Methylene blue for the treatment of septic shock

Administration of methylene blue in septic shock: pros and cons

Septic shock typically requires the administration of vasopressors. Adrenergic agents remain the first choice, namely norepinephrine. However, their use to counteract life-threatening hypotension comes with potential adverse effects, so that non-adrenergic vasopressors may also be considered. The use of agents that act through different mechanisms may also provide an advantage. Nitric oxide (NO) is the main driver of the vasodilation that leads to hypotension in septic shock, so several agents have been tested to counteract its effects. The use of non-selective NO synthase inhibitors has been of questionable benefit. Methylene blue, an inhibitor of soluble guanylate cyclase, an important enzyme involved in the NO signaling pathway in the vascular smooth muscle cell, has also been proposed. However, more than 25 years since the first clinical evaluation of MB administration in septic shock, the safety and benefits of its use are still not fully established, and it should not be used routinely in clinical practice until further evidence of its efficacy is available.

Evaluation of topical methylene blue nanoemulsion for wound healing in diabetic mice

CONTEXT

Diabetic wounds (DW) are a complication of diabetes and slow wound healing is the main manifestation. Methylene blue (MB) has been shown to exhibit therapeutic effects on diabetes-related diseases.

OBJECTIVE

To investigate the mechanisms of action of MB-nanoemulsion (NE) in the treatment of DW.

MATERIALS AND METHODS

The concentration of MB-NE used in the in vivo and in vitro experiments was 0.1 mg/mL. Streptozocin-induced diabetic mice were used as models. The mice were separated into nondiabetic, diabetic, MB-NE treated, and NE-treated groups. Intervention of high glucose-induced human umbilical vein endothelial cells using MB-NE. The mechanism by which MB-NE promotes DW healing is investigated by combining histological analysis, immunofluorescence analysis, TUNEL and ROS assays and western blotting.

RESULTS

In diabetic mice, the MB-NE accelerated DW healing (p < 0.05), promoted the expression of endothelial cell markers (α-SMA, CD31 and VEGF) (p < 0.05), and reduced TUNEL levels. In vitro, MB accelerated the migration rate of cells (p < 0.05); promoted the expression of CD31, VEGF, anti-apoptotic protein Bcl2 (p < 0.05) and decreased the expression of the pro-apoptotic proteins cleaved caspase-3 and Bax (p < 0.05). MB upregulated the expression of Nrf2, catalase, HO-1 and SOD2 (p < 0.05). In addition, MB reduced the immunofluorescence intensity of TUNEL and ROS in cells and reduced apoptosis. The therapeutic effect of MB was attenuated after treatment with an Nrf2 inhibitor (ML385).

DISCUSSION AND CONCLUSION

This study provides a foundation for the application of MB-NE in the treatment of DW.

The gut microbiome and cardiac surgery an unusual symphony

The relationship between the gut microbiome and various organ systems has gained interest throughout the scientific community in recent times. The understanding of these complex relationships has greatly improved with clinical benefits now being seen. Cardiopulmonary bypass (CPB) is a form of extracorporeal circulation that provides circulatory and respiratory support during cardiac surgery. This physiological support facilitates a still and bloodless field facilitating operations on the heart to be performed. Through various mechanisms CPB results in a systemic inflammatory response syndrome (SIRS). This response can vary from mild hypotension to multiple organ failure. It remains difficult to predict the degree to which a patient will experience SIRS post-operatively. The relationship between the composition of the gut microbiome and inflammatory processes associated with disease has been seen across several fields including gastroenterology, neurology, psychiatry and cardiology. To date, minimal research has been undertaken to examine the impact the gut microbiome has on outcomes following cardiac surgery. This review paper explores the pathophysiology behind the SIRS response associated with CPB for cardiac surgery and the hypothesis that a correlation exists between a patients gut microbiome composition and the degree of inflammatory response experienced following cardiac surgery.

Effect of methylene blue on hemodynamic response in the early phase of septic shock: A case series

RATIONALE

Methylene blue (MB) has been used to increase blood pressure in septic shock, acting on the activity of guanylate cyclase and nitric oxide synthase.

PATIENCE CONCERNS

The aim of this study is to demonstrate the benefit of MB in early phase of septic shock.Diagnoses: We report 6 cases of patients with septic shock with up to 72 hours of evolution.

INTERVENTIONS

We used MB after fluid replacement, use of norepinephrine and vasopressin. Patients received a loading dose of MB and maintenance for 48 hours.

OUTCOMES

All patients presented a reduction in the dose of vasopressors and lactate levels soon after the administration of the loading dose of MB, an effect that was maintained with the maintenance dose for 48 hours. Interleukin 6 and interleukin 8 were elevated at the beginning of the septic condition, with a progressive and marked reduction after the beginning of MB infusion, demonstrating a role of MB in reducing the inflammatory activity.

LESSONS

This case series suggests that MB used early in the treatment of septic shock may be useful in reducing vasopressor dose and lactate levels. Further studies are still required to further validate these findings.

Methylene Blue in Refractory Shock

Many patients suffer shock in intensive care units (ICU). The majority of the patients with shock respond to standard treatment with vasopressors in addition to the treatment of underlying etiology. Some may not respond to vasopressors and have high mortality. To those patients who do not respond, methylene blue has been used in the past with some success. We present a case report on the use of methylene blue along with a brief literature review.

Effects of methylene blue on microcirculatory alterations following cardiac surgery: A prospective cohort study

BACKGROUND

Methylene blue is used as rescue therapy to treat catecholamine-refractory vasoplegic syndrome after cardiac surgery. However, its microcirculatory effects remain poorly documented.

OBJECTIVE

We aimed to study microcirculatory abnormalities in refractory vasoplegic syndrome following cardiac surgery with cardiopulmonary bypass and assess the effects of methylene blue.

DESIGN

A prospective open-label cohort study.

SETTING

20-Bed ICU of a tertiary care hospital.

PATIENTS

25 Adult patients receiving 1.5 mg kg-1 of methylene blue intravenously for refractory vasoplegic syndrome (defined as norepinephrine requirement more than 0.5 μg kg-1 min-1) to maintain mean arterial pressure (MAP) more than 65 mmHg and cardiac index (CI) more than 2.0 l min-1 m-2.

MAIN OUTCOME MEASURES

Complete haemodynamic set of measurements at baseline and 1 h after the administration of methylene blue. Sublingual microcirculation was investigated by sidestream dark field imaging to obtain microvascular flow index (MFI), total vessel density, perfused vessel density and heterogeneity index. Microvascular reactivity was assessed by peripheral near-infrared (IR) spectroscopy combined with a vascular occlusion test. We also performed a standardised measurement of capillary refill time.

RESULTS

Despite normalised CI (2.6 [2.0 to 3.8] l min-1 m-2) and MAP (66 [55 to 76] mmHg), patients with refractory vasoplegic syndrome showed severe microcirculatory alterations (MFI < 2.6). After methylene blue infusion, MFI significantly increased from 2.0 [0.1 to 2.5] to 2.2 [0.2 to 2.8] (P = 0.008), as did total vessel density from 13.5 [8.3 to 18.5] to 14.9 [10.1 to 14.7] mm mm-2 (P = 0.02) and perfused vessel density density from 7.4 [0.1 to 11.5] to 9.1 [0 to 20.1] mm mm-2 (P = 0.02), but with wide individual variation. Microvascular reactivity assessed by tissue oxygen resaturation speed also increased from 0.5 [0.1 to 1.8] to 0.7 [0.1 to 2.7]% s-1 (P = 0.002). Capillary refill time remained unchanged throughout the study.

