COW

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G. Patrick Daubert 
KPNC Regional Toxicology Service
Kaiser Permanente
South Sacramento Medical Center

 

51-year-old man presents to the ED after being bit by a snake.  Apparently, he handles snakes as a hobby.  He tells you (with a tear in his eye) the snake is a 9-foot long, female Bushmaster.  He was feeding the snake a rat when it apparently bit him on the dorsum of the right hand.  He tried to drive himself to the hospital but had to pull off of the road because he was concerned that he may crash his car.  He is complaining of some numbness and tingling in the hand and a “funny” sensation around his mouth.  The patient has pain and swelling of his right hand.  He is right handed.  He tells you he had a snakebite about 30 years ago and was treated with antivenom and reportedly had a “minor” reaction at that time.

PMHx/SurgHx: None

Allergies: None

Meds: None

Soc.  He has a history of alcoholism but has not had any alcohol to drink for the past five to six years. He denies tobacco use and does not have any history of any illicit or intravenous drug use.  The man apparently is a neuropsychologist (with reptiles as a hobby).

vs.  T37.7 BP168/119 RR16 HR131

MUSCULOSKELETAL:   He has intact distal pulses. There is significant swelling of the dorsum of his right hand, and there is evidence of a singular wound which is approximately 4 to 5 mm in length over the dorsum of his right hand.  The other extremities have no evidence of any swelling or deformity.

SKIN:  He has a very slight amount of erythema over his abdominal wall and slightly over his forehead, but there is no distinct urticaria. There are no vesicles or pustules, no ulcerations, or any other lesions noted on his skin.  There are no petechiae or ecchymoses noted.  A right femoral central venous line in his right inguinal region was started and there is evidence of some oozing of blood from the insertion site

  1. What is a Bushmaster snake and what is it doing in Michigan?  What type of venom does this snake possess?
  2. How would you initially manage this case?  Based on this envenomization, what labs do you order?
  3. What antivenomn do you use for this snake?  How do you dose/administer antivenom?  What types of antivenom do you commonly have in the ED?  Where do you find more or exotic antivenom?

a) First set of labs come back

b) Na 144, K 3.5, Cl 112, HCO3 23, BUN 21, Cr 1.5, Ca 8.6

c) WBC 28.6, Hb 17.6, Plt 324

d) PT/PTT/INR 22.3/26/2.06, D-dimer 92, Fibrinogen < 50

  1. Does the history of a previous snakebite and treatment of concern?
  2. This patient came back to the hospital (today as a matter of fact) complaining of not feeling well, general body aches, and dark urine.  What illness has he now developed and why?
  3. There are generally two classes of poisonous snakes in the U.S.  What are they and what is the typical clinical picture for each?
  4. When your friend Roger calls you from Joshua Tree in California on his mobile phone stating that he was just bit by a rattlesnake, what first-aid measures do you immediately recommend?
  5. Name the 5 T’s associated with snakebites.

Answers & Discussion

  1. What is a Bushmaster snake and what is it doing in Michigan?  What type of venom does this snake possess?

COW-1Bushmaster (Lachesis muta) is the largest pit viper, up to 3.6 m and is found in southern Central America and northern South America.  Bushmaster bites are rare (we had two of these in as many months this fall), but the case fatality rate is high.  Bushmasters are native to southern Central America and almost all the northern half of South America.  This snake’s venom is not as potent as other related species.  However, bushmasters produce an enormous amount of venom. The average yield of dried venom from a bushmaster is 411 mg (0.014 oz), compared to just 52 mg (0.0018 oz) from the copperhead.

  1. How would you initially manage this case?  Based on this envenomization, what labs do you order?

There are several initial concerns with snakebites (besides acute death) that need to be on your radar screen.  Patients may initially develop an anaphylactic reaction to the snakebite causing immediate airway compromise and hypotension.  We have seen significant facial/oral edema in our two bushmaster snakebite cases.  The second main concern is, of course, the effects of the snake’s venom. 

