Crotaline envenomation: Difference between revisions

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==Crotaline (Pit Vipers)==
==Background==
===Background===
*The Crotalinae subfamily of Viperidae classifies the new world vipers, or ''pit vipers''. The snakes have a pitlike depression behind the nostril that contains a heat-sensing organ used to find prey.
*Includes rattlesnakes and copperheads
*Includes rattlesnakes and copperheads
*Venom causes local tissue injury, hemolysis, coagulopathy, neuromuscular dysfunction
*Venom causes local tissue injury, [[coagulopathy]],and [[thrombocytopenia]]
*Up to 25% of bites are dry bites
*Up to 25% of bites are dry bites


===Clinical Features===
===Common Crotaline (Pit Viper) snake names===
#Fang marks, localized pain, progressive edema extending from bite site
*Rattlesnake
##Edema near the airway or in muscle compartment may threaten life or limb
*Cottonmouth
#Nausea/vomiting, oral numbness/tingling, dizziness, muscle fasciculations
*Copperhead
#Ecchymoses may appear within minutes to hours
*Sidewinder
*Water moccasin
*Massasauga


===Diagnosis===
===Venom===
#Must have a snakebite + evidence of tissue injury:
*Venom form a Crotaline mainly damages local tissue via metalloproteinases and hyaluronidase which cause swelling edema and damage to capillaries.
##Local injury (swelling, pain, ecchymosis)
*Clinical effects consist of:
##Hematologic abnormality (thrombocytopenia, elevated INR, hypofibrinogenemia)
**Local tissue damage
##Systemic effects (oral swelling/paresthesias, metallic taste, hypotension, tachycardia)
**[[coagulopathy|Coagulopathies]] (pro and anti effects)
#Absence of all of the above 8-12hr after bite indicates dry bite
**[[thrombocytopenia|Platelet dysfunction]]
**Neurotoxic effects
 
[[File:Rattle snake.jpg|thumb|[[Rattlesnake]]]]
 
==Clinical Features==
*Fang marks, localized pain, progressive edema extending from bite site
*[[Nausea/vomiting]]
*Oral [[numbness]]/tingling
*[[Dizziness]]
*Muscle fasciculations
*Coagulopathy
**Ecchymoses may appear within minutes to hours
 
==Differential Diagnosis==
*[[Necrotizing fasciitis]]
*[[Cellulitis]]
*[[Allergic Reaction]]
 
{{Bites and stings DDX}}
 
==Evaluation==
*Local injury (pain, progressive swelling, [[compartment syndrome]], lymphangitic spread with pain in the axillae for upper extremity bites or pain in the inguinal region for lower extremity)
**Track progressive edema of the bitten extremity Q2H until progression stops
**Mark on the patient a point in the mid-foot, mid-calf, and mid-thigh (lower extremity bite) vs mid-hand, mid-forearm, and mid-humerus (upper extremity bites) to ensure consistency between measurements.
*Hematologic abnormality ([[thrombocytopenia]], prolonged PT, hypofibrinogenemia) - [[DIC]]-like syndrome
*Systemic effects ([[hypotension]] resulting from third spacing)


===Work-Up===
===Work-Up===
#CBC
*CBC
#Coags
*Coags
#Fibrinogen
*Fibrinogen
#FDP
*Chemistry
#Chemistry
 
==Management==
{{Snake bite local treatment}}
 
===Antivenom administration===
*See below


===Treatment===
===Supportive care===
#Local Care
*[[IVF]] and [[vasopressors]] if needed for hypotension
##Do not:
*Blood products rarely needed
###Attempt to suck out the venom
*Consider early intubation for head and neck envenomations. High risk for edema and airway compromise.
###Place the affected part in cold water
###Use a tourniquet or wrap
##Do:
###Immobilize limb in a neutral position
#Antivenom
##Crotalidae Polyvalent Immune Fab (FabAV)
##Indications:
###Progression of swelling
###Abnormal results on lab tests (plt < 100,000 or fibrinogen < 100)
###Systemic manifestations (unstable vitals or AMS)
##Administration
###The total volume but NOT the number of vials may be reduced in small children
###Establish initial control of envenomation by giving 4-6 vials
####Control achieved? (Cessation of progression of all components of envenomation, including labs checked 2 hours after infusion started)
#####If yes infuse 2-vial doses at 6, 12, and 18hr after initial control achieved
#####If no repeat infusion of 4-6 vials and then re-evaluate for control
##Envenomation control measurement
###Must observe for progression of envenomation during and after antivenom infusion
####Measure limb circumference at several site above and below bite
####Mark advancing border of edema q30min
####Repeat labs q4hr or after each course of antivenom (whichever is more frequent)
##Side Effects
###Acute reactions occur in <10% pts
###If occurs stop infusion and give antihistamines / epi if needed
##Recurrent thrombocytopenia has been described up to 2 weeks after transfusion with FabAV
###Likely result of isolated renal clearance of FabAV and persistent presence of actual venom in serum
###Only described in patients with history of thrombocytopenia during hospital course
###warrants close monitoring of platelets by PMD or return visit after discharge
#Supportive care
##IVF and pressors if needed for hypotension
##Blood component replacement indicated if antivenom fails to stop active bleeding
#Compartment Syndrome
##If signs of compartment syndrome are present and pressure >30:
###Elevate limb
###Administer additional FabAV 4-6 vials IV over 60min
###If elevated compartment pressure persists another 60min consider fasciotomy


