About This Page
This is a clinician-written, evidence-based summary aligned to the USMLE Step 2 CK Content Outline. It is intended for medical students preparing for USMLE Step 2 CK. Management reflects current ACC/AHA, USPSTF, and APA guidelines. Always cross-reference with UpToDate, institutional protocols, and clinical judgment.
Key points
- US venomous snakes include pit vipers (rattlesnakes, copperheads, cottonmouths) and coral snakes.
- Pit viper envenomation: progressive pain, swelling, ecchymosis, tissue injury, thrombocytopenia, hypofibrinogenemia, systemic symptoms.
- Coral snake envenomation can cause delayed neurotoxicity and respiratory failure with minimal local injury.
- Do not cut, suck, ice, apply electric shock, or use tight tourniquets.
- Antivenom is indicated for progressive local injury, systemic toxicity, hematologic toxicity, or neurotoxicity.
Overview
Venomous bite or sting causing local tissue injury, coagulopathy, neurotoxicity, or systemic toxicity requiring supportive care and antivenom when indicated. Emergency management focuses on early recognition, stabilization, targeted investigation, and prompt definitive therapy while avoiding common pitfalls tested on USMLE Step 2 CK.
Epidemiology
This presentation is encountered in emergency and acute care settings. Risk varies by exposure, comorbidity, age, mechanism, and timeliness of treatment. Morbidity and mortality increase when recognition is delayed or when airway, breathing, circulation, antidotal therapy, or definitive source control is postponed.
Clinical Features
Symptoms
Immediate pain, swelling, bruising, paresthesia, or metallic taste after pit viper bite
Progressive swelling crossing a major joint or rapidly expanding local injury
Nausea, vomiting, weakness, dizziness, syncope, hypotension, or bleeding
Coral snake: minimal pain/swelling initially but later diplopia, dysarthria, dysphagia, weakness, respiratory failure
History of attempting tourniquet, incision, suction, or ice may worsen injury
Signs
Fang marks, edema, ecchymosis, bullae, tenderness, lymphangitis
Hypotension, angioedema, bronchospasm, or urticaria suggesting anaphylaxis or systemic venom effect
Bleeding from gums/wounds, petechiae, thrombocytopenia, or hypofibrinogenemia
Compartment syndrome is rare and should not be diagnosed by swelling alone
Neuromuscular weakness after coral snake exposure is a respiratory emergency
Investigations
First-line
Serial wound measurementsMark leading edge of swelling every 15-30 minutes initially; track progression and neurovascular status.
CBC, PT/INR, fibrinogen, plateletsDetect venom-induced coagulopathy and thrombocytopenia.
BMP, CK, urinalysisAssess renal function, rhabdomyolysis, hematuria/myoglobinuria, and electrolyte abnormalities.
Second-line
Type and screenIf significant coagulopathy, bleeding, or severe envenomation.
ECG and monitoringIf systemic symptoms, electrolyte abnormalities, shock, or severe envenomation.
Compartment pressure measurementOnly if true compartment syndrome suspected after antivenom and surgical consultation.
Specialist
Poison center / medical toxicology consultationRecommended for all venomous snakebites to guide antivenom selection, dosing, monitoring, and disposition.
1
Field and initial care
- Move patient away from snake; keep limb at heart level and minimize exertion.
- Remove rings, watches, and constrictive clothing.
- Do not apply ice, incision, suction, electric shock, alcohol, or tight tourniquet.
- Immobilize limb and transport promptly; do not attempt to capture snake.
- Treat airway, breathing, circulation; give tetanus prophylaxis and analgesia.
2
Antivenom indications
- Progressive swelling or local tissue injury.
- Systemic signs: hypotension, vomiting, neurotoxicity, angioedema, severe pain, or shock.
- Hematologic toxicity: thrombocytopenia, elevated PT/INR, low fibrinogen, or clinically significant bleeding.
- Initial control usually requires repeated antivenom dosing until progression stops and labs stabilize.
3
Supportive care
- Opioid analgesia as needed; avoid NSAIDs if coagulopathy risk.
- Avoid prophylactic antibiotics unless infection, gross contamination, or special circumstance.
- Serial labs after antivenom because recurrent coagulopathy can occur.
- Observe dry bites with normal labs/exam for an appropriate period before discharge.
4
Special situations
- Coral snake bite requires prolonged observation and respiratory monitoring because paralysis can be delayed.
- Anaphylaxis to antivenom: treat with epinephrine and supportive care.
- Fasciotomy is rarely needed and should generally follow antivenom and measured compartment pressure confirmation.
Complications
- Coagulopathy: Thrombocytopenia and hypofibrinogenemia may recur after initial control
- Local tissue necrosis: Severe pit viper injury can cause long-term functional impairment
- Respiratory failure: Coral snake neurotoxicity can produce delayed paralysis
- Anaphylaxis: May occur from venom itself or antivenom
- Compartment syndrome: Rare but limb-threatening; swelling alone is not diagnostic
USMLE Step 2 CK Exam Tips
- 1Snakebite field treatment: immobilize and transport — no cutting, suction, ice, or tight tourniquet.
- 2Pit viper = local swelling/ecchymosis + coagulopathy.
- 3Coral snake = neurotoxicity with minimal local findings; monitor respirations.
- 4Antivenom is for progressive local injury, systemic toxicity, coagulopathy, or neurotoxicity.
- 5Do not give NSAIDs when coagulopathy is possible.
- 6Compartment syndrome after snakebite is rare; give antivenom first and measure pressures if suspected.
Put your reading into practice
Topic-specific question practice is not linked for this article yet.
Choose USMLE Step 2 CK questions from the existing bank. General exam practice covers your selected topics; it is not filtered to this article. Your usual question-bank access applies.
Choose USMLE Step 2 CK practiceAfter your session, return to this section to revisit the reading and choose your next review.
Verified Sources & References
related resources
Save your place and choose what comes next
Emergency Medicine · Article 15 of 18