04c: Anesthetics

Question 1

The unimportance of the anesthetic’s (X) suggests that there (are/aren’t) distinctive receptors involved.

Answer 1

X = molecular shape (lack of chemical specificity);

Aren’t

Question 2

Generally, the longer the (X)

chain of the anesthetic, the higher the lipid solubility and the (lower/higher) the anesthetic potency.

Answer 2

X = hydrocarbon

Higher

Question 3

Which key observation argues against the lipid theory of anesthetic effect?

Answer 3

Beyond a certain point of hydrocarbon chain length, potency suddenly drops even though lipid solubility continues to increase

Question 4

Protein theory of anesthesia: Increasing evidence suggests that anesthetics exert their
effects by binding to the protein phase of membranes and acting as (X) (agonists/antagonists).

Answer 4

X = GABA(A)

Agonists

Question 5

The (X) locations in the nervous system may be the most important sites of anesthetic action

Answer 5

X = reticular formation and the

hippocampus

Question 6

T/F: with anesthesia, transmission along

peripheral nerves is not significantly affected.

Answer 6

True

Question 7

List the stages of anesthesia.

Answer 7

1. Analgesia
2. Excitement
3. Surgical anesthesia
4. Medullary paralysis

Question 8

In (X) stage of anesthesia, patient loses consciousness and responds only to (Y).

Answer 8

X = II (excitement stage)
Y = painful stimuli (reflex)

Question 9

In (X) stage of anesthesia, spontaneous movement ceases. Respiration becomes regular/shallow.

Answer 9

X = III (surgical anesthesia)

Question 10

In (X) stage of anesthesia, respiration ceases, along with (Y).

Answer 10

X = IV (medullary paralysis)
Y = vasomotor control
(CV collapse, death in minutes!)

Question 11

T/F: Inhalation anesthetics both enter and leave the body via the lungs.

Answer 11

True

Question 12

Metabolic degradation of anesthetics may be important in determining their (duration of action/toxicity).

Answer 12

Toxicity

Question 13

The more soluble the anesthetic agent is in blood, the (shorter/longer) it takes
for its (X) to increase in blood and the (shorter/longer) it takes for the concentration to increase in brain.

Answer 13

Longer;
X = partial pressure
Longer

Question 14

High Blood:gas partition coefficient means (low/high) (X) solubility. Thus, (shorter/longer) time to reach a given degree of anesthetic effect, and (shorter/longer) the recovery time.

Answer 14

High;
X = blood
Longer; longer

Question 15

Rise in pulmonary ventilation has greatest effect on anesthetics with (X) characteristic.

Answer 15

X = high blood:gas solubility coefficient

due to greater pulmonary blood flow

Question 16

Equilibration of the anesthetic from blood to tissue occurs most rapidly with vessel (rich/poor) group of tissues, such as:

Answer 16

Rich;

brain, heart, liver, kidney

Question 17

The MAC (minimum alveolar concentration) is a key concept in anesthesia. What does it represent?

Answer 17

Amount (% atm P) of anesthetic that prevents movement in 50% of subjects in response to a standard surgical incision

A measure of potency

Question 18

In the operating room, anesthetic concentrations of (X) MAC are frequently used. This is because drugs such as (Y) decrease the anesthetic requirements.

Answer 18

X = 1 or less
Y = morphine, thiopental, diazepam

Question 19

(Hypo/hyper)-natremia, (hypo/hyper)-thermia, and (hypoxia/hypocapnia) decrease MAC/anesthetic requirements.

Answer 19

Hypo; hypo; hypoxia

Question 20

Cocaine, amphetamines and (acute/chronic) EtOH use (increase/decrease) MAC.

Answer 20

chronic; increase

Question 21

MAO inhibitors (increase/decrease) MAC

Answer 21

Increase

Question 22

Perhaps the most widely used inhaled anesthetic agent in the U.S.A today

Answer 22

Isoflurane

Question 23

T/F: Therapeutic index is relatively wide for inhaled anesthetics.

Answer 23

False - very narrow (dangerous drugs)

Question 24

Resp effects of anesthetics:

Answer 24

1. Resp depression; fast, shallow, regular breathing
2. Increase oxygen gradient
3. Inhibit pulmonary hypoxic vasoconstriction

Question 25

Isoflurane is in (X) class of (local/inhaled) anesthetics.

Answer 25

X = Halogenated hydrocarbons | Inhaled

Question 26

Nitrous oxide is in (X) class of (local/inhaled) anesthetics.

