Methylene Blue Reduces Mortality in Critically Ill and Perioperative Patients: A Meta-Analysis of Randomized Trials

Year in Review 2024: Noteworthy Literature in Cardiothoracic Critical Care

This article reviews noteworthy additions to the literature for the management of critically ill cardiothoracic surgical patients published in 2024. We reviewed 8100 articles to identify 10 publications that provided new or updated information across a diverse range of topics including extracorporeal membrane oxygenation (ECMO), sepsis and shock, and acute hypoxemic respiratory failure (AHRF). Additional topics within these publications included prophylaxis guidelines and evidence for prevention of common complications in the intensive care unit, such as bleeding, thrombosis, and acute kidney injury (AKI).

How Would We Prevent Our Own Acute Kidney Injury After Cardiac Surgery?

Acute Kidney Injury (AKI) is a common complication after cardiac surgery affecting up to 40% leading to increased morbidity and mortality. To date, there is no specific treatment for AKI, thus, clinical research efforts are focused on preventive measures. The only pharmacological preventive intervention that has demonstrated a beneficial effect on AKI in a high-quality, double-blind, randomized controlled trial is a short perioperative infusion of a balanced mixture of amino acid solution. Amino acid infusion reduced the incidence of AKI by recruiting renal functional reserve and, therefore, increasing the glomerular filtration rate. The beneficial effect of amino acids was further confirmed for severe AKI and applied to patients with chronic kidney disease. Among non-pharmacological interventions, international guidelines on AKI suggest the implementation of a bundle of good clinical practice measures to reduce the incidence of perioperative AKI or to improve renal function whenever AKI occurs. The Kidney Disease Improving Global Outcomes (KDIGO) bundle includes the discontinuation of nephrotoxic agents, volume status and perfusion pressure assessment, renal functional hemodynamic monitoring, serum creatine, and urine output monitoring, and the avoidance of hyperglycemia and radiocontrast procedures. However, pooled data from a meta-analysis did not find a significant reduction in AKI. The aim of this review is to delineate the most appropriate evidence-based approach to prevent AKI in cardiac surgery patients.

Predicting responsiveness to fixed-dose methylene blue in adult patients with septic shock using interpretable machine learning: a retrospective study

This study aimed to develop an interpretable machine learning model to predict methylene blue (MB) responsiveness in adult patients with refractory septic shock and to identify key factors influencing MB responsiveness using the SHapley Additive exPlanations (SHAP) approach. We retrospectively analyzed data from 416 adult patients with refractory septic shock who received MB treatment at Xiangya Hospital of Central South University between June 2018 and October 2022. MB responders were defined as patients who, within 6 hours after MB administration, exhibited either a reduction in average norepinephrine equivalence (NEE) of ≥ 10% or an increase in mean arterial pressure of ≥ 10 mmHg without an associated increase in NEE. The incidence of MB responders was 38.2%(n=159). Statistical and machine learning methods were used for feature selection, resulting in two datasets (ST and ML). Each dataset was randomly divided into a training set (75%) for model development and a testing set (25%) for internal validation. Prediction models were developed using logistic regression, support vector machine (SVM), random forest, light gradient boosting machine (LightGBM), and explainable boosting machine (EBM). The models were evaluated regarding discrimination, calibration, and clinical benefit. The SVM model trained on the ML dataset demonstrated the best predictive performance, with an area under the curve (AUC) of 0.74 (95% CI 0.62-0.84), 76% accuracy, 36% sensitivity, and 94% specificity. Although the model's sensitivity was low, its high specificity and the safety profile of MB underscore its clinical relevance. The model showed superior net benefit within a 24-85% threshold probability, as determined by decision curve analysis. The SHAP analysis identified the average NEE dose within 6 hours before MB initiation as the most important factor influencing MB responsiveness (P<0.01), with higher doses positively correlating with a greater likelihood of response. Lactate levels were identified as the second most important factor. The optimal model was externally validated in an independent cohort from the same institution, achieving an AUC of 0.75 and an accuracy of 74%.

