Nur 638 Inhalational Anesthetics

Front 1

What is Pharmacolinetics of Inhalational Anesthetics?

Back 1

quantitative study of:
absorption (uptake) from alveoli into pulmonary capillary blood
distribution in the body
metabolism, and
excretion - principally via the lungs

Front 2

What determines the partial pressure of anesthetic in the blood and, ultimately, in the brain?

Back 2

Alveolar Partial Pressure

Front 3

What are three factors that affect anesthetic uptake?

Back 3

solubility in the blood

alveolar blood flow

difference in partial pressure between alveolar gas and venous blood

Front 4

FGF (fresh gas flow) is determined by ________ and __________ settings.

Back 4

vaporizer, flowmeter

Front 5

FI (inspired gas concentration) is determined by ________,_________, ___________ .

Back 5

FGF rate; breathing-circuit volume; circuit absorption

Front 6

FA (alveolar gas concentration) is determined by _________, __________, _______, _______________.

Back 6

uptake; vetilation; concentration effect; second gas effect.

Front 7

Fa (arterial gas concentration) is affected by ____________ mismatching.

Back 7

ventilation/perfusion

Front 8

What is an indirect measurement of anesthetic partial pressure in the brain?

Back 8

Alveolar partial pressure (PA)

PA - mirrors brain level

Front 9

What is concentration effect?

Back 9

high, initial inhaled partial pressure of agent,offsets uptake into the blood and accelerates rate of induction of anesthesia.

Front 10

What is second gas effect?

Back 10

the concentration effect of one gas upon another. Usually refers to nitrous oxide combined with an inhalation agent.

N2O has a low blood solubility, is rapidly absorbed from the alveili into pulmonary circulation to significantly alter concentration of remaining gasses in alveoli.

Front 11

Factors affecting Alveolar concentration

Back 11

Inhaled Partial Pressure of agent

Uptake of inhaled agents into the pulmonary circulation

Alveolar ventilation

Characteristics of delivery system - volume of anesthetic breathing system acts as a buffer to attain high PA. High gas flows negate this buffer effect. "Wash In"

Front 12

What determines the Uptake of inhaled anesthetics from Alveoli to Pulmonary Capillary Blood?

Back 12

Solubility of the anesthetics in blood and body tissue.

Cardiac Output

Alveolar to Venous partial pressure differences (A-vD)

Front 13

Solubility describes the affinity of the gas for a medium such as blood or fat tissue and is expressed as ___________ .

Back 13

Partition Coefficients

Front 14

What is the Ostwald Solubility Coefficient?

Back 14

Volume (ml) of gas dissolved per ml of liquid (blood) at ambient temperature and pressure (assuming body temp 37 C, and atmospheric pressure 760 mm Hg)

Front 15

Partition Coefficients are TEMPERATURE dependent. Solubility of a gas in a liquid is decreased when the temperature of the liquid _______________.

Back 15

increased.

Front 16

Alveolar partial pressure is an indirect measurement of partial pressure in the _________.

Back 16

brain

Front 17

A gas that is highly soluble (high uptake) causes _________ alveolar concentration, therefore a __________ induction

Back 17

lower; slower

Front 18

Low solubility (not easily dissolved in blood, less uptake) = higher alveolar concentration means __________induction and _________ emergence.

Back 18

faster; faster

Front 19

Takes longer to build up partial pressure in the blood and brain if agent has ________solubility, which means _________ alveolar concentration.

Back 19

higher; lower

Front 20

Higher Blood:Gas Partition coefficient, _____ anesthetic's solubility so greater uptake in pulmonary circulation. This means _______ alveolar pressures and ______ induction and emergence.

Back 20

higher; lower; slower

Front 21

Lower Blood:Gas coefficient - less solubility in the blood and less uptake into pulmonary circulation. This means ______ alveolar partial pressure and ______induction and emergence.