CONCLUSION

In refractory vasoplegic syndrome following cardiac surgery, we found microcirculatory alterations despite normalised CI and MAP. The administration of methylene blue could improve microvascular perfusion and reactivity, and partially restore the loss of haemodynamic coherence.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT04250389.

[Vasoactive drugs in the treatment of septic shock]

Septic shock is a high mortality complication frequently associated with sepsis. Early initiation of vasopressor treatment, even before completion of initial fluid resuscitation, is a determining factor in prognosis. In this sense, norepinephrine continues to be the drug of first choice, although there is increasing evidence of benefit combining it with other non-adrenergic drugs, such as vasopressin, instead of escalating norepinephrine doses. The pathophysiology of septic shock is multifactorial, and sometimes is associated with a situation of myocardial dysfunction that contributes to hemodynamic instability. It is essential to identify this situation since it worsens the prognosis and may benefit from combined treatment with inotropic drugs. There are novel vasoactive agents under study, more selective than the classic ones that in a next future could help to design more individualized and precise treatments. In the present work, the current knowledge about vasoactive drugs and their use in the management of septic shock is summarized according to the most recent scientific evidence.

Effect of methylene blue on hemodynamic and metabolic response in septic shock patients

INTRODUCTION

Septic shock is a lethal disease responsible for a large proportion of deaths in the Intensive Care Unit (ICU), even with therapy centered on fluid resuscitation, use of vasopressors and empirical antibiotic therapy applied within the first hour of diagnosis. Considering the multifactorial pathophysiology of septic shock and the mechanism of action of vasopressors, some patients may not respond adequately, which can lead to the maintenance of vasodilatation, hypotension and increased morbidity, and mortality. This protocol aims to verify whether the use of methylene blue in septic patients with an early diagnosis can contribute to an earlier resolution of a shock compared to standard treatment.

METHODS AND ANALYSIS

This is a study protocol for a single-center randomized clinical trial design in an ICU of a tertiary university hospital. In this study, we intend to include 64 patients aged between 18 and 80 years with a diagnosis of septic shock, of any etiology, with up to 72 hours of evolution after volume restoration, using norepinephrine at a dose ≥0.2 μg/kg/min and vasopressin at a dose of 0.04 IU/min. After the initial approach, we will randomize patients into two groups, standard care, and standard care plus methylene blue. The sample size was calculated in order to show 30% differences in septic shock resolution between groups. The Research Ethics Committee approved the study, and all patients included will sign an informed consent form (Clinical registration: RBR-96584w4).

Methylene Blue not Contraindicated in Treating Hemodynamic Instability in Pediatric and Neonate Patients

The present review was carried out to describe publications on the use of methylene blue (MB) in pediatrics and neonatology, discussing dose, infusion rate, action characteristics, and possible benefits for a pediatric patient group. The research was performed on the data sources PubMed, BioMed Central, and Embase (updated on Aug 31, 2020) by two independent investigators. The selected articles included human studies that evaluated MB use in pediatric or neonatal patients with vasoplegia due to any cause, regardless of the applied methodology. The MB use and 0 to 18-years-old patients with vasodilatory shock were the adopted criteria. Exclusion criteria were the use of MB in patients without vasoplegia and patients ≥ 18-years-old. The primary endpoint was the increase in mean arterial pressure (MAP). Side effects and dose were also evaluated. Eleven studies were found, of which 10 were case reports, and 1 was a randomized clinical study. Only two of these studies were with neonatal patients (less than 28 days-old), reporting a small number of cases (1 and 6). All studies described the positive action of MB on MAP, allowing the decrease of vasoactive amines in several of them. No severe side effects or death related to the use of the medication were reported. The maximum dose used was 2 mg/kg, but there was no consensus on the infusion rate and drug administration timing. Finally, no theoretical or experimental basis sustains the decision to avoid MB in children claiming it can cause pulmonary hypertension. The same goes for the concern of a possible deleterious effect on inflammatory distress syndrome.

Methylene Blue to Neonatal Septic Shock treatment in neonate pigs. Clinics (Sao Paulo) 2022;77:100139. [PMID: 36459779 PMCID: PMC9706526 DOI: 10.1016/j.clinsp.2022.100139] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

OBJECTIVE

The authors design an animal model of neonatal sepsis to analyze the treatment of neonatal septic shock with Methylene Blue (MB) in a swine model.

METHODS

The study design included twenty male newborn pigs divided into four groups: 1) The control group; 2) The sepsis group (induced with lipopolysaccharide); 3) The MB group, and 4) The MB-treated sepsis group. Septic shock was defined as Blood Pressure (BP) dropping 20% below the baseline value. Continuous Blood Pressure (BP), Nitric Oxide (NO) levels, cyclic Guanosine Monophosphate (cGMP), malondialdehyde acid, base excess, lactate, arterial blood gases, hematocrit, and echocardiography were analyzed.

RESULTS

The BP of the sepsis group treated with MB showed a slight improvement in the first hour after treatment; however, a significant difference was not observed compared to the untreated sepsis group. Besides hemodynamic stability, the current study did not show symptomatic pulmonary hypertension, suggesting that MB was safe in neonates and children. An improvement in Base Excel (BE) levels after MB administration in septic animals may indicate a possible improvement in microcirculation.

CONCLUSION

The MB improved biomarkers related to septic shock prognosis, although an improvement in the blood levels could not be detected. MB might be a beneficial drug for hemodynamic instability in infants.

Methylene blue versus vasopressin analog for refractory septic shock in the preterm neonate: A randomized controlled trial

BACKGROUND

Refractory septic shock in neonates is still associated with high mortality, necessitating an alternative therapy, despite all currently available treatments. This study aims to assess the vasopressor effect of methylene blue (MB) in comparison to terlipressin (TP) as adjuvant therapy for refractory septic shock in the preterm neonate.

METHODS

A double-blinded randomized controlled trial was conducted in the Neonatal Intensive Care Units at Ain Shams University, Egypt. Thirty preterm neonates with refractory septic shock were randomized to receive either MB or TP as an adjuvant to conventional therapy. Both MB and TP were administered as an intravenous loading dose followed by continuous intravenous infusion. The hemodynamic variables, functional echocardiographic variables, and oxidant stress marker were assessed over a 24 h period together with the side effects of MB.

RESULTS

MB causes significant improvement in mean arterial blood pressure with a significant decrease of the norepinephrine requirements (1.15±0.21μm/kg/min at baseline vs. 0.55±0.15μm/kg/min at 24 h). MB infusion causes an increase of the pulmonary pressure (44.73±8.53 mmHg at baseline vs. 47.27±7.91 mmHg after 24 h) without affecting the cardiac output. Serum malonaldehyde decreased from 5.45±1.30 nmol/mL at baseline to 4.40±0.90 nmol/mL at 24 h in the MB group.

CONCLUSION

Administration of MB to preterm infants with refractory septic shock showed rapid increases in systemic vascular resistance and arterial blood pressure with minimal side effects.

