Snake EnvenomationMANAGEMENT

ENVIRONMENTAL AND EXPOSURE PRESENTATIONS · 12 SECTIONS

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596 items

☷ Legend

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Cardiovascular Presentations71▾

Respiratory Presentations52▾

Neurological Presentations83▾

Gastrointestinal Presentations74▾

Genitourinary and Reproductive Presentations48▾

Infectious Disease Presentations148▾

Trauma Presentations89▾

Toxicologic Presentations80▾

Psychiatric Presentations26▾

Musculoskeletal and Rheumatologic Presentations96▾

Dermatology Presentations23▾

Environmental and Exposure Presentations27▾

Acute Mountain Sickness Arterial Gas Embolism Bee-Wasp Sting (Anaphylaxis)Chilblains Ciguatera Fish Poisoning Coral Cut Decompression Sickness Electrical Burn Injury Envenomation (snake, spider, insect)High Altitude Cerebral Edema (HACE)High Altitude Pulmonary Edema (HAPE)High-altitude illness Hypothermia Hypothermia (Mild)Hypothermia (Severe)Immersion Foot Lightning Strike Injury Scombroid Fish Poisoning Scorpion Envenomation Sea Urchin Injury Shark Bite Snake Envenomation Spider Bite (Black Widow)Spider Bite (Brown Recluse)Stingray Spine Injury Tick paralysis White Phosphorus Burn

Hematologic and Oncologic Presentations36▾

Pediatric-Specific Presentations19▾

Endocrine and Metabolic Presentations45▾

ENT and Maxillofacial Presentations27▾

Ophthalmologic Presentations19▾

Obstetric Presentations23▾

Systemic and Miscellaneous Presentations17▾

01Approach to the Critical Patient/attcp49

Immediate Stabilization

›Airway and breathing priorities

›Airway compromise from head/neck envenomation

›Tongue and pharyngeal edema

›Early intubation before edema progresses

›Respiratory failure in neurotoxic envenomation

›Coral snake or Mojave rattlesnake species

›Mechanical ventilation for respiratory paralysis

›SpO2 target greater than 94%

›Supplemental oxygen for hypoxemia

›HFNC or NIV if inadequate oxygenation

›Circulatory stabilization

›Hypotension from systemic envenomation

›SBP less than 90 mmHg

›IV fluid resuscitation in unaffected extremity

›Distributive shock from venom-induced vasodilation

›Norepinephrine if fluid-refractory hypotension

›Target MAP greater than 65 mmHg

›Hemorrhagic shock from venom-induced consumption coagulopathy

›Antivenom is the primary treatment

›Blood products only concurrently with additional antivenom

Antivenom Administration

›Initiate antivenom as soon as envenomation is confirmed

›CroFab (ovine Fab) for crotaline envenomation

›Initial dose 4-6 vials IV over 60 minutes

›Repeat 4-6 vials if initial control not achieved

›Maintenance 2 vials every 6 hours for 3 doses (18 hours)

›Anavip (equine F(ab')2) alternative for crotaline envenomation

02History/hx69

Envenomation Event

›Bite circumstances

›Time of bite

›Delays greater than 6 hours increase severe systemic envenomation risk (LR 3.4)

›Document exact time for progression monitoring

›Snake identification

›Species, size, color, head shape

›Larger snakes associated with higher venom load (LR 3.1 for severe envenomation)

›Photograph if safely obtained

›Bite location

›Extremity versus trunk versus head versus neck

›Hand and face bites are higher risk

›Number of bites

›Whether snake was provoked

Symptom Progression

›Local symptoms after bite

›Pain at bite site

›Swelling progression

›Rate of spread beyond bite site

›Circumferential measurements trend

›Blistering or ecchymosis

›Paresthesias at bite site or spreading

›Systemic symptoms

›Nausea or vomiting

›Metallic taste (early systemic envenomation)

›Dizziness or syncope

›Diaphoresis

›Neurologic symptoms

03Physical Exam/exam52

Vital Signs

›Hemodynamic parameters

›Blood pressure

›Hypotension SBP less than 90 mmHg suggests systemic envenomation

›Heart rate

›Severe tachycardia HR greater than 150 suggests systemic envenomation

›Respiratory rate

›Tachypnea with respiratory distress

›Temperature

›Fever may indicate secondary infection

›Oxygen saturation

›Hypoxemia in respiratory compromise

Bite Site Assessment

›Local findings at wound

›Fang marks

›May be single, obscured by edema, or appear as abrasion

›Absence of fang marks does not exclude envenomation

›Erythema extent and borders

›Edema

›Mark leading edge with time stamp every 15-20 minutes

›Serial circumferential measurements at multiple points above and below bite

›Ecchymosis

›Blistering

›Serous versus hemorrhagic blisters

Neurologic Exam

›Cranial nerve assessment

›Ptosis (neurotoxic envenomation)

