Inhalational anaesthesia and Maintenance of Anaesthesia Flashcards
Why does sevoflurane give rapid induction?
it is a gas. It is very insoluble so equilibriates quickly with the blood and the partial pressure in the lungs will reflect that in the inspired gas. The blood becomes saturated quickly and so the brain is then exposed to the inhalational agent and anaesthesia results.
Why does ether result in a very prolonged induction?
It is very soluble in blood so the partial pressure in the alveoli takes a long time to rise to that in the inspired gas. As it is soluble, it does not readily transfer into the brain and so the brain partial pressure takes some time to equilibriate.
How do you calculate the partial pressure of the gas that should be delivered?
It should be 3 times the minimum alveolar concentration.
How does cardiac output and ventilation rate affect the rate of induction of anaesthesia?
Higher cardiac output, slower induction of anaesthesia. higher ventilation rate, faster rate of induction.
In what species is lidocaine required for anaesthesia? In what form and why?
cats, pigs, primates. Spray larynx and wait around 1 minute. desensitises it and prevents spasm, allowing intubation.
In what species might you not use a cuffed endotracheal tube and why?
cats. V. sensitive larynx- may rupture.
which maintenance agent does not cause muscle relaxation and what is therefore used with it?
Ketamine, used with a centrally acting muscle relaxant eg midazolam.
At what value do you begin the alveolar concentration of the gas at for surgery?
1-1.5 times MAC
what are alfentanil and remifentanil?
analgesics.
What is the mechanism of aciton of Nirtous oxide?
NMDA andtagonist (good analgesia, poor anaesthesia).
How is Nitrous oxide stored, when should it not be used and how should the patient recover?
stored as a liquid in blue cylinders. Should not be used in bowel obstruction, cases where there is a risk of embolism and other conditions where air is trapped in an enclosed space. Administration should be discontinued 10 minutes before the end of surgery and the animal should be allwed to breathe 100% oxygen to prevent hypoxaemia.
What is the MAC of nitrous oxide?
200%
What effects can nitrous oxide have on people and when, therefore, should it only be used/
inhibits methionine sythetase and is associated with pernicious anaemia, bone marrow suppression and peripheral neuropathies. Should only be used when gas scavenger present.
What is the mechanism of aciton of Isoflurane?
GABA agonist.
What is the MAC of isoflurane in domestic species?
2.05-2.25%