Ultraviolet radiation protection potentials of Methylene Blue for human skin and coral reef health

Methylene blue (MB) is a century-old medicine, a laboratory dye, and recently shown as a premier antioxidant that combats ROS-induced cellular aging in human skins. Given MB's molecular structure and light absorption properties, we hypothesize that MB has the potential to be considered as a sunscreen active for UV radiation protection. In this study, we tested the effects of MB on UVB ray-induced DNA double-strand breaks in primary human keratinocytes. We found that MB treatment reduced DNA damages caused by UVB irradiation and subsequent cell death. Next, we compared MB with Oxybenzone, which is the most commonly used chemical active ingredient in sunscreens but recently proven to be hazardous to aquatic ecosystems, in particular to coral reefs. At the same concentrations, MB showed more effective UVB absorption ability than Oxybenzone and significantly outperformed Oxybenzone in the prevention of UVB-induced DNA damage and the clearance of UVA-induced cellular ROS. Furthermore, unlike Oxybenzone, MB-containing seawater did not affect the growth of the coral species Xenia umbellata. Altogether, our study suggests that MB has the potential to be a coral reef-friendly sunscreen active ingredient that can provide broad-spectrum protection against UVA and UVB.

Protein kinase inhibitors in traumatic brain injury and repair: New roles of nanomedicine

Traumatic brain injury (TBI) causes physical injury to the cell membranes of neurons, glial and axons causing the release of several neurochemicals including glutamate and cytokines altering cell-signaling pathways. Upregulation of mitogen associated protein kinase (MAPK) and extracellular signal-regulated kinase (ERK) occurs that is largely responsible for cell death. The pharmacological blockade of these pathways results in cell survival. In this review role of several protein kinase inhibitors on TBI induced oxidative stress, blood-brain barrier breakdown, brain edema formation, and resulting brain pathology is discussed in the light of current literature.

Turquoise Discoloration of Organs on Autopsy Secondary to Treatment of Septic Shock With Methylene Blue

Septic shock can result from the dissemination of infections and can lead to hypoperfusion secondary to vasodilation. Methylene blue can help stabilize blood pressure refractory to other measures in shock. We report a case of a 58-year-old male who died of septic shock due to Pseudomonas aeroginosa bacteremia secondary to acute folliculitis and epididymo-orchitis. He was given methylene blue for reversal of septic shock but he did not respond and expired. Autopsy findings were significant for bluish-green discoloration of organs, especially the heart, lungs, and brain during prosection secondary to methylene blue treatment. It is important to recognize artifacts of treatment and to discern them from changes due to putrefaction or the classic green pigmentation associated with Pseudomonas aeruginosa infection, such as chloronychia. The case report illustrates that circulating methylene blue and its metabolites can accumulate in the organs in a dose-related fashion, imparting an interesting turquoise to dark blue-green pigment during the autopsy. Additional studies are warranted to enable pathologists to differentiate among the pigmentation associated with Pseudomonas aeruginosa bacteremia, putrefaction, and methylene blue treatment.

Methylene blue may have a role in the treatment of COVID-19

In this paper, we raise the hypothesis that Methylene Blue may be a treatment option for Corona Virus Disease of 2019 specially when combined with Non Steroid Anti-Inflammatory Drugs. In previous publications including ours, the role of kininogen system has been postulated. A correlation between clinical findings of the disease and this mechanism has been drawn to denote a pivotal role of kininogen-kallikrein system in pathophysiology of the disease. Therein the possible role of Icatibant, Ecallantide and Aprotinin in the treatment of this disease has been raised. Here we want to emphasize on an important post-receptor mechanism of bradykinin that is Nitric Oxide. We came to this aim because we found out how access to these novel treatment nominees may be expensive and unaffordable. For this reason we are focusing on possible role of an old albeit “mysterious” drug namely Methylene Blue. This medication may abort effects of Bradykinin by inhibition of Nitric Oxide synthase inhibitor and promote oxygen saturation while it is inexpensive and ubiquitously accessible. Clinical studies cannot be over emphasized.

Extended Continuous Infusion of Methylene Blue for Refractory Septic Shock

Objective

Highlight the utility of methylene blue (MTB) infusion for extended period for refractory vasoplegia.

Introduction

Hypotension refractory to vasopressor therapy in sepsis is associated with high mortality and limited therapeutic options. Dysregulated nitric oxide (NO) pathway seems to be a major driver, and, therefore, MTB, which inhibits inducible NO synthase activity and decreases cyclic guanosine monophosphate (GMP) accumulation by directly competing with NO by binding to soluble guanylyl cyclase, has been explored.

Case description

We describe a successful reversal of refractory septic shock with prolonged MTB infusion in a patient supported on multiple vasopressors at the highest clinical doses as well as venovenous extracorporeal membrane oxygenation (VV-ECMO).

Conclusion and clinical significance

Current report suggests a potential role of MTB infusion in refractory vasoplegia even in advanced vasoplegic shock.

How to cite this article

Jaiswal A, Kumar M, Silver E. Extended Continuous Infusion of Methylene Blue for Refractory Septic Shock. Indian J Crit Care Med 2020;24(3):206–207.

Clinical utility of midodrine and methylene blue as catecholamine-sparing agents in intensive care unit patients with shock

Shock is common in the intensive care unit, affecting up to one third of patients. Treatment of shock is centered upon managing hypotension and ensuring adequate perfusion via administration of fluids and catecholamine vasopressors. Due to the risks associated with catecholamine vasopressors, interest has grown in using catecholamine-sparing agents such as midodrine and methylene blue. Midodrine is an orally administered alpha-1 adrenergic agonist while methylene blue is an intravenously administered blue dye used to restore vascular tone and increase blood pressure. Separate MEDLINE, Scopus, and Embase database searches were conducted to assess literature revolving around these agents. Examples of search terms included "midodrine", "methylene blue", "critically ill", "shock", and "catecholamine-sparing." Several studies have evaluated their use in patients with shock and found potential benefits in terms of causing significant elevations in blood pressure and hastening catecholamine vasopressor discontinuation with few adverse effects; however, robust evidence is lacking for these off-label indications. Because of the variety of dosing strategies used and the incongruences between patient populations, it is also challenging to define finite recommendations. This review aims to summarize current evidence for the use of midodrine and methylene blue as catecholamine-sparing agents in critically ill patients with resolving or refractory shock.

Fe-Based Metallic Glasses and Dyes in Fenton-Like Processes: Understanding Their Intrinsic Correlation

Fe-based metallic glasses have been demonstrated as effective heterogeneous catalysts in Fenton-like processes for dye degradation. Yet, currently corresponding studies have limitations due to the limited study object (dyes) and the correlation between metallic glasses and dye pollutants in Fenton-like processes is still not comprehensively studied. Accordingly, this work intensively investigated the thermal catalytic behavior correlations between two Fe-based metallic glasses (Fe78Si9B13 and Fe73.5Si13.5B9Cu1Nb3) and eight different dyes. Results indicated a lower activation energy in the more active metallic glass and a dependence of the activation energy of Fe-based metallic glasses in dye solutions. In addition, a high H2O2 concentration led to a declined catalytic efficiency but a photo-enhanced Fenton-like process overcame this limitation at high concentration of H2O2 due to the decrease of pH and enhancement of irradiation. Furthermore, the average mineralization rates of Fe78Si9B13 and Fe73.5Si13.5B9Cu1Nb3 have been measured to be 42.7% and 12.6%, respectively, and the correlation between decolorization and mineralization revealed that a faster decolorization in a Fenton-like process contributed to a higher mineralization rate. This work provides an intrinsic viewpoint of the correlation between Fe-based metallic glasses and dyes in Fenton-like processes and holds the promise to further promote the industrial value of metallic glasses.

