratory rate of tachypneic patients and improved oxygenation in hypoxemic patients without any adverse events. CLINICAL IMPLICATIONS: High-dose NO gas might be a valuable treatment option in non-intubated patients with COVID-19 infection. DISCLOSURE: The study medication was provided free of charge by Praxair Inc and by Airgas Healthcare, an Air Liquide company. The non-invasive co-oximeter was provided by Masimo Corp (the companies did not oversight the study). KEYWORD: Nitric Oxide

Methemoglobin Level May Not Predict Organ Failure in Sepsis

Objective: To evaluate the sensitivity, specificity, and area under receiver operating characteristics (AUROC) of methemoglobin levels to predict worsening sequential organ failure assessment (SOFA) scores at 72 hours in sepsis and septic shock in the intensive care setting. Materials and Methods: The authors conducted a prospective pilot study in a single university hospital. The present study subjects were adults aged more than 19 years, sepsis and septic shock patients admitted to intensive care units, with an arterial line in place. All patients’ arterial blood samples were collected and sent to the central laboratory to analyze for methemoglobin levels at the enrolment time, then 12 and 24 hours later. Patient’s characteristics, SOFA scores and other related parameters at enrolment, 12, 24, and 72 hours later were extracted through electronic medical records. Higher SOFA score at 72 hours, comparing to the enrolment value, was considered as a reference standard. Results: Among 30 patients, seven had worsening SOFA scores. Initial methemoglobin level had an AUROC of 0.5404 (95% confidence interval 0.2603 to 0.8204). Using Youden’s index, the determined cut-off value was 0.75%. The sensitivity of this cut-off value was 71.4% (95% confidence interval 29 to 96.3) and the specificity was 52% (95% confidence interval 30.6 to 73.2). Conclusion: Initial Methemoglobin level had an insufficient AUROC of 0.5404 to predict worsening organ failure in critically ill patients with sepsis. As the present study is a pilot study, a larger scale study may be required. Keywords: Sepsis; Methemoglobin; Organ Failure; SOFA; Septic shock

Elevated methemoglobin levels in patients treated with hydroxocobalamin: a case series and in-vitro analysis

Background Historically, the first step in treating cyanide (CN-) toxicity utilized antidotes to induce methemoglobinemia. This is concerning in patients who are already hypoxemic or have elevated carboxyhemoglobin. Hydroxocobalamin (OHCbl) is now the first-line antidote for CN- toxicity and is not known to induce methemoglobinemia. We observed elevated methemoglobin (MetHb) levels in several patients treated with OHCbl and sought to investigate the incidence of MetHb formation following administration of OHCbl. Methods Chart review: A single-center, retrospective case series of patients who received 5 or 10 g of hydroxocobalamin from 01/01/2011 through 04/30/2019. Data was analyzed using descriptive statistics. In-vitro study: Discarded blood was separated into whole blood and plasma samples. OHCbl and normal saline was added to reach 0×, 1×, 2×, and 4× peak therapeutic concentrations and analyzed at times 0, 2, and 4 h after administration. Results Chart review: Twenty-seven cases of OHCbl administration were identified. The median age was 53 years (IQR 38 − 64) and 20 (74.1%) were male. Exposure to a house fire or smoke inhalation was the reason for OHCbl administration in 21 (77.8%) patients. Five (18.5%) patients received 10 g of OHCbl while the rest received 5 g. Six (22.2%) patients developed methemoglobinemia, all after 5 g OHCbl administration; four had been exposed to fire and smoke, two received the medication for severe acidosis of unknown etiology not related to fire or smoke. The median peak level was 7.1% (IQR 2.2 − 16.4%) at a median time of 11.4 h post-administration. Two patients received methylene blue (MB), neither responded. Death occurred in 17 (63%) cases. In-vitro study: We observed a dose dependent elevation in total hemoglobin but did not detect any increase in MetHb. Conclusion We observed a noteworthy temporal association between the formation of methemoglobinemia and the administration of hydroxocobalamin. This does not appear to be an artifact of the CO-oximeters. This could have profound implications for patients who are already hypoxemic or have impaired oxygen carrying capacity from carboxyhemoglobin.

