Pharmacology I - Principles Of Inhalational Anesthesia

Front 1

What type of drugs start out as a liquid, converted in the vaporizer to gas, and inhaled and absorbed via the pulmonary capillaries?

Back 1

Inhalational anaesthetic agents

Front 2

___ is an indication of a liquid's evaporation rate; relates to the tendency of particles to escape from a liquid

Back 2

Vapor pressure or equilibrium vapor pressure

Front 3

In confined space, there equilibrium in which number of molecules entering the gaseous state equals the number leaving it.

This is called ________?

Back 3

saturated vapour pressure (SVP)

At this point, vapour pressure is at a maximum for the liquid

Front 4

If an inhalational agent has a high SVP (saturated vapor pressure), then ________?

what inhalational anesthetic has highest SVP?
(excluding N2O)

Back 4

Very volatile agent (SVP is also temperature dependent)

Desflurane has highest SVP

Front 5

The more insoluble an INHALATIONAL agent is, _______________?

Back 5

The quicker you can change its concentration in the body

MORE INSOLUBLE AN INHALATIONAL ANAESTHETIC AGENT, THE FASTER IS WORKS FOR BOTH INDUCTION AND RECOVERY

Front 6

Saturated vapour pressure is the equilibrium point and is dependent on what two things?

Back 6

SVP dep. on temperature and atmospheric pressure

SVP increases with increasing temperature

Front 7

Which inhalational agents have a large blood: gas coefficient?

Back 7

Soluble inhalational agents

Front 8

What factors determine the extent a tissue takes up anaesthetic?

Back 8

Depends on blood supply
and surface area of tissue

Front 9

What two effects influence the inspired concentration?

Back 9

Concentration effect
Second gas effect

Front 10

Which inhalational agents have a LOW blood: gas coefficient: soluble or insoluble?

Example?

Back 10

Insoluble agents = LOW blood:gas coeff.
(e.g. desflurane)

Remember the more INSOLUBLE an inhalational anaesthetic agent, the FASTER it works for both induction and recovery

Front 11

What inhalational agent causes big drop in blood pressure?

Therefore you would NOT this agent in ___?

Back 11

Halothane

avoid in sick, or animals with foreign object, liver disease blas blas..because reduces organ perfusion (except cranium!)

Front 12

What inhalational agent is somewhat irritating to respiratory tract?

Back 12

isoflourene

Front 13

What inhalational agent are very similar to isoflourene, but more expensive?

Back 13

sevoflurane

Front 14

most effective absorption surface in the body?

why?

Back 14

pulmonary alveolar epithelium

huge surface area...duh

Front 15

do inhalation agents have pre- OR post-synaptic effects?

Back 15

have BOTH pre- and post-synaptic effects

Front 16

True or False:
* inhalation agents never interact with the neuronal plasma membrane
* do not act via second messenger systems

Back 16

FALSE:
* inhalation agents DO interact with the neuronal plasma membrane
* they may also act via second messenger systems

Front 17

What inhalational drug produces metabolite known as 'Compound A' on reaction with soda lime?

Back 17

Sevoflurane

Compound A has no clinical significance...aside from causing renal necrosis in rats.

Front 18

for most inhalational agents, SVP is low OR high?

Back 18

for most inhalational agents, SVP is very HIGH – this is why vaporisers are required

Front 19

What inhalation agent is highest?

Which is lowest?

Back 19

desflurane 664 mm Hg <-- you can pack a whole lot more of this guy into confined space, than you can sevofl.

sevoflurane 160 mm Hg

Front 20

Which 2 inhalants have ~same SVP?

Back 20

halothane 239 mm Hg
isoflurane 240 mm Hg

Front 21

At sea level and room temperature, which can you achieve higher concentrations of : isoflurane, sevo, or desflurane?

What do vaporizers do?

Back 21

At sea level and room temperature, you can achieve concentrations of :
21% sevo
32% halothane
32% isoflurane
86% desflurane

Vaporisers are used to deliver SAFE anaesthetic concentrations of inhalational agent

Front 22

If blood:gas ratio/coefficient is 2:1 or 2; which holds higher concentration - blood or gas?

Back 22

BLOOD

this is principle behind "Solubility partition coefficients"
and blood:gas solubility

Front 23

blood:gas solubility/coefficient is 0.5, what is ratio of blood:gas?

Back 23

1:2 or 2:4, etc.

insoluble agents have a LOW Blood/Gas co-efficient; remember this means works faster!

> do NOT confuse this with SVP

Front 24

body can be considered to consist of four basic groups, based on PERFUSION and PROPORTION OF BODY MASS
(determines how quickly take up drug and reach eq.)

Back 24

1. Vessel rich->75% perfusion (% of CO)
2. Muscle/skin->19% perfusion
3. Fat->6%
4. Vessel poor (ie. CT, bone)->0% perfusion
(see next question!)

Front 25

The vessel-rich group is composed of?

Speed to eq.? Why?

Back 25

brain, heart, liver, kidneys, endocrine glands and splanchnic bed.

Perfused well, have smaller volume (like compared to muscles), so rapidly reach equilibrium

Front 26

Minimum alveolar concentration or MAC describes what ?

Back 26

is a concept used to compare the strengths, or potency of anasthetic..at this conc. 50% patients do not respond to stimulus

Front 27

High MAC means?

Back 27

Drug is poor anesthetic, it is measure of potency (higher value means higher concentration needed to anesthetize animal)


Speed of onset faster?! (wrong)

Front 28

Which has higher MAC: 1. halothane
2. desflurane 3. methoxyflurane

Back 28

desflurane (MAC = 8) > halothane > methoxyflurane (0.23)

desflurane = least potent anesthetic; also fastest onset

Front 29

Key factors determining _____?:
* blood:gas solubility
* Fi:FA ratio
* cardiac output
* partial pressure difference between alveolus and venous
blood (PA - PV)

Back 29

Key factors determining anaesthetic uptake into blood

Front 30

Fi:FA ratio is what?

Back 30

comparing inspired concentration (Fi) to alveolar (FA) concentration of anaesthetic

uptake is determined by the rate and depth of ventilation

Front 31

What is second gas effect?

Hint: Function of nitric oxide

Back 31

Because [NO] is so insoluble, take up rapidly and concentrates other drugs in alveoli, so increases speed they're taken up as well

can use LESS of other inhalation drugs

Front 32

Why is important to minimize the amount of inhalation agents used?

Back 32

All suppress cardiovascular and respiratory centers; so can kill animal very easily

Front 33

What are some factors that decrease MAC?

Back 33

Narcotics
Sedatives
Tranquilizers
Nitrous oxide
Age
Hypothermia
Pregnancy