Snake Bite Treatment Protocol

Snake Bite Treatment Protocol

Dr.Joseph K.Joseph

Little Flower Hospital and Research Centre

Angamali

Snake bite remains a significant cause of morbidity and mortality, particularly in the rural occupational sector. In India on an average about 80,000 snake bites are reported every year, this is only the tip of an iceberg because many cases are not reported and will not come in statistics.  Many of the deaths due to snake bite are preventable provided appropriate treatment is rendered at the correct time. There is an urgent need to educate all healthcare workers on management of snakebite and the use of a standard treatment protocol.

Snake bite treatment protocol should include

1] Diagnostic Protocol

2] Treatment Protocol

The treatment protocol can be discussed in the following subtitles

Management of Pain

The severe pain at the bite site can be treated with pain killers such as Paracetamol. The adult dose is 500 to 1000 mg 6 hourly. Pediatric dose  10mg/kg body wt, every 6 hourly orally. Mild opiates like Ketorelol 50 mg can be used orally for relief of severe pain.

Handling Tourniquets:

Though not recommended, the current practice being followed would see many snake bite victims reaching the emergency with tightly tied tourniquets.Sudden removal can lead to a massive surge of venom leading to neurological paralysis, hypotension due to vasodilation etc.

Anti Snake Venom [ASV]

ASV is the mainstay in the treatment. ASVis available in India in Polyvalent form that is effective against all the four common species namely,  Russels viper[ Dabora russeli] Common Cobra[ Naja Naja], Common Krait[ Bangarus Caeruleus] and Saw scaled Viper[ Echis Carinatus]

There are known species such as Hump Nosed Pit Viper [Hypnale Hypnale] where the polyvalent ASV is known to be ineffective.

ASV is produced in both liquid and lyophilized forms. Liquid ASV requires a reliable cold chain and refrigeration and has a two year shelf life. Lyophilsed ASV in powder form has 5 year shelf life and requires only to be kept cool.

ASV Administration Criteria;

ASV is a scarce, costly commodity and should only be administered only when there are definite signs of envenomation. Unbound, free flowing venom can only be neutralized when it is in the blood stream or in the tissue fluid.In addition; ASV carries risk of anaphylitic reactions ans should not therefore be used unnecessarily.

EVIDENCE OF SYSTEMIC ENVENOMATION

Evidence of coagulopathy; primarily detected by 20 minutes WBCT or visible spontaneous systemic bleeding from gums etc. Further lab tests for thrombocytopenia, hemoglobin abnormalities, PCV Perepheral Smear etc provide confirmation, but the 20 minute WBCT is of paramount importance.

Evidence of Neurotoxicity;Ptosis, External Ophthalmoplegia, inability to lift the head etc.

 Test Dose of ASV

Test dose has no predictive value in detecting anaphylactic or late serum sickness and should not be used. These reactions are not IgE mediated but compliment activated. They may also pre sensitise the patient and thereby create greater risk.

ASV Administration- Dosage-

Russels viper injects on an average 63 mg of venom.1ml of ASV neutralizes 0.6 mg of Russels Viper venom. So the total required dose will be between 10 vials [100mg] to 25 vials [250mg]. Not all victims will require 25 vials as very few are injected with a dose that is an outlier. However starting with 10 vials ensure that there is sufficient neutralizing power to neutralize any remaing free flowing venom.

 1ml of ASV neutralize ---0.6 mg of cobra venom

                                         0.45 mg of krait venom

                                         0.45 mg of saw scaled viper venom

Children; Children receive the same ASV DOSAGE AS ADULTS. The ASV is targeted at neutralizing the venom. Snakes inject the same amount of venom into adults and children.

Mode of Administration and Dosage; Initially 10 vials of ASV diluted in 100ml of isotonic saline or glucose or 5-10 ml / kg body wt of isotonic saline or glucose as an infusion.

 IV Injection – Reconstituted or Liquid ASV is administered by slow IV injection[2 ml/minute]

All ASV to be administered over 1 Hour at constant speed. The patient should be closely monitered for two hours.

NEUROTOXIC ENVENOMATION

The ASV regimen in neurotoxic bites has caused considerable confusion. Neostigmine test will be administered. Neostigmine is an anticholenestrase that prolongs the life of acetyle choline and can therefore reverse respiratory failure and neurotoxic symptoms. It is particularly effective for post synaptic neurotoxins such as those of cobra. There is some doubt   over the usefulness against the presynaptic neurotoxin such as those of krait and russels viper. However it is worth trying.

Neostigmine test;

This test involves the administration of 1.5 to 2 mg of neostigmine  I M together with 0.6 mg  of atropine I V . The pediatric neostigmine dose is 0.04 mg / kg bodywt. The patient should be closely observed for 1 hour to decide whether neostigmine is effective. The following measures are useful objective methods to asses this.

1.      single breath count

2.      mm of iris uncovered [ amount covered by the descending eye lid]

3.      Inter incisor distance [distance between upper and lower incisors]

4.      Length of time upwards gaze can be maintained.

5.      FEVi or FVC, if available

 If the victim responds to neostigmine test then continue with 0.5 mg of neostigmine IM half hourly plus 0.6 mg atropine IV for 5 doses and the 2 to 12 hourly according to recovery.   If there is no improvement in symptoms after 1 hr neostigmine should be stopped.

ASV Regimen in Neurotoxic Bite

Initial dose 10 vials in 100 ml of isotonic saline run over a period of 1 hr. If that is uncessful in reducing the symptoms, or if the symptoms have worsened, or if the patient has gone into respiratory failure, then further dose should be administered after 1-2 hours. This dose should be the same as initial dose. 20 vials is the maximum dose of ASV that should be given in neurotoxic envenomation. Once the patient is in respiratory failure, has received 20 vials of ASV and is supported on a ventilator, ASV therapy should be stopped. This recommendation is due to the assumption that all circulating venom would have been neutralized. By this time, Evidence suggests that reversibility of post synaptic neurotoxic envenomation is only possible in the first few hours. After that the body recovers using its own mechanisms.

ASV dosage in victims requiring life saving surgery.;

Before surgery can take place, coagulation must be restored in the victim in order to avoid catastrophic bleeding. In such cases a higher initial dose of ASV is justified. [ upto 25 vials] solely on the basis of guareenting a restoration of coagulation after 6 hrs

Snake bite in Pregnancy

            Pregnant women are treated exactly the same way as other victims

Victims who arrive late;

Perform a 20 minute WBCT and determine if any coagulopathy is present. If so administer ASV.

SURGICAL INTERVENTION

Faciotomy is required if the intracompartmental pressure is very high to cause blood vessels to collapse and lead to ischemia

Renal Failure and Cardiac Toxicity

 Managed on the merits of the cases

ASV Reactions

·         ASV discontinued temporarily

·         Adrenaline 0.5 mg 1:1000IM for adults. And 0.01 / kg BODY WT FOR CHILDREN

·         Inj Hydrocortisone 100 mg

·         Inj Antihistaminics

·         Drugs not to be used in viper bites- Heparin and Botropase



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