Reversal of severe vasoplegia with single-dose methylene blue after heart transplantation

Vasoplegic syndrome during heart transplantation: A systematic review and meta-analysis

BACKGROUND

Vasoplegic syndrome (VS) is a common occurrence during heart transplantation (HT). It currently lacks a uniform definition between transplant centers, and its pathophysiology and treatment remain enigmatic. This systematic review summarizes the available published clinical data regarding VS during HT.

METHODS

We searched databases for all published reports on VS during HT. Data collected included the incidence of VS in the HT population, patient and intraoperative characteristics, and postoperative outcomes.

RESULTS

Twenty-two publications were included in this review. The prevalence of VS during HT was 28.72% (95% confidence interval: 27.37%, 30.10%). Factors associated with VS included male sex, higher body mass index, hypothyroidism, pre-HT left ventricular assist device or venoarterial extracorporeal membrane oxygenation (VA-ECMO), pre-HT calcium channel blocker or amiodarone usage, longer cardiopulmonary bypass time, and higher blood product transfusion requirement. Patients who developed VS were more likely to require postoperative VA-ECMO support, renal replacement therapy, reoperation for bleeding, longer mechanical ventilation, and a greater 30-day and 1-year mortality.

CONCLUSIONS

The results of our systematic review are an initial step for providing clinicians with data that can help identify high-risk patients and avenues for potential risk mitigation. Establishing guidelines that officially define VS will aid in the precise diagnosis of these patients during HT and guide treatment. Future studies of treatment strategies for refractory VS are needed in this high-risk patient population.

Perioperative Management of Heart Transplantation: A Clinical Review

In this clinical review, the authors summarize the perioperative management of heart transplant patients with a focus on hemodynamics, immunosuppressive strategies, hemostasis and hemorrage, and the prevention and treatment of infectious complications.

HFSA Expert Consensus Statement on the Medical Management of Patients on Durable Mechanical Circulatory Support

The medical management of patients supported with durable continuous flow left ventricular assist device (LVAD) support encompasses pharmacologic therapies administered in the preoperative, intraoperative, postoperative and chronic LVAD support stages. As patients live longer on LVAD support, the risks of LVAD-related complications and progression of cardiovascular and other diseases increase. Using existing data from cohort studies, registries, randomized trials and expert opinion, this Heart Failure Society of America Consensus Document on the Medical Management of Patients on Durable Mechanical Circulatory Support offers best practices on the management of patients on durable MCS, focusing on pharmacological therapies administered to patients on continuous flow LVADs. While quality data in the LVAD population are few, the utilization of guideline directed heart failure medical therapies (GDMT) and the importance of blood pressure management, right ventricular preload and afterload optimization, and antiplatelet and anticoagulation regimens are discussed. Recommended pharmacologic regimens used to mitigate or treat common complications encountered during LVAD support, including arrhythmias, vasoplegia, mucocutaneous bleeding, and infectious complications are addressed. Finally, this document touches on important potential pharmacological interactions from anti-depressants, herbal and nutritional supplements of relevance to providers of patients on LVAD support.

Vasoplegic syndrome in patients undergoing heart transplantation

Objectives

To summarize the risk factors, onset time, and treatment of vasoplegic syndrome in patients undergoing heart transplantation.

Methods

The PubMed, OVID, CNKI, VIP, and WANFANG databases were searched using the terms "vasoplegic syndrome," "vasoplegia," "vasodilatory shock," and "heart transplant*," to identify eligible studies. Data on patient characteristics, vasoplegic syndrome manifestation, perioperative management, and clinical outcomes were extracted and analyzed.

Results

Nine studies enrolling 12 patients (aged from 7 to 69 years) were included. Nine (75%) patients had nonischemic cardiomyopathy, and three (25%) patients had ischemic cardiomyopathy. The onset time of vasoplegic syndrome varied from intraoperatively to 2 weeks postoperatively. Nine (75%) patients developed various complications. All patients were insensitive to vasoactive agents.

