Gastric lavage can be performed in case of poisoning by:

Correct Answer: B. Carbolic acid

Gastric lavage is a decontamination procedure that removes unabsorbed poison from the stomach. The key principle is that it can only be safely performed when the poison does NOT cause severe corrosive injury to the gastrointestinal tract. Carbolic acid (phenol) is a corrosive poison, but unlike strong mineral acids and alkalis, it causes relatively slower tissue penetration and necrosis. More importantly, phenol is poorly absorbed from the stomach — it undergoes local coagulation necrosis at the site of contact, creating an eschar that limits further absorption. This makes gastric lavage feasible within the first 1–2 hours of ingestion, as the goal is to mechanically remove the poison before significant systemic absorption occurs. The procedure must be done cautiously with small volumes of water or saline, avoiding aggressive irrigation. In Indian toxicology practice (per Forensic Medicine textbooks), gastric lavage for phenol poisoning is considered acceptable when performed early, though activated charcoal is not effective for phenol. The critical distinction is that carbolic acid does NOT cause the explosive, full-thickness corrosive injury seen with strong acids and alkalis, making mechanical removal feasible.

Why the other options are wrong

A. Strychnine — Strychnine is a rapidly absorbed alkaloid that causes CNS stimulation and tetanic convulsions within minutes of ingestion. By the time gastric lavage is considered, strychnine has already been absorbed into systemic circulation, making gastric decontamination ineffective. The priority in strychnine poisoning is seizure control with benzodiazepines and supportive care, not gastric lavage. This is a common NBE trap pairing a poison with a decontamination method that arrives too late. C. Kerosene oil — Kerosene and other volatile hydrocarbons are contraindicated for gastric lavage because mechanical manipulation increases the risk of aspiration into the lungs, causing severe chemical pneumonitis and pulmonary edema. The standard teaching in Indian toxicology is to avoid gastric decontamination entirely for hydrocarbon ingestion unless the volume is massive (>1 mL/kg). Observation and supportive care are the mainstay of management. D. Sulphuric acid — Sulphuric acid is a strong mineral acid that causes immediate, severe corrosive injury with full-thickness necrosis, perforation, and hemorrhage. Gastric lavage is absolutely contraindicated because mechanical manipulation worsens tissue damage, increases perforation risk, and may cause vomiting with further esophageal injury. Management focuses on neutralization and supportive care, never decontamination by lavage.

High-Yield Facts

Mnemonics

CHAPS — Contraindications to Gastric Lavage Corrosive acids/alkalis (strong), Hydrocarbons (volatile), Alkaloids (rapidly absorbed: strychnine, nicotine), Perforation risk, Seizure-causing poisons. Use this to rule out when lavage is unsafe. Phenol is SAFE for Lavage Phenol causes local eschar (not full-thickness perforation) and slow absorption, giving a window for mechanical removal. Remember: phenol = coagulation necrosis = eschar = time to lavage.

NBE Trap

NBE pairs corrosive poisons (carbolic acid, sulphuric acid) to test whether students know the mechanistic difference: carbolic acid causes local eschar with slow absorption (lavage feasible), while strong mineral acids cause full-thickness necrosis (lavage contraindicated). The trap is assuming all corrosives are equally dangerous for lavage.

Clinical Pearl

In Indian emergency departments, the reflex to "lavage all poisonings" is dangerous. Carbolic acid is the rare exception where early lavage (within 1–2 hours) is justified because phenol's local eschar formation buys time before systemic absorption. For all other corrosives and hydrocarbons, lavage worsens outcomes — a critical distinction that saves lives in rural and urban toxicology practice.

_Reference: Forensic Medicine & Toxicology (Reddy, 3rd Ed.) Ch. 18 — Poisoning & Decontamination; Parikh's Textbook of Medical Jurisprudence Ch. 12_