Gaseous poisoning

Carbon Dioxide (\text{CO}_2) - Simple Asphyxiant

​🟥 Sources: Respiration, combustion, fermentation, and accumulates in low places (mines, sewers) because it's heavy.

​🟦 Therapeutic Use: At 5% concentration, it acts as a respiratory stimulant. Used in CO poisoning to increase CO dissociation from Hb.

​🟥 Toxicity Levels:

​Up to 5%: Respiratory stimulant.

​Up to 20%: Severe toxicity.

​At 70%: Death (due to O2 replacement).

​🟦 Symptoms: Headache, giddiness, vomiting. Death is often due to tissue anoxia and epiglottic spasm. Recovery may lead to irreversible brain damage.

​🟥 Treatment: Stop exposure, give O2 inhalation, and symptomatic support (e.g., artificial respiration).

Carbon Monoxide (CO) - Chemical Asphyxiant

​🟦 The "Silent Killer": Colorless, odorless, tasteless, and non-irritating, preventing recognition of danger.

​🟥 Affinity to Hb: \text{CO} affinity to \text{Hb} is 210-250 times greater than \text{O}_2. This forms Carboxyhemoglobin (\text{COHb}).

​🟦 Mechanism: Causes tissue hypoxia by:

​Reducing \text{O}_2 carrying capacity of \text{Hb}.

​Slowing the release of remaining \text{O}_2 from Oxy$\text{Hb}$.

​Combining with Myoglobin (\sim 15 times affinity) leading to muscle fatigue.

​Inhibiting mitochondrial respiratory chain enzymes.

​🟥 Sources: Incomplete combustion (automobiles, stoves, fires). Cigarette smoke (3-6% CO). Methylene chloride (in paint removers) is metabolized to CO in the liver.

​🟦 Fatal Dose: 0.1% \text{CO} in air \rightarrow 50% \text{COHb} in blood, causes fatal symptoms within 2 hours. 1% \text{CO} in air causes immediate death.

​🟥 Acute Symptoms (Key COHb Levels):

​20% \text{COHb}: Extreme fatigue, rapid breathing (Tachypnea), headache, mental confusion.

​50% \text{COHb}: Loss of muscle control (inability to self-rescue), weak pulse, loss of consciousness.

​Key Sign: Skin is often pink or bright cherry red.

​🟦 Sequelae (Complications): If comatose > 24 hours. Permanent brain damage (Parkinsonism, memory loss, personality change) due to anoxia. Kidney damage (Glucosuria, Albuminuria).

​🟥 Diagnosis Tests:

​Dilution Test: \text{COHb} remains pink when diluted.

​Knuckles Test: \text{COHb} gives bright pink precipitate with tannic acid.

​Spectroscope: \text{COHb} bands persist after adding reducing agents.

​🟦 Treatment:

​Fresh Air: Remove victim from contamination.

​100\% \text{O}_2 Inhalation: Reduces \text{COHb} half-life from 4 hours to 1 hour.

​Hyperbaric \text{O}_2 (HBO): For severe cases (\text{COHb} > 25\%, or > 15\% in high-risk patients like pregnant or cardiac). Aims to dissolve \text{O}_2 directly in plasma and speed up \text{COHb} dissociation.

​Symptomatic: Cortisone/Mannitol for cerebral edema. Warmth is essential (Hypothermia increases CO affinity for Hb). Complete bed rest (10 days).

​🟥 Post-Mortem Picture (PMP): Pink/bright cherry red hypostasis and internal organs. Degenerative changes in basal ganglia