Conclusions

Vasoplegic syndrome can occur at any time during the perioperative period of heart tranplantation, especially after the discontinuation of bypass. Methylene blue, angiotensin II, ascorbic acid, and hydroxocobalamin have been used to treat refractory vasoplegic syndrome.

Clinical approach to vasoplegia in the transplant patient from the Pediatric Heart Transplant Society

This manuscript outlines a clinical approach to vasoplegia incorporating the current state of knowledge regarding vasoplegia in pediatric patients immediately post-transplant and to identify modifiable factors both pre- and post-transplant that may reduce post-operative morbidity, end-organ dysfunction, and mortality. Centers participating in the Pediatric Heart Transplant Society (PHTS) were asked to provide their internal protocols and rationale for vasoplegia management, and applicable adult and pediatric data were reviewed. The authors synthesized the above protocols and literature into the following description of clinical approaches to vasoplegia highlighting areas of both broad consensus and of significant practice variation.

Vasoplegic Syndrome after Cardiopulmonary Bypass in Cardiovascular Surgery: Pathophysiology and Management in Critical Care

Vasoplegic syndrome (VS) is a common complication following cardiovascular surgery with cardiopulmonary bypass (CPB), and its incidence varies from 5 to 44%. It is defined as a distributive form of shock due to a significant drop in vascular resistance after CPB. Risk factors of VS include heart failure with low ejection fraction, renal failure, pre-operative use of angiotensin-converting enzyme inhibitors, prolonged aortic cross-clamp and left ventricular assist device surgery. The pathophysiology of VS after CPB is multi-factorial. Surgical trauma, exposure to the elements of the CPB circuit and ischemia-reperfusion promote a systemic inflammatory response with the release of cytokines (IL-1β, IL-6, IL-8, and TNF-α) with vasodilating properties, both direct and indirect through the expression of inducible nitric oxide (NO) synthase. The resulting increase in NO production fosters a decrease in vascular resistance and a reduced responsiveness to vasopressor agents. Further mechanisms of vasodilation include the lowering of plasma vasopressin, the desensitization of adrenergic receptors, and the activation of ATP-dependent potassium (KATP) channels. Patients developing VS experience more complications and have increased mortality. Management includes primarily fluid resuscitation and conventional vasopressors (catecholamines and vasopressin), while alternative vasopressors (angiotensin 2, methylene blue, hydroxocobalamin) and anti-inflammatory strategies (corticosteroids) may be used as a rescue therapy in deteriorating patients, albeit with insufficient evidence to provide any strong recommendation. In this review, we present an update of the pathophysiological mechanisms of vasoplegic syndrome complicating CPB and discuss available therapeutic options.

Vasoplegia from Continuous Flow Left Ventricular Assist Devices

PURPOSE OF REVIEW

The contribution of continuous flow left ventricular assist devices (c-LVAD) to vasoplegic syndrome and postoperative outcomes after orthotopic heart transplant (OHT) is contested in the literature. A standardized definition of vasoplegic syndrome (VS) is needed to better recognize and manage vasoplegic shock.

RECENT FINDINGS

Vasoplegic syndrome occurs after orthotopic heart transplant more frequently than after other surgeries requiring cardiopulmonary bypass. c-LVADs lead to small vessel endothelial dysfunction and desensitized adrenal receptors; however, their contribution to the development of vasoplegia is debated in clinical studies. Pulsatility may mitigate vascular dysfunction resulting from long-term continuous flow, and should be further explored in the clinical setting when considering risk factors for vasoplegic syndrome. The incidence of vasoplegic syndrome after orthotopic heart transplant is rising with the increasing use of c-LVAD bridge to therapy. Robust clinical studies are needed to advance our understanding and approach to mitigating VS after OHT.

Vasoplegia in patients following ventricular assist device explant and heart transplantation

BACKGROUND

Vasoplegia has been shown to be associated with increased morbidity and mortality in patients undergoing cardiac surgery. It has been previously stated that low pulsatile states as seen with current left ventricular assist devices (LVADs) may contribute to vasoplegia post LVAD-explant and heart transplant. We sought to examine the literature regarding vasoplegia in the post-operative setting for patients undergoing LVAD explant and heart transplant.

