Inhaled Anesthetics

Front 1

most potent inhaled anesthetic

Back 1

isoflurane

Front 2

least soluble anesthetic

Back 2

desflurane

Front 3

least irritating anesthetic

Back 3

sevolfurane

Front 4

what is diffusion hypoxia

Back 4

washout of nitrous oxide can lower alveolar concentrations of oxygen and carbon dioxide

Front 5

Definition of MAC
What is the MAC for loss of awareness,
what is MAC awake

Back 5

alveolar concentration of an inhaled anesthetic at one atmosphere that prevents movement in response to a surgical stimulus in 50% of patients. Concentrations of inhaled anesthetics that provide loss of awareness and recall are about 0.4 to 0.5 MAC.
Mac awake is about 0.2

Front 6

how does MAC change w/ age

Back 6

decreases about 6% each decade ( excluding kids less than 1 yr old)

Front 7

what is vapor pressure?

Back 7

At equilibrium, the pressure exerted by molecular collisions of the gas against the container walls, as long as any liquid remains in the container, the vapor pressure is independent of the volume of that liquid.

Front 8

vapor pressure and temp?

Back 8

proportional relationship.

Front 9

what is partial pressure?

Back 9

For any mixture of gases in a closed container, each gas exerts a pressure proportional to its fractional mass.

Front 10

Dalton's law regarding total pressure of a container?

Back 10

The sum of the partial pressures of each gas in a mixture of gases equals the total pressure of the entire mixture

Front 11

what is the ideal gas law?

Back 11

each gas in a mixture of gases at a given volume and temperature has a partial pressure that is the pressure it would have if it alone occupied the volume. The entire mixture behaves just as if it were a single gas according to the ideal gas law.

Front 12

what does the concentration of any one gas in a mixture of gases in solution depend on?

Back 12

(1) its partial pressure in the gas phase in equilibrium with the solution, and (2) its solubility within that solution.
anesthetic gases administered via the lungs diffuse into blood until the partial pressures in alveoli and blood are equal

Front 13

what is Fi

Back 13

fractional concentration of a gas leaving the circuit

Front 14

what is FA

Back 14

fractional concentration of a gas in the alveoli

Front 15

what is partition coefficient, δ

Back 15

the ratio of dissolved gas (by volume) in two-tissue compartments at equilibrium.

Front 16

factors that increase the rise of FA/FI

Back 16

1.Low λB, The lower the blood:gas solubility
2. Low Q, The lower the cardiac output
3. High V.A, The higher the minute ventilation
4. High (PA - Pv), pulmonary arterial and venous blood partial pressure difference in partial pressures.

Front 17

overpressurization definition

Back 17

analogous to an intravenous bolus. This is the administration of a higher partial pressure of anesthetic than the alveolar concentration (FA) actually desired for the patient. Inspired anesthetic concentration (FI) can influence both FA and the rate of rise of FA/FI

Front 18

second gas effect

Back 18

Along with the concentration of potent agent in the alveoli via its uptake, there is further concentration via the uptake of nitrous oxide,

Front 19

factors affecting recovery from inhaled anesthetics?

Back 19

anesthetic solubility, cardiac output, and minute ventilation. Solubility is the primary determinant of the rate of fall of FA

Front 20

partial pressures in muscle and fat depend on

Back 20

the inspired concentration during anesthesia, the duration of administration, and the anesthetic tissue solubilities

Front 21

diffusion hypoxia def

Back 21

washout of high concentrations of nitrous oxide can lower alveolar concentrations of oxygen and carbon dioxide. The resulting alveolar hypoxia can cause hypoxemia, and alveolar hypocarbia can depress respiratory drive, which may exacerbate hypoxemia. It is therefore appropriate to initiate recovery from nitrous oxide anesthesia with 100% oxygen rather than less concentrated O2/air mixtures.

Front 22

molecular structure of isoflurane?

Back 22

halogenated methyl ethyl ether that is a clear

Front 23

whic inhaled anesthetic has lowest blood:gas solubility

Back 23

desflurane

Front 24

metabolism of sevo

Back 24

results in inorganic fluoride
sevoflurane is not metabolized to trifluoroacetate

Front 25

Sevo and dry CO2 canisters

Back 25

Sevoflurane can form carbon monoxide during exposure to dry CO2 absorbents, and an exothermic reaction in dry absorbent has resulted in canister fires

Front 26

what is compound A

Back 26

Sevoflurane also breaks down in the presence of the carbon dioxide absorber to form a vinyl halide called compound A. Nephrotoxin in rats, not in humans. Negligible formation at higher gas flows

Front 27

Xenon
mac?