Blue Hopes, Red Flags: The Methylene Blue Dilemma in Sepsis Shock

How to cite this article: Govil D, Pachisia AV. Blue Hopes, Red Flags: The Methylene Blue Dilemma in Sepsis Shock. Indian J Crit Care Med 2025;29(2):95-97.

Haemodynamic management of septic shock

Septic shock is a significant challenge in the management of patients with burns and traumatic injuries when complicated by infection, necessitating prompt and effective haemodynamic support. This review provides a comprehensive overview of current strategies for vasopressor and fluid management in septic shock, with the aim to optimize patient outcomes. With regard to vasopressor management, we elaborate on the pharmacologic profiles and clinical applications of catecholamines, vasopressin derivatives, angiotensin II, and other vasoactive agents. Noradrenaline remains central to septic shock management. The addition of vasopressin, when sequentially added to noradrenaline, offers a non-catecholaminergic vasoactive effect with some clinical benefits and risks of adverse effects. Emerging agents such as angiotensin II and hydroxocobalamin are highlighted for their roles in catecholamine-resistant vasodilatory shock. Next, for fluid management, crystalloids are currently preferred for initial resuscitation, with balanced crystalloids showing benefits over saline. The application of albumin in septic shock warrants further research. High-quality evidence does not support large-volume fluid resuscitation, and an individualized strategy based on haemodynamic parameters, including lactate clearance and capillary refill time, is recommended. The existing knowledge suggests that early vasopressor initiation, particularly noradrenaline, may be critical in cases where fluid resuscitation takes inadequate effect. Management of refractory septic shock remains challenging, with novel agents like angiotensin II and methylene blue showing potential in recent studies. In conclusion, Further research is needed to optimize haemodynamic management of septic shock, particularly in developing novel vasopressor usage and fluid management approaches.

Non-adrenergic vasopressors for vasodilatory shock or perioperative vasoplegia: a meta-analysis of randomized controlled trials

BACKGROUND

Excessive exposure to adrenergic vasopressors may be harmful. Non-adrenergic vasopressors may spare adrenergic agents and potentially improve outcomes. We aimed to conduct a systematic review and meta-analysis of randomized controlled trials (RCTs) to evaluate the efficacy of non-adrenergic vasopressors in adult patients receiving vasopressor therapy for vasodilatory shock or perioperative vasoplegia.

METHODS

We searched PubMed, Embase, and Cochrane Library for RCTs comparing non-adrenergic vasopressors with adrenergic vasopressors alone or placebo in critically ill or perioperative patients. Each eligible study was categorized into septic shock, cardiac surgery, or non-cardiac surgery. Non-adrenergic vasopressors included vasopressin, terlipressin, selepressin, angiotensin II, methylene blue, and hydroxocobalamin. The primary outcome was mortality at longest follow-up. We conducted a random-effects meta-analysis. We registered the protocol in PROSPERO International Prospective Register of Systematic Reviews (CRD42024505039).

RESULTS

Among 51 eligible RCTs totaling 5715 patients, the predominant population was septic shock in 30 studies, cardiac surgery in 11 studies, and non-cardiac surgery in 10 studies. Cochrane risk-of-bias tool for randomized trials version 2 identified 17 studies as low risk of bias. In septic shock, mortality was significantly lower in the non-adrenergic group (960/2232 [43%] vs. 898/1890 [48%]; risk ratio [RR], 0.92; 95% confidence interval [95% CI], 0.86-0.97; P = 0.03; I2 = 0%), with none of the individual non-adrenergic vasopressors showing significant survival benefits. No significant mortality difference was observed in patients undergoing cardiac surgery (34/410 [8.3%] vs. 47/412 [11%]; RR, 0.82; 95% CI, 0.55-1.22; P = 0.32; I2 = 12%) or those undergoing non-cardiac surgery (9/388 [2.3%] vs. 18/383 [4.7%]; RR, 0.66; 95% CI, 0.31-1.41; P = 0.28; I2 = 0%).

