P - ISSN : 2349-6592    |    E - ISSN : 2455-7099
Year : 2016 | Volume : 3 | Issue : 2 | Page : 42-48
Source of Funding:None Conflict of Interest:None
Keywords:Scorpion, envenomation, sting ,bite, poisoning
Scorpion sting is a life threatening medical emergency. The effect of envenomations greatest among children below 5 years of age .Mortality in pre prazocin era was as high as 30%. It is worthwhile to remember Dr.H.S.Bawaskar, a private practitioner from Maharashtra who for the first time in world has introduced the usefulness of alpha blocker in scorpion sting nearly 25 years ago and has helped to reduce the mortality.
In India deaths due to scorpion sting occurs across the country but do not get due attention. Larger the scorpion population, greater is the number of scorpion sting cases. Scorpion stings are reported more from rural areas and the rural to urban ratio is approximately 3:1. Mostly stings occur between 6 P.M. to mid-night and between6 A.M. to 12 Noon, which correlate very well with human activity. Scorpion sting occur more in temperate and tropical zones, and more during summer than winter.
Eco- biological aspects of scorpion
Scorpions are shy creatures and not aggressive by and large. These are nocturnal creatures and hunt for their prey at night. Scorpions hide normally in crevices and burrows during daytime to avoid light. Scorpions are found elsewhere outside the environmental range. eg, accidentally crawl into luggage, boxes, containers, or shoes, pile of bricks, wooden materials,firewood, etc. They may also be transported in traveller‘s luggage and cargo.There are about 1500 scorpion species of which 50 are dangerous. In India 86 species of scorpion have been identified. Among them, Mesobuthus tamulus and Palamneus swammer-dami are important medically. Except Hemiscorpius species, all lethal scorpions belong to the family called the Buthidae. The lethal members of Buthidae family include the genera of Buthus, Parabuthus, Mesobuthus, Tityus Leiurus, Andractonus and Centruroides. Among the 30 scorpion species found in USA, only one of them is dangerous to human beings.Scorpions live in temperate and tropical regions especially between the latitudes of 500 north and 500 south of equator. The distinguishing features between lethal and nonlethal scorpions are provided in Table 1 .
Scorpions use their pincers to grasp the prey. It arches its tail over its body and stings into its prey. Thus it injects its venom, sometimes more than once. The venom glands are situated in the tail. The striated muscles in the stings regulate the amount of venom injected. When entire venom is used, it takes several days to replenish venom.Scorpion with large venom sacs such as Parabuthus species can even squirt their venom.
Components of Venom and Mechanisms of action
The components of venom are cardiotoxin, hemotoxin, nephrotoxin, neurotoxin, hyaluronidases, phosphodiesterases, phopholipases, glycosaminoglycans, histamine,serotonin, tryptophan and cytokine releasers. Among all, the most potent is the neurotoxin. There are two classes of neurotoxins (long chain & short chain polypeptide) which are heat stable, have a low molecular weight and are responsible for causing cell impairment in nerves, muscles, and the heart by altering sodium and potassium channel permeability. The long chain polypeptide neurotoxin induces continuous, prolonged, repetitive firing of somatic, sympathetic and parasympathetic neurons which results in autonomic, and neuromuscular over excitation symptoms. It also prevents normal nerve impulse transmissions. Further, it results in release of neurotransmitters viz., epinephrine, nor-epinephrine, acetylcholine, glutamate, and aspartate excessively. The short chain polypeptide neurotoxin blocks the potassium channels.
Clinical course of scorpion sting is usually less alarming but in some cases it may progress to maximum severity in about 5 hours to 12 hours and starts subsiding within a day or two. Even if the patient has features of autonomic nervous system manifestations, it may start subsiding by 12 hours after initiating treatment. Tachycardia usually subsides within 24 to 48 hours. Hypertension may last for 4 to 8 hours. Hypotension and bradycardia are encountered usually within 2 hours. Once treatment is started, the signs of recovery begins within 48 or 72 hours. In some cases pulmonary edema may develop within 30 minutes to 3 hours, usually secondary to myocardial dysfunction. Unfortunately some cases of scorpion sting may die within 30 minutes and this may be related to ventricular arrhythmias or non cardiac pulmonary edema due to ARDS [often reported from Brazil]. Central nervous system manifestations with or without convulsions may occur within one to two hours in fatal cases.