Back 21

higher; faster

Front 22

What is Blood:Gas solubility for:

Desflurane _____
N20 ___________
Sevo ___________
Iso _________

Back 22

0.42
0.47
0.69
1.43

(remember from smallest to greatest)

Front 23

Brain:Blood Solubility of

N2O ________
Des_______
Iso ________
Sevo_________

Back 23

0.5
1.3
1.6
1.7

Front 24

Ultimate goal of anesthesia is adequate _______ level to have desired effect.

Back 24

Brain

Front 25

In the absence of pulmonary shunt, Alveolar blood flow is equal to _______

Back 25

Cardiac Output (CO)

Front 26

Increase in CO will _________ in anesthesia uptake and will _________ in alveolar concentration. Induction will be ______.

Back 26

increase; decrease; delayed

Front 27

Decrease in CO will ___________ in anesthesia uptake and _________ in alveolar concentration. Induction will be ______

Back 27

decrease; increase; fast

Front 28

In the absence of an intra-cardiac or intrapulmonary shunt, PA and Pa of inhaled anesthetics are essentially ________

Back 28

identical

Front 29

Right-to-left shunt, dilutes effect on the partial pressure of anesthetic in blood coming from ventilated alveoli, = ______ in arterial concentration, _______ of induction

Back 29

decrease; slowing

Front 30

What reflects tissue uptake of the inhaled anesthetic. This gradient depends upon tissue uptake.

Back 30

Alveolar-to-venous (A-vD) partial pressure differences

Front 31

What are three things that determine transfer of anesthetic agent from the blood to the tissues?

Back 31

1) Tissue solubility (tissue/blood partition coeffecient)

2) Tissue blood flow

3) difference in arterial and tissue partial pressure of the anesthetic agent

Front 32

What determines the uptake of inhaled anesthetics from Alveoli to Pulmonary Capillary Blood?

Back 32

1) solubility of the anesthetic in blood and body tissues

2) Cardiac Output

3) Alveilar to venous partial pressure differences (A-vD)

Front 33

What is the Context - Sensitive Half Time?

Back 33

Computer simulations determining the time needed for a 50% decrease in anesthetic concentration of volatile agents. Initial phase of elimination. Primary a function of alveolar ventilation.

Front 34

What factors speed up induction and recovery?

Back 34

high fresh gas flows
low anesthetic - circuit volume
decreased solubility of agent
increased ventilation

Front 35

What is Diffusion Hypoxia and how to prevent it?

Back 35

occurs when inhalation of Nitrous Oxide is discontinued abruptly. Causes reversal of partial pressure gradients. N2O leaves blood and enter alveoli.

Prevented by adm 100% O2 for 5-10 min after discontinuing N2O

Front 36

Potency is related to _________

Back 36

lipid solubility (gets through lipid membrane faster)

Front 37

General anesthetics are "dangerous" with therapeutic indixes _________

Back 37

2-4 (can produce circulatory failure)

Front 38

Although brain is site of action, anesthetic potency is measured on the basis of ___________ that produces immobility in 50% of patients exposed to painful stimuli.

Back 38

alveolar gas concentration

Front 39

Awareness or recall is highly unlikely at the MAC levels of________

Back 39

1.2-1.3 MAC

Front 40

MAC is inversely related to ________

Back 40

potency

Front 41

Define Potency.........

Back 41

a content of drug required to produce a desired specific effect. A highly potent drug gives a large response at low concentrations. A lower potency drug evokes a small response at low concentrations.

Front 42

Define Efficacy............

Back 42

relationship between occupancy of the receptor and ability to start a response

Front 43

Define Affinity .............

Back 43

the ability of the drug to bind to the receptors.

Front 44

MOA of Inhaled Anesthetics and what is Meyer - Overton rule.....

Back 44

MOA is poorly understood

Meyer-Overton rule - proposes that all inhalation agents share a common MOA at the molecular level;

anesthetic potency of inhalation correlates directly with their lipid solubility

Meyer-Overton rule also postulates that the number of molecules dissolved in the lipid cell membrane, and not the type of inhalation causes anesthesia.

