First Aid Guide – Snake Bite
Snake bite is prevalent in our community for generations, and we are not able to prevent it. Education of the common man is required from snake bite, as well as measures to be taken after the bite. Snake bite may occur at any time during lifetime. WHO (2004) provided recommendations to reduce death due to snake bite as per international norms. A primary recommendation, based on evidence based procedures, was to establish a single protocol for both first-aid and treatment, and is relevant in Indian context as well.
Remember, traditional therapy have no proven benefit in the treatment of snake bite. Do not waste time and send the patient to hospital at the earliest.
First- Aid treatment protocol:
First-aid currently recommended may be remembered by mnemonic ‘’ CARRY NO R.I.G.H.T’’
CARRY: Do not let victim to walk even for short distance. Transport by conveyance, especially when bite is in legs.
NO:
NO- Tourniquet.
NO- Cutting.
NO- Electrotherapy.
NO- Pressure immobilisation, nitric oxide donor (nitrogesic ointment/nitrate spray)
R.I.G.H.T:
R: Reassure patient, since 70% of all snake bites are from non-venomous species. Only 50% of bites by venomous type of snakes actually envenomate (poison with venom) victims.
I: Immobilise limb in a fashion similar to a fractured limb, in case of bites on the limb. A bandage or cloth is used to hold the splints. Do not apply pressure and ensure that blood supply is not blocked. Compression in the form of tight ligatures does not work and may be dangerous even.
GH: Get to Hospital immediately.
T: Tell any systemic symptoms that manifest on way to hospital.
Do not waste time in first aid management by traditional methods which may dangerously delay effective treatment.
Diagnosis phase:
Resuscitation and treatment of breathing problem is a priority. Life threatening injuries should also be taken care of.
Patient is monitored for any worsening of symptoms, chiefly breathing or pertaining to cardiovascular system.
Look for fang (poisonous tooth) marks in the area of bite.
Limbs are divided into compartments of muscles, blood vessels and nerves. Compartment syndrome is a rare complication. It is seen in excessively swollen limbs. Severe swelling may cut off blood circulation to a particular compartment.
I. Diagnosis phase general assessment:
Diagnosis phase general assessment depends upon the type of symptoms. Depending upon the species, clinical features may include:
- Local pain/ tissue damage. Bite area may show signs such as painful and tender wound, swelling, or blister formation.
- Ptosis (drooping of upper eyelids)/ neurological signs. Local or systemic effect of venom may stop action of breathing muscles, resulting in death in untreated cases. Victim may have vision problem or difficulty in speaking.
- Haemostatic abnormality leading to localised or diffuse bleeding.
- Muscle death: Venom from certain snakes may produce muscle death. Debris of protein from dead muscle cells may affect kidney, since it may not be filtered out.
- Renal damage.
Response to neostigmine and anti- snake venom (ASV) may be studied.
II. Diagnosis phase investigations:
- 20 minute Whole Blood Clotting Test (20WBCT): This is most reliable bedside test of coagulation. A few milli-liter of fresh venous blood is taken in small test tube of glass. It is left undisturbed at room temperature for 20 minutes. After 20 minutes, tilt the test tube to check coagulability. If the blood is still liquid, then the patient has incoagulable blood. The test is carried out every half an hour for three hours and then at hourly intervals. If incoagulable blood is discovered, then six hourly cycle of ASV is adopted.
Send blood and urine samples to the laboratory to look for any evidence of bleeding, muscle death and for assessment of kidney function.
Management:
Management should be carried out under medical supervision.
Snakes can continue to bite and inject venom with successive bites till the venom is exhausted. Prevent a second bite or attack on another victim. Therefore, do not try to catch snake as this may lead to further bites. Identify the snake if possible but not at the cost of additional bite.
Every snake bite victim should attend emergency department in a hospital.
I. General:
- Pain: Snake bite often causes severe pain locally. This may be treated with pain killers such as paracetamol.
- Tourniquets: Though tourniquets are not advised, many a times these are still used. When used by someone, sudden removal of tight tourniquets may lead to massive surge of venom leading to neurological paralysis or hypotension. Tourniquet removal should be done under medical supervision, more so when pulse distal to it is absent.
Patients with local necrosis may be given antibiotics and tetanus toxoid booster.
Remove any constricting item such as ring which may cut off blood flow in case of swelling of bite area.
In past, suction was applied to remove toxin. It is no longer recommended, since suction may further damage local tissue.
II. Anti- snake venom:
When indicated, start ASV with whatever dose is available in hand (pending availability of full dose). In India, only polyvalent ASV is available. It is effective only against four common varieties of snakes (king cobra, Russells viper, saw scaled viper and common krait). Bites by other species, depending upon the geography, require special measures. These species need to be identified first.
Criteria for ASV administration:
ASV is a costly and scarce item. It should be administered only when there are definite signs of envenomation. Only free flowing and unbound venom, in tissue fluid or bloodstream can be neutralised.
ASV carries the risk of anaphylactic shock and therefore, should not be used unnecessarily.
