Exam 4 - Envenomation Flashcards
what snakes are included in crotalids (pit vipers) that are venomous in the united states? what about elapidae?
crotalids
1. copperheads
2. cottonmouths (water moccasin)
3. rattlesnakes
elapidae
1. coral snakes
2. cobras
what do venomous snakes look like?
head is distinctly triangular when viewed from above
elliptical pupils
pits & nostrils are present
undivided scales on the underside of the tail (except for northern copperhead - ends in a rattle)
what 2 pit vipers have this distribution?
copperheads & timber rattlesnake
what pit viper has this distribution?
western diamondback
what pit viper has this distribution?
cottonmouth
what pit viper has this distribution?
mojave rattlesnake
what is the largest group of venomous snakes?
pit vipers
when do we see the most snake bites from pit vipers?
april-october & snakes are most active around dusk
how many pit viper snake bites are seen annually?
150,000
what are the primary functions of pit viper venom?
immobilize, digest, & kill
from most venomous to least, rank the pit vipers
rattlesnake > cottonmouth > copperhead
what are the snake factors of venom?
amount injected, multiple bites, agonal bites, & age of snake
what are the patient factors in regards to snake venom?
size of the patient, location of the bite, time to presentation, & physical activity
what local effects are seen with snake bites? these signs are most common with what pit vipers?
rapid swelling, pain, edema, bruising, & necrosis
copperheads & cottonmouths
what systemic effects are seen with snake bites? these signs are most common with what pit viper?
hypotension, coagulopathies, petechiae, weakness, cyanosis, altered mentation, convulsions, lymphadenopathy
rattlesnakes
what are the proteolytic enzymes in venom?
hydrolases, hyaluronidase, thrombin-like enzymes, collagenase, phospholipase A2
what neurotoxin is apart of venom?
mojave toxin
what renal effects are seen with envenomation?
myoglobinuria & hypovolemia
what coagulopathy effects are seen with envenomation?
thrombin like enzymes have anticoagulant properties, fibrinolytic products, platelet adhesion & aggregation, & destruction of megakaryocytes
what may be seen on a blood smear of a dog bitten by a pit viper?
echinocytes
what red cell morphology is seen in this smear? what is it supportive of?
echinocytes - envenomation
what effect does venom have on endothelial cells?
polypeptides cause direct damage & inflammation & extravasation
what may be seen on a CBC in a patient that was bit by a pit viper?
echinocytes, thrombocytopenia, leukocytosis, hypoproteinemia, & increased PCV
what is the snake bite minimum database?
electrolytes, kidney values, blood smear for RBC morphology & platelet count, PT/PTT
what may be seen on urinalysis in a patient that was bit by a pit viper?
hemoglobinuria & myoglobinuria
what may be seen on a chem panel in a patient that was bit by a pit viper?
hypokalemia, increased CK, & azotemia
what is the treatment for snake bite envenomation?
no prophylactic antibiotics
clip, clean, & dry bite
pain meds - opioids
IVF
why are steroids contraindicated for envenomation patients?
risks for complications - shock
increase risk of secondary infection
worsen outcomes in human studies
why not use frozen plasma or fresh frozen plasma for envenomation patients?
the venom inhibits any therapeutic effects to treat the coagulopathy
what are some indications for antivenin administration?
coagulopathy, shock, neurologic signs, or life threatening swelling
how do you administer antivenin?
reconstitute & give IV ASAP for best concentration at the site - dilute it in 100-200ml 0.9% saline given over 1-4 hours & monitor like a transfusion
typically 1-2 vials given to effect for reversal of shock, coagulopathy, neuro signs, & swelling
T/F: the dose of antivenin is related to the amount of venom, not the size of the patient, so repeat dosing may be needed
true
what do you do if you have a patient that has an anaphylactic (type I hypersensitivity) reaction to the antivenin?
epinephrine & IV fluids - animal may have had previous exposure
what clinical signs may be seen if you have a patient that has a serum sickness (type III hypersensitivity) reaction to the antivenin?
polyarthritis, myositis, vasculitis, glomerulonephritis, fever - delayed by 2-4 weeks
what are some contraindicated first aid treatments commonly used for envenomation?
oral suction, incising fang marks, ice or heat, tourniquet, constriction bands, or electrocution
what snake has this distribution?
coral snakes
what does the venom of the coral snake cause?
neurotoxin that causes flaccid paralysis - potential for ventilatory failure within 4 hours
what is the treatment for envenomation by a coral snake?
supportive care, ventilation for respiratory failure, & hospitalize for 24-48 hours for monitoring
why hospitalize an asymptomatic patient bitten by a coral snake?
clinical signs can be delayed up to 12 hours but will be progressive & there is no antivenin available
what kind of snake is this?
king snake - red & black bands touch each other
what kind of snake is this?
coral snake - yellow bands touch the red
what evil thing has this distribution?
brown recluse
what is the major problem in brown recluse venom?
sphingomyelinase D
what is the treatment for a brown recluse bite?
supportive care & wound management - culture the wound
antivenin - not widely available, administer within 1 hour
tetracyclines - apply topically, inhibits MMPs
what is the major venom component that black widows have? what does it do?
alpha-latrotoxin
stimulates release of neurotransmitters from axon terminals leading to an eventual blockade & clinical signs developing within 8 hours
what are the hallmark clinical signs of a black widow bite?
abdominal rigidity!!!! muscle spasms & tremors
paralysis in cats
what is the treatment used for black widow bites?
antivenin, calcium gluconate, muscle relaxants, & opioids