Sepsis 2019: What Surgeons Need to Know

The definition of sepsis continues to be as dynamic as the management strategies used to treat this. Sepsis-3 has replaced the earlier systemic inflammatory response syndrome (SIRS)-based diagnoses with the rapid Sequential Organ Failure Assessment (SOFA) score assisting in predicting overall prognosis with regards to mortality. Surgeons have an important role in ensuring adequate source control while recognizing the threat of carbapenem-resistance in gram-negative organisms. Rapid diagnostic tests are being used increasingly for the early identification of multi-drug-resistant organisms (MDROs), with a key emphasis on the multidisciplinary alert of results. Novel, higher generation antibiotic agents have been developed for resistance in ESKCAPE (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species) organisms while surgeons have an important role in the prevention of spread. The Study to Optimize Peritoneal Infection Therapy (STOP-IT) trial has challenged the previous paradigm of length of antibiotic treatment whereas biomarkers such as procalcitonin are playing a prominent role in individualizing therapy. Several novel therapies for refractory septic shock, while still investigational, are gaining prominence rapidly (such as vitamin C) whereas others await further clinical trials. Management strategies presented as care bundles continue to be updated by the Surviving Sepsis Campaign, yet still remain controversial in its global adoption. We have broadened our temporal and epidemiologic perspective of sepsis by understanding it both as an acute, time-sensitive, life-threatening illness to a chronic condition that increases the risk of mortality up to five years post-discharge. Artificial intelligence, machine learning, and bedside scoring systems can assist the clinician in predicting post-operative sepsis. The public health role of the surgeon is key. This includes collaboration and multi-disciplinary antibiotic stewardship at a hospital level. It also requires controlling pharmaceutical sales and the unregulated dispensing of antibiotic agents globally through policy initiatives to control emerging resistance through prevention.

Vasopressor therapy in critically ill patients with shock

BACKGROUND

Vasopressors are administered to critically ill patients with vasodilatory shock not responsive to volume resuscitation, and less often in cardiogenic shock, and hypovolemic shock.

OBJECTIVES

The objectives are to review safety and efficacy of vasopressors, pathophysiology, agents that decrease vasopressor dose, predictive biomarkers, β1-blockers, and directions for research.

METHODS

The quality of evidence was evaluated using Grading of Recommendations Assessment, Development, and Evaluation (GRADE).

RESULTS

Vasopressors bind adrenergic: α1, α2, β1, β2; vasopressin: AVPR1a, AVPR1B, AVPR2; angiotensin II: AG1, AG2; and dopamine: DA1, DA2 receptors inducing vasoconstriction. Vasopressor choice and dose vary because of patients and physician practice. Adverse effects include excessive vasoconstriction, organ ischemia, hyperglycemia, hyperlactatemia, tachycardia, and tachyarrhythmias. No randomized controlled trials of vasopressors showed a significant difference in 28-day mortality rate. Norepinephrine is the first-choice vasopressor in vasodilatory shock after adequate volume resuscitation. Some strategies that decrease norepinephrine dose (vasopressin, angiotensin II) have not decreased 28-day mortality while corticosteroids have decreased 28-day mortality significantly in some (two large trials) but not all trials. In norepinephrine-refractory patients, vasopressin or epinephrine may be added. A new vasopressor, angiotensin II, may be useful in profoundly hypotensive patients. Dobutamine may be added because vasopressors may decrease ventricular contractility. Dopamine is recommended only in bradycardic patients. There are potent vasopressors with limited evidence (e.g. methylene blue, metaraminol) and novel vasopressors in development (selepressin).

CONCLUSIONS

Norepinephrine is first choice followed by vasopressin or epinephrine. Angiotensin II and dopamine have limited indications. In future, predictive biomarkers may guide vasopressor selection and novel vasopressors may emerge.

Vasopressor therapy in critically ill patients with shock

BACKGROUND

Vasopressors are administered to critically ill patients with vasodilatory shock not responsive to volume resuscitation, and less often in cardiogenic shock, and hypovolemic shock.

OBJECTIVES

The objectives are to review safety and efficacy of vasopressors, pathophysiology, agents that decrease vasopressor dose, predictive biomarkers, β1-blockers, and directions for research.

METHODS

The quality of evidence was evaluated using Grading of Recommendations Assessment, Development, and Evaluation (GRADE).

RESULTS

Vasopressors bind adrenergic: α1, α2, β1, β2; vasopressin: AVPR1a, AVPR1B, AVPR2; angiotensin II: AG1, AG2; and dopamine: DA1, DA2 receptors inducing vasoconstriction. Vasopressor choice and dose vary because of patients and physician practice. Adverse effects include excessive vasoconstriction, organ ischemia, hyperglycemia, hyperlactatemia, tachycardia, and tachyarrhythmias. No randomized controlled trials of vasopressors showed a significant difference in 28-day mortality rate. Norepinephrine is the first-choice vasopressor in vasodilatory shock after adequate volume resuscitation. Some strategies that decrease norepinephrine dose (vasopressin, angiotensin II) have not decreased 28-day mortality while corticosteroids have decreased 28-day mortality significantly in some (two large trials) but not all trials. In norepinephrine-refractory patients, vasopressin or epinephrine may be added. A new vasopressor, angiotensin II, may be useful in profoundly hypotensive patients. Dobutamine may be added because vasopressors may decrease ventricular contractility. Dopamine is recommended only in bradycardic patients. There are potent vasopressors with limited evidence (e.g. methylene blue, metaraminol) and novel vasopressors in development (selepressin).

CONCLUSIONS

Norepinephrine is first choice followed by vasopressin or epinephrine. Angiotensin II and dopamine have limited indications. In future, predictive biomarkers may guide vasopressor selection and novel vasopressors may emerge.

Vasoactive Agents for Adult Septic Shock: An Update and Review

PURPOSE

The objective of this article is to discuss the pharmacology, side effects, and clinical application of vasoactive therapy in the management of adult septic shock.

SUMMARY

Sepsis is one of the most common reasons for admission to an intensive care unit with the incidence estimated to be greater than 750 000 cases per year in the United States. Clinicians should understand the basic pharmacology of available vasoactive agents to allow for routine and complex management of septic shock.

CONCLUSION

While advances in research, identification, and early implementation of best practices for the treatment of sepsis has reduced mortality, rates remain high. Vasopressors and inotropes remain part of the core therapeutic modalities of sepsis management. Norepinephrine is the first-line vasopressor of choice for septic shock, though secondary vasopressors can be used depending on the patient's circumstances.

Pathophysiology of Septic Shock

Fundamental features of septic shock are vasodilation, increased permeability, hypovolemia, and ventricular dysfunction. Vasodilation owing to increased nitric oxide and prostaglandins is treated with vasopressors (norepinephrine first). Increased permeability relates to several pathways (Slit/Robo4, vascular endothelial growth factor, angiopoietin 1 and 2/Tie2 pathway, sphingosine-1-phosphate, and heparin-binding protein), some of which are targets for therapies. Hypovolemia is common and crystalloid is recommended for fluid resuscitation. Cardiomyocyte-inflammatory interactions decrease contractility and dobutamine is recommended to increase cardiac output. There is benefit in decreasing heart rate in selected patients with esmolol. Ivabradine is a novel agent for heart rate reduction without decreasing contractility.

