---

Snake Bites: Classification, Clinical Features & Management

1. Identifying Venomous vs. Non-Venomous Snakes

---

2. Classification of Venomous Snakes

By Family

Medically Important Species by Region

---

3. Types of Venom and Mechanisms

Neurotoxic Venom (Elapidae, Hydrophidae)

• Acts via d-tubocurarine-like neuromuscular blockade causing flaccid paralysis
• Primary toxicity to respiratory and cardiac centers
• Rich in cholinesterase; little/no proteolytic activity
• Examples: cobras, kraits, coral snakes, sea snakes

Vasculotoxic/Hemotoxic Venom (Viperidae/Crotalidae)

• Causes intravascular hemolysis, coagulopathy, thrombocytopenia
• Contains proteases (Russell's viper activates the clotting cascade via two proteases)
• Rich in hyaluronidase, L-amino acid oxidase, hemorrhagins
• Examples: Russell's viper, puff adder, rattlesnakes

Myotoxic Venom (Sea snakes)

• Causes rhabdomyolysis and myoglobinuria
• Can lead to acute kidney injury
• Venom travels via lymphatics and superficial veins

Cytotoxic Venom

• Local tissue destruction, necrosis
• Examples: Spitting cobras, some rattlesnakes (cottonmouth, copperhead)

Key note: Up to 25% of crotaline bites are "dry bites" - no venom is injected. Most snake bites overall are from non-venomous snakes, and even in venomous bites, inadequate venom is injected in >50% of cases. - Tintinalli's Emergency Medicine

---

4. Clinical Features by Snake Type

Symptoms at a Glance

Crotaline (Pit Viper) Bite

• Local: Fang marks, immediate pain, progressive edema (within 15-30 min), ecchymosis, hemorrhagic blebs
• Systemic: Nausea/vomiting, weakness, oral numbness/tingling, metallic taste, tachycardia, hypotension, coagulopathy (elevated PT, hypofibrinogenemia, thrombocytopenia)
• Edema can involve an entire limb within 1 hour in severe cases
• Angioedema may occur rapidly

Elapid (Cobra/Krait/Mamba) Bite

• Cobra bite: Small red/blue wheal at site with burning pain; minimal local swelling; systemic onset ~30 min - ptosis (first sign), ophthalmoplegia, progressive flaccid paralysis (legs → trunk → respiratory muscles → death)
• Krait bite: Often painless, no local swelling; profound drowsiness and intoxication; albuminuria
• Coral snake: Neurologic dysfunction only - no significant local injury; effects may be delayed hours
• Spitting cobra: Venom ophthalmia (eye pain, corneal injury, temporary blindness) if spit in eyes

Russell's Viper/Saw-scaled Viper Bite

• Severe pain within 8 minutes, red/painful area
• Blisters appear at ~12 hours, progressing to whole limb
• Persistent bleeding from bite site
• Spontaneous systemic bleeding (gums, nose, skin)
• DIC, acute kidney injury

Malayan Pit Viper / Viperidae Local Effects

Sea Snake Bite

• Bite is initially painless (wading fishermen may not notice)
• Severe myalgia develops within 2-3 hours
• Myoglobinuria, elevated creatine kinase
• Neurotoxic symptoms (flaccid paralysis, respiratory failure)
• If no symptoms by 6-8 hours, envenomation unlikely

---

5. General Management

Step 1: First Aid (Pre-hospital)

• Reassure and calm the patient (fear alone can mimic envenomation)
• Immobilize the bitten limb below heart level (splint/sling)
• Transport quickly and passively to hospital
• Remove rings, watches, tight clothing from bitten limb
• Establish IV access in the contralateral limb
• Administer oxygen en route
• For elapid/sea snake bites only: apply pressure immobilization bandage (elastic bandage from bite site proximally + splint)

• Cut or incise the wound
• Apply suction (Sawyer extractor ineffective and potentially harmful)
• Apply ice or immerse in cold water (worsens injury)
• Apply electric shock
• Use tourniquets for viper/crotaline bites (causes ischemia)
• Give alcohol or herbal remedies
• Try to catch/handle the snake (photograph only if safe)

