Getting stung by black scorpion Androctonus crassicauda

Introduction

The annual number of scorpion stings exceeds 1.2 million leading to 100,000 medically significant stings and more than 3,250 deaths (0.27%). ¹ Of the 650 known living species of scorpions, most of the lethal species are in the family Buthidae including Centruroides, Tityus, Leiurus, Androctonus, Buthus, and Parabuthus. The most important lethal species in the Middle East include Androctonus crassicauda, Androctonus australis, Buthus minax , Buthus occitanus, and Leiurus quinquestriatus. ² Local manifestations may exist in 90% of scorpion stings and 10% of cases can be life-threatening in a serious medical emergency situation. ³

Scorpion stings produce a local reaction consisting of intense local pain, erythema, tingling or burning, and sometimes discoloration and necrosis. Depending on the scorpion species involved, systemic effects such as autonomic storm consisting of cholinergic and adrenergic effects may occur. ¹ Different cardiotoxic effects and electrocardiographic (ECG) abnormalities may be present, as well. Presence of different ECG changes as well as lung complications without a clear history of scorpion sting may mimic other diagnoses including myocardial infarction and complicate the treatment plan. ⁴ We present a case of scorpion sting in an old woman first diagnosed to be acute myocardial infarction who was successfully treated by low dose of antivenom.

Case report

A 65-year-old woman travelling in an intercity bus had the sensation of being bitten in the left calf and left flank while she was still in the bus. After arrival to the destination (Tehran), she began to experience pain and swelling in the left calf and one episode of vomiting and referred to a general physician who administered her hydrocortisone and intravenous (IV) promethazine with the diagnosis of hypersensitivity due to an unknown bite. She was brought to our emergency department (ED) 3.5 h later due to severe agitation and slurred speech. This was while the primary treatment had not been effective.

In the first examination performed, the patient’s vital signs were as follow: respiratory rate: 32 breaths/min, pulse rate: 160 beats/min, blood pressure: 120/80 mmHg, and temperature: 36.5°C. In ECG, tachycardia and tall T waves in precordial leads, stress test (ST) depression in V5–V6, and long QT interval (QT _Corrected: 485 ms) were observed. In arterial blood gases analysis, a pH of 7.29, partial pressure of carbon dioxide (PCO₂) of 37.6, and bicarbonate (HCO₃) of 17.1 were detected (PaO₂/fraction of inspired oxygen (FiO₂) = 247). O₂ saturation was 81.5%. Lab tests including blood urea nitrogen, creatinine, and liver function tests as well as the electrolytes were within normal limits. Blood glucose was 258 mg/dL, creatine kinase-MB (CK-MB) and troponine I were checked and reported to be 35 U/L and 0.5 ng/ml, respectively (normal values: <5% and 0.00–0.14, respectively) while a CK level of 1500 was noted (normal values in female 26–140 U/L)

A small papule without erythema and swelling was detected on the lateral surface of the left calf and two macules were noted on the left flank (Figure 1). After receiving the second IV dose of antihistamine and hydrocortisone, the patient suddenly became severely agitated. Her agitation was controlled by the IV administration of 2 mg of midazolam. She then became drowsy, tachycardic, tachypneic, and pale and had weak radial pulses and severe sweating as well as cold extrimities and miotic pupils. Diffuse fine crackles were auscultated all over the lungs. The patient was immediately incubated. Chest x-ray revealed radiological findings of pulmonary edema. In the second ECG performed, ST segment elevations in precordial leads as well as sinus tachycardia (150 bpm) were noticed. After consultation with a cardiologist, she was recommended to be admitted in coronary care unit with the diagnosis of myocardial infarction. The first physician who had visited the patient in his office called 15 min later and said he had found a black scorpion on the patient’s bed (Figure 2).

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Figure 1.

Two stings of Androctonus crassicauda on the left flank which are more than 3 mm in length.

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Figure 2.

Black Androctonus crassicauda found on patient’s bed clothes.

Immediately, 10 mL polyvalent scorpion antivenom was intravenously administered and the patient was admitted to intensive care unit. After about 30 min, her skin was warm and sweating diminished. However, she was still agitated and had tachycardia (119 bpm), tachypnea, and tongue fasciculation. About 1 h later, the vital signs were stable, skin was normal, pulmonary edema had resolved, the lung was clear in auscultation, ECG was normal, and the level of consciousness had increased. In another 5 h the patient was extubated and transferred to the ward. Troponine I was reported to be negative. The patient was discharged 1 day later in good condition and completely symptom-free.