CONCLUSIONS

Administration of non-adrenergic vasopressors was significantly associated with reduced mortality in patients with septic shock. However, no single agent achieved statistical significance in separate analyses. Although the pooled effects of non-adrenergic vasopressors on survival did not reach statistical significance in patients undergoing cardiac or non-cardiac surgery, the confidence intervals included the possibility of both no effect and a clinically important benefit from non-adrenergic agents. These findings justify the conduct of further RCTs comparing non-adrenergic vasopressors to usual care based on noradrenaline alone.

Protective hemodynamics: a novel strategy to manage blood pressure

PURPOSE OF REVIEW

This editorial aims to highlight the evolving concept of protective hemodynamics in the management of critically ill patients.

RECENT FINDINGS

Recent literature underscores the limitations of rigid blood pressure targets, particularly in the context of critical care and perioperative management. High blood pressure targets, especially when coupled with high-dose vasopressors, can lead to poor outcomes. 'Protective hemodynamics' aims to maintain cardiovascular stability while reducing risks associated with interventions.

SUMMARY

The implications of adopting protective hemodynamics are profound for both clinical practice and research. Clinically, this approach can reduce iatrogenic harm and improve long-term outcomes for critically ill patients. For research, it opens new avenues for investigating individualized hemodynamic management strategies that prioritize overall patient stability and long-term health over rigid target attainment.

A retrospective cohort analysis comparing the effectiveness and safety of perioperative angiotensin II to adrenergic vasopressors as a first-line vasopressor in kidney transplant recipients

BACKGROUND

Perioperative adrenergic vasopressors in kidney transplantation have been linked to negative outcomes and arrhythmias. Synthetic angiotensin II (AT2S) could improve renal hemodynamics, preserve allograft function, and reduce arrhythmias.

OBJECTIVE

We aimed to compare the effectiveness and safety of AT2S to adrenergic vasopressors when used for perioperative hypotension in kidney transplant.

METHODS

This single-center, retrospective cohort study included adults with perioperative shock requiring AT2S or adrenergic agents as first-line vasopressors during kidney transplant. The primary outcome was the need for a second continuous infusion vasopressor agents beyond the first-line agent. Secondary outcomes assessed adverse events and early allograft outcomes.

RESULTS

Twenty patients receiving AT2S and 60 patients receiving adrenergic vasopressor agents were included. Intraoperatively, 1 of 20 patients (5%) in the AT2S group needed a second continuous vasopressor compared to 7 of 60 patients (11.7%) who needed a second continuous vasopressor in the adrenergic vasopressor group (P = 0.672). Postoperatively, 1 of 20 patients (5%) in the AT2S group compared to 12 of 60 patients (20%) in the adrenergic vasopressor group required a second vasopressor (P = 0.168). There were significantly fewer arrhythmias (1/20 [5%] vs. 17/60 [28.3%]), P = 0.03) and ischemic complications (0/20 [0%] vs. 11/20 [18.3%], P = 0.031) in patients who received AT2S. There were no differences in immediate, slow, or delayed graft function or in discharge, 1-month, and 3-month glomerular filtration rates (p > 0.05). CONCLUSION AND RELEVANCE: Both AT2S and adrenergic vasopressors are effective for perioperative hypotension in kidney transplant, with AT2S showing a lower incidence of arrhythmias and ischemic complications.

Anesthesia for Combined Heart-Liver Transplantation: A Narrative Review

In 1984, 21 years after the first liver transplantation, Thomas Starzl achieved a milestone by performing the world's first combined heart-liver transplantation. While still uncommon, the practice of combined heart-liver transplants is on the rise globally. In this review, the authors delve into the current literature on this procedure, highlighting the evolving landscape and key considerations for anesthesiologists. Over the years, there has been a remarkable increase in the number of combined heart-liver transplantations conducted worldwide. This surge is largely attributed to the growing population of adult survivors with single-ventricle physiology, palliated with a Fontan procedure, who later present with late Fontan failure and Fontan-associated liver disease. Research indicates that combined heart-liver transplantation is an effective treatment option, with reported outcomes comparable with isolated heart or liver transplants. Managing anesthesia during a combined heart-liver transplant procedure is challenging, especially in the context of underlying Fontan physiology. International experience in this field remains somewhat limited, with most techniques derived from expert opinions or experiences with single-organ heart and liver transplants. These procedures are highly complex and performed infrequently. As the number of combined heart-liver transplants continues to rise globally, there is a growing need for clear guidance on periprocedural surgical and anesthetic management. Anesthesiologists overseeing these patients must consider multiple factors, balancing various comorbidities with significant hemodynamic and metabolic shifts. An increase in (multicenter) studies focusing on specific interventions to enhance patient and organ outcomes is anticipated in the coming years.

