Hello ladies and gentlemen.
Welcome back to our ongoing discussion
of Anesthesiology. In this lecture, we're going to talk
about some of the effects that anesthetics have
on basic body functions. We're going to emphasize
the effect on the respiratory system
and the cardiovascular system. And then briefly cover
effects on the hemostatic system and the acid
base balance. So, does general anesthesia
have an impact upon respiratory function?
Anesthetic vapours reduce the breathing
center's response to changes
in arterial carbon dioxide or partial pressure
of carbon dioxide in the blood. Vapours
increase the rate of breathing, but decrease
tidal volume. And the overall effect is
to reduce minute ventilation. This has the effect
of allowing carbon dioxide to rise in the blood.
In extreme cases, very extreme
cases, Oxygen level may also
drop resulting in hypoxemia or low
blood oxygen, and reduction in the general
oxygen delivery to tissues.
Opiates and opioids also have
a major effect upon the respiratory system.
They also reduce the brain's response to rising
carbon dioxide in the blood. But the increase
in tidal volume, but they increase the tidal volume
dramatically and decrease respiratory rate,
thus reducing minute ventilation. So they work
exactly the opposite of how vapours work.
The overall effect however is still to allow carbon dioxide
to rise, which under normal circumstances
would have a major stimulating effect upon
the respiratory center. However, the presence
of vapours or opiates interferes with
that response from the respiratory center.
So, carbon dioxide continues to rise and
does not stimulate more breathing.
So how do we take care of these changes?