Back 27

nonpungent, and odorless, and thus can be inhaled with ease
MAC 71%
has analgesic properties

Front 28

Nitrous
- mac
- controversy for use?

Back 28

MAC = 104%
does not produce significant skeletal muscle relaxation, analgesic effects
- flammable, B12 vit inactivation, nausea, potential MI, expantsion of gas bubbles, teratogen

Front 29

some factors that increase MAC

Back 29

Increased central neurotransmitter levels (monoamine oxidase inhibitors, acute dextroamphetamine administration, cocaine, ephedrine, levodopa)
Hyperthermia
Chronic ethanol abuse (determined in humans)
Hypernatremia

Front 30

what is hysteresis?

Back 30

that it quite consistently takes 0.4 to 0.5 MAC to lose consciousness, but less than that (as low as 0.15 MAC) to regain consciousness. This may be because of the speed of alveolar wash-in versus wash-out

Front 31

what is MAC-BAR?

Back 31

alveolar concentration of anesthetic that blunts adrenergic responses to noxious stimuli, has likewise been established and is approximately 50% higher than standard MAC.13 MAC also has been established for discreet levels of EEG activity, such as onset of burst suppression or isoelectricity.

Front 32

Administering 0.5 MAC of a potent agent and 0.5 MAC of nitrous oxide is equivalent to

Back 32

1 MAC

Front 33

Factors that decrease MAC

Back 33

Increasing age
Metabolic acidosis
Hypoxia (PaO2, 38 mm Hg)
Induced hypotension (mean arterial pressure <50 mm Hg)
Decreased central neurotransmitter levels (α-methyldopa, reserpine, chronic dextroamphetamine administration, levodopa)
α2-Agonists
Hypothermia
Hyponatremia
Lithium
Hypo-osmolality
Pregnancy
Acute ethanol administration
Ketamine
Pancuronium
Physostigmine (10 times clinical doses)
Neostigmine (10 times clinical doses)
Lidocaine
Opioids
Opioid agonist-antagonist analgesics
Barbiturates
Chlorpromazine
Diazepam
Hydroxyzine
Δ-9-Tetrahydrocannabinol
Verapamil , Anemia (<4.3 mL O2/dL blood)

Front 34

factors that do not alter MAC

Back 34

including duration of inhaled anesthetic administration, gender, type of surgical stimulation, thyroid function, hypo- or hypercarbia, metabolic alkalosis, hyperkalemia, and magnesium levels

Front 35

Sevoflurane and EEG

Back 35

High, long-lasting concentrations of sevoflurane (1.5 to 2.0 MAC), a sudden increase in cerebral sevoflurane concentrations, and hypocapnia can trigger EEG abnormalities that often are associated with increases in heart rate in both adults and children. maybe not best for pt w/ epilepsy

Front 36

Potent agents and CBF

Back 36

all incrase
Isoflurane, sevoflurane, and desflurane cause far less cerebral vasodilation per MAC-multiple than halothane

Front 37

what is uncoupling w/ respect to CBF and inhaled agents?

Back 37

The increase in CBF with increasing dose caused by the potent agents occurs despite decreases in CMR.

Front 38

effect of potent agents on brain autoregulation?

Back 38

Because the volatile anesthetics are direct vasodilators, all are considered to diminish autoregulation in a dose-dependent fashion such that at high anesthetic doses CBF is essentially pressure-passive

Front 39

volatile agents and effect on ICP?

Back 39

Like isoflurane, both sevoflurane and desflurane >1 MAC produce mild increases in ICP, paralleling their mild increases in CBF

Front 40

which agent depresses CSF production

Back 40

sevo at1 MAC depresses CSF production up to 40%

Front 41

volatile agents and EEG

Back 41

All three currently used agents at <1 MAC and N2O at 30 to 70% can produce shifts to increasing frequencies. Between 1 and 2 MAC the potent agents produce shifts to decreasing frequencies and increases in amplitude. At >2 MAC, all of the potent agents can produce burst suppression or electrical silence.