Discussion

The majority of stings occurring in Iran are attributed to the Buthidae family, one of the most important is A. crassicauda. ^5,6 It is widely distributed in Iran. Its venom is a potent autonomic stimulator with high affinity to muscle and nerve voltage-gated Na²⁺ channels. It is due to this characteristic that, when present at high concentrations, shows variable toxic effects on nervous, cardiovascular, and respiratory systems. The most common symptom of envenoming by A. crassicauda in stung patients is local burning pain in the sting site. This symptom could not easily been detected in our patient because she was agitated from the very first moment of presentation and could not tell us about this very important discriminating symptom. The other frequent symptoms are tachypnea, decreased level of consciousness, miosis, increased secretion from endocrine glands, and some gastrointestinal manifestations such as diarrhea or defecation and urination. ^7,8 Severity of the symptoms depends on the size of the victim, season, and time elapsed between sting and hospitalization. Vomiting, profuse sweating, priapism, mild pain at the sting site, local urticaria, and cool extremities are early signs of autonomic stimulation due to scorpion sting ^3,9 described life threatening (class 3) envenomation based on presence of one of the following signs: hypotension, bradycardia, venticular arrhytmia, cardiovasucular collapse, cyanosis, dyspnea, pulmonary edema, paralysis and Glasgow coma scale ≤6. Fatality after scorpion envenoming may be the result of cardiovascular failure complicated by pulmonary edema and respiratory arrest. There are two different hypotheses that explain mechanisms of pulmonary edema: cardiac dysfunction and, increased capillary permeability. Most studies support cardiogenic nature of pulmonary edema based on: (a) increased circulating catecholamine secondary to a direct stimulatory effect of the venom on the adrenals and on sympathetic nerve endings leading to massive discharge of catecholamines during the so called autonomic storms, (b) direct effect of the venom on the myocardium leading to “scorpion myocarditis”, and (c) myocardial hypoperfusion and ischemia. ^4,9

The A. crassicauda sting is usually more than 3 mm in length (Figure 1) comparing to the very small sting of Hemiscorpius lepturus (<1 mm) which is the most fatal scorpion in Iran. ⁸ According to the results of Ozkan et al, intoxications caused by A. crassicauda in Southeast Anatolia region were seen in summer and in hot months, especially in August. Females and males older than 15 years old were mostly affected and stung in extremities. In clinical evaluations, 17.7% of the cases showed systemic effects and parasympathetic effects were superior to the sympathetic ones. ¹⁰

As described in Goldfrank’s Toxicologic Emergencies textbook, scorpion sting can cause myocarditis, dysrhythmias, and myocardial infarction. ECG abnormalities including sinus tachycardia or bradycardia, bizarre broad notched biphasic T-wave changes with additional ST elevation or depression in the limb and precordial leads, appearance of tiny Q waves in the limb leads consistent with an acute myocardial infarction pattern, occasional electrical alternans, and prolonged QT interval may also happen. ² Acute lung injury and shock are of the less common signs of scorpion sting. These signs and symptoms as well as autonomic symptoms including hypertension, tachycardia, diaphoresis, emesis, and bronchoconstriction without a clear history of scorpion sting may interfere with the correct diagnosis of scorpion sting as in our case. This is the point previously noticed in the literature ^{11 – 14} ; however, the clinicians may still forget such an important point in the management of the patients. Such a mistake can potentially accompany with critical mismanagement due to erroneous diagnoses. This is while somatic motor symptoms including ataxia, muscular fasciculation, restlessness, thrashing, and opsoclonus may help the correct diagnosis. ²

As obvious, this case dramatically responded to the administration of the antivenom. Especially the cholinergic and sympathetic signs, pulmonary edema, and ECG changes were fully and almost immediately recovered by the antivenom administration which further emphasizes the importance of the correct diagnosis in the correct early management of the patient. The importance of the time between bite and treatment, spreading of awareness about types of scorpion and symptoms of envenoming, exploring the suitable protocol to treat such cases or inventing new protocols may reduce mortality due to scorpion bites in endemic areas.