METHOD

A literature review was conducted to firstly define vasoplegia in the setting of LVAD patients, and secondly to better understand the relationship between vasoplegia and LVAD explantation in the postoperative heart transplant patient cohort. A keyword search of 'vasoplegia' OR 'vasoplegic' AND 'transplant' was used. Search engines used were PubMed, Cochrane Library, ClinicalTrials.gov, Ovid, Scopus and grey literature.

RESULTS

17 studies met the selection criteria for review. Three key themes emerged from the literature. Firstly, there is limited consensus regarding the definition of vasoplegia. Secondly, patients with LVADs experienced higher rates of vasoplegia following heart transplant than their counterparts and thirdly, increased cardiopulmonary bypass time was associated with a higher rate of vasoplegia.

CONCLUSION

Vasoplegia is not clearly defined in the literature as it pertains to the LVAD patient cohort. Patients bridged with LVADs appear to have higher rates of vasoplegia, however the aetiology of this is unclear and may be associated with continuous flow physiology or prolonged cardiopulmonary bypass time. A universal definition will aid in risk stratification, early recognition and management.

Vasoplegia after cardiopulmonary bypass: A narrative review of pathophysiology and emerging targeted therapies

Cardiovascular disease remains the leading cause of death in the United States, and cardiopulmonary bypass is a cornerstone in the surgical management of many related disease states. Pathophysiologic changes associated both with extracorporeal circulation and shock can beget a syndrome of low systemic vascular resistance paired with relatively preserved cardiac output, termed vasoplegia. While increased vasopressor requirements accompany vasoplegia, related pathophysiologic mechanisms may also lead to true catecholamine resistance, which is associated with further heightened mortality. The introduction of a second non-catecholamine vasopressor, angiotensin II, and non-specific nitric oxide scavengers offers potential means by which to manage this challenging phenomenon. This narrative review addresses both the definition, risk factors, and pathophysiology of vasoplegia and potential therapeutic interventions.

Vasoplegia following heart transplantation and left ventricular assist device explant is not associated with inferior outcomes

Background

Vasoplegia has been associated with inferior outcomes following heart transplantation (HTx). This observational study was designed to investigate outcomes in recipients with vasoplegia following left ventricular assist device (LVAD) explant HTx.

Methods

Patients undergoing LVAD explant followed by HTx from 01/2013–12/2018 at our centre were included. Vasoplegia was defined as the requirement for high dose vasopressor [noradrenaline (>0.5 μg/kg/min) and vasopressin (>1 U/h)] over the first 24 hours following HTx. Demographic and outcome data were retrieved from the transplant unit database.

Results

During the study period 24 patients underwent LVAD explant HTx. Of these, 13 (54.2%) developed vasoplegia. Both groups had similar duration of LVAD support (median 684 vs. 620 days P=0.62). There was a higher incidence of driveline infection in patients developing vasoplegia (69.2% vs. 18.2% P=0.02). HTx following donation after circulatory death (DCD) occurred in 9 (37.5%) patients and was not associated with a higher incidence of vasoplegia (P=0.21). Vasoplegia developed early following reperfusion and intensive care unit admission vasopressor-inotrope scores were significantly higher in patients with vasoplegia (P=0.002). Patients developing vasoplegia had similar ICU (P=0.79) and hospital (P=0.93) lengths of stay. Survival was equivalent both at 30-day (92.3% vs. 100% P=0.99) and 1-year (67.7% vs. 74.7% P=0.70). Our overall HTx 1-year survival was 89.3% over this period.

Conclusions

Vasoplegia is seen with a high incidence in HTx recipients bridged with an LVAD. This appears to be associated with the presence of driveline infections. Early aggressive management is advocated, resulting in equivalent 1-year survival to those patients not developing vasoplegia.

