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Flashcards in Pharm- 16 Deck (68)
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What is P(CNS)?

CNS Partial pressure --> the level of the anesthetic in the CNS


Can you measure P(CNS) directly?



So how can you measure P(CNS)?

using P(Alv)


What is P(Alv)?

The partial pressure of the anesthetic in the lungs. basically the balance between the anesthetic delivered to the alveoli and the loss from the lungs (to blood + tissues)


So how does anesthetic get into the tissues from the alveoli space (generally)?

down a concentration gradient cuz theres a crap ton in the alvoli and nothing in the tissues


And how does the anesthetic get out of the tissues and back into the lungs?

remove the anesthetic from the lungs --> moves down its concentration gradient back ot to the lung space


WHat is the minimum alveolar concentration (MAC)?

It's the P(alv) that results in the lightest possible anesthesia. basically the point in which anesthesia is induced.


True or false: a lower MAC means an lower potency of anesthesia.

FALSE. lower MAC = higher potency. takes less partial pressure to cause anesthesia.


What is AP50?

the partial pressure where analgesia (no pain) results in 50% of pts


Define: this is the partial pressure where movement is lost in 50% of pts when cut during surgery



What is the analgesic index?

Ratio of MAC to AP50


If there is an increase in analgesic index, is there an increase or decrease in the partial pressure of anesthetic needed to gain anesthesia than that required for surgical anesthesia?



What is the therapeutic index?


(MAC is the same as the ED50 for nongaseous things)


Do you want the therapeutic index to be high or low? Why?

High because you want a high LD50 (only kills pts at a very high conc) and you want a low MAC (drug works at a lower conc)


What is the danger of some analgesics which have a lot therapeutic index?

Respiratory depression + cardiac arrest


Why must the dosing must be very accurate for analgesics?

There are no antagonists to their actions. To get rid of it if you OD you just need time and ventilation lol. Call an MD.


What exactly is the LD50?

lethal dose in 50% of subjects


What is the ED50/MAC?

the effective dose that gives desired effect in 50% of pt


What is the meyer overton rule?

Greater the lipid solubility (greater oil/gas coefficient) of anesthetic in olive oil = greater its potency


What is the oil/gas partition coefficient good at showing?

predictor of how soluble an anesthetic is in olive oil- essentially defines the potency (larger coefficient = more soluble = more potent).


What is the solvent/gas partition coefficent good at predicting?

predictor of how soluble an anesthetic is in a solvent (blood and plasma). High coefficient = more soluble


What is the diffusion of the anesthetic dependent on?

this is proportional to the tissue area as well as the partial pressure difference between the alveoli and the capillary beds


What is the role of perfusion of the anesthetic?

capillary beds then deliver the O2 + anesthesia to cells in body. THIS IS THE RATE LIMITING STEP.


What is the anesthetic flow rate?

the rate at which the blood perfuses the tissue and anesthetic reaches tissue


Why do you need do some changes for a fat person vs a muscular person as far as dosages of anesthetics?

i. Fat pt is going to have a lot of volume (fat) therefore he will store a more lipid soluble anesthetic MUCH more than a muscular patient.
ii. This means that the anesthetic will affect him much more as well as he will be MUCH slower to recovery and for the anesthetic to leave his body


What is the time constant for anesthetics?

If you increase the flow rate, you will decrease the time it takes to equilibrate between blood and tissue (faster) and vice versa


How well are anesthetics delivered to well-rich groups?

• CNS + visceral organs
• Low capacity for anesthetic + high blood flow for delivery


How well are anesthetics delivered to muscle groups?

• Muscle + skin
• High capacity + moderate blood flow = longer equilibrium time


How well are anesthetics delivered to fat groups?

• High capacity for anesthetic + low flow for delivery = extremely long equilibrium time


How well are anesthetics delivered to vessel-poor groups?

• Bone, ligaments, cartilage
• Negligible flow + capacity