Methaemoglobinaemia in pregnancy: Real world experience in a single centre in Malaysia

The literature on methaemoglobinaemia in pregnancy is scarce, imposing clinical challenges to both obstetricians and haematologists. We report a total of nine pregnancies with methaemoglobinaemia treated in our centre. Their methaemoglobin levels, mode of delivery, pregnancy management and outcome were summarized.

Nitric oxide donor 8-bromo-cGMP suppresses cholesterol depleted RBCs band 3 dysfunction.

Red blood cells (RBCs) carry large cholesterol fractions and imbalance in them leads to several vascular complications. RBCs band 3 protein plays an important role in maintaining membrane integrity and there are many reports on cholesterol and band 3 protein interaction. Yet, RBCs band 3 protein role in regulating cholesterol homeostasis needs to be investigated. In this study, we induced cholesterol-depletion and band 3 inhibition in RBCs; both of which cause stress by decreasing band 3 channel activity with an increase in RBCs adhesion to endothelial cells (EC) by elevating band 3 phosphorylation (Tyr21), methemoglobin level and decreasing nitric oxide level. We hypothesized that nitric oxide (NO), a prominent determinant for RBC structural stability, would protect RBCs from stressors. To estimate this, we used three NO donors (SpNO, Sildenafil citrate and 8-Bromo-cGMP) and found that all 3 NO donors were able to recover, with 8-Bromo-cGMP being the most effective as it not only increased band 3 channel activity but also decreased RBC-EC adhesiveness and methemoglobin level in both stressors. Whereas NO donor's treatment did not display an ameliorative impact when both stresses were combined. Overall, these findings may shed light on the role of 8-bromo-cGMP in regulating RBC cholesterol homeostasis by maintaining band 3 function. Further studies in this direction might help identify targets for the therapeutic use of NO donors in the treatment of blood disorders.

Retrospective evaluation of carboxyhemoglobin and methemoglobin levels in dogs and cats with respiratory disease

To evaluate carboxyhemoglobin (COHb) and methemoglobin (MetHb) levels in dogs and cats with respiratory disease in the ICU. Retrospective study. University veterinary teaching hospital. The ICU census was searched for dogs (n=466) and cats (n=97) hospitalized within the ICU between January 2016 and January 2019 in whom blood gas with co-oximetry was performed. Dogs and cats were stratified into those with primary respiratory and nonrespiratory categories; the underlying cause of the disease was also noted. Venous blood gas, co-oximeter, PaO2 /FiO2 (PF ratio), physical examination findings, and outcome were recorded. The median COHb and MetHb in dogs hospitalized in the ICU were 2.6% (0.1%-5.6%) and 1.1% (0.1%-2.9%), respectively. The median COHb and MetHb in cats hospitalized in the ICU were 2.2% (0.1%-5.4%) and 1.0% (0%-2.1%), respectively. Dogs with respiratory disease had a higher COHb than dogs without respiratory disease (median, 2.7% [range, 0.3%-5.0%] vs. 2.5% [0.1%-5.6%]; P=0.0148). COHb was positively associated with survival in cats (median, 2.2% [range, 0.1%-5.4%] vs. 1.9% [0.1%-3.9%]; P=0.0433). Both COHb and MetHb were higher in septic dogs than in nonseptic dogs (median COHb, 2.8% [range 0.3%-4.5%] vs. 2.6% [0.1%-5.6%]; P=0.02 and median MetHb, 1.1% [0.1%-2.9%] vs. 1.1% [0.1%-2.4%]; P=0.01, respectively). There may be a positive association between COHb and respiratory disease in dogs; prospective studies are needed to evaluate this further. No association between COHb and respiratory disease in cats or MetHb and respiratory disease in either species was detected. Additional prospective studies are needed to determine whether COHb and MetHb are biomarkers for sepsis in dogs and whether COHb is an indicator of mortality in cats.