›Extraocular movement deficits

04Differential Diagnosis/ddx38

Venomous Animal Envenomation

›Pit viper species (crotalinae)

›Rattlesnake (Crotalus species) ICD-10 T63.011-T63.019

›Most common severe envenomation in North America

›Cytotoxic and hemotoxic venom

›Copperhead (Agkistrodon contortrix) ICD-10 T63.061-T63.069

›Less severe local tissue injury

›Rarely causes severe systemic envenomation

›Cottonmouth (Agkistrodon piscivorus) ICD-10 T63.061-T63.069

›Similar to copperhead in severity profile

›Coral snake (Micrurus species)

›ICD-10 T63.021-T63.029

›Neurotoxic venom primarily

›Minimal local findings, delayed neurologic presentation up to 12 hours

›Exotic or non-native snake species

›Requires Poison Control for antivenom sourcing

Non-venomous Bite Mimics

›Dry bite from venomous snake

›10-90% of bites by venomous snakes inject no venom

›Requires minimum 8-hour observation

›Non-venomous snakebite

›Local pain and puncture wounds without systemic features

›Insect or spider bite

›Brown recluse (necrotic wound) ICD-10 T63.331

›Black widow (systemic symptoms) ICD-10 T63.311

Infectious and Inflammatory Mimics

›Cellulitis or abscess

›Presenting late without witnessed bite

05Laboratory Tests/lt39

Initial Hematologic Panel

›Complete blood count

›Hemoglobin baseline and for hemorrhage monitoring

›Platelet count (thrombocytopenia in VICC)

›WBC for secondary infection

›Coagulation studies

›PT/INR

›Elevated in venom-induced consumption coagulopathy

›Repeat every 4-6 hours for minor, hourly after antivenom for moderate/severe

›aPTT

›Prolonged in fibrinogenolytic envenomation

›Fibrinogen

›Decreased in VICC

›Repeat at 2-3 days and 5-7 days after last antivenom dose for delayed coagulopathy

›D-dimer

›Elevated in fibrinolysis from venom

Metabolic and Organ Function

›Basic metabolic panel

›Renal function (venom-induced AKI)

›Creatinine and BUN

›Electrolytes

›Glucose

›Liver function tests

›Hepatic dysfunction from direct venom toxicity

›Creatine kinase

›Total CK for rhabdomyolysis

›Dark urine suggests significant myoglobinuria

›Urinalysis

06Diagnostic Tests/dt71

Scoring Systems

›Snakebite Severity Score (SSS)

›Six domains: pulmonary, cardiovascular, local wound, GI, hematologic, CNS

›Scoring categories

›No effect: score 0-1

›Mild: score 2

›Moderate: score 3-7

›Severe: score 8 or greater

›Performance characteristics

›Change of 1 point has 97% sensitivity and 81% specificity for detecting clinical worsening

›Developed as research tool with limitations for individual prognostication

›Unified Severity Grading

›Minimal severity

›Pain and swelling at bite site only

›No systemic signs

›Normal coagulation

›Moderate severity

›Swelling extending greater than 50 cm from trunk bite

›Nausea, vomiting, mild hypotension SBP greater than 90 mmHg, mild tachycardia HR 150 or less

›Coagulation may be abnormal without clinical bleeding

›Severe severity

›Swelling involving full extremity or airway threat

›Severe altered mental status, hypotension, tachycardia, respiratory insufficiency

›Abnormal coagulation with serious bleeding

›20-Minute Whole Blood Clotting Test (20WBCT)

›Bedside test for coagulopathy

›Particularly useful in resource-limited settings

›Positive if blood fails to clot within 20 minutes

07Disposition/dispo39

Admission Criteria

›ICU admission indications

›Severe envenomation with end-organ damage

›Hypotension or shock

›Respiratory failure or airway threat

›Neurologic compromise or seizures

›Severe coagulopathy with clinical bleeding

›Rhabdomyolysis with renal compromise

›Ward admission indications

›Moderate envenomation with progressive local findings

›Systemic symptoms requiring antivenom

›Any envenomation requiring antivenom administration

Observation Criteria

›Observation periods by severity

›Dry bite or no envenomation

›Minimum 8 hours observation

›Baseline labs and repeat before discharge

›Minor nonprogressive envenomation without systemic signs

›12-24 hours observation

›Labs every 4-6 hours and before discharge

›Coral snake bite

›Minimum 12-24 hours even if asymptomatic

›Delayed neurotoxicity can develop up to 12 hours post-bite

Transfer Criteria

›Transfer indications to higher level of care

›Antivenom not available at presenting facility

›Exotic or non-native snake requiring specialized antivenom

›Severity exceeding facility capability (ICU, mechanical ventilation)