Methylene Blue for Acute Septic Cardiomyopathy in a Burned Patient

The objective of this case summary was to describe the use of methylene blue (MB) in a burned patient with acute septic cardiomyopathy. A 60-year-old Caucasian man was admitted to the Burn Intensive Care Unit with 45% TBSA burns after a house explosion. During the course of his care, he experienced hypotension that was refractory to fluid therapy and vasoactive medications. Echocardiography and right heart catheterization showed new acute systolic dysfunction with concurrent elevated systemic vascular resistance (SVR). High-dose inotropic agents did not improve cardiac function, and septic shock rendered him a poor candidate for mechanical intra-aortic balloon pump support. MB was administered to sensitize the myocardium to catecholamines and improve contractility with the goal of weaning the other vasoactive medications and diuresing for afterload reduction when hemodynamic stability was achieved. MB has been described in critical care medicine predominately for vasoplegia after cardiopulmonary bypass and vasodilatory septic shock., Our patient had acute septic cardiomyopathy that was refractory to standard pharmacologic approaches to inotropy with concurrent elevated SVR. Hypothesizing the differential temporal effect of inducible nitric oxide synthase on the vasculature and myocardium, we administered MB to improve contractility and support the impending vasodilatory effects of distributive shock. Although MB is not a new drug, the application for septic cardiomyopathy with a supranormal SVR is a unique application. Because of the risk profile associated with MB, we recommend drug monitoring utilizing serial echocardiography and/or right heart catheterization.

Vasoplegia treatments: the past, the present, and the future

Vasoplegia is a ubiquitous phenomenon in all advanced shock states, including septic, cardiogenic, hemorrhagic, and anaphylactic shock. Its pathophysiology is complex, involving various mechanisms in vascular smooth muscle cells such as G protein-coupled receptor desensitization (adrenoceptors, vasopressin 1 receptors, angiotensin type 1 receptors), alteration of second messenger pathways, critical illness-related corticosteroid insufficiency, and increased production of nitric oxide. This review, based on a critical appraisal of the literature, discusses the main current treatments and future approaches. Our improved understanding of these mechanisms is progressively changing our therapeutic approach to vasoplegia from a standardized to a personalized multimodal treatment with the prescription of several vasopressors. While norepinephrine is confirmed as first line therapy for the treatment of vasoplegia, the latest Surviving Sepsis Campaign guidelines also consider that the best therapeutic management of vascular hyporesponsiveness to vasopressors could be a combination of multiple vasopressors, including norepinephrine and early prescription of vasopressin. This new approach is seemingly justified by the need to limit adrenoceptor desensitization as well as sympathetic overactivation given its subsequent deleterious impacts on hemodynamics and inflammation. Finally, based on new pathophysiological data, two potential drugs, selepressin and angiotensin II, are currently being evaluated.

Methylene Blue for Vasoplegic Syndrome Postcardiac Surgery

Objectives:

cardiopulmonary bypass (CPB) can be complicated by vasoplegia that is refractory to vasopressors. Methylene blue (MB) represents an alternative in such cases.

Patients and Methods:

Retrospective observational historical control-matched study. From 2010 to 2015, all patients who received MB for vasoplegia post-CPB were included in this study. Historical controls from the period of 2004 to 2009 were matched. End-points were the time till improvement of vasoplegia (Ti), 30-day mortality, cardiac surgical Intensive Care Unit (CSICU) morbidity, and length of stay (LOS).

Results:

Twenty-eight patients were matched in both groups. There were no statistically significant differences between the two groups in demographic, laboratory data on admission, or hemodynamic profile before use of MB. Ti and time to complete discontinuation of vasopressors were statistically significant less in MB group (8.2 ± 2.6 vs. 29.7 ± 6.4, P = 0.00 and 22.6 ± 5.2 vs. 55.3 ± 9.4, P = 0.00) respectively. Mortality at day 30 was significantly higher in controls compared to MB (1 patient [3.6%] vs. 6 patients [21.4%], long rank P = 0.04). CSICU, hospital LOS, and incidence of renal failure was significantly higher in control group (12.4 ± 3.7 vs. 7 ± 1.4, P = 0.03), (19.5 ± 2.4 vs. 10.9 ± 3.2, P = 0.05) and (9 patients [32.1%] vs. 2 patients [7.1%], P = 0.04), respectively. Duration of mechanical ventilation was less in MB patients; however, did not reach statistical significance.

Conclusions:

the use of MB for vasoplegia postcardiac surgery was associated with rapid recovery of hemodynamics, shorter need for vasopressors, less ICU mortality, less incidence of renal failure, and shorter LOS.

Severe Undifferentiated Vasoplegic Shock Refractory to Vasoactive Agents Treated with Methylene Blue

Methylene blue is a phenothiazine-related heterocyclic aromatic molecule presently used in the treatment of methemoglobinemia. Recently, it has been implicated in the treatment of severe refractory vasoplegic shock caused by anaphylaxis, sepsis, or postcardiopulmonary bypass. We present a case of a 27-year-old male with profound vasoplegic shock of unknown etiology which was refractory to vasopressors who responded within hours to a single dose of methylene blue. Additionally, we review the evidence of methylene blue's role in the treatment of shock. This case illustrates a diagnostic approach and treatment options in the setting of undifferentiated vasodilatory shock and outlines a new and emerging role for methylene blue in this clinical setting.

Targeting mitochondrial dysfunction in CNS injury using Methylene Blue; still a magic bullet?

Complex, multi-factorial secondary injury cascades are initiated following traumatic brain injury, which makes this a difficult disease to treat. The secondary injury cascades following the primary mechanical tissue damage, are likely where effective therapeutic interventions may be targeted. One promising therapeutic target following brain injury are mitochondria. Mitochondria are complex organelles found within the cell, which act as powerhouses within all cells by supplying ATP. These organelles are also necessary for calcium cycling, redox signaling and play a major role in the initiation of cell death pathways. When mitochondria become dysfunctional, there is a tendency for the cell to loose cellular homeostasis and can lead to eventual cell death. Targeting of mitochondrial dysfunction in various diseases has proven a successful approach, lending support to mitochondria as a pivotal player in TBI cell death and loss of behavioral function. Within this mixed mini review/research article there will be a general discussion of mitochondrial bioenergetics, followed by a brief discussion of traumatic brain injury and how mitochondria play an integral role in the neuropathological sequelae following an injury. We will also give an overview of one relatively new TBI therapeutic approach, Methylene Blue, currently being studied to ameliorate mitochondrial dysfunction following brain injury. We will also present novel experimental findings, that for the first time, characterize the ex vivo effect of Methylene Blue on mitochondrial function in synaptic and non-synaptic populations of mitochondria.

Anti-Aging Potentials of Methylene Blue for Human Skin Longevity

Oxidative stress is the major cause of skin aging that includes wrinkles, pigmentation, and weakened wound healing ability. Application of antioxidants in skin care is well accepted as an effective approach to delay the skin aging process. Methylene blue (MB), a traditional mitochondrial-targeting antioxidant, showed a potent ROS scavenging efficacy in cultured human skin fibroblasts derived from healthy donors and from patients with progeria, a genetic premature aging disease. In comparison with other widely used general and mitochondrial-targeting antioxidants, we found that MB was more effective in stimulating skin fibroblast proliferation and delaying cellular senescence. The skin irritation test, performed on an in vitro reconstructed 3D human skin model, indicated that MB was safe for long-term use, and did not cause irritation even at high concentrations. Application of MB to this 3D skin model further demonstrated that MB improved skin viability, promoted wound healing and increased skin hydration and dermis thickness. Gene expression analysis showed that MB treatment altered the expression of a subset of extracellular matrix proteins in the skin, including upregulation of elastin and collagen 2A1, two essential components for healthy skin. Altogether, our study suggests that MB has a great potential for skin care.

