Physiology of Anaesthesia notes

Question 1

Systems most affected by anaesthesia

Answer 1

CENTRAL NERVOUS SYSTEM, CARDIOVASCULAR SYSTEM, RESPIRATORY SYSTEM.

In addition, the renal and hepatic systems are involved in the metabolism and excretion of anaesthetic drugs.

Question 2

The main control mechanism involved in respiration is ….

Answer 2

the regulation of carbon dioxide levels

Question 3

Hyperventilation - definiton, cause, comments

Answer 3

Excessive ventilation
Excessive level of breathing eg. Light GA or over-ventilating (IPPV)
Will cause CO2 levels to decrease (hypocapnia) causing respiratory alkalosis

Question 4

Hypoventilation - definiton, cause, comments

Answer 4

Inadequate ventilation
Decreased respiratory rate eg. GA overdose, decreased Vt, increased Vd
Will cause CO2 levels to rise (hypercapnia) causing respiratory acidosis

Question 5

Hypercapnia - definition, cause, comments

Answer 5

Abnormally high CO2 levels in the blood
Hypoventilation
Results in respiratory acidosis

Question 6

Hypocapnia - definition, cause, comments

Answer 6

Abnormally low CO2 levels in the blood
Hyperventilation
Breathing will often stop until CO2 levels rise again

Question 7

Hypoxia - definition, cause, comments

Answer 7

Abnormally low oxygen tension
Decreased O2 in inspired gas under GA (eg. Faulty/empty cylinder, decreased RR, decreased Vt, increased Vd, lung pathology, anaemia, decreased cardiac output, etc.
Tissue hypoxia can cause cell death and if the heart is affected this can cause cardiac arrest.

Question 8

Respiratory Acidosis - definition, cause, comments

Answer 8

Decreased pH of blood
Increased carbon dioxide
A result of hypercapnia

Question 9

Respiratory Alkalosis - definition, cause, comments

Answer 9

Increased pH of blood
Decreased carbon dioxide
Result of hypocapnia