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🐍 SNAKEBITE - Complete PSM Exam Notes

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1. INTRODUCTION (1-2 lines for intro paragraph)

• Snakebite is an acute, life-threatening, time-limiting medical emergency
• WHO estimates: 5.4 million bites/year worldwide, 1.8-2.7 million envenomations, 81,000-1,38,000 deaths/year
• India is the world's snakebite capital - highest burden globally
• Around 70% of all snakebites are from NON-venomous snakes (dry bites)

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2. THE "BIG FOUR" SNAKES OF INDIA

Memory trick: "Come Kill Russell's Saw" = Cobra, Krait, Russell's, Saw-scaled

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3. TWO MAIN TYPES OF SNAKE FAMILIES

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4. TYPES OF SNAKEBITE PRESENTATION

A) Dry Bite

• Bite from venomous snake but NO venom injected
• ~70% of all bites are non-venomous/dry bites
• Patient may show anxiety symptoms only (palpitations, sweating, tachycardia - these are NOT envenomation)

B) Venomous Bite - 4 Main Clinical Syndromes

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5. NEUROPARALYTIC SYMPTOMS - "5D + 2P" (MOST IMPORTANT!)

5 D's:

1. Dyspnea (difficulty breathing)
2. Dysphonia (voice becomes soft/less pitch)
3. Dysarthria (speech difficulty)
4. Diplopia (double vision)
5. Dysphagia (difficulty swallowing)

2 P's:

1. Ptosis (drooping of eyelids - appears FIRST)
2. Paralysis

• Cobra bite: symptoms in 30 min - 6 hours
• Krait bite: symptoms in 6 - 24 hours (ptosis even up to 36 hours!)

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6. VASCULOTOXIC/HAEMOTOXIC SYMPTOMS

• Bleeding from gums, nose, bite site, eyes
• Hematuria (blood in urine)
• Incoagulable blood (most important sign)
• Hypotension, shock
• Renal failure

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7. KEY DIAGNOSTIC TEST - 20 WBCT (20-Minute Whole Blood Clotting Test)

1. Take 2 ml of blood in a clean, dry glass tube (not plastic)
2. Leave it undisturbed for 20 minutes
3. Tilt the tube at 20 minutes

• Blood does NOT clot in 20 min = Viper bite (vasculotoxic) - give ASV
• Blood clots normally = No vasculotoxic envenomation

This test is a BEDSIDE test - cheap, simple, no lab required. Perfect for rural/PHC settings!

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8. FIRST AID - DO's and DON'Ts

DO's:

• Reassure the patient (most bites are non-venomous)
• Immobilize the bitten limb (keep below heart level)
• Remove rings, bangles, tight clothing near bite site
• Transport immediately to hospital
• Mark the swelling edge with pen and note time

DON'Ts (FORBIDDEN - Very important in exam!):

• Do NOT cut and suck the wound
• Do NOT apply tourniquet (causes more necrosis and ischemia)
• Do NOT apply ice
• Do NOT give electric shock
• Do NOT give aspirin (worsens bleeding)
• Do NOT try to kill or catch the snake (risk of second bite)

Pressure immobilization bandage - used ONLY for neurotoxic (elapid) bites in Australia/specialized settings; NOT recommended routinely in India

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9. TREATMENT - ANTI-SNAKE VENOM (ASV)

What is ASV?

• Made from horse/sheep plasma hyperimmunized with snake venom
• Indian polyvalent ASV covers the Big Four snakes
• It is an immunoglobulin (F(ab')2 fragments of IgG)
• It is the ONLY specific antidote for snake venom

Indications for ASV (give if ANY ONE present):

1. Abnormal 20WBCT (blood not clotting)
2. Spontaneous bleeding
3. Signs of neuroparalysis (ptosis, paralysis, etc.)
4. Hypotension/shock
5. Renal failure
6. Myoglobinuria (cola-colored urine)
7. Rapidly spreading local swelling

ASV Dose (Indian Polyvalent):

How to give ASV:

• Always IV route (slow infusion over 1 hour) - NEVER IM injection
• Dilute in normal saline (250-500 ml)
• Keep adrenaline ready before infusion (for anaphylaxis)

Repeat ASV if:

• Blood still incoagulable (20WBCT positive) after 6 hours
• Bleeding continues after 1-2 hours
• Neurological signs worsen after 1 hour

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10. SUPPORTIVE TREATMENT

• Give neostigmine 0.5-2.5mg IV + atropine 0.6mg IV
• If ptosis improves = neurotoxin is post-synaptic (Cobra) - neostigmine helps
• Krait has pre-synaptic toxin - neostigmine usually does NOT help

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11. PSM-SPECIFIC POINTS

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12. QUICK SUMMARY TABLE FOR REVISION

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13. MNEMONICS SUMMARY

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14. ONE-LINE FACTS FOR MCQ/SHORT ANSWER

• Snakebite = notifiable emergency, time-sensitive condition
• 70% bites = non-venomous
• First sign of neuroparalytic bite = Ptosis
• Best bedside test = 20 WBCT
• Specific antidote = ASV (Anti-Snake Venom)
• ASV route = IV only (NOT IM)
• ASV is made from horse/sheep
• Krait bite symptoms can appear up to 36 hours later
• ASV is raised against Big Four in India
• Dry bite = bite with no venom injected

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🐍 KRAIT vs COBRA - How to Differentiate?

