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Indian snake bites

Meenakshi Girish and Nilofer Mujawar explain how to manage bites in primary care

India is home to some of the most poisonous snakes in the world, most of which are found in rural areas where only primary health care facilities are available.¹ A snake bite is a medical emergency, and timely treatment can save lives. We focus on what a primary caregiver must do.

Snake bites cause substantial mortality and morbidity in India. Local superstitions, wrong practices, misconceptions regarding management,^{2 3} and impractical guidelines impede doctors,⁴ especially those working in primary health centres.

Of more than 3000 known species of snakes, only about 300 are poisonous and in India of the 216 species only 52 are poisonous. Of these, the cobra, common krait, Russell’s viper, and the saw scaled viper are the most common in India.⁵

Diagnosis

The first step is to determine whether the snake was poisonous. Physical examination of the snake is rarely possible, but it can help to plan treatment.⁶ Do not search for the bite marks to determine whether the snake was poisonous or not. Fang marks may not be easily visible, and non-venomous snakes may leave just two punctures resembling fang marks.⁷

Bites from poisonous snakes often give rise to considerable local pain and progressive swelling. However, bites from some snakes, especially kraits, may not cause any local symptoms but may lead to serious systemic effects.

There are three main systemic effects of poisonous bites. Neurological effects are seen mainly after bites from cobras and kraits. Cobra bites are associated with neurological signs that range from mild drowsiness and ptosis (drooping of eyes) to weakness of respiratory muscles and death. Coagulopathy caused by bites from vipers results in bleeding from multiple sites. And renal failure is another systemic effect, especially after viper bites.

Sometimes, a poisonous snake may bite but not envenomate, this is known as dry bite, and should be considered if local symptoms do not appear within six hours in viper bites.^{8 9}

Management

If there is snake phobia among the public, there is phobia of treating snake bites among doctors, and few centres accept patients with snake bite. This is for three reasons. Firstly, the misconception that without antivenom there is no point in managing such a case.¹⁰ Secondly, that the lack of easy availability of antivenom,¹¹ variable storage facilities, and irregular demand discourages pharmacies from stocking the antivenoms. And thirdly, a fear of anaphylaxis caused by antisnake venom.²

• Do not send the patient away to another centre without first aid, especially if it is far away.
• Do not give sedatives to calm the patient.
• Do not tie a tourniquet above the site of bite.¹²
• Do not use ice packs, give incision, or perform suction at the site of bite.
• Do not elevate the limb unless antivenom is available immediately.
• Do not use antivenom unless specifically indicated.^{13 14}

The mnemonic RIGHT gives the initial steps to be taken in a hospital or primary health care facility.¹⁵

R—Reassure the patient. Snake bite understandably causes great fear in the patient. Seventy per cent of all snake bites are non-venomous. Even in bites by venomous snakes, envenomation occurs in only 50% of cases.

I—Immobilise in the same way as you would a fractured limb, using splint and bandage. This goes a long way in slowing the spread of the venom in the body.

G—Grade the degree of envenomation (see below). This will help in assessing the need for dose of antivenom and the quantity of the initial dose.

H—Admit the patient to hospital even if your hospital is not equipped for such cases. Correct initial steps will ensure stabilisation of the patient while transport is being organised.

T—Take a blood sample.

After the initial stabilisation, which also includes assessment of the airway, breathing, and circulation, locally clean the wound, give tetanus toxoid vaccine if the immunisation is incomplete, and insert a large bore intravenous line. A sample should be collected for:

Blood grouping—This should be done immediately before coagulopathy starts after which typing may be impossible.¹⁶

Twenty minutes whole blood clotting test—This is a simple test to detect coagulopathy and is easy to perform if facilities for coagulation profile are not available.¹⁷ A clean, new, and dry test tube is needed. A few millilitres of fresh venous blood is left undisturbed for 20 minutes and then gently tilted. If the blood is still liquid this is evidence of coagulopathy, which is a predominant feature of viper bites.

Antivenom—Whether antivenom is needed and the dose needed are the most important decisions in the initial management of snake bites. Antivenom is most effective if given within four hours of the bite, and it is only effective if given before symptoms develop, especially in neurotoxic bites. It cannot reverse symptoms. Attempts to get a minimum of 8-10 vials of antivenom should begin early.

Severity of envenomation¹⁸

Grade 0—No envenomation—No local signs by six hours and no systemic signs by 24 hours.