Venom is very complex with a multitude of components.  The venom from the bushmaster is primarily hemorrhagic.  One portion of the bushmaster’s hemorrhagic venom is LHF-I.  Lachesis Hemorrhagic Factor I (LHF-I) is a glycoprotein that hydrolyzes the alpha-chain of fibrinogen (greater than the beta-chain) and hydrolyzes selectively the alpha-chain of fibrin, leaving the other chains unaffected.  This, of course, leads to a significant coagulopathy.  In fact, the first patient we had, his blood wouldn’t clot on any of the DMC machines.  We were using a stopwatch to time the coagulation times and dosing antivenom accordingly.

The labs in this case need to focus on the coagulation cascade.  A CBC, coag profile, fibrin, fibrinogen, and D-dimer are needed.  Electrolytes and a urine analysis will also help in the initial management.  Local wound care is important here is well.  Localized edema occurs early and may be rapid.  The affected limb should have areas marked to measure sequential circumferences.  For instance, this patient was bit on the hand.  We marked off zones with a marker at the hand, forearm, elbow, and upper arm to measure circumferences every 15-30 minutes.  An advanced edge of swelling should also be marked.  Continued swelling is an indicator of the need for more antivenom.  A compartment syndrome may develop.  If this occurs, the limb should be elevated and more antivenom administered.  Please try and keep the surgeons away from this until your medical management is exhausted (including mannitol).  Tetanus immunization should be updated based on the patient’s history.

  1. What antivenomn do you use for this snake?  How do you dose/administer antivenom?  What types of antivenom do you commonly have in the ED?  Where do you find more or exotic antivenom?

Many emergency departments will stock either Wyeth [Antivenin (Crotalidae) Polyvalent (ACP) (horse)] or CroFab® [Crotalidae PolyvalentImmune Fab (sheep)] antivenom, but many do not.  The resources for finding antivenom are twofold.  Call the poison center or call the Zoo.   Poison centers will help you track down the antivenom you need.  Most zoos have snakes and therefore are required to have antivenom.  In this case, we tracked down antivenom through the Detroit, Toledo, Cincinnati, and Kentucky zoos.  We used these sources to track down Lachesis antivenom from Costa Rica.  Cool.

It is common in the literature to see skin testing recommended before the use of equine-based antivenom.  However, skin testing has no predictive value. A negative skin test does not guarantee lack of hypersensitivity; conversely, a positive skin test does not predict the development of an acute reaction.  In summary, don’t worry about doing it.  If a reaction occurs during antivenom administration, stop the infusion (early reactions usually result from too rapid an infusion rate). After administration of epinephrine, H1 and H2 blockers, and isotonic fluids, the antivenom can be further diluted and the infusion resumed at a slower

rate.

    1. First set of labs come back
    2. Na 144, K 3.5, Cl 112, HCO3 23, BUN 21, Cr 1.5, Ca 8.6
    3. WBC 28.6, Hb 17.6, Plt 324
    4. PT/PTT/INR 22.3/26/2.06, D-dimer 92, Fibrinogen < 50

Due to our previous experience and in knowing the snake, we felt that Wyeth (ACP) was our best bet for the bushmaster until we could get the Lachesis antivenom.  In general, patients who have minimal envenomation require no antivenom, moderate cases usually require 10 to 15 vials (100–150 mL) of ACP initially, and severe cases at least 15 vials (150 mL). Patients who have profound circulatory collapse should receive 20 vials (200 mL) initially (CroFab is dosed as 6 vials initially).  Reconstituted ACP antivenom should be diluted in 250 to 1000 mL of normal saline or 5% dextrose in water and given by IV drip, slowly, at 50 to 75 mL/hour for the first 10 minutes.  If no reaction occurs, the remainder can be infused over 1 hour.  Antivenom should never be injected into the finger or toe.  The need for additional antivenom doses should be guided by monitoring for progression of local, systemic, or coagulopathic abnormalities. If local findings, other signs, or laboratory test results progress, the initial dose of antivenom is repeated every 1 to 2 hours.