Methylene Blue in Septic Shock: A Systematic Review and Meta-Analysis

OBJECTIVES

Although clinicians may use methylene blue (MB) in refractory septic shock, the effect of MB on patient-important outcomes remains uncertain. We conducted a systematic review and meta-analysis to investigate the benefits and harms of MB administration in patients with septic shock.

DATA SOURCES

We searched six databases (including PubMed, Embase, and Medline) from inception to January 10, 2024.

STUDY SELECTION

We included randomized clinical trials (RCTs) of critically ill adults comparing MB with placebo or usual care without MB administration.

DATA EXTRACTION

Two reviewers performed screening, full-text review, and data extraction. We pooled data using a random-effects model, assessed the risk of bias using the modified Cochrane tool, and used Grading of Recommendations Assessment, Development, and Evaluation to rate certainty of effect estimates.

DATA SYNTHESIS

We included six RCTs (302 patients). Compared with placebo or no MB administration, MB may reduce short-term mortality (RR [risk ratio] 0.66 [95% CI, 0.47-0.94], low certainty) and hospital length of stay (mean difference [MD] -2.1 d [95% CI, -1.4 to -2.8], low certainty). MB may also reduce duration of vasopressors (MD -31.1 hr [95% CI, -16.5 to -45.6], low certainty), and increase mean arterial pressure at 6 hours (MD 10.2 mm Hg [95% CI, 6.1-14.2], low certainty) compared with no MB administration. The effect of MB on serum methemoglobin concentration was uncertain (MD 0.9% [95% CI, -0.2% to 2.0%], very low certainty). We did not find any differences in adverse events.

CONCLUSIONS

Among critically ill adults with septic shock, based on low-certainty evidence, MB may reduce short-term mortality, duration of vasopressors, and hospital length of stay, with no evidence of increased adverse events. Rigorous randomized trials evaluating the efficacy of MB in septic shock are needed.

REGISTRATION

Center for Open Science (https://osf.io/hpy4j).

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.

Effect of methylene blue on outcomes in patients with distributive shock: a meta-analysis of randomised controlled trials

OBJECTIVE

This meta-analysis aimed to demonstrate the effect of methylene blue (MB) in patients with distributive shock.

DESIGN

Meta-analysis.

METHODS

According to the Prospective International Register of Systematic Reviews (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines, we searched the relevant randomised controlled trials (RCTs) via PubMed, Embase and Cochrane Library from the date of database inception to 19 April 2023. The primary outcome was mortality during follow-up, and secondary outcomes included mean arterial pressure (mm Hg), mechanical ventilation time (hours), intensive care unit (ICU) length of stay (LOS) (days), hospital LOS (days) and heart rate (times/min).

RESULTS

This study included six RCTs with 265 participants. The study showed no significant difference in mortality between the MB and placebo groups (ORs: 0.59; 95% CI 0.32 to -1.06). However, MB reduced the duration of mechanical ventilation (mean difference (MD): -0.68; 95% CI -1.23 to -0.14), ICU LOS (MD: -1.54; 95% CI -2.61 to -0.48) and hospital LOS (MD: -1.97; 95% CI -3.92 to -0.11).

CONCLUSIONS

The use of MB may not reduce mortality in patients with distributive shock, but may shorten the duration of mechanical ventilation, ICU LOS and hospital LOS. More clinical studies are needed to confirm these findings in the future.

TRIAL REGISTRATION NUMBER

CRD42023415938.