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THE BIG COMPARISON TABLE

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CLASSIC EXAM SCENARIO - REMEMBER THIS!

"Patient wakes up in the morning, no history of snakebite, no bite marks, has abdominal pain and slowly gets weakness/ptosis"

"Patient comes with painful swelling on hand, bite marks visible, ptosis developing within 2 hours"

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WHY THE DIFFERENCE? (The Mechanism - Very Important!)

COBRA = POST-SYNAPTIC toxin (alpha-bungarotoxin-like / cobrotoxin)

• Toxin sits on the acetylcholine receptor and blocks it
• ACh is released normally but cannot bind to the receptor
• Neostigmine (anticholinesterase) → increases ACh in synapse → can overcome the block → patient improves ✅

KRAIT = PRE-SYNAPTIC toxin (beta-bungarotoxin)

• Toxin destroys the nerve terminal that releases ACh
• ACh simply cannot be released at all
• Neostigmine has nothing to work with → patient does NOT improve ❌

Memory trick: "Krait Kills the Kitchen (pre-synaptic = the factory is destroyed). Cobra Chokes the Customer (post-synaptic = the receiver is blocked)"

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NEOSTIGMINE TEST (Exam Favourite!)

• Give Neostigmine 1.5mg IM + Atropine 0.6mg IV (atropine prevents muscarinic side effects)
• Wait 20-30 minutes
• Ptosis improves = Cobra bite (post-synaptic, responds)
• No improvement = Krait bite (pre-synaptic, no response)

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QUICK 3-POINT SUMMARY TO WRITE IN EXAM

1. Local signs: Cobra has them (pain, swelling, necrosis). Krait has NONE.
2. Time: Cobra = 30 min to 6 hours. Krait = 6 to 36 hours (patient often wakes up paralyzed with NO bite history).
3. Neostigmine: Cobra responds (post-synaptic). Krait does NOT respond (pre-synaptic).

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APPEARANCE OF THE SNAKES (bonus - if examiner asks)

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🍽️ KWASHIORKOR vs MARASMUS - Complete PSM Exam Notes

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FIRST - UNDERSTAND THE SIMPLE CONCEPT

Marasmus = Child gets nothing at all (no food, no protein, no calories - total starvation) Kwashiorkor = Child gets some food but almost no protein (eats rice/carbs but no protein)

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THE CLINICAL PHOTO (from Robbins Pathology)

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THE BIG COMPARISON TABLE

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THE ONE-LINE TRICK TO REMEMBER EDEMA

"Kwashiorkor has Komedo (edema = swelling)" - both start with similar sounds OR simply: "Kwashiorkor = Kudos (puffy, bloated look)"

• No protein → No albumin made by liver
• No albumin → No oncotic pressure in blood vessels
• Water leaks out of blood into tissues → EDEMA

• Yes, protein is also low, but the body adapts slowly (chronic starvation)
• The body breaks down its own muscle to maintain just enough albumin to prevent edema

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KEY FEATURES SIDE BY SIDE (Visual Memory)

MARASMUS                    KWASHIORKOR
-----------                 ------------
Total starvation            Only protein deficient
< 1 year                    1-5 years
Bones visible               Puffy/swollen
"Old man face"              "Moon face"
NO edema                    EDEMA (hallmark!)
NO liver enlargement        Fatty liver +++
Alert, wants food           Apathetic, no appetite
"Bag of bones"              "Bloated child"
Hair: sparse, dry           Hair: flag sign, depigmented
Skin: dry/wrinkled          Skin: "flaky paint" rash

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WHY FATTY LIVER IN KWASHIORKOR? (Examiner loves this!)

• No protein available → Cannot make lipoprotein carrier
• Fat gets made but cannot be exported
• Fat accumulates inside liver cells = Fatty liver (hepatic steatosis)

Memory: "Kwashiorkor = K for Kept fat in liver (can't export it)"

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MARASMIC-KWASHIORKOR (Mixed Type)

• When features of BOTH are present
• Child has wasting (from marasmus) + edema (from kwashiorkor)
• This is most common type seen in practice
• Also called "Mixed PEM"
• Park says: "Marasmus and kwashiorkor represent two ends of a spectrum, and considerable overlap exists"

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PSM-SPECIFIC POINTS (Park's Book)

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WELLCOME CLASSIFICATION (Important for MCQ!)

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3-LINE EXAM SUMMARY

1. Kwashiorkor = Protein deficiency only, age 1-5 yrs, edema + moon face + fatty liver + flaky paint skin + flag sign hair + apathy - child looks puffy but is actually wasted underneath
2. Marasmus = Total starvation, under 1 year, NO edema, severe wasting, old man face, bones visible, alert child - child looks like a skeleton
3. Key difference = EDEMA - present in Kwashiorkor, ABSENT in Marasmus. And Kwashiorkor has fatty liver, flag sign hair, and flaky paint skin which Marasmus does NOT have.

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