  1. Does the history of a previous snakebite and treatment of concern?

Absolutely!  This should prompt you to have epinephrine, H1 and H2 blockers, and steroids at the ready.  Close monitoring is essential as this patient may develop a life threatening hypersensitivity reaction.

  1. This patient came back to the hospital (today as a matter of fact) complaining of not feeling well, general body aches, and dark urine.  What illness has he now developed and why?

This is serum sickness.  Roughly every vial of antivenom administered increases your risk of serum sickness by 10%.  So, once you get 10 vials you are going to inevitably develop serum sickness.  As you may recall, serum sickness is a type III hypersensitivity reaction usually appearing 5-14 days after administration of an allergen.  It is characterized by fever, arthralgias, skin rash and lymphadenopathy.  Treatment should begin in the hospital with a 3-week course of tapering steroids.  Otherwise, the treatment is supportive with diphenhydramine and prednisone.  Symptoms usually resolve in a few weeks.

  1. There are generally two classes of poisonous snakes in the U.S.  What are they and what is the typical clinical picture for each?

Only 25 of the more than 120 species of snakes indigenous to the United States are venomous. The majority of these snakes belong to the subfamily Crotalinae (pit vipers: rattlesnakes, cottonmouths, and copperheads). The coral snake (Elapidae) is the only other native venomous snake. At least one species of indigenous poisonous snake has been identified in every state except Alaska, Maine, and Hawaii.

  1. When your friend Roger calls you from Joshua Tree in California on his mobile phone stating that he was just bit by a rattlesnake, what first-aid measures do you immediately recommend?

Place him at rest, reassure him, and keep Roger warm, and then get Roger to the nearest medical facility as soon as possible. The injured area should be immobilized in a functional position below the level of the heart. All rings, watches, and constrictive clothing should be removed.  Previously recommended first aid measures involving the use of tourniquets, incision and suction, cryotherapy, and electric shock therapy are strongly discouraged.  The Sawyer snakebite extractor on the market doesn’t work.  It has been proven more than once that is doesn’t extract any significant amount of venom.  Tell Roger to throw it away.

  1. Name the 5 T’s associated with snakebites.

He has all his Teeth, no Tattoos, was not inToxicated, apparently does not own a Truck, and of course, is a male and therefore has Testaterone.  This list is provided as a summary of the 5 T’s of snake bites – typically people are missing teeth, have tattoos, are intoxicated and own a truck.  Most are male.  Yet, another reason why women are smarter then men.

7 Responses

  1. A little more involved than the usual multiple choice questions, but here it goes… 🙂

    1. I think it’s a pit viper, and it’s probably in Michigan because somebody brought it here. It’s a long way form home.

    2. The usual but especially coags/DIC labs. Maybe also myoglobin. In terms of initial management, get help from your friendly toxicologist.

    3. I don’t know, but I bet the Poison Center could tell me. I know for the Western Diamondback we used CroFab. The local EDs likely stock only a little bit of antivenom for the primary indigenous snakes–or none at all. At least in Denver, the zoo had access to more exotic antivenom.

    4.Yes– the risk of anaphylaxis with antivenom is higher

    5. Rhabdo (from the bite) or maybe serum sickness (from the antivenom)

    6. Pit vipers (pretty wide geographic distribution)–tissue necrosis and coagulopathy and coral snakes (mostly southern US)–neuromuscular blockade

    7. Call for help and immobilize the extremity. No ice! (Not that he is likely to have a bunch of ice in the middle of Joshua Tree)