Grade 1—Minimal envenomation—Local swelling and pain without progression, no systemic or lab abnormalities. Needs only pain control and careful observation.

Grade 2—Moderate envenomation—Swelling, pain, or ecchymosis progressing beyond site of injury; mild systemic signs of nausea, vomiting, perioral and scalp parasthesias and fasciculations, or lab manifestations in the form of evidence of coagulopathy. Antivenom should be given.⁶

Grade 3—Severe envenomation—Marked local response with development of vesicles and bullae, systemic findings as in moderate plus hypotension, shock, bleeding diathesis and respiratory distress and evidence of coagulopathy plus anaemia and metabolic acidosis. Antivenom should be given.⁶

A progression of local swelling is best recognised if the circumference of bitten limb is taken every 15 minutes and a demarcation line is drawn on the upper limit of the initial swelling or the fang marks.

Most envenomations become symptomatic in minutes and almost always within six hours. Delayed signs of envenomation have been reported in some species of snakes, especially kraits, so all patients with presumed dry snake bite should be admitted to hospital and observed for at least 24 hours.

Antivenom

In settings with scarce antivenom, poor transport facilities, and inadequate laboratories, administration of antivenom is guided by the 20 minute whole blood clotting test and clinical symptoms.¹⁹ Perform the test every six hours. The protocol in the table is best suited for primary care facilities.

Frequency of evaluation	Clotting time and neurotoxicity	Antivenom in 1 hour (ml)
Hourly	>20 min or presence of neurotoxicity or both	80-100 (first dose)
Second hour from first dose	Worsening neurotoxicity	80-100
Sixth hour from first dose and subsequently every six hours	Still >20 min	80-100 and subsequently every six hours till clotting time is normal

Dilute antivenom in 100-500 ml of isotonic fluid or 5% dextrose. In case of neurotoxic bites, further worsening after two doses will require mechanical ventilation. Antivenom may not help at this stage.²⁰ In viperine bites repeat antivenom every six hours until coagulopathy is corrected.

Adverse reactions to antivenom

Fear of anaphylactic reactions to antivenom is common among clinicians. These reactions are easily handled even in the smallest hospital if proper precautions are taken and healthcare workers are aware of the signs of anaphylaxis—urticaria; itching; fever; shaking chills; nausea, vomiting, diarrhoea, abdominal cramps; and tachycardia, hypotension, bronchospasm, angioedema.

In cases of anaphylactic reactions stop giving antivenom. Give 0.5 mg of 1:1000 adrenaline intramuscularly. To provide protection against delayed anaphylactic reactions give 100 mg (2 mg/kg) of hydrocortisone intravenously, and give 0.2 mg /kg of the H₁ antihistamine chlorpheniramine intravenously.

If the symptoms do not improve in the next 10-15 minutes, give another intramuscular dose of 0.5 mg adrenaline. A third dose may also be given if necessary. Once the patient has recovered, antivenom can be restarted slowly for 10-15 minutes under close observation. Normal drip rate may then be resumed. Anaphylaxis to antivenom is not a contraindication to further administration of antivenom.^{14 15}

Sensitivity tests to antivenom have been abandoned. They have no predictive value in anaphylactic or late serum reactions and may presensitise the patient to the serum.

Supportive treatment²¹

The following supportive treatments may be needed.

• Blood or blood products for disseminated intravascular coagulation.
• Ventilatory support for respiratory failure.
• Use of anticholinesterase agents for reversal of paralysis (0.5 mg neostigmine intramuscularly every half hour up to six doses and 0.6 mg atropine intravenously, if the patient visibly improves after the first dose. This should be started with the first evidence of neurotoxicity.
• Peritoneal dialysis in case of renal failure.
• Surgery if compartment syndrome develops.

Patients receiving antivenom should be followed up for several days because delayed reactions can occur and their frequency is proportional to the amount of antivenom given.

Even without immediate access to tertiary healthcare facilities, much can be done to improve a patients chances of survival.²² Proper first aid, availability of antivenom, determining the severity of envenomation, and overcoming the fear of anaphylaxis are four of the major areas which must be addressed.

Competing interests: None declared.

Provenance and peer review: Not commissioned; externally peer reviewed.

Meenakshi Girish associate professor, Department of Pediatrics, N K P Salve Institute of Medical Sciences, Digdoh, Nagpur, Maharashtra, India
min_gir@rediffmail.com
Nilofer Mujawar associate professor
Student BMJ 2008;16:408 | 10

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