Methylene blue and the NO/cGMP pathway in solid organs transplants

The nitric oxide/cyclic guanosine monophosphate (NO/cGMP) pathway has a significative influence in hemodynamic changes that occur in transplants. Classically, the ischemia-reperfusion syndrome (IRS) is characterized by hypotension and low vascular resistance, when cGMP and nitric oxide (NO) are increased, contributing to oxidative stress, within an inflammatory context. These mechanisms occur in several types of transplants, such as liver, heart, lungs, kidney, which are a therapeutic choice in several clinical conditions when conventional treatments failed. It is well known the significant relation between graft dysfunction or rejection and ischemia-reperfusion injury that is linked to inflammatory response and NO/cGMP pathway activation. This review aims to study the NO/cGMP pathway in solid organ transplants. Finally, we inquire whether physicians do not underestimate the NO/cGMP pathway.

Vasoplegia During Cardiopulmonary Bypass: Current Literature and Rescue Therapy Options

Vasoplegia syndrome in the cardiac surgical intensive care unit and postoperative period has been an area of interest to clinicians because of its prevalence and effects on morbidity and mortality. However, there is a paucity of evidence regarding the treatment of vasoplegia syndrome during cardiopulmonary bypass (on-CPB VS). This review aims to detail the incidence, outcomes, and possible treatment options for patients who develop vasoplegia during bypass. The pharmacologic rescue agents discussed are used in cases in which vasoplegia during CPB is refractory to standard catecholamine agents, such as norepinephrine, epinephrine, and phenylephrine. Methods to improve vasoplegia during CPB can be both pharmacologic and nonpharmacologic. In particular, optimization of CPB parameters plays an important nonpharmacologic role in vasoplegia during CPB. Pharmacologic agents that have been demonstrated as being effective in vasoplegia include vasopressin, terlipressin, methylene blue, hydroxocobalamin, angiotensin II (Giapreza), vitamin C, flurbiprofen (Ropion), and hydrocortisone. Although these agents have not been specifically evaluated for vasoplegia during CPB, they have shown signs of effectiveness for vasoplegia postoperatively to varying degrees. Understanding the evidence for, dosing, and side effects of these agents is crucial for cardiac anesthesiologists when treating vasoplegia during CPB bypass.

When the pressure drops: A case of vasoplegia during a structural heart intervention

A 67-year-old male underwent general anesthesia for left atrial appendage occlusion. During the procedure, the patient developed catecholamine refractory hypotension requiring the administration of several vasopressin boluses to maintain adequate perfusion pressure. At the conclusion of the procedure, mild venous bleeding necessitated the administration of protamine. This led to a further decrease in the patient's blood pressure. Tamponade and continued volume loss were quickly ruled out leading to a diagnosis of vasoplegia syndrome (VS). The patient was appropriately treated with a vasopressin infusion with normalization of blood pressure and no significant morbidity or adverse outcome. With the use of general anesthesia during structural heart interventions on the rapid rise, we discuss the two common causes for vasoplegia along with evidence-based treatments and possible prevention strategies.

Vasoplegic syndrome in cardiac surgery: Definitions, pathophysiology, diagnostic approach and management

Vasoplegic syndrome is a state of vasopressor resistant systemic vasodilation in the presence of a normal cardiac output. Its definition, pathophysiology, risk factors, diagnosis and therapeutic approach will be reviewed in this paper. It occurs frequently during cardiac surgery and is associated with high morbidity and mortality. A search in the LILACS, MEDLINE, and GOOGLE SCHOLAR databases was conducted to find the most relevant papers during the last 18 years. Prompt identification and diagnosis of patients at risk must be undertaken in order to implement an optimal therapeutic approach. This latter includes early treatment with vasopressors with different mechanisms of action.

Perioperative Management of the Cardiac Transplant Recipient

Management of the cardiac transplant recipient includes careful titration of inotropes and vasopressors. Recipient pulmonary hypertension and ventilatory status must be optimized to prevent allograft right ventricular failure. Vasoplegia, coagulopathy, arrhythmias, and renal dysfunction also require careful management to achieve an optimal outcome. Primary graft dysfunction (PGD) can be an ominous problem after cardiac transplantation. Although mild degrees of PGD may be managed medically, mechanical circulatory support with extracorporeal membrane oxygenation or temporary ventricular assist devices may be required. Retransplantation may be necessary in some cases.