08Treatment/t92

Prehospital Interventions

›Immediate scene actions

›Move patient away from the snake

›Photograph snake if safely possible for identification

›Do not attempt to capture or handle the snake

›Remove jewelry and constricting items

›Before edema prevents removal

›Loosely splint bitten extremity

›Immobilize at heart level

›Rapid transport via EMS to antivenom-capable facility

›Prehospital interventions to avoid

›Tourniquets

›Associated with OR 15.45 for amputation risk

›Suction devices

›Ineffective for venom removal

›Incision at bite site

›Causes additional tissue damage

›Ice or cold application

›Worsens vasoconstriction and tissue injury

›Electric shock treatment

›No evidence of benefit

Emergency Department Initial Management

›Immediate ED actions

›IV access in unaffected extremity

›Large-bore peripheral IV

›Continuous cardiac monitoring

›Clean wound

›Inspect for retained fangs

›Update tetanus prophylaxis as indicated

›Contact Poison Control 1-800-222-1222

Antivenom Therapy

›CroFab (crotalidae polyvalent immune Fab ovine)

›Initial control phase

›4-6 vials IV over 60 minutes minimum

›Repeat 4-6 vials if initial control not achieved after first dose

›Define initial control as arrest of swelling progression, improvement of systemic signs, normalization of coagulation

›Maintenance phase

›2 vials IV every 6 hours for 3 doses (18 hours total)

›Monitor for recurrent local tissue effects

›Pediatric dosing

›Same dose as adult; venom load is independent of body size

›Anavip (crotalidae immune F(ab')2 equine)

›Initial control phase

›10 vials IV over 60 minutes

›Repeat 10 vials as needed for uncontrolled envenomation

›Additional dosing

›4 vials for re-emerging symptoms

›Observation after administration

›Minimum 18 hours post-treatment

›Antivenom hypersensitivity management

›Epinephrine at bedside for anaphylaxis

›Epinephrine 0.3-0.5 mg IM for anaphylaxis

›Diphenhydramine 25-50 mg IV for urticaria or mild reactions

›Slow infusion rate for mild reactions and premedicate

Coagulopathy Management

›Venom-induced consumption coagulopathy (VICC)

›Antivenom is the primary treatment

›Does not administer blood products without concurrent additional antivenom

›FFP without antivenom adds substrate for unneutralized venom

›Fresh frozen plasma

›Only with concurrent additional antivenom if clinically needed

›Heparin

›Ineffective for VICC; contraindicated

›Antifibrinolytics

›Lack evidence of effectiveness as routine adjuncts

Compartment Syndrome Management

›Treatment algorithm

›Antivenom and elevation are first-line

›Antivenom reduces venom-mediated tissue injury

›Elevate bitten extremity

›Direct compartment pressure measurement

›Pressure greater than 30 mmHg is concerning

›Fasciotomy is last resort only

›Only if circulatory compromise persists despite antivenom

›Fasciotomy has not been shown to improve outcomes in snake envenomation

Neurotoxic Envenomation Management

›Coral snake and Mojave rattlesnake envenomation

›Airway management priority

›Early intubation before respiratory paralysis

›Mechanical ventilation for respiratory failure

›Anticholinesterase agents

›Neostigmine may be effective for post-synaptic neurotoxicity in some elapid bites

›Consult toxicology before use

›Coral snake antivenom (Micrurus fulvius)

›Contact Poison Control for availability (limited supply)

Supportive Care

›Pain management

›Acetaminophen 500-1000 mg PO every 6 hours

›Opioids as needed

›Avoid if neurotoxic envenomation suspected (masks neurologic signs)

›Avoid NSAIDs and aspirin (worsen coagulopathy)

›Wound care

›Clean wound thoroughly

›Elevate bitten extremity

›Prophylactic antibiotics not recommended

›Use only with clinical or microbiologic evidence of infection or necrosis

›IV fluid resuscitation

›Aggressive hydration with rhabdomyolysis

›Target urine output greater than 0.5 mL/kg/hour for myoglobinuria

09Special Populations/sp43

Pregnancy

›Physiologic considerations

›Fetal loss risk is highest when bite occurs before 20 weeks gestation

›Antivenom indications are the same as in non-pregnant patients

›Do not withhold antivenom; untreated envenomation poses greater risk than antivenom

