Asphyxiants: Carbon Monoxide (CO)

Introduction:

• Carbon  monoxide reacts  200 times  more  tightly  with hemoglobin  than  oxygen and causes  anemic  type  of hypoxia.
• CO combines reversibly with hemoglobin to form carboxyhemoglobin (COHb) producing  anemic
• hypoxia  (blood O₂ -carrying capacity is reduced).
• It inhibits the electron transport by blocking cytochrome A₃ oxidase and cytochrome P450 and hence  intracellular respiration.

Signs and Symptoms: Signs  and  symptoms  of CO  poisoning  depends upon  the  percentage  of hemoglobin, which  has been  saturated with  CO.

acute symptoms:

• Headache (dull, frontal and continuous),
• Dizziness, weakness.
• Nausea and confusion.

COHb (%)	Signs and symptoms
0–10	No symptoms
10–20	Breathlessness, mild headache, abdominal pain
20–30	Throbbing headache, irritability, emotional instability, buzzing in the ears
30–40	Severe headache, nausea, vomiting, dizziness, dimness of vision, confusion, ataxia.
40–50	Increasing confusion, hallucinations, rapid respiration, staggering and incoordination mistaken for drunkenness
50–70	Weak thready pulse, hypotension, irregular respiration convulsions, coma and death.
> 80	Rapid death from respiratory arrest

•  The upper  limit  of safety  of CO in air is  0.01%.
• Postmortem  findings:
• Fine froth  at  mouth  and nose.
• Bright  cherry  red  discolouration: (skin,  mucorrs membranes,  nail-beds, blood,  tissues  and internal  organs. Cyanide  poisoning  and  exposure  to  cold  causes similar  redness).
• Blood  is  fluidish  thin, hyperemia  (congestion)  is  general,  and serous  effusion  are common.
• Skin blisters,  or red patches
• Lungs  show  congestion.
• Bilateral symmetrical  necrosis  and  cavitation  of basal  ganglia.
• Spectroscopic  examination,  Hoppe – Seyler’s test (l0%NaOH),  kunkel’s (tannic  acid) test  and  adding  water  (15  ml) in  2 drops  of blood  can detect  CO,

Exam Important

Don’t Forget to Solve all the previous Year Question asked on Asphyxiants: Carbon Monoxide (CO)