CO2 narcosis

Question 1

What is meant by CO₂ narcosis?

Answer 1

carbon dioxide poisoning or intoxication -hypercapnia leading to frank depressed mental status including confusion, somnolence and lethargy which may lead to coma and death

Question 2

What are the 4 possible causes of hypercapnia?

Answer 2

1. Increased concentration of carbon dioxide in the inspired gas
2. Increased carbon dioxide production e.g. malignant hyperpyrexia, sepsis, laparoscopic surgery(absorption from peritoneum)
3. Hypoventilation - commonest cause. COPD
4. Increased dead space e.g. incorrectly configured breathing apparatus or pathological

Question 3

What are 3 examples of increase carbon dioxide ‘production’ leading to hypercapnia?

Answer 3

1. Malignant hyperpyrexia
2. Sepsis
3. Increased absorption from peritoneum during laparoscopic surgery

Question 4

What is the commonest cause of hypercapnia?

Answer 4

hypoventilation due pathology

Question 5

What is the commonest cause of long-standing hypercapnia?

Answer 5

COPD

Question 6

What are 5 clinical signs of hypercapnia?

Answer 6

1. Hyperventilation - cardinal sign
2. Dyspnoea
3. Flushed skin
4. Full and bounding pulse
5. Occasional extrasystoles
6. BP often raised
7. Muscle twitching
8. CO2 flap
9. Convulsions
10. Coma

Question 7

How is hypercapnia diagnosed?

Answer 7

arteiral blood gas - PCO₂

Question 8

What are 3 aspects of the management of hypercapnia?

Answer 8

1. ventilation: NIV e.g. full face mask+BiPAP or intubation
2. medication: nebulisers, steroids, abx
3. oxygen therapy: supplemental O2 with NIV, adjusted to 88-92% in all causes of acute hypercapnic respiratory failure