===Disposition===
==Crotalidae Polyvalent Immune Fab (FabAV) Antivenin ([[Crofab]])==
#Must observe all snakebite pts for at least 8hr before determining patient disposition
===Indications===
##Bites that initially appear innocuous and labs normal at presentation can be deceptive
The following are criteria for administration after Crotalidae bite<ref>Crofab treatment agorithmn http://www.crofab.com/documents/CroFab-Treatment_Algorithm.pdf</ref>
#Discharge if symptom-free after 8hr
#Admit all pts receiving antivenom to the ICU
#Admit pts to the ward if have completed or do not require further antivenom therapy


==Coral Snakes==
*Progression of swelling
===Background===
*Abnormal results on lab tests (platelet < 100,000 or fibrinogen < 100)
#All coral snakes are brightly colored with black, red, and yellow rings
*Systemic manifestations (unstable vitals or altered mental status)
##Red and yellow rings touch in coral snakes, but are separated in nonpoisonous mimics
###"Red touch yellow, kills a fellow; red touch black, venom lack"


===Clinical Features===
{{Crofab dosing}}
#Local injury is often minimal
#Venom effects may develop hours after a bite


===Treatment===
==Crotalinae equine immune F(ab')2 antivenom ([[Anavip]])<ref>FDA Insert -ANAVIP https://www.fda.gov/media/92139/download</ref>==
#Antivenom
*Approved in 2015 for use in N. American pit viper envenomations.
##Give 3-5 vials of Antivenin to ALL pts who have definitely been bitten
*Similar treatment indications
###It may not be possible to prevent further effects or reverse effects once they develop
*Given as 10 vials IV
###Additional doses of antivenom are reserved for cases in which symptoms/signs appear
**Repeated Q1H as needed for initial control until local signs of envenomation are not progressing, systemic symptoms are resolved, and coagulation and other laboratory parameters have normalized or are trending toward normal.
#Monitor for respiratory respiratory failure
*4 Vials IV maintenance dosing PRN for recurrence of symptoms.
*Longer half life thought to reduce need for readministration and may reduce risk of recurrent subacute coagulopathy and bleeding vs Crofab <ref>Bush SP, Ruha AM, Seifert SA, et al. Comparison of F(ab')2 versus Fab antivenom for pit viper envenomation: a prospective, blinded, multicenter, randomized clinical trial. Clin Toxicol (Phila). 2015;53(1):37-45. doi:10.3109/15563650.2014.974263</ref>


===Disposition===
==Disposition==
#Admit all pts (even if initially symptom free)
*Observe all snakebite patients for at least 6hr before determining patient disposition
**Bites that initially appear innocuous and labs normal at presentation can be deceptive
*Discharge if symptom-free after 6hr
*Admit all patients receiving antivenom to the ICU


==Source==
==See Also==
Tintinalli
*[[Snake bites]]
*[[Envenomations, bites and stings]]
*[[Crotalidae polyvalent immune Fab (Crofab)]]


==References==
<references/>


[[Category:Environ]]
[[Category:Environmental]]
[[Category:Tox]]
[[Category:Toxicology]]

Latest revision as of 21:19, 2 August 2021

Background

  • The Crotalinae subfamily of Viperidae classifies the new world vipers, or pit vipers. The snakes have a pitlike depression behind the nostril that contains a heat-sensing organ used to find prey.
  • Includes rattlesnakes and copperheads
  • Venom causes local tissue injury, coagulopathy,and thrombocytopenia
  • Up to 25% of bites are dry bites

Common Crotaline (Pit Viper) snake names

  • Rattlesnake
  • Cottonmouth
  • Copperhead
  • Sidewinder
  • Water moccasin
  • Massasauga

Venom

  • Venom form a Crotaline mainly damages local tissue via metalloproteinases and hyaluronidase which cause swelling edema and damage to capillaries.
  • Clinical effects consist of:
Rattlesnake

Clinical Features

  • Fang marks, localized pain, progressive edema extending from bite site
  • Nausea/vomiting
  • Oral numbness/tingling
  • Dizziness
  • Muscle fasciculations
  • Coagulopathy
    • Ecchymoses may appear within minutes to hours