Sulfide Intoxication-Induced Circulatory Failure is Mediated by a Depression in Cardiac Contractility

Hydrogen sulfide (H2S) intoxication produces a rapid cardio-circulatory failure leading to cardiac arrest. In non-lethal forms of sulfide exposure, the presence of a circulatory shock is associated with long-term neurological sequelae. Our aim was to clarify the mechanisms of H2S-induced circulatory failure. In anesthetized, paralyzed, and mechanically ventilated rats, cardiac output, arterial pressure and ventricular pressures were determined while NaHS was infused to increase arterial concentration of soluble H2S (CgH2S) from undetectable to levels leading to circulatory failure. Compared to control/saline infusion, blood pressure started to decrease significantly along with a modest drop in peripheral vascular resistance (-19 ± 5%, P < 0.01), when CgH2S reached about 1 μM. As CgH2S exceeded 2-3 μM, parameters of ventricular contractility diminished with no further reduction in peripheral resistance. Whenever H2S exposure was maintained at a higher level (CgH2S over 7 μM), a severe depression of cardiac contractility was observed, leading to asystole within minutes, but with no evidence of peripheral vasoplegia. The immediate and long-term neurological effects of specifically counteracting sulfide-induced cardiac contractility depression following H2S exposure remain to be investigated.

Improvement in Hemodynamics After Methylene Blue Administration in Drug-Induced Vasodilatory Shock: A Case Report

INTRODUCTION

The purpose of this study is to describe a case where methylene blue improved hemodynamics in a poisoned patient.

CASE REPORT

This is a single case report where a poisoned patient developed vasodilatory shock following ingestion of atenolol, amlodipine, and valsartan. Shock persisted after multiple therapies including vasopressors, high-dose insulin, hemodialysis, and 20% intravenous fat emulsion. Methylene blue (2 mg/kg IV over 30 min) was administered in the ICU with temporal improvement as measured by pulmonary artery catheter hemodynamic data pre- and post-methylene blue administration. Within 1 h of methylene blue administration, systemic vascular resistance improved (240 dyn s/cm5 increased to 1204 dyn s/cm5), and vasopressor requirements decreased with maintenance of mean arterial pressure 60 mmHg.

DISCUSSION

Methylene blue may improve hemodynamics in drug-induced vasodilatory shock and should be considered in critically ill patients poisoned with vasodilatory medications refractory to standard therapies.

Methylene blue, midodrine, and pseudoephedrine: a review of alternative agents for refractory hypotension in the intensive care unit

Hypotensive episodes are common among patients in the intensive care unit and can lead to multiorgan failure if uncontrolled. Fluid administration and continuous infusion of vasoactive agents are frequently used for management of hypotension; however, both therapies may be associated with adverse effects including pulmonary edema and tissue necrosis. In addition, availability of these first-line agents has been impacted by the increasing occurrence of drug shortages. Methylene blue, pseudoephedrine, and midodrine have been considered potential alternatives to standard therapy. These agents may not only be used when first-line agents are unavailable due to shortages, but they may also aid in reducing the cumulative dose of other vasoactive agents used. The purpose of this review was to discuss strategies for the safe and effective use of methylene blue, pseudoephedrine, and midodrine for the treatment of hypotension in the critically ill.

Methylene blue counteracts H2S toxicity-induced cardiac depression by restoring L-type Ca channel activity

We have previously reported that methylene blue (MB) can counteract hydrogen sulfide (H2S) intoxication-induced circulatory failure. Because of the multifarious effects of high concentrations of H2S on cardiac function, as well as the numerous properties of MB, the nature of this interaction, if any, remains uncertain. The aim of this study was to clarify 1) the effects of MB on H2S-induced cardiac toxicity and 2) whether L-type Ca(2+) channels, one of the targets of H2S, could transduce some of the counteracting effects of MB. In sedated rats, H2S infused at a rate that would be lethal within 5 min (24 μM·kg(-1)·min(-1)), produced a rapid fall in left ventricle ejection fraction, determined by echocardiography, leading to a pulseless electrical activity. Blood concentrations of gaseous H2S reached 7.09 ± 3.53 μM when cardiac contractility started to decrease. Two to three injections of MB (4 mg/kg) transiently restored cardiac contractility, blood pressure, and V̇o2, allowing the animals to stay alive until the end of H2S infusion. MB also delayed PEA by several minutes following H2S-induced coma and shock in unsedated rats. Applying a solution containing lethal levels of H2S (100 μM) on isolated mouse cardiomyocytes significantly reduced cell contractility, intracellular calcium concentration ([Ca(2+)]i) transient amplitudes, and L-type Ca(2+) currents (ICa) within 3 min of exposure. MB (20 mg/l) restored the cardiomyocyte function, ([Ca(2+)]i) transient, and ICa The present results offer a new approach for counteracting H2S toxicity and potentially other conditions associated with acute inhibition of L-type Ca(2+) channels.

Methylene blue exerts a neuroprotective effect against traumatic brain injury by promoting autophagy and inhibiting microglial activation

Traumatic brain injury (TBI) leads to permanent neurological impairment, and methylene blue (MB) exerts central nervous system neuroprotective effects. However, only one previous study has investigated the effectiveness of MB in a controlled cortical impact injury model of TBI. In addition, the specific mechanisms underlying the effect of MB against TBI remain to be elucidated. Therefore, the present study investigated the neuroprotective effect of MB on TBI and the possible mechanisms involved. In a mouse model of TBI, the animals were randomly divided into sham, vehicle (normal saline) or MB groups. The treatment time-points were 24 and 72 h (acute phase of TBI), and 14 days (chronic phase of TBI) post-TBI. The brain water content (BWC), and levels of neuronal death, and autophagy were determined during the acute phase, and neurological deficit, injury volume and microglial activation were assessed at all time-points. The injured hemisphere BWC was significantly increased 24 h post-TBI, and this was attenuated following treatment with MB. There was a significantly higher number of surviving neurons in the MB group, compared with the Vehicle group at 24 and 72 h post-TBI. In the acute phase, the MB-treated animals exhibited significantly upregulated expression of Beclin 1 and increased LC3-II to LC3-I ratios, compared with the vehicle group, indicating an increased rate of autophagy. Neurological functional deficits, measured using the modified neurological severity score, were significantly lower in the acute phase in the MB-treated animals and cerebral lesion volumes in the MB-treated animals were significantly lower, compared with the other groups at all time-points. Microglia were activated 24 h after TBI, peaked at 72 h and persisted until 14 days after TBI. Although the number of Iba-1-positive cells in the vehicle and MB groups 24 h post-TBI were not significantly different, marked microglial inhibition was observed in the MB group 72 h and 14 days after-TBI. These results indicated that MB exerts a neuroprotective effect by increasing autophagy, decreasing brain edema and inhibiting microglial activation.

