Toxic Gases (CO)

Question 1

Endogenous source of CO:

Answer 1

Catabolism of protoporphyrin ring of Hb
Normally does not exceed 4-6%

Question 2

Exogenous sources of CO:

Answer 2

• Automobile exhaust (mainly)
• Incomplete combustion of Carbon containing material
• All heater types at home
• Fires
• Tobacco cigarettes

Question 3

Factors affecting CO toxicity:

Answer 3

1. Duration of exposure
2. Concentration of the gas.
3. High altitude (low O2).
4. disease in the CVS or RS
5. Hematological disease (anemia)
6. Neonate and infants.

Question 4

Pathophysiology of CO :

Answer 4

• Hypoxia high affinity to Hb (210 times than O2)
• ⬇⬇O2 release: shifting of dissociation curve of remaining oxyhemoglobin to the left less O2 available to tissues

Question 5

Other mechanims of CO:

Answer 5

• Myoglobin impairment: Affinity is 40 times more than O2 ( myocardial depression & arrhythmia )
• Mitochondrial impairment: bind to mCytochrome aa3 and block of cellular O2 uptake.
• brain reperfusion injury: **lipid peroxidatin & luekocyte mediated inflammatory change … demylination of brain.

Question 6

Clinical manifestations of CO toxicity:
Most common symptoms:

Answer 6

N&V, headache, dizziness, lethargy, and feeling of weakness.

Question 7

When does the recurrent symptoms syndrome occurs:

Answer 7

After lucid Interval (1-40 days) in moderate CO toxicity
Incidence: 10-20%

Question 8

CNS symptoms of CO toxicity:

Answer 8

Note : cns is the most sensitive
Headache, dizziness, ataxia, syncope, seizures, and coma.

Question 9

What is the delayed neuropsychiatric sequence:

Answer 9

delayed neuropsychiatric sequence (DNS) can occure in 50% of patients who have survived from acute CO poisoning.

It’s characterised by slowness, Parkinsonism and cognitive impairment.

Question 10

S&S of DNS:

not domain name system 🙃

Answer 10

Depression, emotional liability, hallucinations, personality changes, and verbal aggressiveness.

Children: behavioral changes and learning difficulties

Question 11

Clinical manifestations of CO in CVS:

Answer 11

• Tachycardia is common. Bradycardia occurs in severe cases. Why?🙃
• Palpitation and chest pain.
• Patchy myocardial infarction with ECG changes of ischemia (ST-segment deviations, T wave inversion, and Q-waves).
• A&V arrhythmia
• Hypotension

Question 12

Dermal changes in CO toxicity:

Answer 12

Cherry red in non survival
Pallor or cyanosis
Blisters due to pressure necrosis and direct effects of CO on the epidermis.

Question 13

Renal manifestations of CO toxicity:

Answer 13

Oliguric and non-oliguric renal failure

Question 14

CO Eye signs:

Answer 14

Retinal vein
- bright red
- congested
- tortuous

vision
- blurred vision
- loss of dark adaptation
- blindness

other
- disk edema
- flame shaped hemorrhage

Question 15

Respiratory symptoms of CO toxicity:

Answer 15

Non-cardiogenic pulmonary edema
Cardiogenic pulmonary edema
Explain why???

Question 16

Other symptoms of CO toxicity:

Answer 16

GIT: N&V, abdominal pain, may be diarrhea, so may be misdiagnosed as gastroenteritis or food poisoning, especially in children.
Bood: DIC and TTP
Muscles: rhabdomyolysis
Metabolic: lactic acidosis, hyperglycemia, and hypercalcemia.

Question 17

CO investigations:

Answer 17

Carboxy Hemoglobin level:
Measured by oximeter :10% in smoker and 0-5% in normal
ABG:
O2 may be normal
Oximeter shows false ⬆ O2 saturation and can not be relied
Metabolic acidosis if preset usually from lactic acidosis which is bad prognosis sign

Question 18

Management of CO toxicity:

Answer 18

• Rapid removal from continued exposure
• 100% O2 should be provided
• Cardiac monitoring and IV access
• Hyperbaric oxygen (HBO)
• Do not aggressively treat acidosis with pH above 7.15

Question 19

What is hyperbaric oxygen?
And what can it do?

Answer 19

Oxygen at 2-3 atmospheric pressure.
It decreases CO half-life to 20 min

Question 20

Why should we not treat acidosis above 7.15 in cases of carbon monoxide poisoning?

Answer 20

This can increase tissue hypoxia by the left shift of the oxyhemoglobin dissociation curve.

Question 21

Post-mortem appearance of CO toxicity

Answer 21

• Cherry red appearance especially in the area of postmodern lividity
• Skin Blisters are seen sometimes in claves, buttocks, wirst, and knee.
• Cherry pink color of blood and tissues.
• Pulmonary edema
• in delayed death: necrosis and cavitation of basal ganglia, especially globus pallidus.