Indications of ASV:
I. Systemic envenoming
- Evidence of coagulopathy: Visible spontaneous systemic bleeding or coagulopathy is detected by 20WBCT.
- Evidence of neurotoxicity: Victim is having muscle paralysis, ptosis, external ophthalmoplegia or is unable to lift head.
- Abnormalities of cardiovascular system: Victim has signs of hypotension, systemic shock, cardiac arrhythmia or has abnormal electrocardiogram.
- Severe and persistent vomiting or pain abdomen.
II. Severe current local envenoming
- Severe current local swelling: Severe current local swelling involving more than half of the bitten limb, in the absence of tourniquet. In cases of severe swelling after bites on digits (toes and especially fingers) from species causing necrosis.
- Rapid extension of swelling: Rapid extension of swelling (e.g. beyond ankle or waist within few hours of bites on hands or feet). Swelling arising after elapse of long hours of bite is not a ground for giving ASV.
Purely local swelling, even if accompanied by bite mark/s from an apparently venomous snake, is not a ground for giving ASV.
ASV administration:
Clinical decision is very important and the dose of ASV required varies from case to case. Ten to thirty vials are usually required. All victims do not require 10 vials of ASV. However, starting with 10 vials ensures sufficient neutralising power against average amount of injected venom. It also ensures neutralisation during next 12 hours of any free flowing venom.
No ASV test dose is given, since it does not have predictive value in detecting anaphylactic or late serum sickness reactions. Rather, these may pre-sensitise the victim and may pose greater risk.
Two methods of administration are recommended
- Intravenous “push” injection: Reconstituted freeze-dried anti-venom or neat liquid anti-venom is injected by slow intravenous injection (not more than 2 ml per minute).
- Intravenous infusion: Reconstituted freeze-dried anti-venom or neat liquid anti-venom is diluted in about 5 ml of isotonic fluid (isotonic saline or 5% dextrose) per kg of body weight, and is infused at a constant rate over a period of about 30- 60 minutes.
Recommended initial doses of ASV:
- Neurotoxic/ haemostatic cases: Neurotoxic/ haemostatic 10 vials of ASV are needed, and the same amount of ASV is given to adults, children and even pregnant women. Snakes inject the same amount of venom in adults and children.
ASV is administered over 30- 60 minutes at constant speed. Liquid or reconstituted ASV in isotonic saline or glucose without any diluent fluid in volume overload victims is given.
Local administration of ASV near the site of bite is ineffective, painful and in fact raises intra-compartmental pressure. Particularly, it is not injected in digits.
How long anti-venom is expected to be effective after the bite:
Anti-venom should be given as soon as it is indicated. It may reverse systemic envenoming even when it has persisted for several days, and in case of haemostatic abnormalities, for two or more weeks. It is appropriate to give anti-venom as long as evidence of coagulopathy persists.
ASV reactions:
- Anaphylaxis: Anaphylaxis is a life threatening emergency. Victim is monitored for features such as fever, chills, itching, urticaria, hypotension and bronchospasm. ASV should be discontinued in anaphylaxis. Adrenaline should always be at hand. An extra dose of adrenaline may be required in patients who do not respond to initial doses. Noradrenaline and nitroglycerine should be available to correct hypotension in elderly. Intravenous fluids may be required for any haemodynamic instability.
On recovery, ASV may be restarted slowly for 10- 15 minutes, keeping the patient under close observation. After that, normal flow is maintained.
- Late serum sickness: Late serum sickness may be treated with oral steroids. Antihistaminics may provide additional symptomatic relief.
III. Neurotoxic envenomation:
- Neostigmine: Neostigmine, an anticholinesterase, may reverse respiratory failure and neurotoxic symptoms by prolonging the life of acetylcholine.
IV. Anti-haemostatic repeat dose:
In case of anti-haemostatic envenomation, adopted ASV strategy is to keep six hour time period in which clotting time is repeated. Repeat ASV dose is given over one hour in case of persisting coagulation defect. Same cycle is repeated until coagulation is restored or the species of snake is identified against which polyvalent ASV is ineffective. Repeat dose may be ten vials of ASV similar in quantity to the first dose.
V. Haematotoxic repeat dose:
Normal guidelines are to administer ASV every six hours until coagulation is restored. What should be done when 30 vials have been exhausted and the coagulation abnormality persist. One study has shown that even up to 50 vials (500 ml) may be given for haematotoxic poisoning. Envenomation by certain species does not respond to ASV. Coagulopathy may persist for up to three weeks in those cases.
VI. Role of surgery:
- Surgical debridement: Surgical debridement of necrotic tissue may be done.
- Fasciotomy: Fasciotomy is required when intra-compartmental pressure is high enough to collapse blood vessels leading to ischaemia. The role of fasciotomy is questionable.
- Multiple puncture technique: Multiple puncture technique with large bore needle may be done to reduce intra-compartmental pressure. Intra-compartmental pressure may be measured using saline manometers.
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