Step 2: Hospital Assessment

• Fang marks, wound site edema, ecchymosis, bullae
• Ptosis (earliest sign of neurotoxic envenomation)
• Respiratory muscle strength (inability to raise head from supine = imminent respiratory failure)
• Gingival/nasal bleeding, spontaneous systemic hemorrhage
• Regional lymphadenopathy

• CBC, platelet count
• INR/prothrombin time, PTT, fibrinogen
• Serum electrolytes, glucose, BUN, creatinine
• Creatine kinase
• Fibrin degradation products
• ABG (if respiratory compromise)
• ECG (patients >50 or cardiac history)
• Urinalysis (myoglobinuria in sea snake bites)

---

6. Specific Treatment: Antivenom

Indications for Antivenom

• Hypotension, shock, cardiovascular toxicity
• Neurotoxicity (ptosis, paralysis, respiratory compromise)
• Spontaneous systemic bleeding
• Non-clotting blood (DIC)
• Rhabdomyolysis
• Local envenomation: swelling >50% of bitten limb, rapid progression, digit bite

Antivenom Types

FabAV Dosing Protocol

• Initial: 4-6 vials of FabAV to establish "initial control" (cessation of progression of local, systemic, and hematologic effects)
• If initial control achieved: additional 2-vial maintenance doses at 6, 12, and 18 hours
• If initial control NOT achieved: repeat the 4-6 vial dose
• Dilute in crystalloid and infuse over 1 hour IV
• Children require the same number of vials as adults (the venom dose is the same regardless of victim size; only reduce total volume)
• Initial dose of most antivenoms = minimum 5 × 10 mL ampoules
• For procoagulant venoms: repeat initial dose every 6 hours until blood coagulability is restored

Antivenom Reactions

Pre-treatment skin or conjunctival tests are of no predictive value and should not be used. - Pye's Surgical Handicraft

---

7. Specific Antidotes and Supportive Measures

Neurotoxic (Elapid) Bites

• Neostigmine test: 1.5-2 mg neostigmine IM (with atropine 0.6 mg) - may produce dramatic reversal of paralysis in post-synaptic neurotoxins (cobra); does not work on pre-synaptic toxins (mamba, krait, taipan)
• Endotracheal intubation + mechanical ventilation for respiratory failure
• Prolonged ventilatory support may be needed (days to weeks for kraits)
• Baseline and serial pulmonary function (inspiratory pressure, vital capacity) for coral snake bites

Hemotoxic (Viper) Bites

• IV crystalloids for hypovolemia (up to 1/3 blood volume may extravasate)
• Whole blood clotting test (WBCT) every 6 hours to monitor DIC
• Avoid heparin unless indicated
• Fresh frozen plasma or cryoprecipitate if needed

Sea Snake Bites

• Pressure immobilization (elastic bandage)
• Monitor renal, metabolic, and respiratory functions in ICU
• Dialysis if acute kidney injury develops

Surgical Aspects

• Fasciotomy: Only for confirmed compartment syndrome with measured pressures >30-40 mmHg (not routine)
• Debridement of necrotic tissue
• Split-skin grafting for large necrotic areas
• Amputation in very severe irreversible cases

---

8. Prevention

• Wear boots and long trousers in endemic areas
• Do not handle snakes
• Sleep on raised beds (krait bites often occur at night while sleeping on the ground)
• Seek immediate medical care after any bite - even if initially asymptomatic (effects can be delayed hours)
• Snake bite incidence peaks during rice planting/harvesting seasons in Southeast Asia

---

Quick Reference Summary Table

---

• Tintinalli's Emergency Medicine: A Comprehensive Study Guide, Chapters 212 & 213
• Pye's Surgical Handicraft (22nd ed.), Chapter 28
• The Essentials of Forensic Medicine and Toxicology (36th ed.)
• Mulholland and Greenfield's Surgery (7th ed.)