Vasoplegia after heart transplantation: outcomes at 1 year

OBJECTIVES

Vasoplegia syndrome is a potentially life-threatening condition that can occur following cardiopulmonary bypass. Heart transplantation is a recognized risk factor for developing this vasodilatory state. The objective of this study was to determine the effects of vasoplegia syndrome on 1-year heart transplant outcomes.

METHODS

A retrospective review of orthotopic heart transplants at a single institution between November 2010 and December 2014 was performed. Of the 347 consecutive adult patients, 107 patients (30.8%) met criteria for vasoplegia syndrome. Preoperative factors and intraoperative variables were collected and compared between vasoplegia and non-vasoplegia cohorts. The incidence of postoperative complications, transplant rejection and patient survival within 1 year were evaluated.

RESULTS

Demographics and preoperative medication profiles were similar in both groups, while mechanical circulatory support device use was associated with vasoplegia syndrome (30.8% vs 20.0%; P = 0.039). Perioperative characteristics such as longer cardiopulmonary bypass [165.0 (interquartile range [IQR] 74) min vs 140.0 (IQR 42.7) min; P < 0.001] and increased blood product usage (24.7 ± 17.2 units vs 17.7 ± 14.3 units; P < 0.001) were associated with vasoplegia. Non-vasoplegia patients were more likely to be extubated [42.9 (IQR 37.3) h vs 66.8 (IQR 50.2) h; P < 0.001] and discharged earlier [10.0 (IQR 6) days vs 14.0 (IQR 11.5) days; P < 0.001]. One-year patient survival (92.0% vs 88.6%; P = 0.338) and any-treated rejection rates (82.7% vs 84.3%; P = 0.569) were not significantly different between groups.

CONCLUSIONS

Although vasoplegia syndrome was associated with an increase in perioperative morbidity, including greater mechanical ventilation time and hospital length of stay, no significant differences in survival or allograft rejection at 1 year was demonstrated.

Methylene Blue for Vasoplegic Syndrome After Cardiac Operation: Early Administration Improves Survival

BACKGROUND

Vasoplegic syndrome, defined by hypotension despite normal or increased cardiac output, is associated with high mortality rate after cardiopulmonary bypass. Methylene blue (MB) is reported to ameliorate vasoplegic syndrome through the nitric oxide pathway. We hypothesized that early administration of MB would improve outcomes in patients with vasoplegic syndrome after cardiopulmonary bypass.

METHODS

All patients that underwent cardiopulmonary bypass at our institution (Jan 1, 2011 to Jun 30, 2016) were identified through our Society of Thoracic Surgery database. Pharmacy records identified patients receiving MB within 72 hours of cardiopulmonary bypass. Multivariate logistic regression identified predictors of major adverse events among patients receiving MB.

RESULTS

A total of 118 cardiopulmonary bypass patients (3.3%) received MB for vasoplegic syndrome. These patients had a higher incidence of comorbidities, and these cases were more commonly reoperative (76.1% versus 41.2%, p < 0.0001) and complex (70.3% versus 31.8%, p < 0.0001). The only difference in preoperative medications was that MB patients had a higher rate of amiodarone use (15.3% versus 2.2%, p < 0.0001). MB patients had significantly higher rates of postoperative complications, except atrial fibrillation. Early (operating room, 40.7%) versus late (intensive care unit, 59.3%) administration of MB was associated with significantly reduced operative mortality rate (10.4% versus 28.6%, p = 0.018) and risk-adjusted major adverse events (odd ratio 0.35, p = 0.037).

CONCLUSIONS

Operative mortality rate is high in patients receiving MB for the treatment of vasoplegia after cardiopulmonary bypass. Early administration of MB improves survival and reduces the risk-adjusted rate of major adverse events in these patients.

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.