Evidence that general anesthetics may act by binding to only a small number of targets in the CNS.
Voltage-Gated Channels - unlikely to play a substantial role production of anesthetic state.
Ligand-Gated Ion Channels - may enhace affinity of GABA for its receptor-relevant to production of anesthetic-induced immobility

Front 45

Oldest anesthetic agent sill in use today_________

Back 45

Nitrous Oxide

Front 46

Gas that is ONLY inorganic anesthetic gas in clinical use is_________

Back 46

Nitrous Oxide

Front 47

Only inhalational anesthetic used today that is not a vapor and is a true gas by definition is_________

Back 47

Nitrous Oxide

Front 48

What gas is this?

MOA - unknown
Prominent analgesia BUT minimal muscle relaxation
Causes PONV. MAC 104%
Can lease blood to enter an air-filled cavity 34 times faster than nitrogen.
Minimal if any effects on liver, kidney or GI tract

Back 48

Nitrous Oxide
N=N=O

Front 49

What gas is this?


Flammable, irritating vapor, slow onset and prolonged recovery. Exposion hazard.

Back 49

Diethyl Ether

Front 50

What gas is this?

Halogenated alkane (Alkane contain only H and C atoms bonded by single bond)
Halogenated - replacement of one or more hydrogen atoms by a halogen (fluorine chlorine bromine or iodine)
THYMOL - is the preservative. Stays in vaporizers after and can cause malfunction.
Non flammable, relatively POTENT. Unpredictible CHEMICAL HEPATITIS
Significant Myocardial Depression & irritability.

Back 50

Halothane

Front 51

Back 51

halogenated methyl ethyl ether
Less arrhythmia, N/V, post-op shivering than Halothane
High potency, rapid onset and recovery, muscle relaxation
Concern in pts w/SEIZURE Disorder
Used in adults not so much on peds
Metabolite FLUORIDE usually does not reach levels required for renal toxicity

Front 52

Back 52

halogenated methyl ethyl ether
Chemical ISOMER of Enflurane, but has different chemical properties
Rapid, smooth depth of anesthesia with limited effects on pulse or respiration
NO hepatic/renal toxicity
CBF and ICP reaily controlled
Arrhythmia uncommon
Skeletal muscle relaxation

Front 53

Back 53

fluorinated methyl etheyl ether. Differs from Iso only by substitution of a fluorine atom for a Cl atom.
High vapor pressure, BOILS at room temp.
Heated and pressurized and requires electrical power.
Limit solubility - RAPID ONSET & RECOVERY.
Little renal/hepatic metabolism
Airway irritant, NOT FOR INDUCTION

Front 54

Back 54

Fluorinated methyl isopropyl ether
Vapor pressure resembles Halothane & Iso
LOW blood solubility, HIGH potency
3-5% metabolized, releasing more Floride. Does not cause hepatitis
Degradation in CO2 absorber. Can form Compound A. Keep fresh gas flows above 1L/min

Front 55

********FACTS********
Halogenation reduces flammability
Fluorination reduces solubility
Fluorination decrease potency
Substitution of Cl for F (Iso vs. Des)
decreases solubility
decreases potency
increase Vapor pressure and decreases boiling point

Back 55

************more FACTS**********
All inhaled anesthetics liquid at 20 C
Vapor Pressure: Pressure exerted by the molecules of the vapor phase at equilibrium of molecules moving in and out of liquid phase
Vapor Pressure dependent on temp and physical characteristics of liquid, independent of atmospheric pressure
Increased temp increases vapor pressure
Boiling Point: Temp at which vapor pressure equals atmosphetic pressure

Front 56

Variable Bypass Vaporizer (Datex Ohmeda Tec 4,5,7 or North American Drager Vaporizer 19.n and 20.n

Back 56

Halothane
Enflurane
Isoflurane
Sevo

Front 57

Tec 6 Vaporizer: Electroniclly heated, thermostatically controlled, pressurized, electromechanically coupled, dual circuit gas-vapor blender

Back 57

Desflurane