Snake Bites

Snake bite is one of the major problem in tropical country like Napal whose main source of income is agriculture and more than 80% of population is dependent on agriculture. Terai is the major vulnerable area from where most of the cases are reported each year. Due to lack of knowledge about proper filed management by local people and inability to do timely intervention at hospital level, it has led to most of the deaths. Me, myself being from the Terai region, I have noticed the situations closely. I used to be so afraid of snake bite problem and I have also noticed few cases of death due to snake bite which might have prevented if  community people had good knowledge about field management. So, hereby this document I wish non-medical peoples(Mainly) and medical personnels also will have some level of understanding about approach and management of snakebites.

1.       Snakes can be venomous as well as non venomous

2.       Bite rates are highest in tropical region(Agriculture)

3.       1.2 to 5.5 millions snake bites/year worldwide

Snakes

·         Snake venom apparatus consist of Bilateral venom glands situated below and behind eyes and connected by ducts to hollow anterior Maxillary teeth

·         How to know differentiate venomous form from non-venomous one?

1.       Venomous form: triangular head, elliptical pupils, enlarged maxillary fangs and paired foveal organs(In pit vipers) and rattle on the tip of tail(New world rattle snake).But these findings are not specific.

Clinical features:

·         Progressive local swelling, pain , echhymosis and over a period of days, hemorrhagic bullae and serum filled vesicles seen.

·         In serious bites, tissue loss may be significant

1.       Systemic findings: Change in taste, Mouth numbness, Muscle fasciculation, Tachy or bradycardia, Hypotension, Pulmonary edema, Hemorrhage, Renal dysfunction, If neurotoxic, causes CN weakness and even paralysis.

·         Time of onset of snake venom intoxication depends on:

1.       Species involved

2.       The location of bite

3.       Amount of venom injected

Field Management

·         Rapid delivery to medical facility which can provide supportive care (ABC) and antivenom administration.

·         Most of the first aid techniques and traditional healers used in past are of no use,rather harmful except the few.

·         Reasonable to apply splint to the bitten extremity to lessen bleeding and discomfort

·         Keep the extremity at heart level if possible

·         Don’t incise the wound or suction: may only exacerbate local tissue damage with no efficacy

·         Don’t apply poultices, ice and electric shock

·         Don’t apply the techniques to limit venom spread(Tourniquets or lymphoocclusiive bandages) are ineffective(Rather can cause more local tissue damage and even amputation in absence of venom)

·         Elapid venoms (Neurotoxic with no significant effect on local tissue) may be localized by pressure immobilization i.e. entire limb is wrapped immediately with bandage and immobilized(Certain pressure criteria) Warning: Apply only if snake is identified.

·          Victims must be carried, not allowed to walk to avoid muscle pump action(Regardless of site) which may  disperse venom

Hospital Management

·         Victim is closely monitored(Vital signs, cardiac rhythm, oxygen saturation, urine output)

·         Quick Hx and rapid examination is performed

·         For objective evaluation of progression of locan envenomation, level of swelling is marked and limb circumference is measured every 15 mins until the swelling subsides

·         Position the extremity at hert level

·         Measures applied in the field(e.g. tourniquets) should only be removed once i.v. access has been obtained(Because release of them earlier may result in hypotension or dysarrhythmia when stagnant acidotic blood is released to the central circulation)

·         Large bore i.v. access in one or both unaffected extremities should be established

·         Early hypotension is due to pulling of blood in the pulmonary and splanchnic vascular beds.Later, systemic bleeding, hemolysis and loss of intravascular volume in soft tissue counts

·         If any hemodynamic instability, fluid resuscitation with isotonic saline(20-40 mL/kg IV) and if patient fails to response trial of 5% albumin(10-20 mL/kg).

·         Blood drawn for  typing and cross matching and for labevaluation(CBC,RFT,LFT,coagulation studies) if possible.

·         ABG,ECG,CXR may be helpful in severe envenomation

Antivenom therapy

·         Goal: bind up circulating venom components before they can attach to target tissue and cause deterious effects

·         May be monospecific or polyspecific but rarely offer cross pretection against snake species than those used in their production unless they have homologues venoms

·         Antivenom choice must be specific if not it may lead to further problem that cure

·         Antivenom is effective only in reversing the active venom toxicity doesn’t cause reverse of effects that have already been established

·         When sign of acute renal failure, consult nephrologist and do peritoneal dialysis or hemodialysis

·         Acetylcholinesterase inhibitors(e.g. edrophonium and neostigmine) may promote neurologic improvement in patient bitten by snakes with post synaptic neurotoxins

Care of bite wound

o   application of a dry sterile dressing and splinting of the extremity with padding between the digits

o   Once the administration of an indicated antivenom  has been initiated, the extremity should be elevated above heart level to relieve edema

o   Tetanus immunization should be updated as appropriate

o   Prophylactic antibiotics are unnecessary, as the incidence of secondary infection following venomous snakebite is quite low.

o   If swelling in the bitten extremity raises concern that subfascial muscle edema maybe impeding tissue perfusion (muscle-compartment syndrome), intracompartmental pressures should be checked by any minimally invasive technique (e.g., a wick catheter). If pressures are elevated and remain so despite additional antivenom administration and elevation of the extremity, surgical consultation for possible fasciotomy should be obtained. This complication, fortunately, is rare after snakebites.

o   Whether or not antivenom is given, any patient with signs of venom poisoning should be observed in the hospital for at least 24 h.

o   Any patient requiring antivenom treatment should be admitted to an intensive care setting.

Follow Up care

o   Physiotherapy

o   victims of viperid bite should be reevaluated for evidence of recurrent coagulopathy _48 h after discharge and as needed thereafter. These patients should be warned to avoid anyroutine surgery for the first few weeks, as occult coagulopathy can recur up to 2 weeks after a viperid bite.

o   Morbidity: Such loss maybe due to muscle, nerve, or vascular injury or to scar , contracture

Reference:

Harrison