Developing effective countermeasures against acute hydrogen sulfide intoxication: challenges and limitations

Hydrogen sulfide (H2 S) is a chemical hazard in the gas and farming industry. As it is easy to manufacture from common chemicals, it has also become a method of suicide. H2 S exerts its toxicity through its high affinity with metalloproteins, such as cytochrome c oxidase and possibly via its interactions with cysteine residues of various proteins. The latter was recently proposed to acutely alter ion channels with critical implications for cardiac and brain functions. Indeed, during severe H2 S intoxication, a coma, associated with a reduction in cardiac contractility, develops within minutes or even seconds leading to death by complete electromechanical dissociation of the heart. In addition, long-term neurological deficits can develop owing to the direct toxicity of H2 S on neurons combined with the consequences of a prolonged apnea and circulatory failure. Here, we review the challenges impeding efforts to offer an effective treatment against H2 S intoxication using agents that trap free H2 S, and present novel pharmacological approaches aimed at correcting some of the most harmful consequences of H2 S intoxication.

Twenty years of vasoplegic syndrome treatment in heart surgery. Methylene blue revised

Objective

This study was conducted to reassess the concepts established over the past 20 years, in particular in the last 5 years, about the use of methylene blue in the treatment of vasoplegic syndrome in cardiac surgery.

Methods

A wide literature review was carried out using the data extracted from: MEDLINE, SCOPUS and ISI WEB OF SCIENCE.

Results

The reassessed and reaffirmed concepts were 1) MB is safe in the recommended doses (the lethal dose is 40 mg/kg); 2) MB does not cause endothelial dysfunction; 3) The MB effect appears in cases of NO up-regulation; 4) MB is not a vasoconstrictor, by blocking the cGMP pathway it releases the cAMP pathway, facilitating the norepinephrine vasoconstrictor effect; 5) The most used dosage is 2 mg/kg as IV bolus, followed by the same continuous infusion because plasma concentrations sharply decrease in the first 40 minutes; and 6) There is a possible "window of opportunity" for MB's effectiveness. In the last five years, major challenges were: 1) Observations about side effects; 2) The need for prophylactic and therapeutic guidelines, and; 3) The need for the establishment of the MB therapeutic window in humans.

Conclusion

MB action to treat vasoplegic syndrome is time-dependent. Therefore, the great challenge is the need, for the establishment the MB therapeutic window in humans. This would be the first step towards a systematic guideline to be followed by possible multicenter studies.

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.

Methylene blue: potential use of an antique molecule in vasoplegic syndrome during cardiac surgery

Vasoplegic syndrome is a common complication of cardiopulmonary bypass, appearing with an incidence ranging between 5 and 25%. It is characterized by significant hypotension, high or normal cardiac output and low systemic vascular resistance. This syndrome is hypothesized to be caused by the inflammation-mediated dysregulation of endothelial homeostasis and subsequent endothelial dysfunction. In vasoplegic syndrome, the inhibition of the nitric oxide/cyclic guanosine monophosphate pathway with concomitant administration with traditional ionotropes may represent a promising therapeutic option. Methylene blue, an inhibitor of nitric oxide synthase and guanylate cyclase, may contribute to the improvement of refractory hypotension associated with endothelial dysfunction in vasoplegia. In this article, we will update evidence on the potential therapeutic use of methylene blue in vasoplegic syndrome.

The Role of Methylene Blue in the Pediatric Patient With Vasoplegic Syndrome

Patients with vasoplegic syndrome (VPS) in the post-cardiopulmonary bypass setting usually require escalating vasopressor support. The utilization of methylene blue (MB) in the treatment of VPS in the adult population has been well described. We present a 5-year-old girl who developed vasodilatory shock due to VPS that was resistant to escalating doses of adrenergic agonists following cardiac transplantation. After receiving 1 mg/kg of MB, there was a significant improvement in the patient’s mean arterial pressure which allowed for progressive weaning of the vasopressor support. To date, there are limited data regarding the use of MB in pediatric patients with VPS following cardiothoracic surgery. The cellular mechanisms of MB in VPS are discussed and reports of its use in the adult and pediatric population are reviewed. Dosing regimens and potential adverse effects of MB are presented.