    8. I give up. Is one “toxicologist?” 🙂

  2. 1. The Bushmaster is a Pit Viper from South America. Some people own them as pets. There aren’t any laws against owing them as pets but many communities have ordinances against possessing venomous snakes. The bushmaster possesses a hemotoxic venom that destroys RBCs and causes a DIC-like response.
    2. Apply a compression dressing proximal to the puncture wound (s). Apply a Sawyer Pump extractor (suction) over the puncture site if one is available. Intradermal skin testing with the antivenom serum. A CBC, BMP, PT/INR, aPTT, D-dimer, and fibrinogen should be ordered.
    3. Wyeth Crotalidae Polyvalent intravenously at a rate of 1 vial (10cc) every 5-10 minutes until reaction subsides (20-40 vials). Mixture of 5 vials per 50cc of LR. Monovalent and divalent antivenom serums are the two types however most EDs do not stock them. They are dispatched from the Florida Antivenom Bank unless local Zoos have the serum. This can be checked using AZA (Association of Zoo’s and Aquariums).
    4. If the patient had an allergic reaction to the first antivenom serum, he/she should be pretreated with 125mg Solution-Medrol and have Benadryl and Epinephrine ready if anaphylaxis ensues.
    5. Most likely serum sickness as he had an allergic reaction the first time therefore would not be as delayed of a response the second time.
    6. Pit Viper and Coral Snake. They both have similar long term effect however the Coral Snake bite is often painless at first whereas Pit Viper bites are immediately painful. A bite from a Coral Snake can take several hours to manifest symptoms.
    7. Don’t panic! Chill out. Place a splint around the affected limb to reduced the amount of movement. Immediate transport to medical center is appropriate. Call ahead to expedite the availability of the antivenin..
    8. Toothlessness, Tattoos, Truck, inToxicated, Testosterone

    This might have been the worst one yet!! We should get credit for 5 hours of lecture for this one alone!!

  3. wow, ummm.
    1 crotalid, here because someone needs a better hobby? hemotoxin?
    2 xray to r/o retained tooth and pain control, admit. Monitor the limb, compartment syndrome is expected but does not classically respond well to fasciotomy but should be considered, CBC, lytes, coags, DIC workup = fibrinogen/ddimer
    3 crofab, IV. I doubt we have crofab in the ED, but the zoo is my 2nd call after tox.
    4 I’d like to know what the “minor reaction” is, but most antivenim is made in horse or something non-human so this could be a reaction to the horse antigen. We’d have to monitor the crofab administration for allergic rxn.
    5: serum sickness! 2nd time seeing serum from i think horses or rabbits or whatever, now hes got a memory response from immune system and his antibodies complex with crofab and create type 3 autoimmune syndrome with complex deposition in capillary beds
    6: hemotoxin: DIC picture with large area of tissue destruction.
    Neurotoxin: parasthesia/paralysis
    7: get away from snake, take a picture of it for ID if you can. No tourniquet as this is not a neurotoxic snake and don’t cut and suck the venom out. take off jewlery and watches. Go to ER
    8: trauma, terrible bleeding, terrible compartment syndrome, thrombocytopenia, tingling lips?

  4. I don’t know much of anything about snakes, but based on my reading and pearls from tox…
    1. Bushmaster=pit viper, Lachesis if you want to get fancy, with hemotoxic venom. Many people (illegally) own exotic snakes but sadly many dont’t own the antivenom.
    2. Start with the basics: ABCs, Start IV, put on monitor. Give tetanus and fentanyl (for pain) and apply constricting band to stop venom spread if <30 min After a good history and physical, especially of neuro system, measure circumference and provide local wound care. Important labs are CBC, UA, PT/PTT, chem7, fibrinogen & fibrin split products, CPK and type and screen or type and cross.
    3. Ideally, you use CroFab, dosed based on severity and give more based on symptoms. You reconstitute powder in fluids and give each vial over 20 min. Officially even the poison center doesn't have Wyeth antivenom since according to the bottle it's expired, though Rosen's says your ED is more likely to have this than CroFab. You probably won't have that snake's antivenom on hand unless you have a responsible owner who had purchased the antivenom for his snake. If you need more, the zoo may help you depending on the species, (though they don't legally have to they usually will), or the poison center can contact other zoos or private collectors (the latter who for a price can get you antivenom).
    4. Yes, there is an allergic component to your reaction and a previous bite likely indicates sensitization.
    5. Sounds like DIC; because the toxin effects coagulation.
    6. Hemotoxic (Crotalidae) & neurotoxic (Elapidae). Hemotoxic are painful, cause tissue breakdown and inflammation and interrupts clotting. Neurotoxic interfere with propagation of nerve signals potentially causing systems to fail (eg respiratory failure, cardiac failure etc). Most snake's venomn is a combo of both.
    7. A. Get snake detached if currently attached
    B. Calm Roger down, immobilize area and do pressure dressing that doesn't cut off arterial flow.
    C. ID snake if possible, if can bring dead snake, great; don't mess with if still alive
    D. Get EMS or get to hospital ASAP
    E. DON'T incise at all
    8. I found the 7 T's of a victim profile: Tattoos, Testerone, Tequila, T-shirt, Truck, Teasing snake, Teeth missing

