Methemoglobinemia after a Blast Injury

Methemoglobinemia screening and treatment in tank warfare survivors

INTRODUCTION

Methemoglobinemia, characterized by the conversion of functional hemoglobin to methemoglobin, can significantly impede tissue oxygenation. Prompt diagnosis and treatment of methemoglobinemia are critical to optimizing clinical outcomes. Although the underlying etiology of methemoglobinemia is often attributed to a medication reaction or chemical exposure, its association with battlefield trauma remains underexplored. This case series explores the presence of methemoglobinemia in nine soldiers evacuated from tanks targeted by explosives, shedding new light on screening needs and treatment strategies.

CASES DESCRIPTION

Nine combat trauma patients with methemoglobinemia were admitted to Soroka Medical Center over a two-month period. Detailed case descriptions illustrate the diverse presentations and treatment responses. Notably, the administration of methylene blue resulted in rapid methemoglobin reductions and an improvement in oxygenation without any observed side effects.

DISCUSSION

This series highlights an unexpected consequence of an explosion within an armored fighting vehicle and the challenges related to standard pulse oximetry interpretation and accuracy in the presence of methemoglobinemia, emphasizing the need for vigilant monitoring and co-oximetry utilization. Additionally, the coexistence of carboxyhemoglobin further warrants attention due to its synergistic and deleterious effects on oxygen delivery. Collaborative efforts with military authorities should aim to explore the underlying mechanisms associated with trauma and methemoglobinemia and optimize battlefield care.

CONCLUSION

This case series underscores the significance of methemoglobinemia screening in combat trauma patients, and advocates for systematic co-oximetry utilization and methylene blue availability in combat zones. Early detection and intervention of methemoglobinemia in combat soldiers are often difficult in the context of battlefield injuries but are necessary to mitigate the potentially fatal consequences of this condition.

Metabolic activation of 2,4,6-trinitrotoluene; a case for ROS-induced cell damage

The explosive compound 2,4,6-trinitrotoluene (TNT) is well known as a major component of munitions. In addition to its potential carcinogenicity and mutagenicity in humans, recent reports have highlighted TNT toxicities in diverse organisms due to its occurrence in the environment. These toxic effects have been linked to the intracellular metabolism of TNT, which is generally characterised by redox cycling and the generation of noxious reactive molecules. The reactive intermediates formed, such as nitroso and hydroxylamine compounds, also interact with oxygen molecules and cellular components to cause macromolecular damage and oxidative stress. The current review aims to highlight the crucial role of TNT metabolism in mediating TNT toxicity, via increased generation of reactive oxygen species. Cellular proliferation of reactive species results in depletion of cellular antioxidant enzymes, DNA and protein adduct formation, and oxidative stress. While TNT toxicity is well known, its ability to induce oxidative stress, resulting from its reductive activation, suggests that some of its toxic effects may be caused by its reactive metabolites. Hence, further research on TNT metabolism is imperative to elucidate TNT-induced toxicities.

Evaluation of blast injury patients from the 2015 Tianjin explosions in China

OBJECTIVES

To perform a descriptive analysis of blast injury patients from the Tianjin explosions that occurred August 12, 2015 and provide a reference for triage and treatment of patients in similar situations in the future.

METHODS

The medical records of patients with blast injuries admitted to our hospital following the 2015 Tianjin explosions were retrospectively reviewed. The results were compared with the literature for other recent mass casualty events.

RESULTS

The 75 patients with blast injuries included 58 men (77.3%) and 17 women (22.7%), who had an average age of 36.39±12.3 years. Multidimensional injuries affecting almost every organ system were observed in these patients. The distribution of the types of blast injuries included 36 (48.0%) with primary blast injuries, 63 (84.0%) with secondary injuries, 33 (44.0%) with tertiary injuries and 32 (42.6%) with quaternary injuries. A total of 52 (69.3%) patients suffered more than two types of blast injury. Burns affecting different areas and different depths were present in 41.3% of the patients with blast injuries, and these were divided into the following four groups: a minor group (18.7%), a moderate group (10.7%), a severe group (5.3%), and an extra severe group (6.7%). The total body surface area (TBSA) affected by the burn ranged from 1% to 75%. Additionally, 6.7% of the patients were diagnosed with an inhalational injury, and 2.7% of the patients were diagnosed with chemical poisoning. There were significant differences in the department distribution (especially in the burn unit and ophthalmology department) and ICU treatment between civilians and firefighters.

CONCLUSION

Various types of injury, with overlapping injuries present in many patients, were observed in the victims after the Tianjin explosions. An evaluation of the distribution of blast injuries is important for optimizing strategies to triage and treat survivors after mass casualty events.

Blast injuries

Health-care providers are increasingly faced with the possibility of needing to care for people injured in explosions, but can often, however, feel undertrained for the unique aspects of the patient's presentation and management. Although most blast-related injuries (eg, fragmentation injuries from improvised explosive devices and standard military explosives) can be managed in a similar manner to typical penetrating or blunt traumatic injuries, injuries caused by the blast pressure wave itself cannot. The blast pressure wave exerts forces mainly at air-tissue interfaces within the body, and the pulmonary, gastrointestinal, and auditory systems are at greatest risk. Arterial air emboli arising from severe pulmonary injury can cause ischaemic complications-especially in the brain, heart, and intestinal tract. Attributable, in part, to the scene chaos that undoubtedly exists, poor triage and missed diagnosis of blast injuries are substantial concerns because injuries can be subtle or their presentation can be delayed. Management of these injuries can be a challenge, compounded by potentially conflicting treatment goals. This Seminar aims to provide a thorough overview of these unique primary blast injuries and their management.

L’administration prophylactique de bleu de méthylène chez un patient atteint de méthémoglobinémie congénitale

PURPOSE

To report the beneficial effect of prophylactic methylene blue administration before induction of anesthesia in a patient with congenital methemoglobinemia.

CLINICAL FEATURES

A 26-yr-old male patient known to have congenital methemoglobinemia was scheduled for turbinectomy under general anesthesia. The patient was clinically cyanotic with a pulse oximetry of 91%. Arterial blood gas analysis showed a partial pressure of oxygen (PaO(2)) of 81.3 mmHg associated with a fractional oxyhemoglobin of 80.7%, and a methemoglobin fraction of 0.159. Preoperative iv administration of 1 mg.kg(-1) of methylene blue resulted, within five minutes, in a decrease of methemoglobin fraction down to 0.05 associated with an increase of the fractional oxyhemoglobin saturation up to 94.7%. After two hours, the methemoglobin fraction decreased to 0.01 and the fractional oxyhemoglobin concentration increased to 97.7%. Induction of anesthesia as well as intraoperative and postoperative course were uneventful without any episode of hypoxemia. Postoperatively, the methemoglobin fractions remained low for 24 hr, to be followed by a gradual increase up to 0.02 on the second day to reach 0.094 on the fifth day.

CONCLUSION

The prophylactic preoperative methylene blue administration in a patient with congenital methemoglobinemia significantly decreased the methemoglobin level and increased the fractional oxygen saturation with a consequent increase of the safety margin against perioperative hypoxemia.