Acquired methemoglobinemia in children presenting to Italian pediatric emergency departments: a multicenter report

Introduction Methemoglobinemia (MetHb) is a rare inherited or acquired cause of cyanosis in children. Owing to its rarity, case reports and case series are mostly available in the current literature. This study reports data on a large sample of children with acquired MetHb. Methods Data on patients admitted for acquired MetHb between January 2007 to December 2020 was extracted from the databases of five Italian pediatric emergency departments (EDs). Demographical and clinical characteristics was reported and discussed. Results Nineteen cases of acquired MetHb were evaluated. Ten patients (52.6%) were male and 9 (47.4%) were female. The median age was 8.23 months. The median time from trigger to symptom onset was 6 hours. Mostly, the intoxication presumptively occurred by home ingestion of contaminated food, mainly badly preserved vegetable broth. All patients were cyanotic at admission, most patients also presented tachycardia and/or tachypnea, and two patients were comatose. Antidotal therapy with methylene blue was given in 14 patients (73.7%). The median hospital stay was 2 days. All patients survived. Discussion As MetHb leads to the pathognomonic brown blood discoloration, blood gas analysis is mandatory immediately upon hospital arrival of a cyanotic patient. A correct medical history is crucial to identify the trigger and remove it. In our sample, the age onset was much lower than in the previous literature, and MetHb mainly due to ingestion of contaminated vegetable broth. Methylene blue led to a rapid recovery in all patients. Oxygen therapy may well lead to complete recovery when methemoglobin levels do not exceed 30% in asymptomatic and 20% in mildly symptomatic patients. Conclusions The diagnosis and management of acquired MetHb in the emergency setting requires acknowledgment of this condition as a cause of cyanosis in the weaning child. Indeed, when promptly recognized and treated, this severe condition rapidly resolves with no significant acute sequelae.

Food‐induced methemoglobinemia: A systematic review

AbstractMethemoglobinemia is a sporadic, potentially fatal disease of poor tissue oxygenation in which ferrous hemoglobin (Fe2+) is oxidized to the ferric (Fe3+) state, rendering it incapable of binding oxygen (O2). Fortunately, it is diagnosable and treatable. Here, we present a systematic review of food‐induced methemoglobinemia. PubMed and Embase databases were searched using the term “methemoglobin*,” for articles up to December 31, 2020. Inclusion criteria were confirmed or probable cases of methemoglobinemia with an oxidant confirmed in food or body tissue samples, or the oxidant likely to have come from food. We found 97 articles describing 568 cases. Median age was 6 years (range: 2 weeks to 80 years). Median methemoglobin fraction was 30% (n = 142). Oxidizing agents were predominantly nitrites and nitrates. The commonest type of presentation was children eating vegetables (30%), followed by accidental ingestions (27%), and meat curing misadventures (22%). Favism was found to result in mild methemoglobinemia, highest fraction reported was 15.8%. Of the 35 deaths, 32 were from accidental ingestions (91%). In some fatal cases, diagnosis was likely delayed or missed, and antidote was not administered. The majority of cases survived, even with severe methemoglobin levels of up to 89%, provided that methylene blue was administered. Treatment with methylene blue alone resulted in an average methemoglobin drop of 39.1% (n = 22). Methemoglobinemia cases continue to occur due to accidental exposure, meat curing misadventures, and babies ingesting nitrate‐rich vegetables which have been inappropriately stored. Early recognition of the toxidrome, instituting antidote treatment, and notifying public health authorities are key to improved outcomes.

Effect of Local Injection of Lidocaine and Articaine plus Epinephrine on Methemoglobin Level during General Anesthesia.

Statement of the Problem: Methemoglobinemia is a potentially life-threatening rare medical condition, which refers to an increase in the level of oxidized form of hemoglobin (methemoglobin). Excessive replacement of hemoglobin with methemoglobin leads to functional hypoxia and even fatal conditions.Purpose: The aim of this study was to evaluate the effect of two common local anesthetic agents namely lidocaine and articaine administered for hemostasis during surgery on methemoglobin level.Materials and Method: This prospective cohort study was conducted from January 2017 to December 2019. Demographic data including age, gender, and weight of patients were collected. Sixty patients were randomly divided into three groups (n=20) regarding the local anesthetic agent administered for hemostasis during surgery as lidocaine group (group 1), articaine group (group 2), and control group (no local anesthetic; group 3). The patients were candidates for orthognathic surgery, reconstruction of the maxillary and mandibular atrophic ridges with autogenous grafts, and reconstruction of maxillofacial fractures. The methemoglobin level was measured before surgery and six hours after the initiation of surgery.Results: The mean age and weight of patients were not significantly different among the three groups (p= 0.891 and p= 0.416, respectively). No significant differences were observed among the three groups regarding the gender distribution (p= 0.343) or type of surgery (p= 0.990). Statistical analysis did not show any significant difference in the mean baseline methemoglobin level among the three groups (p= 0.109). Although the mean methemoglobin values increased in the three groups, paired sample t-test did not show any significant change in the values at six hours after the initiation of surgery compared with baseline in any of the three groups (p= 0.083 for group 1, p= 0.096 for group 2, and p= 0.104 for group 3).Conclusion: The results demonstrated that administration of lidocaine and articaine plus epinephrine for hemostasis during general anesthesia are equally safe.