A Novel Use of Methylene Blue in the Pediatric ICU

Methylene blue (MB) is a medication commonly used to treat methemoglobinemia, reducing methemoglobin to hemoglobin. A novel use of MB, as detailed here, is in the treatment of refractory hypotension. A number of reports have detailed use of MB for this purpose in adults, but few data in pediatrics. A 22-month-old girl with Noonan syndrome, biventricular hypertrophic cardiomyopathy, and chronic positive pressure ventilation developed shock with tachycardia, hypotension, and fever after 3 days of diarrhea. She was critically ill, with warm extremities, bounding pulses, and brisk capillary refill. Laboratory tests revealed metabolic acidosis, low mixed venous oxygen saturation, and leukocytosis with bandemia. Treatment of severe septic shock was initiated with fluid resuscitation, inotropic support, sedation, and paralysis. She remained hypotensive despite norepinephrine at 0.7 μg/kg per minute, dopamine at 20 μg/kg per minute, and vasopressin at 0.04 U/kg per hour. Her vasoplegic shock worsened, despite aggressive conventional therapy. Intravenous MB was initiated, with a loading dose of 1 mg/kg followed by a continuous infusion at 0.25 mg/kg per hour. Upon initiation of MB, her systolic blood pressure increased by 33 points (40% increase), and diastolic blood pressure increased by 20 points (46% increase). She was able to wean off all inotropes quickly after initiation of MB. MB should be considered in the setting of refractory vasoplegic shock in the PICU.

Shock Management for Cardio-surgical ICU Patients - The Golden Hours

Postoperative shock following cardiac surgery is a serious condition with a high morbidity and mortality. There are four types of shock: cardiogenic, hypovolemic, obstructive and distributive and these can occur alone or in combination. Early identification of the underlying diseases and understanding of the mechanisms at play are key for successful management of shock. Prompt resuscitation measures are necessary to reverse the shock state and avoid permanent organ dysfunction or death. In this review, the authors focus on the management during the first 6 hours of shock (the 'golden hours'). They discuss how to optimise preload, vascular tone, contractility, heart rate and oxygen delivery. The review incorporates the findings of recent trials on early goal-directed therapy and includes practical recommendations in areas in which the evidence is scare or controversial. While the review focuses on cardio-surgical patients, the suggested treatment algorithms might be usefully expanded to other critically ill patients with shock arising from other causes.

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BACKGROUND

Methylene blue is used in medical practice for various reasons. Recent findings point to a potential interaction with serotonin reuptake inhibitors (SRIs) that could lead to serotonergic toxicity.

OBJECTIVE

To describe the risk of serotonergic toxicity associated with the interaction between methylene blue and SRIs.

DATA SOURCES

Relevant publications were searched systematically via MEDLINE (1946 to March 21, 2013) and Embase (1974 to 2013, week 11) with the following search terms: "methylene blue", "methylthioninium", "monoamine oxidase inhibitors", "serotonin reup-take inhibitors", and "serotonin syndrome". No restrictions were applied in relation to the indication for methylene blue or the language of publication. The reference lists of identified articles were also searched.

STUDY SELECTION AND DATA EXTRACTION

Eighteen case reports and 2 case series were identified for inclusion. To date, no randomized controlled trials have been published.

DATA SYNTHESIS

The first case report indicating suspicion of an interaction between methylene blue and SRIs was published in 2003. Seventeen other case reports describing the same type of interaction have been published since then. The 2 case series provided data from about 325 parathyroidectomies in which methylene blue was used for staining. The 17 patients who experienced central nervous system toxicity were all taking SRIs in the preoperative period.

CONCLUSION

When administered in combination with SRIs, methylene blue may lead to serotonergic toxicity at doses as low as 0.7 mg/kg. Methylene blue would seem to have monoamine oxidase A inhibitory properties. Precautions should be taken to avoid this interaction. [Publisher's translation].

Immediate and Long-Term Outcome of Acute H2S Intoxication Induced Coma in Unanesthetized Rats: Effects of Methylene Blue

BACKGROUND

Acute hydrogen sulfide (H2S) poisoning produces a coma, the outcome of which ranges from full recovery to severe neurological deficits. The aim of our study was to 1--describe the immediate and long-term neurological effects following H2S-induced coma in un-anesthetized rats, and 2--determine the potential benefit of methylene blue (MB), a compound we previously found to counteract acute sulfide cardiac toxicity.

METHODS

NaHS was administered IP in un-sedated rats to produce a coma (n = 34). One minute into coma, the rats received MB (4 mg/kg i.v.) or saline. The surviving rats were followed clinically and assigned to Morris water maze (MWM) and open field testing then sacrificed at day 7.

RESULTS

Sixty percent of the non-treated comatose rats died by pulseless electrical activity. Nine percent recovered with neurological deficits requiring euthanasia, their brain examination revealed major neuronal necrosis of the superficial and middle layers of the cerebral cortex and the posterior thalamus, with variable necrosis of the caudate putamen, but no lesions of the hippocampus or the cerebellum, in contrast to the typical distribution of post-ischemic lesions. The remaining animals displayed, on average, a significantly less effective search strategy than the control rats (n = 21) during MWM testing. Meanwhile, 75% of rats that received MB survived and could perform the MWM test (P<0.05 vs non-treated animals). The treated animals displayed a significantly higher occurrence of spatial search than the non-treated animals. However, a similar proportion of cortical necrosis was observed in both groups, with a milder clinical presentation following MB.

CONCLUSION

In conclusion, in rats surviving H2S induced coma, spatial search patterns were used less frequently than in control animals. A small percentage of rats presented necrotic neuronal lesions, which distribution differed from post-ischemic lesions. MB dramatically improved the immediate survival and spatial search strategy in the surviving rats.

H2S induced coma and cardiogenic shock in the rat: Effects of phenothiazinium chromophores

CONTEXT

Hydrogen sulfide (H2S) intoxication produces an acute depression in cardiac contractility-induced circulatory failure, which has been shown to be one of the major contributors to the lethality of H2S intoxication or to the neurological sequelae in surviving animals. Methylene blue (MB), a phenothiazinium dye, can antagonize the effects of the inhibition of mitochondrial electron transport chain, a major effect of H2S toxicity.

OBJECTIVES

We investigated whether MB could affect the immediate outcome of H2S-induced coma in un-anesthetized animals. Second, we sought to characterize the acute cardiovascular effects of MB and two of its demethylated metabolites-azure B and thionine-in anesthetized rats during lethal infusion of H2S.

MATERIALS AND METHODS

First, MB (4 mg/kg, intravenous [IV]) was administered in non-sedated rats during the phase of agonal breathing, following NaHS (20 mg/kg, IP)-induced coma. Second, in 4 groups of urethane-anesthetized rats, NaHS was infused at a rate lethal within 10 min (0.8 mg/min, IV). Whenever cardiac output (CO) reached 40% of its baseline volume, MB, azure B, thionine, or saline were injected, while sulfide infusion was maintained until cardiac arrest occurred.

RESULTS

Seventy-five percent of the comatose rats that received saline (n = 8) died within 7 min, while all the 7 rats that were given MB survived (p = 0.007). In the anesthetized rats, arterial, left ventricular pressures and CO decreased during NaHS infusion, leading to a pulseless electrical activity within 530 s. MB produced a significant increase in CO and dP/dtmax for about 2 min. A similar effect was produced when MB was also injected in the pre-mortem phase of sulfide exposure, significantly increasing survival time. Azure B produced an even larger increase in blood pressure than MB, while thionine had no effect.