›Hemodynamic changes in pregnancy

›Physiologic hypotension of pregnancy may complicate severity assessment

›Aortocaval compression in supine position

›Management modifications

›Obstetric consultation for all pregnant patients with envenomation

›Fetal monitoring throughout observation period

›Left lateral decubitus positioning for hemodynamically unstable patients

›Earlier threshold for antivenom administration given fetal risk

›Coagulopathy concerns

›Pre-existing hypercoagulable state of pregnancy

›VICC may be more difficult to assess against pregnancy baseline

Geriatric

›Physiologic considerations

›Cardiovascular comorbidities reduce tolerance for hemodynamic instability

›Baseline renal dysfunction increases AKI risk

›Polypharmacy

›Anticoagulant or antiplatelet agents increase hemorrhagic risk

›Beta-blockers may mask tachycardia response

›Management modifications

›Lower threshold for ICU admission

›More aggressive monitoring of renal function

›Careful fluid resuscitation to avoid volume overload

›Antivenom dose not modified based on age

10Background/b57

Epidemiology

›Incidence and burden

›Approximately 7,500-10,000 venomous snakebites occur annually in the United States

›More than 95% caused by crotaline pit vipers

›Rattlesnakes

›Copperheads

›Cottonmouths

›Small minority caused by coral snakes (Elapidae)

›Globally: 1.8-2.7 million envenomations per year with 81,000-138,000 deaths (WHO)

›Demographics and risk

›Spring, summer, and early fall peak incidence

›Rural settings, hiking, gardening, agricultural work

›Males more commonly bitten than females

›Significant proportion from intentional snake handling

›Severity distribution

›Pooled prevalence of severe systemic envenomation approximately 14%

›Severe tissue injury approximately 14%

›Severe hematologic effects approximately 18%

›Mortality is low in North America with appropriate antivenom treatment

Pathophysiology

›Crotaline venom mechanism

›Cytotoxic components

›Phospholipases, proteases, and hyaluronidase cause local tissue destruction

›Progressive edema from direct tissue injury and increased vascular permeability

›Hemotoxic components

›Thrombin-like enzymes cleave fibrinogen causing fibrinogen depletion

›Factor X activation and consumption of coagulation factors

›Thrombocytopenia from platelet aggregation and destruction

11Patient Discharge Instructions/pdi32

copy discharge instructions

›Discharge information for snake envenomation

›Activity restrictions

›Avoid contact sports for at least 2 weeks

›Avoid dental extractions, tattoos, piercings, and elective surgery for at least 2 weeks

›Gradual return to normal activities as swelling and pain improve

›Wound care at home

›Keep bite area clean and dry

›Watch wound for signs of infection: increasing redness, warmth, pus, fever

›Follow up for wound checks especially if necrosis was present

›Medication instructions

›Acetaminophen for pain as needed

›Avoid ibuprofen, aspirin, and blood thinners unless directed by physician

›Complete any prescribed medications (tetanus, antibiotics if given)

›Follow-up blood tests

›Blood tests required at 2-3 days and 5-7 days after last antivenom dose

›Tests check for delayed blood clotting problems

›Do not miss these appointments even if feeling well

›Watch for serum sickness (7-21 days after antivenom)

›Fever, joint pain, rash, or swollen lymph nodes

›Return to emergency department or call physician

›Expected recovery

›Local swelling may take days to weeks to fully resolve

›Early rehabilitation helps minimize residual disability

›Full recovery expected for most mild to moderate envenomation

›Return to emergency department immediately for

›Worsening or spreading swelling

›New bleeding from gums, urine, or stool

12References/r15

Guidelines and Key Sources

›Primary references for snake envenomation management

›Lieu K, Livshits Z, LeSaint KT. Venomous Snakes and Snakebites. JAMA. 2025

›Seifert SA, Armitage JO, Sanchez EE. Snake Envenomation. N Engl J Med. 2022

›Gold BS, Dart RC, Barish RA. Bites of Venomous Snakes. N Engl J Med. 2002

›Gerardo CJ et al. Does This Patient Have a Severe Snake Envenomation? JAMA Surgery. 2019

›Kanaan NC et al. Wilderness Medical Society Practice Guidelines for Pitviper Envenomations. Wilderness Environ Med. 2015

›Warrell DA, Williams DJ. Clinical Aspects of Snakebite Envenoming. Lancet. 2023

›Hewett Brumberg EK et al. 2024 AHA and American Red Cross Guidelines for First Aid. Circulation. 2024

›Fu G, He F, Xiong K. Predictors and Nomogram for Amputation Risk in Pit Viper Snakebite. Scientific Reports. 2025

FDA Drug Labels

›Antivenom regulatory sources

›CroFab FDA Drug Label. Food and Drug Administration. Updated 2018

›Crotalidae polyvalent immune Fab (ovine) dosing and safety

›Anavip FDA Drug Label. Food and Drug Administration. Updated 2015

›Crotalidae immune F(ab')2 (equine) dosing and safety

›Arthur Chang and Michael Yeh. Poisonings, Envenomations, and Toxic Exposures During Travel. CDC Yellow Book. 2025

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Reviewed by SymptomDx Medical Team · Last reviewed August 18, 2026

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