  5. 1. Bushmaster snake-largest pit viper in the world. Type of venomous snake from central /South America . Snake either found as Zoo or. Purchased from exotic pet dealer. Venom is haemotoxic, crotaline venom
    2. Initially, ABC,IV, o2 monitor. Immediate fluid resuscitation with isotonic fluids. Watch for hypovolemia and coagulopathy. Send CBC, coags, fibrinogen, lytes, ECG, abg

    3. Anti venom- crotalidae polyvalent immune tab. Admin 4-6 vials initially then additional 2 vials at 6, 12, 18 hrs. If need more all local zoo.

    4. No

    5. Rhabdomyalisis 2/2 venom, muscle breakdown, myotoxins

    6. Pit vipers- crotaline, hypovolemia, coagulopathy, local site injury
    Coral snakes- elapidae, neurotoxin, no local injury, delayed onset

    7. Retreat, remain calm, immobilize extremity in neutral position below heart. Prompt transport to medical facility. Constriction band only if transport is long. No tourniquets.

    8. Toothlessness, tattoos, pickup truck, intoxicated, testicles

  6. 1) pitviper, crotaline venom
    2) Place arm in splint in full extension and elevate to avoid dependent edema, tetanus prophylaxis, pain control, Labs = CBC, BMP, UA, BUN, Cr, PT, PTT, fibrinogen.
    3) Crofab, start with 4-6 vials. Each vial of crofab is reconstituted in 10 mL of sterile saline. Mix 4-5 reconstituted vials with 250 cc .9 NaCl and infuse over 1 hour. Once intial control established, start maintenance infusion of 2 vials every 6 hours x 3 doses. I’d contact poison control for suggestions on where to get antivenom. The local zoo most likely carries antivenom for snakes.
    4) You should use CroFab instead of the equine derived crotaline polyvalent antivenom.
    5) rhadomyolysis
    6) Crotaline and Elapidae. Crotaline typically get more severe local reaction. Non specific weakness, malaise, nausea, and restlessness. Can delevelop tachycardia, hypotension, metallic taste, diarrhea. Rarely can cause DIC and multiorgan failure. Elapidae – little local reaction. Delayed systemc effects, paralysis and pulmonary aspiration requiring ventilator support.
    7) immobilize patients arm and have them rapidly transported to hospital. Avoid physical activity like walking because it can hasten systemic absorption of venom.
    8) 5T –

  7. 1. bushmaster is found in americas usually southern, he brought it here.it is a pitviper, it is a hemotoxic venom
    2.Coags DIC pannel- LDH fibrinogen ddimer, cbc
    3.Crofab 4-6 vials in 250cc saline slow over 10 min and continue for 1hr.
    repeat 2X this dose.
    then 2 vials in 250cc at 6 ,12,18 hour we have equine antivenon and possibly crofab.

    4.yes because he might have been treated with same antibodies
    5.serum sickness possibly due to antivenom
    6. coral snakes – systemic cardiotoxic, pit vipers- hemotoxic localized
    7. extremity below heart with pressure dressings and get away from snake. dont try to suck out poison.
    8. actually 7 taught to us in tox : tattoos , teeth missing, tequilla, testosterone (men), t-shirt , teasing, truck driving —in reference to those who get bitten by snakes

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