CONCLUSION

MB can counteract NaHS-induced acute cardiogenic shock; this effect is also produced by azure B, but not by thionine, suggesting that the presence of methyl groups is a prerequisite for producing this protective effect.

Glycyrrhetinic acid reverses the lipopolysaccharide-induced hypocontractility to noradrenaline in rat aorta: implications to septic shock

Septic shock and associated vascular hyporeactivity to vasoconstrictor agonists remain a major problem of critical care medicine. Here we report that glycyrrhetinic acid (GA), the active component of licorice, effectively restores vascular contractility in the model of lipopolysaccharide (LPS)-treated rat aorta. GA was as effective as the NO synthase inhibitor N(G)-nitroarginine methylester. GA did not affect the vascular NO levels (measured by EPR spin trapping) and relaxations to L-arginine in LPS-treated rings as well as relaxation to S-nitroso-N-acetylpenicillamine in control rings. Thus, GA may represent an interesting alternative to NO synthase inhibitors in sepsis-associated vascular dysfunction.

Methylene blue attenuates traumatic brain injury-associated neuroinflammation and acute depressive-like behavior in mice

Traumatic brain injury (TBI) is associated with cerebral edema, blood brain barrier breakdown, and neuroinflammation that contribute to the degree of injury severity and functional recovery. Unfortunately, there are no effective proactive treatments for limiting immediate or long-term consequences of TBI. Therefore, the objective of this study was to determine the efficacy of methylene blue (MB), an antioxidant agent, in reducing inflammation and behavioral complications associated with a diffuse brain injury. Here we show that immediate MB infusion (intravenous; 15-30 minutes after TBI) reduced cerebral edema, attenuated microglial activation and reduced neuroinflammation, and improved behavioral recovery after midline fluid percussion injury in mice. Specifically, TBI-associated edema and inflammatory gene expression in the hippocampus were significantly reduced by MB at 1 d post injury. Moreover, MB intervention attenuated TBI-induced inflammatory gene expression (interleukin [IL]-1β, tumor necrosis factor α) in enriched microglia/macrophages 1 d post injury. Cell culture experiments with lipopolysaccharide-activated BV2 microglia confirmed that MB treatment directly reduced IL-1β and increased IL-10 messenger ribonucleic acid in microglia. Last, functional recovery and depressive-like behavior were assessed up to one week after TBI. MB intervention did not prevent TBI-induced reductions in body weight or motor coordination 1-7 d post injury. Nonetheless, MB attenuated the development of acute depressive-like behavior at 7 d post injury. Taken together, immediate intervention with MB was effective in reducing neuroinflammation and improving behavioral recovery after diffuse brain injury. Thus, MB intervention may reduce life-threatening complications of TBI, including edema and neuroinflammation, and protect against the development of neuropsychiatric complications.

Efficacy of methylene blue in an experimental model of calcium channel blocker-induced shock

STUDY OBJECTIVE

Calcium channel blocker poisonings account for a substantial number of reported deaths from cardiovascular drugs. Although supportive care is the mainstay of treatment, experimental therapies such as high-dose insulin-euglycemia and lipid emulsion have been studied in animal models and used in humans. In the most severe cases, even aggressive care is inadequate and deaths occur. In both experimental models and clinical cases of vasodilatory shock, methylene blue improves hemodynamic measures. It acts as a nitric oxide scavenger and inhibits guanylate cyclase that is responsible for the production of cyclic guanosine monophosphate (cGMP). Excessive cGMP production is associated with refractory vasodilatory shock in sepsis and anaphylaxis. The aim of this study is to determine the efficacy of methylene blue in an animal model of amlodipine-induced shock.

METHODS

Sprague-Dawley rats were anesthetized, ventilated, and instrumented for continuous blood pressure and pulse rate monitoring. The dose of amlodipine that produced death within 60 minutes was 17 mg/kg per hour (LD50). Rats were divided into 2 groups: amlodipine followed by methylene blue or amlodipine followed by normal saline solution, with 15 rats in each group. Rats received methylene blue at 2 mg/kg during 5 minutes or an equivalent amount of normal saline solution in 3 intervals from the start of the protocol: minutes 5, 30, and 60. The animals were observed for a total of 2 hours after the start of the protocol. Mortality risk and survival time were analyzed with Fisher's exact test and Kaplan-Meier survival analysis with the log rank test.

RESULTS

Overall, 1 of 15 rats (7%) in the saline solution-treated group survived to 120 minutes compared with 5 of 15 (33%) in the methylene blue-treated group (difference -26%; 95% confidence interval [CI] -54% to 0.3%). The median survival time for the normal saline solution group was 42 minutes (95% CI 28.1 to 55.9 minutes); for the methylene blue group, 109 minutes (95% CI 93.9 to 124.1 minutes). Pulse rate and mean arterial pressure (MAP) differences between groups were analyzed until 60 minutes. Pulse rate was significantly higher in the methylene blue-treated group beginning 25 minutes after the start of the amlodipine infusion (95% CI 30 to 113 minutes) that was analyzed until 60 minutes. MAP was significantly higher in the methylene blue-treated group starting 25 minutes after the amlodipine infusion (95% CI 2 to 30 minutes) that was analyzed until 60 minutes.

CONCLUSION

Methylene blue did not result in a significant difference in mortality risk. There was an increased pulse rate, MAP, and median survival time in the methylene blue group.

Attenuation of noise-induced hearing loss using methylene blue

The overproduction of reactive oxygen species (ROS) and reactive nitrogen species (RNS) has been known to contribute to the pathogenesis of noise-induced hearing loss. In this study, we discovered that in BALB/c mice pretreatment with methylene blue (MB) for 4 consecutive days significantly protected against cochlear injury by intense broad-band noise for 3 h. It decreased both compound threshold shift and permanent threshold shift and, further, reduced outer hair cell death in the cochlea. MB also reduced ROS and RNS formation after noise exposure. Furthermore, it protected against rotenone- and antimycin A-induced cell death and also reversed ATP generation in the in vitro UB-OC1 cell system. Likewise, MB effectively attenuated the noise-induced impairment of complex IV activity in the cochlea. In addition, it increased the neurotrophin-3 (NT-3) level, which could affect the synaptic connections between hair cells and spiral ganglion neurons in the noise-exposed cochlea, and also promoted the conservation of both efferent and afferent nerve terminals on the outer and inner hair cells. These findings suggest that the amelioration of impaired mitochondrial electron transport and the potentiation of NT-3 expression by treatment with MB have a significant therapeutic value in preventing ROS-mediated sensorineural hearing loss.

Therapeutic strategies for high-dose vasopressor-dependent shock

There is no consensual definition of refractory shock. The use of more than 0.5 mcg/kg/min of norepinephrine or epinephrine to maintain target blood pressure is often used in clinical trials as a threshold. Nearly 6% of critically ill patients will develop refractory shock, which accounts for 18% of deaths in intensive care unit. Mortality rates are usually greater than 50%. The assessment of fluid responsiveness and cardiac function can help to guide therapy, and inotropes may be used if hypoperfusion signs persist after initial resuscitation. Arginine vasopressin is frequently used in refractory shock, although definite evidence to support this practice is still missing. Its associations with corticosteroids improved outcome in observational studies and are therefore promising alternatives. Other rescue therapies such as terlipressin, methylene blue, and high-volume isovolemic hemofiltration await more evidence before use in routine practice.