IAA Flashcards
What is MAC?
Minimum alveolar concentration- where 50% of the patients do not respond to painful stimulus
What is MAC awake?
It is a third of MAC and the patient starts to wake up but is still in sleep
What is MAC Bar?
It stands for Minimum alveolar concentration that blocks autonomic response- so things like pupil dilation,heart rate and blood pressure
What factors decreases MAC?
- shock
- pregnancy
- acute alcohol intoxication
- Elderly
- low body temperature
What factors increases MAC?
- chronic alcohol intoxication
- ephedrine
- cocaine
- acute amphetamine
What receptor does N20 work at and what does it do?
It works at NMDA and it inhibits it
Where do the 4 IAA work on?
GABA A receptor and it increases it
What is a medical metabolism condition that halothane is assciated with?
Hepatitis because 15-20% of it is metabolised in the liver
What is the effect of halothane on the cardiovascular system?
-Decreases BP
-Decreased CO
-Decreased Heart Rate
which leads to hypercarbia and evidently ventricular extra systoles (VES)
What is the MAC of halothane?
0,75 which means it is the most potent of all the IAA drugs
What can we use halothane for when it comes to bronchospasm?
It can be used as a potent bronchodilator
Which IAA smells noxious?
isoflurane
What is the MAC of isoflurane?
1,15
Which IAA do we prefer for liver and neurosurgery?
Isoflurane
What is the MAC of sevoflurane?
2
Which IAA smells the best?
sevoflurane
Why is sevoflurane faster for the pt to wake up?
Because the blood gas ratio is 0,65 which means it is not very soluble in the blood and so we can reverse it easily
What about sevoflurane makes it nephrotoxic?
Potential to have compound A in rats which is nephrotoxic
Why is desflurane not recommended for inhaled induction?
It causes severe laryngospasm and coughing and possible increase in airway resistance
What is the effect of halothane, isoflurane and sevoflurane on the respiratory system?
It causes bronchodilation
Properties of N20 that are positve?
- It is a drug used concurrently with other IAA
- has a fast wash in and wash out mechanism(so has low solubility)
- analgesic
Disadvantages of N20?
- mac 105%
- hypoxic diffusion
- suppresses vitamin B12
- Expands air filled spaces(cannot use in pneumothorax)
What are some basic influences of the alveolar concentration?
- Fresh Gas Flow
- Inspiratory fraction of the inhalational agent
- alveolar minute ventilation
What would cause a decrease in the alveolar inhalational agent concentration?
- Cardiac output- a increase in co means that blood flows past the alveolar more
- solubility of the IAA
- Mixed venous concentration IAA
Which two inhalational agent drugs can be used with or without nitrous oxide and suitable for children?
-halothane and sevoflurane
What is the second gas effect?
When nitrous oxide is added with an inhalational gas to speed up induction
What is alveolar concentration directly proportional to?
-It is directly proportional to alveolar partial pressure which will in turn affect how much anaesthetic agent is in the blood and then the brain
What colour gas cylinder is NO2?
BLUE
What is entonox?
-it is a mixture of 50% oxygen and 50% nitrous oxide that is used for analgesia in labor and mild procedures
What is diffusion hypoxia?
- this is a phenomenon that happens after we switch off N2O and it diffuses from the blood back into the alveoli and causes decreased oxygen and hypoxia
- because of this we have to give oxygen at 80-100% for 5-10 minutes after N20 is switched off
Which gas contributes potently to PONV?
-Nitrous oxide
Which IAA does not contribute to malignant hyperthermia?
-nitrous oxide
What effect does halothane have on the CNS?
-It increases the ICP and bloodflow
What is the effect of isoflurane on CVS?
- Decreases blood pressure
- decreases SVR
- increases HR
What is compound A?
-Compound A is a toxic end product found when sevoflurane reacts with soda lime
Which two gases are not used as inhalational induction agents?
-isoflurane and desflurane
What is the Mac of N20?
105%
