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Scorpion Sting – clinical features & treatment

The scorpions belong to the group arachnoids and there are as many as 650 species of them in the world which belong to 6 families, of which Buthidae is the largest family of the scorpions.

The incidence of Scorpion Sting is prevalent in the tropical and subtropical countries of Africa, Middle East, Latin America, China India, Mexico and Mkst Indies. India harbors more than 80 species of it and these are primarily seen in Andhra Pradesh, Chennai Rajasthan and few regions of Haryana, Punjab, Orissa, Bihar.

By far the most venomous species of it is the red scorpion (Mesobuthus Tamulus Buthidae) which is responsible for great number of morbidity and mortality especially in children and young adults.

A scorpion generally measures from 70-90 mm, with cephalothorax, abdomen and six segmented tail with telson. The paired poison glands are situated in the last segment with two ducts which join in front of the point of the sting.

The sting faces upward when the tail is extended but downwards when it poises for attack. When it strikes, the muscles of the body simultaneously squeeze the glands and force the venom into the victim’s body.

Scorpion Sting

Toxicity of scorpion venom is worse than that of snake venom. The venom contains toxalbumin with neurotoxin, coagulins, agglutinins, lecithin, cardiotoxin, proteases, amylase and 5-nucleotidase activity.

Experimental studies on scorpions venom have demonstrated cardiac sarcolemal defects (initial transient hypertension, followed by hypotension and shock) hyperglycemia, changes in insulin levels, bleeding disorders (increased clotting time, prothrombia time, decrease in fibrinogen levels, platelet count) and increased lactic acid and ketoacid levels.

Scorpion Sting produce both local and systemic effects. Severe poisoning results in autonomic storm, producing multisystem organ failure. There is vomiting, profuse sweating, tingling, parasthesia, tachycardia, tachypnoea and pulmonary oedema.

Clinical features of Scorpion Sting

There is generally an acute sharp tingling pain at the site of sting. In some it is just a mild reaction which lasts from a few hours to a day or so while in others there is oedema, itching and dislocation of skin. There is often nausea and vomiting.

An allergic reaction in the form of swollen eye lids, tongue and lymph adenopathy may develop in some. If poison is of mild nature, all local signs and symptoms subside within 24 hours.

Systemic effects

Depending on toxicity of neurotoxin present in the scorpion sting, serious systemic effects involving nervous system, heart, gastro intestinal system, haematological and respiratory system develop.

Neurological effects

These are like that of strychnine poisoning (muscle contraction, spasms) and autonomic storm due to excessive catecholamine secretions and direct effect of venom on sympathetic nervous system.

There is profuse sweating, rapid breathing palpitation, vomiting, pupillary contraction, hypersalivation, abdominal pain, agitation, tremulosness, heat intolerance, increased secretion of lacrimal glands paroxysmal hypertension, syncope or shock. A feeling of numbness, parasthesia convulsions and chest pain resembling angina pain occurs. Oculogyric crisis, cyanosis and coldness of extremities are other effects.

Cardiac effects

Because of high levels of circulating catecholamines there is initial hypertension followed by hypotension and shock. Cardiac arrhythmias may develop. A small number of patients may develop pulmonary oedema and congestive failure.

Gastrointestinal effects

Acute pancreatitis is one of the major effects. There is acute pain in epigastric region with elevation of serum Amylase levels. There is vomiting and increased gastro intestinal motility.

Haematological effects: Since the scorpion sting contains coagulins or agglutinins, there is development of intravascular coagulation thrombosis and bleeding tendencies.

Respiratory system: Bronchial constriction, pulmonary oedema and ARDS (Acute Respiratory Distress Syndrome) are common complications.

Management

It shall depend on the severity of the Scorpion Sting. No case of its bite should be ignored and always observed especially if the victim is a child and has been stung at variable places. In mild cases a cube of ice is placed at the site of sting along with analgesics to relieve pain. If the pain is not tolerable sting site must be treated by local infiltration with 0.1% Xylocaine. There is no need for local incision. In fact it may invite infection.

Ligature: Cryotherapy treatment is also advocated in which a ligature is placed at once between the site of sting and the body. The area of sting is then placed immersed in ice cold water for two hours. This delays the absorption of venom.

The ligature is released every 10-15 minutes taking care not to traumatize the tissues. Hypothermia is discontinued gradually in 2-3 hours by allowing water to come to room temperature.

Mild sedation may be given but morphine and pethidine should not be used as they synergize the effects of venom. Local injection of Dehydroemetine (0.1-0.2 ml) through puncture also gives relief. Tetanus toxiod and antihistamines may also be needed.

Patients who develop autonomic nervous system disturbances, Prazosin a selective peripheral alpha-i adreneigic antagonist in a dose of 0.25-0.5 mg every 4-6 hours should be given. Care should be taken that patient is not in hypotension.

Antivenins

The scropion venom has a half life of 24 hrs indicating its slow elimination. As the venom stays in the body for more than 36 hours, neutralizing the venom at the earliest should be the primary aim of treatment.

Anti scorpion venom serum (ASCVs), a monovalent enzyme refined immuno globuline specific for the scorpion mesobuthus tamulus Pocock has been found to be effective in neutralizing the effect of venom. It is administered either by TIM or I.V route (5-10 ml given slowly). Improvement after injection of antivenin is seen within 1 or 2 hours.

Adjuvant therapy with carticosteroids and antihistaminic is beneficial. Only side effect of antivenin is allergic reaction to foreign proteins. Failure with antivenin therapy is due to delay in administration of the drug, sudden relapse of symptoms and rapid development of bulbar toxicity.

Treatment of complications

Presence of complications shall carry poor prognosis. Treatment of various complications shall be govemed by the pathophysiological changes.

To counteract excess para symptathomimetic effects like salivation, rhinorrhea, diaphoresis etc inj. Atropine 2 mg in adults and 0.25-1 mg in children is administered. Intravenous injection of calcium gluconate (1-2 gm in adults) is useful in relieving muscle spasm. Inj Diazepam or Phenobarbitone help in controlling convulsions.

Pancreatitis is managed on medical lines. Massive pulmonary oedema shall respond to Diuretics (I/V Frusemide) intravenous aminophylline or I/V sodium Nitroprusside (0.1-0.2 mg/mt in drip with a watch on systolic BP). Rapid digitilization is of value. Vaso dilator therapy may be used for refractory heart failure.

When due to autonomic storm there is rise of blood pressure sublingual Nifedipine is beneficial. Cardiac arrhythmias are controlled by propranolol / mexiletine / Lignocaine.

Positive pressure breathing for short periods is of great help in improving ventilation. Mr ways must be cleared, Mechanical ventilation may be employed. For patients with bleeding tendencies, fresh blood transfusion is given. For DIC, intravenous heparin is the drug of choice.

Prognosis

It shall depend on the age of the patients, number of scorpion stings and development of systemic complications. The interval between the sting and death varies from few minutes to 30 hours. Mortality is higher in children (25%) as compared to adults (0.25-0.5%).

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