AIM Step 10 • Student Memory Support
Corrosive, Acid, Alkali and Cyanide Poisoning
4th Year MBBS • GIT Module • High-yield memory reinforcement and last-minute revision
Structured according to the supplied AIM Student Memory Support requirements. :contentReference[oaicite:0]{index=0}
1. High-Yield Flashcards
Tap each question to reveal the answer.
What type of necrosis is produced by strong mineral acids?
Coagulative necrosis with protein denaturation and eschar formation.
What type of necrosis is typical of strong alkali injury?
Liquefactive necrosis caused by protein dissolution and fat saponification.
Which mineral acid is classically used in lead-acid batteries?
Sulphuric acid.
What characteristic tissue appearance may occur with concentrated sulphuric acid?
Brown-black charring due to severe corrosive and dehydrating action.
Which mineral acid produces characteristic yellow staining of tissues?
Nitric acid through the xanthoproteic reaction.
Which strong alkali is commonly found in drain-cleaning products?
Sodium hydroxide, also called caustic soda.
Why can alkali injury penetrate deeply into tissues?
Liquefactive necrosis allows continued chemical penetration rather than forming a limiting eschar.
What important late complication can follow severe alkali ingestion?
Esophageal fibrosis and stricture causing persistent dysphagia.
What characteristic local feature helps identify phenol poisoning?
Pale or white corrosive burns that may initially be relatively painless.
Why may a phenol burn initially be less painful than expected?
Phenol has a local anesthetic effect.
What is the major systemic biochemical effect of oxalic acid?
Binding of calcium with formation of calcium oxalate, producing hypocalcemia.
Which renal finding supports oxalic acid poisoning?
Calcium oxalate crystals in renal tubules.
Which mitochondrial enzyme complex is inhibited by cyanide?
Cytochrome c oxidase, also called Complex IV.
What type of hypoxia occurs in cyanide poisoning?
Histotoxic hypoxia because cells cannot utilize available oxygen.
Which antidote directly binds cyanide?
Hydroxocobalamin, which forms cyanocobalamin.
Why is sodium thiosulfate useful in cyanide poisoning?
It provides sulfur for conversion of cyanide to less toxic thiocyanate.
2. Mnemonics
Mnemonic Title: Major Mineral Acids
SHN
Meaning: Sulphuric acid • Hydrochloric acid • Nitric acid
Mnemonic Title: Oxalic Acid Systemic Effects
CaRK
Meaning: Ca = calcium binding/hypocalcemia • R = renal oxalate crystals • K = kidney injury
Mnemonic Title: Cyanide Core Sequence
CHAL
Meaning: Complex IV block → Histotoxic hypoxia → Anaerobic metabolism → Lactic acidosis
3. Memory Tables
Strong Acids vs Strong Alkalis
| Feature | Strong Acids | Strong Alkalis |
|---|---|---|
| Necrosis | Coagulative | Liquefactive |
| Main mechanism | Protein denaturation | Protein dissolution + fat saponification |
| Penetration | Eschar may partly limit depth | Deeper tissue penetration |
| Important late problem | Scarring / narrowing | Esophageal stricture |
Specific Poison Recognition
| Poison | High-Yield Clue | Major Consequence |
|---|---|---|
| Sulphuric acid | Brown-black charring | Severe corrosive injury |
| Nitric acid | Yellow staining | Coagulative necrosis |
| Phenol | Pale, less painful burn | CNS depression |
| Oxalic acid | Hypocalcemia | Renal crystal injury |
| Cyanide | Rapid collapse + lactic acidosis | Histotoxic hypoxia |
4. Rapid Revision Points — Last-Minute Revision
Must Remember:
- Mineral acids include sulphuric, nitric and hydrochloric acids.
- Strong acids mainly produce coagulative necrosis; alkalis mainly produce liquefactive necrosis.
- Sulphuric acid may produce brown-black charring because of severe corrosive and dehydrating action.
- Nitric acid causes characteristic yellow staining by the xanthoproteic reaction.
- Phenol produces pale burns and may cause CNS and cardiovascular depression.
- Oxalic acid causes hypocalcemia and calcium oxalate deposition in renal tubules.
- Cyanide blocks cytochrome c oxidase and prevents cellular utilization of oxygen.
- Severe cyanide poisoning commonly produces marked lactic acidosis and rapid neurological/cardiovascular collapse.
- Do not induce vomiting or attempt chemical neutralization after significant corrosive ingestion.
- Bright-red lividity or bitter-almond odor may support cyanide exposure but is not diagnostic by itself.
Common KMU Trap: Minimal oral burns do not exclude severe internal injury after alkali ingestion.
5. Clinical Memory Hooks
Yellow oral and gastric burns after corrosive ingestion → nitric acid → xanthoproteic reaction
Deep dysphagia after drain-cleaner ingestion with mild oral burns → alkali injury → deep esophageal liquefactive necrosis
Muscle cramps + ECG changes + renal injury after rust-remover ingestion → oxalic acid → hypocalcemia + calcium oxalate deposition
Rapid collapse with severe lactic acidosis after electroplating or enclosed-fire exposure → cyanide → histotoxic hypoxia
6. Starred High-Yield Exam Points
- ⭐ Strong acids → coagulative necrosis; strong alkalis → liquefactive necrosis.
- ⭐ Nitric acid → yellow xanthoproteic staining of exposed tissue.
- ⭐ Oxalic acid → hypocalcemia + calcium oxalate renal crystals.
- ⭐ Cyanide → cytochrome c oxidase inhibition → histotoxic hypoxia.
- ⭐ Hydroxocobalamin directly binds cyanide and forms cyanocobalamin.
- ⭐ Sodium thiosulfate promotes conversion of cyanide to thiocyanate.
- ⭐ Bright-red blood/lividity and bitter-almond odor are supportive clues, not definitive proof of cyanide poisoning.