Methaemoglobinemia after Liposuction under Tumescent Local Anaesthesia - Diagnostic Value of Pulse Oximetry.

Background:Tumescent local anaesthesia with prilocain can lead to clinically significant methemoglobin levels. New generation multiple wavelength pulse oximeters (e. g. Masimo Radical 7®) can measure methemoglobin levels. Methods:In this prospective observational study we compared the venous methemoglobin levels and the corresponding pulse oximetric values of the Radical 7® in patients undergoing tumescent local anaesthesia for liposuction procedures. The measurements were performed in Hanseklinik, Luebeck, Germany between 2008 and 2011.Results:In 133 patients, we measured a maximum methemoglobin level of 18 per cent. In a Bland-Altman analysis we found a mean bias of +2.2 % (-4.1 to 8.4 limits of agreement) for pulse oximetric values compared to hemoximetry. Conclusion:Pulse oximetric measurement of methemoglobin is an early-warning tool for the detection of clinically significant methaemoglobinemia in patients with tumescent local anaesthesia.

Phenazopyridine-Induced Methaemoglobinaemia The Aftermath of Dysuria Treatment.

IntroductionPhenazopyridine is an over-the-counter urinary analgesic commonly used to alleviate the burning and urgency associated with lower urinary tract infections. Methaemoglobinaemia is an uncommon adverse effect of phenazopyridine use. We report a case of methaemoglobinaemia in a patient prescribed daily phenazopyridine to treat urethral and bladder irritation caused by a chronic indwelling Foley catheter.Case descriptionA 55-year-old female resident of a long-term acute care facility with a chronic Foley, tracheostomy and ventilator-dependent respiratory failure was observed to have generalized dusky skin and hypoxia. Pulse oximetry was reading in the high 80s despite administration of 100% FiO2. ABG revealed paO2 of 451, oxyhaemoglobin level 75% and methaemoglobin level 22%. Medication review indicated that the patient was prescribed phenazopyridine 400 mg TID for the previous 2 months. This medication was discontinued. Considering she was chronically taking mirtazapine, she can increase risk of serotonin syndrome should she be administered first-line treatment with methylene blue. Vitamin C was thus instead administered as a second-line agent. Serial ABGs showed a rapid decline in methaemoglobin levels and an increase in oxyhaemoglobin within 2 days.DiscussionAcquired methaemoglobinaemia is a rare adverse effect of treatment with phenazopyridine. This risk increases when drug dosage and duration exceed manufacturer specifications. Treatment typically includes cessation of the offending drug and administration of methylene blue in severe cases. A thorough medication reconciliation should be performed prior to methylene blue initiation, as patients taking serotonergic medications (for example, MAOIs, SSRIs, SNRIs, TCAs) are at increased risk of serotonin toxicity with co-administration of methylene blue. In these instances, ascorbic acid/vitamin C can be chosen as an alternative treatment agent.ConclusionWork-up of refractory hypoxia should involve a thorough review of medications as even some over-the-counter drugs can cause the fatal side effect of methaemoglobinaemia. Treatment with vitamin C should be considered over methylene blue if serotonergic medications have been recently prescribed in order to avoid risk of serotonin syndrome.LEARNING POINTSMethaemoglobinaemia is an uncommon, life-threatening adverse effect of phenazopyridine use. Presentation depends on the severity of the disorder, ranging from headache, weakness, lightheadedness and dyspnoea, to arrhythmias, confusion, seizures and multiorgan failure.Workup of refractory hypoxia should involve a comprehensive medication review as even some over-the-counter drugs can cause methaemoglobinaemia.Management of methaemoglobinaemia involves cessation of the offending drug, administration of supplemental oxygen and treatment with methylene blue (1–2 mg/kg) if MetHb >30%, or for symptomatic patients with MetHb >20%. Vitamin C can be used as an alternative agent if there is a contraindication to methylene blue (for example, with patients simultaneously receiving serotonergic medications and/or those with G6PD deficiency).