Vasoplegia during cardiac surgery: current concepts and management

Vasoplegic syndrome (VS) is a recognized and relatively common complication of cardiopulmonary bypass (CPB), appearing with an incidence ranging between 5% and 25%. It is characterized by significant hypotension, high or normal cardiac outputs and low systemic vascular resistance (SVR), and increased requirements for fluids and vasopressors during or after CPB. Patients developing VS are at increased risk for death and other major complications following cardiac surgery. This review will focus on the pathophysiology and contemporary strategies of treating VS encountered after CPB.

Early on-cardiopulmonary bypass hypotension and other factors associated with vasoplegic syndrome

BACKGROUND

Vasoplegic syndrome is a form of vasodilatory shock that can occur after cardiopulmonary bypass (CPB). We hypothesized that the severity and duration of the decline in mean arterial pressure immediately after CPB is begun can be used as a predictor of patients will develop vasoplegia in the immediate post-CPB period and of poor clinical outcome. We quantified the decline in mean arterial pressure by calculating an area above the mean arterial blood pressure curve.

METHODS AND RESULTS

We retrospectively analyzed 2823 adult cardiac surgery cases performed between July 2002 and December 2006. Of these 2823, 577 (20.4%) were vasoplegic after separation from CPB. We found that 1645 patients (58.3%) had a clinically significant decline in mean arterial pressure after starting CPB (area above the mean arterial blood pressure curve >0) and were significantly more likely to become vasoplegic (23.0% versus 16.9%; odds ratio, 1.26; 95% confidence interval, 1.12 to 1.43; P<0.001). These patients were also far more likely either to die in hospital or to have a length of stay >10 days (odds ratio, 3.30; 95% confidence interval, 1.44 to 7.57; P=0.005). Additional risk factors for developing vasoplegia that were identified included the additive euroSCORE, procedure type, prebypass mean arterial pressure, length of bypass, administration of pre-CPB vasopressors, core temperature on CPB, pre- and post-CPB hematocrit, the preoperative use of beta-blockers or angiotensin-converting enzyme inhibitors, and the intraoperative use of aprotinin.

CONCLUSIONS

The results of this investigation suggest that it is possible to predict vasoplegia intraoperatively before separation from CPB and that the presence of a clinically significant area above the mean arterial blood pressure curve serves as a predictor of poor clinical outcome.

Methylene blue in the treatment of vasoplegia following severe burns

Vasoplegia resulting from severe burns may persist despite adequate fluid resuscitation and treatment with norepinephrine (NE), vasopressin (VP), and steroids. The adenylate cyclase inhibitor methylene blue (MB), currently used in the burn patient to treat methemoglobinemia, has been used to treat vasoplegia after cardiopulmonary bypass. We report the case of MB infusion in two burn patients refractory to NE. The patients had severe burns, 95 and 80% TBSA not responding to conventional treatment. Fluid requirements were estimated according to Parkland formula and then to maintain a urinary output of 30-50 ml/hr. Patient #1, 95% TBSA, was adrenally insufficient and was receiving steroids according to the Annane protocol, as well as VP at 0.2 U/min. His NE requirements were 55 mcg/kg/min. Patient #2, 80% TBSA, was receiving 20 mcg/kg/min of NE. Circulatory failure was defined as inability to maintain mean arterial pressure >70 mm Hg. Hemodynamic and physiologic parameters were measured before and after infusion of a single dose of 2 mg/kg of MB. Both patients showed dramatic improvements in their shock after MB. Patient #1 had an initial reaction within 30 minutes and reached peak effect at 1 hour. His NE requirements decreased to 0.2 mcg/kg/min and VP decreased to 0.04 U/min. Patient #2 showed effects within 15 minutes of the infusion and by 2 hours the NE was stopped. No adverse side effects were noted in either of the two patients. The fact that MB successfully reversed refractory vasoplegia after severe burns suggests a new tool for treating a small subgroup of patients who exhibit persistent vasoplegia from their burn injury. A controlled randomized trial is needed to test its effects on a large number of patients and graft survival.

