Acute methemoglobinemia after a blast injury: a case report

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J Trauma Inj. 2022;35(Suppl 1):S15-S17

Publication date (electronic) : 2021 December 10

doi : https://doi.org/10.20408/jti.2021.0089

Donghoon Kim, MD^1,2,3, Yoonhyun Lee, MD², Sung Yub Jeong, MD², Hojun Lee, MD^,2

¹Department of Critical Care Medicine, Armed Forces Capital Hospital, Seongnam, Korea

²Armed Forces Trauma Center, Armed Forces Capital Hospital, Seongnam, Korea

³Division of Cardiology, Department of Internal Medicine, Armed Forces Capital Hospital, Seongnam, Korea

Correspondence to Hojun Lee, MD Armed Forces Trauma Center, Armed Forces Capital Hospital, 81 Saemaeul-ro 177beon-gil, Bundang-gu, Seongnam 13574, Korea Tel: +82-31-789-2848 E-mail: dhltkd01@mnd.go.kr

Received 2021 September 5; Revised 2021 November 29; Accepted 2021 December 1.

Abstract

INTRODUCTION

Methemoglobin (MetHb) is a modified form of hemoglobin, in which Fe²⁺ (ferrous ion) is oxidized to Fe³⁺ (ferric ion). MetHb cannot bind oxygen; hence, it cannot carry oxygen. 2,4,6-trinitrotoluene (TNT) is a well-known explosive material. Methemoglobinemia induced by occupational exposure to TNT has been previously reported [1,2]. However, this is the first report describing the occurrence of methemoglobinemia in a man who was exposed to a blast injury while manipulating a TNT bomb in Korea.

This study was done in accordance with the Ethical Principles for Medical Research Involving Human Subjects outlined in the Helsinki Declaration in 1975 (revised 2013). The study was ap­proved by the Institutional Review Board of the Armed Forces Capital Hospital (No. AFCH-21-IRB-006). The Institutional Re­view Board waived the requirement for written informed con­sent.

CASE REPORT

A previously healthy 27-year-old male sergeant was admitted because of a blast injury during the welding of tank shells. He had multiple burns in his abdomen and open fractures in his right leg (Fig. 1). His body temperature was 36.3°C, heart rate was 80/min, respiratory rate was 20/min, and arterial blood pressure was 159/90 mmHg. His chest X-ray was normal; however, nasal oxygen therapy was applied to deal with possible inhalation burns. His arterial blood was chocolate-colored, and the results of the arterial gas analysis are shown in Table 1. The analysis revealed acute methemoglobinemia. We could not use methylene blue for treatment since it was out of stock. Besides treating the wounds by surgery, we administered oxygen therapy and performed blood transfusion. His methemoglobinemia normalized after 4 days of hospital stay. A glucose-6-phosphate dehydrogenase (G-6-PDH) test was performed to identify the genetic cause of methemoglobinemia; the resulting (6.4 U/gHb) was within the normal range. The explosive component of the tank shells was TNT. Therefore, the patient was diagnosed with acute acquired methemoglobinemia caused by nitroglycerin exposure.

Fig. 1.

Front surface of the right leg at admission. The patient provided written informed consent for the publication of the image.

Table 1.

Arterial blood gas analysis (ABGA) on admission

DISCUSSION

Acute methemoglobinemia may be caused by genetic factors [3,4]. G-6-PDH deficiency and hemoglobin M disease are genetic factors that lead to methemoglobinemia, but their prevalence in the Korean population is very low [5-8]. However, the prevalence of these conditions in Korea is increasing with the increase in the number of Southeast Asian immigrants. Therefore, it should be considered in the differential diagnosis. Most cases of methemoglobinemia in Korea are due to exposure to various drugs or chemical compounds [9]. The patient in the present case did not have a family history or genetic cause other than his exposure to TNT after the blast injury. TNT is absorbed into the body via the digestive system, skin, or respiratory system [1]. In this case, it is suspected to have been absorbed via aspiration or through the skin. In the present case, the MetHb concentration was 13.5% and the ambient oxygen saturation as measured by pulse oximetry was 92.0%.

When treating patients exposed to explosives in military or industrial settings, methemoglobinemia caused by exposure to nitroglycerin should be suspected. MetHb levels should be measured early through arterial blood gas analysis. Then, the necessary tests for tissue hypoxia should be performed. Patients with methemoglobinemia often show normal pulse oxygen saturation, even when experiencing severe tissue hypoxia; this may be misinterpreted as early hypoxia [10]. Since hypoxia can persist even with intensive oxygen therapy, early ventilator care may be required. If G-6-PDH deficiency is excluded and methemoglobinemia is severe and uncorrected, methylene blue may be used as the first-line treatment if available. However, in cases of trauma, where methylene blue is unavailable, red blood cell transfusion to correct bleeding may be used for treatment for methemoglobinemia. Active correction was required in this case, with repeated MetHb follow-up tests. Regarding this case, we believed that it was important for the Armed Forces Capital Hospital to report this case of poisoning due to an explosion, since this is the first such report in Korea.

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