---

Snake Bites: Classification, Clinical Features & Management

1. Identifying Venomous vs. Non-Venomous Snakes

---

2. Classification of Venomous Snakes

By Family

Medically Important Species by Region

---

3. Types of Venom and Mechanisms

Neurotoxic Venom (Elapidae, Hydrophidae)

• Acts via d-tubocurarine-like neuromuscular blockade causing flaccid paralysis
• Primary toxicity to respiratory and cardiac centers
• Rich in cholinesterase; little/no proteolytic activity
• Examples: cobras, kraits, coral snakes, sea snakes

Vasculotoxic/Hemotoxic Venom (Viperidae/Crotalidae)

• Causes intravascular hemolysis, coagulopathy, thrombocytopenia
• Contains proteases (Russell's viper activates the clotting cascade via two proteases)
• Rich in hyaluronidase, L-amino acid oxidase, hemorrhagins
• Examples: Russell's viper, puff adder, rattlesnakes

Myotoxic Venom (Sea snakes)

• Causes rhabdomyolysis and myoglobinuria
• Can lead to acute kidney injury
• Venom travels via lymphatics and superficial veins

Cytotoxic Venom

• Local tissue destruction and necrosis
• Examples: Spitting cobras, some rattlesnakes (cottonmouth, copperhead)

Key note: Up to 25% of crotaline bites are "dry bites" - no venom is injected. Most snake bites overall are from non-venomous snakes, and even in venomous bites, inadequate venom is injected in >50% of cases. - Tintinalli's Emergency Medicine

---

4. Clinical Features by Snake Type

Symptoms at a Glance

Crotaline (Pit Viper) Bite

• Local: Fang marks, immediate pain, progressive edema (within 15-30 min), ecchymosis, hemorrhagic blebs
• Systemic: Nausea/vomiting, weakness, oral numbness/tingling, metallic taste, tachycardia, hypotension, coagulopathy (elevated PT, hypofibrinogenemia, thrombocytopenia)
• Edema can involve an entire limb within 1 hour in severe cases
• Angioedema may occur rapidly

Elapid (Cobra/Krait/Mamba) Bite

• Cobra bite: Small red/blue wheal at site with burning pain; minimal local swelling; systemic onset ~30 min - ptosis (first sign), ophthalmoplegia, progressive flaccid paralysis (legs → trunk → respiratory muscles → death)
• Krait bite: Often painless, no local swelling; profound drowsiness and intoxication; albuminuria
• Coral snake: Neurologic dysfunction only - no significant local injury; effects may be delayed hours
• Spitting cobra: Venom ophthalmia (eye pain, corneal injury, temporary blindness) if spit into eyes

Russell's Viper / Saw-scaled Viper Bite

• Severe pain within 8 minutes, red/painful area
• Blisters appear at ~12 hours, progressing to whole limb
• Persistent bleeding from bite site
• Spontaneous systemic bleeding (gums, nose, skin)
• DIC, acute kidney injury

Viperidae Local Effects

Sea Snake Bite

• Bite is initially painless (wading fishermen may not notice)
• Severe myalgia develops within 2-3 hours
• Myoglobinuria, elevated creatine kinase
• Neurotoxic symptoms (flaccid paralysis, respiratory failure)
• If no symptoms by 6-8 hours, envenomation unlikely

---

5. General Management

Step 1: First Aid (Pre-hospital)

• Reassure and calm the patient (fear alone can mimic envenomation)
• Immobilize the bitten limb below heart level (splint/sling)
• Transport quickly and passively to hospital
• Remove rings, watches, tight clothing from bitten limb
• Establish IV access in the contralateral limb
• Administer oxygen en route
• For elapid/sea snake bites only: apply pressure immobilization bandage (elastic bandage from bite site proximally + splint)

• Cut or incise the wound
• Apply suction (ineffective and potentially harmful)
• Apply ice or immerse in cold water (worsens injury)
• Apply electric shock
• Use tourniquets for viper/crotaline bites (causes ischemia)
• Give alcohol or herbal remedies
• Try to catch/handle the snake (photograph only if safe)

Step 2: Hospital Assessment

• Fang marks, wound site edema, ecchymosis, bullae
• Ptosis (earliest sign of neurotoxic envenomation)
• Respiratory muscle strength (inability to raise head from supine = imminent respiratory failure)
• Gingival/nasal bleeding, spontaneous systemic hemorrhage
• Regional lymphadenopathy

• CBC, platelet count
• INR/prothrombin time, PTT, fibrinogen
• Serum electrolytes, glucose, BUN, creatinine
• Creatine kinase
• Fibrin degradation products
• ABG (if respiratory compromise)
• ECG (patients >50 or cardiac history)
• Urinalysis (myoglobinuria in sea snake bites)