Currently recommended First aid
R = Reassure the patient.
I = Immobilization of the limb in the same way as a fractural limb.
G. H. = Get to Hospital Immediately.
T = Tell the doctor all that happened from the time of scorpion sting
(Traditional remedies have NO PROVEN benefit in treating scorpion sting). However, local application of ice bags (one of the traditional methods) to reduce the pain is acceptable for some time if not contraindicated
1) Admit all victims of scorpion sting & keep the victims under observation for 24 to 48 hrs. (If scorpion is brought try to identify the color and size of it).
2) a) Ask for the details of scorpion sting and never be carried away with the sting marks either for diagnosis or for assessment of severity.
b] Ask for the time interval between the sting and arrival at the hospital.
c] Ask for the details of traditional medicines or household remedies used, as it may sometimes cause confusing symptoms or interfere with other drugs to be administered.
d] Ask for clinical symptoms and correlate with the progression of symptoms and signs due to scorpion sting
3] Assess the following quickly.
a] Airway, Breathing and Circulation
b] Vitals HR, RR, BP and Pulse oximetry
c] Site of sting and the probable route of envenomation - (Intravenous have immediate effects, while subcutaneous and intramuscular routes take several minutes to hours to cause effect)
d] Chest expansion
e] Clinically from head to foot as well as back
f] For associated co-morbid illness[es]
g] For consuming any medication[s]
5] Administer medication meticulously
a] Tetanus Toxoid injection intramuscularly
b] Topical anesthetic agent to the site of sting to decrease paraesthesia.
c] Injection lignocaine 1% without adrenaline; (after test dose for lignocaine)(0.1 to 0.2mg/kg body weight for children)
d] Oral rehydration solution to hydrate the patient if not contraindicated.
e] Tab. Paracetamol 10mg/kg body weight to reduce pain
f] Tab. Prazosin [plain 1mg]
Pharmacological aspects of Prazosin
Prazosin is an alpha blocker. It is well absorbed after oral administration. Its half-life in the plasma is approximately 2-3 hours and the action lasts 4-6 hours. Peak concentration of prazosin in the plasma reached 1-3 hours .It counteracts scorpion induced adrenergic cardiovascular effects and reduces pulmonary edema through vasodilator effect, Usually it is started with small dose using plain tablet but not exceeding 5mg/day. For children the dose preferred is 30 microgram / kg body weight. Though pediatric requirement has not been established, it is started with small dose. Prazosin can be given irrespective of blood pressure, provided there is no hypovolemia It should be avoided, if the patient is hypersensitive to prazosin. Always exercise caution if patient has renal insufficiency and hypertension.
ASV: Antiscorpion venom; SNP: Sodium nitropruside; NTG: Nitroglycerine; NIV:non invasive ventilator; MV: Mechanical ventilator Since 2002, nonspecific F(ab)2 SAV has been available for clinical use from Haffkine Biopharma Mumbai. addition of scorpion antivenom to prazosin enhances recovery time and shortens hospital stay of patients with grade 2 Mesobuthus Tamulus envenomation. The maximum volume of venom injected in one sting by Indian red scorpion is 1.5 mg, and each ml of antivenom is capable of neutralizing 1.2 to 1.5 mg venom hence give 30 Ml of antivenom , however more may be required for severe sting. High circulating catecholamine induced by venom prevent a reaction to antivenom and act as a prophylaxis against anaphylaxis.
1) Severe local pain at the site of sting is unlikely to progress to systemic manifestations.
2) Traditional remedies have NO PROVEN benefit in treating scorpion sting
3) Autonomic storm is the basic pathogenic mechanism leading to all clinical features and complications of Scorpion sting.
4) Pulmonary edema is the most important manifestation.
5) Warming up of extremities and appearance of local pain are suggestive of recovery.
6) Scorpion antivenom is available. Addition of scorpion antivenom to prazosin enhances recovery time and shortens hospital stay of patients
7) Prazosin is alpha blocker and dose is 30 microgram/kg/dose.
8) Massive pulmonary edema needs SNP drip.
9) Avoid using atropine, steroids, lytic cocktail, morphine, nifedipine and captopril
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