anaesthesia

Question 1

Gormley et al 2001

Answer 1

Children also have higher rate of oxygen consumption per unit of body weight, which is approximately 7ml/kg/min - almost double that of an adult.

Question 2

How does airway resistance change in anaesthesia?

Answer 2

1. Airway resistance increases as lung volume decreases as it does in anaesthesia.
2. However, the volatile anaesthetics induce bronchodilation, which opposes this increase in resistance.
3. Thus there is usually no significant net change in resistance under GA.
4. Compliance is a measure of the ease of expansion of the lungs (change in vol/change in pressure)
5. Compliance falls quickly on induction of anesthesia, and can remain low for 1-2 days afterwards.
6. This may be due to the alteration of the properties of surfactant (which usually reduces surface tension and increases compliance).

Question 3

Ferguson et al 2006

Answer 3

Showed that hyper-polarization of respiratory neurons from opioids can disrupt this rhythmic pattern, resulting in a decline in respiratory rate.

Question 4

Chemosensitivity

Answer 4

1. The glomus cells of the carotid bodies constitute the peripheral chemoreceptors, and respond to PaO2 < 60 mmHg by increasing the discharge in the glossopharyngeal nerve. Increasing ventilation in response to hypoxia = hypoxic ventilatory response (HVR).
2. Increased PaCO2 is sensed by the medullary chemoreceptors (predominantly the retrotrapezoid nucleus (RTN), by changes in pH. Hypercapnia increases the ventral respiratory drive (hypercapnic ventilatory response (HCVR).