---

6. Specific Treatment: Antivenom

Indications for Antivenom

• Hypotension, shock, cardiovascular toxicity
• Neurotoxicity (ptosis, paralysis, respiratory compromise)
• Spontaneous systemic bleeding
• Non-clotting blood (DIC)
• Rhabdomyolysis
• Local envenomation: swelling >50% of bitten limb, rapid progression, digit bite

Antivenom Types

FabAV Dosing Protocol

• Initial: 4-6 vials of FabAV to establish "initial control" (cessation of progression of local, systemic, and hematologic effects)
• If initial control achieved: additional 2-vial maintenance doses at 6, 12, and 18 hours
• If initial control NOT achieved: repeat the 4-6 vial dose
• Dilute in crystalloid and infuse over 1 hour IV
• Children require the same number of vials as adults (only reduce total infusion volume if needed)
• Initial dose for most antivenoms = minimum 5 × 10 mL ampoules
• For procoagulant venoms: repeat initial dose every 6 hours until blood coagulability is restored

Antivenom Reactions

Pre-treatment skin or conjunctival tests are of no predictive value and should not be used. - Pye's Surgical Handicraft

---

7. Specific and Supportive Measures

Neurotoxic (Elapid) Bites

• Neostigmine test: 1.5-2 mg neostigmine IM (with atropine 0.6 mg) - may dramatically reverse paralysis for post-synaptic neurotoxins (cobra); does not work on pre-synaptic toxins (mamba, krait, taipan)
• Endotracheal intubation + mechanical ventilation for respiratory failure
• Prolonged ventilatory support may be needed (days to weeks for kraits)
• Serial pulmonary function monitoring (inspiratory pressure, vital capacity) for coral snake bites

Hemotoxic (Viper) Bites

• IV crystalloids for hypovolemia (up to 1/3 of circulating blood volume may extravasate into swollen limb)
• Whole blood clotting test (WBCT) every 6 hours to monitor DIC
• Fresh frozen plasma or cryoprecipitate if indicated
• Avoid heparin unless specifically indicated

Sea Snake Bites

• Pressure immobilization (elastic bandage)
• ICU monitoring of renal, metabolic, and respiratory functions
• Dialysis if acute kidney injury develops

Surgical Aspects

• Fasciotomy: Only for confirmed compartment syndrome with measured pressures >30-40 mmHg - not routine
• Debridement of necrotic tissue
• Split-skin grafting for large necrotic areas
• Amputation in very severe irreversible cases

---

8. Quick Reference Summary

---

• Tintinalli's Emergency Medicine: A Comprehensive Study Guide, Chapters 212 & 213
• Pye's Surgical Handicraft (22nd ed.), Chapter 28
• The Essentials of Forensic Medicine and Toxicology (36th ed.)
• Mulholland and Greenfield's Surgery (7th ed.)

• 5 embedded clinical images from the medical textbooks (pit viper head anatomy, Malayan pit viper bite necrosis, gum bleeding from Echis envenomation, venomous vs. non-venomous comparison diagram, and the FabAV antivenom dosing flowchart)
• All classification, venom mechanism, clinical feature, and management tables
• Color-coded DO / DO NOT first aid table
• Antivenom types, dosing protocol, and reaction management
• Quick reference summary table at the end
• Sources listed at the bottom

---

Marrow App

What Exams It Covers

• NEET PG / NExT (primary focus)
• FMGE (Foreign Medical Graduate Exam / MCI Screening)
• INI-CET (AIIMS, JIPMER, PGI, NIMHANS)
• NEET SS (Superspecialty - Medicine, Surgery, Paediatrics)
• USMLE (some content)
• MBBS First Year subjects (newer addition)

Key Features

What Makes It Unique

• All content is peer-reviewed and referenced against the latest standard textbooks
• MCQs and videos are designed so you understand concepts before memorizing facts
• Faculty includes some of India's most respected teachers across all subjects (Dr. Rebecca James for Biochemistry, Dr. Ravi Raj for Anatomy, Dr. Krishna Kumar for Physiology, etc.)
• Simulates the real exam environment closely

Who Uses It

Platforms

---