Scorpion sting is an important hazard in tropical regions, more so rural areas in south and central India.
Clinicians feel that scorpion bite, even though potentially very dangerous, is underrated among the public probably due to the small size of this reptile. Around 150 species of scorpions exist in the world of which 30 are there in India.
Toxin from scorpions can affect nervous system, heart, and respiration. The Patient may require care at an intensive care unit. Since scorpion is very small, people may not notice its bite and only when the pain develops, they give attention. This can lead to delay in seeking health care which can jeopardize the life of the patient. It has been proven that scorpion venom is more lethal than snake venom or cyanide. Its mortality is worse than snake bite, deaths occurring chiefly in patients with delayed diagnosis or therapy.
Pathogenesis
Scorpion venom is a complex mixture of various bio-active molecules such as mucopolysaccharides, hyaluronidase, phospholipase, acetylcholinesterase, serotonin, histamine, protease inhibitors, histamine releasers and neurotoxins. The neurotoxin acts by inhibiting the inactivation of sodium channels in the neurons during depolarization of neurons, resulting in membrane hyper-excitability, repetitive uncontrolled firing of axons, enhanced release of neurotransmitters at synapses and neuromuscular junction, excessive neuromuscular activity and autonomic dysfunction.
The venom of the Asian black scorpion has high concentrations of noradrenaline and acetylcholine, due to which localized burning and algesia will be present at bite site. Drop in blood pressure and cardiac pumping can occur secondary to transient autonomic dysfunction caused by these bio-active molecules or severe inflammatory response syndrome.
Neurotoxicity
A toxicity to brain and nerves after envenomation is categorized into four clinical grades, and they are:
1) Local pain and altered sensations at the sting site without inflammation.
2) Local symptoms and remote pain and altered sensations (radiating proximally up the affected limb or generalized) with aggressive behavior or irritability.
3) Cranial nerve dysfunction (blurred vision, slow and roving eye movements; slurred speech, tongue twitching, increased saliva production) or somatic neuro-muscular dysfunction (restlessness, fasciculations, bow like posturing of body, irritability) in an alert individual.
4) Presence of both cranial nerve dysfunction and somatic skeletal neuro-muscular dysfunction.
Autonomic storm, a life threatening event, can happen which is characterized by vomiting, profuse sweating, hyper-salivation, bradycardia, improper heart beats, priapism and hypotension which will be followed by cold extremities, hypertension, palpitations, pulmonary edema and low blood pressure.
This condition is suddenly progressing and within 5 hours, it can reach its maximum severity. Children are at more risk of this condition and can collapse quite easily; hence they require more intensive care.
Treatment
Prevention is better than cure and same is the case in scorpion bite too.
- Use footwear which covers the entire foot whenever you step outside your house if it is an endemic area.
- If you keep your shoes outside of your house, regularly check and clean before wearing it.
- It is also important to search for bite marks if you are failing severe pain at a local area of your body and if found, immediately seek professional health care. There have been many instances in which, precious time was wasted by taking the patient to local faith healers assuming that they were capable of managing scorpion sting. Not all stings will be life threatening, but that doesn’t mean that it can be managed at home or by faith healers.
The management of scorpion stings involves relief of pain which can be attained by paracetamol or ibuprofen and wound cleaning. All patients must receive tetanus prophylaxis if they haven’t received tetanus shot recently. These patients must be kept under observation for 6 to 12 hours. Most of the stings do not cause envenomation hence a majority can be managed in OP facility itself.
Severe cases with restlessness, muscle twitching, hypersalivation, cranial nerve dysfunction and roving eye movements require monitoring for respiratory distress, hyperthermia, rhabdomyolysis (muscle injury and subsequent release of myoglobin) or multiple organ failure. Patient may require intravenous fluids to compensate the losses occurred due to vomiting, increased saliva production and sweating. Doctors must anticipate the need for mechanical ventilation if patient has abnormal breathing pattern or pulmonary edema. Oral secretions should be suctioned frequently to maintain patency of the airway.
Patient can have severe muscle spasm and anxiety which can be relieved by using medication like midazolam. It provides sedation and relief from muscle spasticity.
Intravenous fentanyl is preferred to morphine for pain relief, since it does not cause histamine (the mediator of allergic reactions, also a part of scorpion toxin) release.
Prazosin is useful in the management of vasoconstriction and hypertension associated with alpha receptor stimulation. Alpha receptor stimulation in blood vessels by scorpion toxin can reduce filling of blood at heart. It can also increase the oxygen demand of heart. Prazosin can counter both these adverse effects. Patients with dysfunction of left side of heart due to hypertension may benefit from sodium nitroprusside infusion or use of an angiotensin converting enzyme inhibitor.
Scorpion anti-venom reverses the excitatory effects of the venom and neutralizes circulating unbound venom to minimize parasympathetic stimulation. Its use reduces the duration of symptoms and the need for benzodiazepines like midazolam. Scorpion-specific F(ab’) equine anti-venom should be administered as early as possible to patients with Grade III or IV neurotoxicity. While specific anti-venom is not available in India, nonspecific anti-venom can be procured. Goat-derived anti-venom carries risks of anaphylaxis and delayed serum sickness.
So, in short, scorpion sting is a potentially dangerous condition but has effective treatment. All you need to do is to take the patient to a hospital as soon as possible. If you google, you will see the claims of many alternative medicine healers that herbal remedies can cure scorpion sting. That is totally wrong and following such advice can put the life of patient at stake.
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