In severe snakebites antisera to the venom can be used. However, since serious immune reactions may occur, the antivenom should only be used when clearly indicated.
Indications for Antivenom Use
Severe Local Envenomation:
(1) venom known to induce tissue necrosis (vipers, African spitting cobras, Asian cobras)
(2) swelling spreading to involve more than half of the bitten limb
(3) rapidly progressive local swelling
(4) bites involving fingers and into other tight fascial compartments (anterior tibial compartment, etc.)
Systemic Envenomation:
(1) hypotension or shock unresponsive to symptomatic treatment
(2) cardiac arrhythmias, ECG abnormalities
(3) neurotoxic signs: ptosis, ophthalmoplegia, bulbar or respiratory paralysis
(4) impaired consciousness of any cause, including respiratory or circulatory failure
(5) coagulopathy, with spontaneous systemic bleeding or excessive bleeding from new and old wounds
(6) rhabdomyolysis (dark urine, tender and stuff muscles, elevated CK)
(7) severe leukocytosis (> 20,000 per µL)
(8) protracted gastrointestinal symptoms
(9) severe acidosis
(10) hemolytic anemia
Patients at risk:
(1) small children
(2) pregnant women
Antivenom Administration
Antivenoms available are hyperimmune immunoglobulin concentrates, usually prepared from horses or sheep
Selection of antivenom:
(1) If the snake responsible is identified, then an appropriate mono-specific or polyspecific antivenom should be used.
(2) If the snake is unknown or uncertain, then a polyspecific antivenom covering the medically important species in the geographic area should be used.
(3) If the patient is known to be sensitive to a given antivenom preparation, then an alternative formulation should be sought.
Complications in the use of antivenom:
(1) allergic reactions
(2) anaphylactic reaction
(3) serum sickness 5-10 days after administration
Dosing:
(1) The initial depends on the particular antivenom used, the species of snake, and the severity of the envenomation.
(2) Dosing may be repeated every 6 hours if symptoms persist or additional ones appear.
Administration:
(1) The antivenom should be given as a slow intravenous injection or infusion.
(2) Patients may be predosed with antihistamines and corticosteroids to reduce allergic reactions.
(3) Epinephrine and equipment to handle an anaphylactic reactions should be immediately available.
