5 Snakebites Flashcards
3 major groups of venomous snakes
Viperidae (includes the crotaline snakes - pit vipers)
Elapidae (coral snakes)
Colubridae (colubrid snakes)
pathophysiology of crotaline venom
crotaline snakes = pit vipers
1.) quickly alters blood vessel permeability –> loss of plasma and blood –> hypovolemia
2.) activates and consumes fibrinogen and platelets –> coagulopathy
3.) in some species, specific venom fractions block neuromuscular transmission, which leads to cranial nerve weakness (e.g. ptosis), respiratory failure, and altered sensorium
remarks regarding dry bites
Up to 25% of crotaline snakebites are dry bites: venom effects do not develop
Absence of local injury, hematologic abnormality, or systemic effects for a period of 8-12 hours following the bite indicates a dry bite
cardinal manifestations of crotaline envenomation
presence of one or more fang marks
localized pain
progressive edema extending from the bite site
systemic effects of crotaline envenomation
tachypnea, tachycardia, hypotension, altered level of consciousness
oral swelling or paresthesia
metallic or rubbery taste in mouth
recommended first aid measures for snakebites
1.) Retreat well beyond striking range
2.) Remain calm (Movement will increase venom absorption)
3.) Immobilize the extremity in a neutral position below the level of heart
4.) Ensure prompt transport to a medical facility whether or not there are signs of envenomation
5.) Constriction bands can be applied if there is no nearby medical facility
Other remarks on first aid on snakebites
First aid measures should never substitute for definitive medical care or delay the administration of antivenom.
Avoid dangerous first aid treatments such as suction and incision
Do not use tourniquets because they obstruct arterial flow and cause ischemia.
Remarks on constriction bands
A constriction band can delay venom absorption without causing increased swelling.
Do NOT remove tourniquets or constriction bands until antivenom is available, except where there is clear arterial vascular compromise threatening limb viability; in this latter situation, anticipate possible rapid development of systemic envenomation upon removal
How to apply constriction bands
Piece of clothing or the like wrapped circumferentially above the bite and applied with enough tension to restrict superficial venous and lymphatic flow while maintaining distal pulses and capillary filling.
Apply the band snugly but loose enough to avoid arterial compromise. It should be easy to insert one or two fingers under the band.
remarks on pressure immobilizaiton
In distinction to a constriction band, a pressure immobilization bandage is a compression pad placed over the bite site combined with a snug elastic bandage wrap and extremity immobilization.
This technique is recommended for coral snake and other elapid snake bites, but is generally discouraged for crotaline bites because it may increase pain at the site
mainstay of therapy for venomous snakebites
antivenom
Administer antivenom IV to establish “initial control”
Initial control is cessation of progression of 3 clinical evaluation parameters:
1.) local effects
2.) systemic effects
3.) hematologic effects
It is crucial to document initial control because the most common error in management is insufficient dosing early in treatment
remarks on administering antivenom
Do not inject antivenom IM or directly into a digit, because venom-induced hypovolemia may retard absorption of antivenom.
“The package insert is useful as a guide for antivenom preparation”
Give antivenom in a critical care facility such as an ED or ICU, under direct physician supervision, and with resuscitative drugs (including epinephrine and equipment available
General strategy for administration of antivenom for pit viper envenomation
1.) Administer if there’s indication
2.) Establish initial control of envenomation by administering 4-6 vials of FabAV
3.) if initial control is not achieved, repeat step 2
4.) if initial control is achieved, infuse additional 2-vial doses at 6, 12, and 18 hours thereafter
Management of compartment syndrome caused by crotaline snake envenomation
1.) determine intracompartmental pressure.
2.) if pressure is not elevated, continue standard management.
3.) If signs of compartment syndrome are present and compartment pressure is >30 mm Hg:
» elevated limb
» administer mannitol, 1-2 g/kg IV over 30 mins
» simultaneously adminsiter additional antivenom over 60 mins
4.) If elevated compartment pressure persists another 60 mins, consider fasciotomy
remarks on local edema
Measure limb circumference at several sites above and below the bite, and outline the advancing border of edema with a pen every 30 minutes
These measures serve as an index of the progression as well as a guide for antivenom administration.