Methylthioninium chloride: pharmacology and clinical applications with special emphasis on nitric oxide mediated vasodilatory shock during cardiopulmonary bypass

Vasodilatory shock after cardiopulmonary bypass is a common complication requiring treatment with high doses of inotropes and prolonged stays in the intensive care unit. The vasodilatory shock is initiated by an inflammatory response to the extracorporeal circuit. The inflammatory response results in endothelial synthesis and release of nitric oxide resembling the clinical features observed in vasodilatory shock caused by septicaemia. During vasodilatory shock, the inhibition of nitric oxide synthase and the nitric oxide/cyclic guanylyl monophosphate pathway is an attractive adjunct to therapy with traditional inotropes. Methylthioninium chloride inhibits nitric oxide/cyclic guanylyl monophosphate mediated vasodilation and can successfully be used as a supplement in the treatment of vasodilatory shock associated with cardiopulmonary bypass. The application of methylthioninium chloride in septicaemia has not produced comparable positive clinical results.

Methylene blue reduces mortality and morbidity in vasoplegic patients after cardiac surgery

BACKGROUND

The discovery of nitric oxide as mediator in cardiac postoperative vasoplegia encourages the use of inhibitory drugs such as methylene blue. This drug has been used with favorable results in isolated cases. The purpose of this article is to analyze the incidence of the postoperative vasoplegic syndrome, to consider its prognosis, and to evaluate the effect of intravenous methylene blue on mortality.

METHODS

Cardiac surgery patients were consecutively included. Vasoplegic syndrome was defined by the presence of the following five criteria: (1) hypotension, (2) low filling pressures, (3) high or normal cardiac index, (4) low peripheral resistance, and (5) vasopressor requirements. Those with vasoplegia were randomized to receive 1.5 mg/Kg of methylene blue or a placebo. A p value less than 0.05 was considered significant.

RESULTS

Six hundred thirty eight cardiac surgery patients were consecutively included in this study. Fifty-six of these patients fulfilled vasoplegia criteria (8.8%) resulting in higher mortality (10.7% or 6 of 56 patients vs 3.6% or 21 of 582 patients; p value = 0.02). Those treated with methylene blue showed morbidity and mortality reductions (0% versus 21.4% or 6 of 28 patients; p value = 0.01). The duration of the vasoplegic syndrome was shorter in those patients treated with the drug, lasting less than 6 hours in all patients. Patients in the control group showed a slower recovery, lasting more than 48 hours in 8 patients (p value = 0.0007).

CONCLUSIONS

Vasoplegic postoperative syndrome was seen in 8.8% of all patients. Outcome in patients with vasoplegia was worse with increased morbidity and mortality. The use of methylene blue reduced the high mortality in this population.

Methylene blue: the drug of choice for catecholamine-refractory vasoplegia after cardiopulmonary bypass?

OBJECTIVES

Vasoplegia is a frequent complication after cardiopulmonary bypass that often requires the application of norepinephrine. In a number of cases, however, vasoplegia is refractory to norepinephrine. The guanylate cyclase inhibitor methylene blue could be an attractive treatment alternative in such cases. This study examines the results of methylene blue therapy for norepinephrine-refractory vasoplegia after cardiopulmonary bypass.

METHODS

A total of 54 patients with norepinephrine-refractory vasoplegia after cardiopulmonary bypass were treated with methylene blue (2 mg/kg) administered intravenously through a period of 20 minutes. The effects on hemodynamics, norepinephrine dosage, and clinical outcome were evaluated.

RESULTS

Three patients (5.6%) died during the hospital stay. A clinically relevant increase in systemic vascular resistance and a decrease in norepinephrine dosage were observed in 51 patients within 1 hour after methylene blue infusion. Four patients (7.4%) had no response to methylene blue. No adverse effects related to methylene blue were observed.

CONCLUSIONS

A single dose of methylene blue seems to be a potent approach to norepinephrine-refractory vasoplegia after cardiopulmonary bypass for most patients, with no obvious side effects. Guanylate cyclase inhibitors could be a novel class of agents for the treatment of norepinephrine-refractory vasoplegia after cardiopulmonary bypass. A controlled clinical trial is now needed to evaluate the role of methylene blue in this situation.