Front 42

what other than volatile agents influences EEG reading?

Back 42

hypoxia, hypercarbia, and hypothermia

Front 43

volatile agents and cortical somatosensory evoked potentials.

Back 43

All of the volatile agents cause a dose-dependent increase in latency and decrease in amplitude in all cortical SEP modalities

Front 44

volatile agents and motor evoked potentials?

Back 44

all agents depress them.

Front 45

Nitrous and cerebral blood flow and CMR

Back 45

preserved CBF but decreased CMRO2

Front 46

Nitrous and neuroprotection?

Back 46

antineuroprotective effect, as addition of N2O to isoflurane during temporary ischemia is associated with greater tissue damage and worsened neurologic outcome

Front 47

spontaneous ventilation and CO, HR and SV

Back 47

spontaneous ventilation decreases systemic vascular resistance and increases heart rate, cardiac output, and stroke volume as contrasted to positive pressure ventilation

Front 48

volatile anesthetics and pacemaker cells

Back 48

Sinoatrial node discharge rate is slowed by the volatile anesthetics and conduction in the His-Purkinje system and conduction pathways in the ventricle also is prolonged by the volatile anesthetics

Front 49

which anesthetic has a potential for coronary steal?

Back 49

iso
Isoflurane (and most other potent volatile anesthetics) increases coronary blood flow many times beyond that of the myocardial oxygen demand

Front 50

volatile anesthetics and cardioprotection

Back 50

mimic ischemic preconditioning and trigger a similar cascade of intracellular events resulting in myocardial protection that lasts beyond the elimination of the anesthetic. Preconditioned hearts may tolerate ischemia for 10 minutes longer than nonconditioned hearts

Front 51

which drugs abolish the cardioprotection?

Back 51

sulfonylurea
hyperglycemia as well, so insulin needs to be started.

Front 52

Des and autonomic nervous system?

Back 52

increase in resting sympathetic nervous system activity and plasma norepinephrine levels
Adequate concentrations of opioids or clonidine given prior to increasing the concentration of desflurane have been shown to attenuate these responses

Front 53

Volatile agents and minute ventilation?

Back 53

All volatile anesthetics decrease tidal volume and increase respiratory rate such that there are only minor effects on decreasing minute ventilation

Front 54

volatile agents and response to hypercarbia?

Back 54

All of the inhaled anesthetics produce a dose-dependent depression of the ventilatory response to hypercarbia

Front 55

what happens to the apneic threshold under anesthesia?

Back 55

It is generally 4 to 5 mm Hg below the prevailing resting Paco2 and unrelated to the slope of the co2 response curves or to the level of the resting Paco2.

Front 56

volatile agents and response to hypoxia

Back 56

depressed response

Front 57

volatile anesthetics and effect on pulmonary artery pressure?

Back 57

minimal since it doesn't affect the smooth muscle in the PA and depresses the CO
attenuate hypoxic pulmonary vasoconstriction (HPV).

Front 58

National Institute for Occupational Safety and Health recs for nitrous exposure

Back 58

25 parts per million (ppm) as a time-weighted average over 8 hours. The 1-hour exposure limit for halogenated anesthetics without nitrous oxide exposure is 2 ppm, and with nitrous oxide is 0.5 ppm.

Front 59

what is compound A

Back 59

Sevoflurane undergoes base-catalyzed degradation in carbon dioxide absorbents to form a vinyl ethe

Front 60

which absorbents cause more compound A production w/ sevo

Back 60

Barium hydroxide lime produces more compound A than soda lime and this can be attributed to slightly higher absorbent temperature during CO2 extraction

Front 61

when is CO produced in anesthesia machines?

Back 61

CO2 absorbents degrade sevoflurane, desflurane, and isoflurane to carbon monoxide when the normal water content of the absorbent (13 to 15%) is markedly decreased <5%. Exothermic reaction.

Front 62

which gas produces most CO?

Back 62

des

Front 63

which gas produces most heat w/ dessicated CO2 absorbers?

Back 63

sevo

Front 64

enflurane toxicity?

Back 64

nephrotoxicity presents as a high-output renal insufficiency that is unresponsive to vasopressin and is characterized by dilute polyuria, dehydration, serum hypernatremia, hyperosmolality, elevated blood urea nitrogen, and creatinin