Anesthhetic Pharmacology (Mod 2) Flashcards
Pharmacodynamics vs Pharmacokinetics?
- Deals the mechanism of drug action (anticholingerics/mimetic and that crap)
- What does the body do to the drug (i.e metabolism)
Define Induction
Transition from an awake state to an anesthetize state
Define Recovery
State of consciousness of an individual when hey are awake or easily arousable and aware of surroundings following the elimination of an anesthetic
What is the purpose of inhaled anesthetic agents?
Inhaled anesthetic are primarily used to maintain the anesthetic state AFTER induction by some other agent (like propofol)
What is the ciruclation/distribution pathway of inhaled anesthetic?
Distributes well to all parts, but becomes most concentrated in the fatty tissue
- this occurs because this area is not as well vascularized
- it gets held because it takes longer to get there and exit (its more like a storage place where it gets saturated as a uptake area)
What is Minimum Alveolar Concentratino (MAC)
- Important
Dose that we’re going to providing, but it is not dose specific. It’s the minimum we need.
- Levels associated with partial pressures to deliver the desired range by varying the inspired partial pressure (Pi)…we set this. measure is not precise
- Controls the depth of anesthesia, anesthesiologist have precise control of the level of anesthetic in the CNS
How is level of anesthetic in the CNS (Pcns) determined?
The CNS partial pressure (Pcns) is monitored via alveolar partial pressure (Palv) because it cannot be directly monitored.
- its a substitute method for Pcns because Pcns tracks palv with only a small lag time
How is alveolar partial pressure (Palv) measured?
Palv is measured directly as the partial pressure of anesthetic in the end tidal exhaled gas, when dead space no longer contributes to the exhaled gas
Why is the potency of anesthetic is related inversely to its Minimum Alveolar Concentration (MAC)
- what doe sit mean?
- edit this is a important point
MAC is alveolar partial pressure that abolishes a movement response to a surgical incision in 50%, so you need to give MORE than you need bc they may not be affected by it
- If the MAC is small, the potency is high and relatively low partial pressure of anesthetic will be sufficient to cause anesthesia
- MAC is associated with how much drug they are getting, partial pressure deals with how it is being delivered??? —> Partial pressure is associated how much more gas is needed to deliver the drug itself, lower MAC needs less partial pressure
What is the alveolar partial pressure that results in the lightest possible anethesia called?
Minimum alveolar concentration (MAC)
What could be indicators of movement response if a paralytic is applied?
Vitals such as HR.
- so the patient may not necessarily grimace or flinch in response to surgical incisions
What MAC concentration do you typically want to aim for?
edit
1.1-1.3
- as you increase the dose, more people will not response to surgical incision
- standard deviation is approx 10% (MAC + 1SD)
- Example: Refer to slide 7. to achieve 68% anesthetic state, you want to multiply the partial pressure MAC (slide 8) of a drug by 1.1
How are separate douses of anesthetic gasses admined overtime over affect?
Effects of anesthetic are additive (they stack)
- 0.5 of 1 in combo w/another 0.5 drug will increase potency to 1 MAC of a single agent
What conditions would require a patient to need a higher MAC (increased MAC) of anesthetic gas?
- aka more mac needed to induce them
- Pt with Hyperthermia
- Chronic alcohol abuse
- Pt with that drug use or amphetamines, and CNS stimulants (they have higher tolerances)
What conditions would require a patient to need a lower MAC (decreased MAC) of anesthetic gas?
- aka less mac needed less to induce them
The following will need less anesthetic drug use:
- Advanced age
- Hypothermia
- Severe hypotension
- Otehr agents; opiates, valium
- Acute drugs or ETOH into
- Pregnancy
- High PCO2 or Low PO2
What is the Meyer Overton Rule?
Oil/gas partition coefficient that helps us understand the potency of the anesthetic gas
- As the oil/gas partition increases, MAC decreases
- The potency of an anesthetic increases as its solubility in oil increases
- The gases do not bind to receptors, they disrupt the nervous system in the body enters the lipid bilayers in the CNS
What are the benefits of using a mixture of inhaled anesthetic gasses? (3)
Allows for:
- Anesthetic potency
- Recovery
- Inhaled agents and IV agent combinations allows for the above goals to be achieved
What are pharmacokinetics characteristics of an ideal inhaled anesthetic? (2)
- Provides a rapid and pleasant induction of surgical anesthesia
- Provides a smooth and rapid recovery to a fully functional and concisions state
what factor limits the transfer of anesthetic in both lungs and the tissue in terms of capillary beds and blood?
Perfusion rates rather than difffusion rates
- The transfer of anesthetic is limited by perfusion rather than diffusion
- increasing the rate of diffusion will not increase the rate of induction of anesthesia
In the realm of the pharmkinentics of anesnethic gasses; what does the concept of compartments refer to?
The different spaces agents need access to, to achieve their desired effect
What pathway does anesthetic gas generally diffuse within the body?
- Pt breathes in gas (spontaneous or via vent)
- Anesthetic reaches the alveoli; must diffuse across the AC membrane into the pulmonary capillaries
- Gas should diffuse into the blood
- Blood brain barrier (site of action) aka CNS
Why is partial pressure of alveolar and systemic arterial pressure nearly the same in healthy adults?
edit
- add more to this card aka be more specific
The lungs optimize gas diffusion and Inspired Partial pressure
- The capillary beds in tissues delivery oxygen rapidly to all cells in the body through a series.
- The end goal will be D, but gas will still pass through ABC eventually filling the capacities in this areas
- All compartments will equilibrate to equal Pi
What does a compartments equilibrium depend on?
The volume capacity and flow rate of blood (and subsequent diffusion) -> which is perfusion limited.
- Blood flow refers to level of blood flow delivering anesthetic
- Equilibrium of partial pressure of the compartment with he incoming flow takes place more quickly when the inflow is larger or compartment capacity is smaller
What is the primary determinant of diffusion?
Partial pressure of gas