Differential Diagnosis

Envenomations, bites and stings

Evaluation

  • Local injury (pain, progressive swelling, compartment syndrome, lymphangitic spread with pain in the axillae for upper extremity bites or pain in the inguinal region for lower extremity)
    • Track progressive edema of the bitten extremity Q2H until progression stops
    • Mark on the patient a point in the mid-foot, mid-calf, and mid-thigh (lower extremity bite) vs mid-hand, mid-forearm, and mid-humerus (upper extremity bites) to ensure consistency between measurements.
  • Hematologic abnormality (thrombocytopenia, prolonged PT, hypofibrinogenemia) - DIC-like syndrome
  • Systemic effects (hypotension resulting from third spacing)

Work-Up

  • CBC
  • Coags
  • Fibrinogen
  • Chemistry

Management

Local Care

  • Do:
    • Remove all jewelry
    • Mark the leading edge of erythema/edema
  • Do not:
    • Attempt to suck out the venom
    • Place the affected part in cold water
    • Use a tourniquet or wrap
    • Antivenom is first line treatment for compartment syndrome; fasciotomy is last resort if elevated pressures persist.

Antivenom administration

  • See below

Supportive care

  • IVF and vasopressors if needed for hypotension
  • Blood products rarely needed
  • Consider early intubation for head and neck envenomations. High risk for edema and airway compromise.

Crotalidae Polyvalent Immune Fab (FabAV) Antivenin (Crofab)

Indications

The following are criteria for administration after Crotalidae bite[1]

  • Progression of swelling
  • Abnormal results on lab tests (platelet < 100,000 or fibrinogen < 100)
  • Systemic manifestations (unstable vitals or altered mental status)

Initial Administration

  • Initial dose: 6 vials[2]
  • Typically diluted into 250 cc or 1 L of normal saline and infused over an hour
  • Same dose for both adults and pediatrics (may have to adjust the dilution of CroFab for small children so that they are not volume overloaded)

Maintenance therapy

  • May repeat dose (2 vials) at 6, 12, and 18 hours later if symptoms not controlled[3]
    • Maintance therapy may be indicated after initial dosing based on local protocols even if control is achieved.[4]

Envenomation control measurement

  • Observe for progression of envenomation during and after antivenom infusion
  • Measure limb circumference at several sites above and below bite
  • Mark advancing border of edema q30min
  • Repeat labs q4hr or after each course of antivenom (whichever is more frequent)

Side Effects

  • Acute allergic reactions occur in <10% pts
    • If occurs stop infusion and give epinephrine/antihistamines if needed
  • Recurrent thrombocytopenia has been described up to 2 weeks after transfusion with FabAV and is likely a result of isolated renal clearance of FabAV and persistent presence of actual venom in serum.[5]
    • Warrants close monitoring of platelets by primary physician or return visit after discharge
  • Serum sickness is unlikely but precautions should be given to patents upon discharge

Crotalinae equine immune F(ab')2 antivenom (Anavip)[6]

  • Approved in 2015 for use in N. American pit viper envenomations.
  • Similar treatment indications
  • Given as 10 vials IV
    • Repeated Q1H as needed for initial control until local signs of envenomation are not progressing, systemic symptoms are resolved, and coagulation and other laboratory parameters have normalized or are trending toward normal.
  • 4 Vials IV maintenance dosing PRN for recurrence of symptoms.
  • Longer half life thought to reduce need for readministration and may reduce risk of recurrent subacute coagulopathy and bleeding vs Crofab [7]

Disposition

  • Observe all snakebite patients for at least 6hr before determining patient disposition
    • Bites that initially appear innocuous and labs normal at presentation can be deceptive
  • Discharge if symptom-free after 6hr
  • Admit all patients receiving antivenom to the ICU

See Also

References

  1. ↑ Crofab treatment agorithmn http://www.crofab.com/documents/CroFab-Treatment_Algorithm.pdf
  2. ↑ Gerardo CJ. The efficacy of crotalidea polyvalent immune fab (ovine) antivenom versus placebo plus optional rescue therapy on recovery from copperhead snake envenomation: A randomized, double-blind, placebo-controlled, clinical trial. Annals of EM. August 2017. 70(2):233-244.
  3. ↑ Gerardo CJ. The efficacy of crotalidea polyvalent immune fab (ovine) antivenom versus placebo plus optional rescue therapy on recovery from copperhead snake envenomation: A randomized, double-blind, placebo-controlled, clinical trial. Annals of EM. August 2017. 70(2):233-244.
  4. ↑ Crofab treatment agorithmn http://www.crofab.com/documents/CroFab-Treatment_Algorithm.pdf
  5. ↑ Ruha AM et al. Late hematologic toxicity following treatment of rattlesnake envenomation with crotalidae polyvalent immune Fab antivenom. Toxicon. 2011;57:53–59.
  6. ↑ FDA Insert -ANAVIP https://www.fda.gov/media/92139/download
  7. ↑ Bush SP, Ruha AM, Seifert SA, et al. Comparison of F(ab')2 versus Fab antivenom for pit viper envenomation: a prospective, blinded, multicenter, randomized clinical trial. Clin Toxicol (Phila). 2015;53(1):37-45. doi:10.3109/15563650.2014.974263
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