Answer 26

X = inorganic agents | Inhaled

Question 27

Local anesthetics are agents that prevent/relieve (X) sensation by which mechanism?

Answer 27

X = pain Interrupting nerve conduction in peripheral nervous tissue (bind R within the pore of Na+ channels in nerves and block ion movement through)

Question 28

T/F: When local anesthetics applied to nerve tissue, they cause both sensory and motor paralysis

Answer 28

True

Question 29

List the amide-type Local Anesthetics. Star the long-acting one.

Answer 29

1. Lidocaine 2. Bupivacaine* *note: amide, lido, bupivac all have letter "i"

Question 30

List the ester-type Local Anesthetics. Star the long-acting one.

Answer 30

1. Procaine | 2. Tetracaine*

Question 31

Local anesthetics have hydrophilic property conferred by (X) part of structure and lipophilic property conferred by (Y) part of structure.

Answer 31

``` X = tertiary amino group (pKa 8-9) Y = aromatic ring ```

Question 32

(X) is the major difference | between Ester and Amide Local Anesthetics. What are the enzymes that work on each class?

Answer 32

X = biotransformation Amides: CYP450 Ester: Pseudocholinesterase (plasma and tissues)

Question 33

Which mechanism contributes to the toxicity of local anesthetics?

Answer 33

nonselective block of the Na+ | channel (as well as other voltage-gated and ligand-gated ion channels)

Question 34

Local anesthetics are (strong/weak) (acids/bases) with pKa range of (X). They're formulated as (Y) for increased (aqueous/lipid) solubility/stability.

Answer 34

Weak bases; X = 7.5-9 Y = salts aqueous

Question 35

Local anesthetics are predominantly in the (charged/uncharged), form at physiologic pH. Which form crosses the membrane? Which form binds the active site on Na channel?

Answer 35

Charged (cationic form) | Uncharged form crosses, charged form in cytoplasm binds active site

Question 36

T/F: Increased lipophilicity of local anesthetics increases distribution into nerve fiber and increases potency.

Answer 36

True

Question 37

T/F: Increased lipophilicity of local anesthetics increases duration of action.

Answer 37

True

Question 38

High pKa of local anesthetics (increases/decreases) (X).

Answer 38

decreases | X = onset time (slower distribution into nerve fiber)

Question 39

Inflammation, causing (rise/drop) in pH, has which effect on local anesthetics?

Answer 39

Drop (so more H ions and protonated drug); | decreases onset time

Question 40

T/F: Different types of neurons have different sensitivities to Local Anesthetics agents

Answer 40

True - based on size and myelination

Question 41

What's the order of nerve blockade by local anesthetics from greatest to least blockade (based on myelination and size of n fiber)?

Answer 41

1. Small, myelinated 2. Small, unmyelinated 3. Large, myelinated 4. Large, unmyelinated

Question 42

List the order of loss of function (sensation, muscle, etc.) conferred by local anesthetics.

Answer 42

*remember, depends on which fiber type affected most by blockade* 1. Pain 2. T 3. Touch 4. Proprioception 5. Muscle tone

Question 43

Frequently firing pain fibers have (lower/higher) sensitivity to local anesthetics compared to resting fibers.

Answer 43

Higher; | greater access to active site if Na channel is open/inactivated

Question 44

T/F: Local anesthetic blocks circumferential fibers before those in core.

Answer 44

True

Question 45

In large mixed nerve bundle in extremities, block with local anesthetics (sensory analgesia) begins (proximally/distally) and spreads (proximally/distally). Why?

Answer 45

Proximally; distally proximal sensory fibers more circumferential in bundle; distal more at core

Question 46

Potential CNS adverse effects of local anesthetics.

Answer 46

Tremor, Restlessness, Convulsions

Question 47

Potential CV adverse effects of local anesthetics.

Answer 47

Decreased automaticity, Myocardial depression, arteriolar relaxation

Question 48

Antidote for local anesthetic toxicity.

Answer 48

20% IV lipid emulsion (pulls anesthetics out, like a lipid sink)

Question 49

Hypersensitivity reaction is risk with (amide/ester) local anesthetics and is attributed to (X) metabolite.

Answer 49

Ester X = PABA (para-aminobenzoic acid metabolite)

Question 50

Effects of Vasoconstrictor use with local anesthetics.

Answer 50

1. Increases duration of effect (increase neuronal uptake, decrease absorption in blood) 2. Decreases risk of local side effects in brain and CV

Question 51

Local anesthetics: spinal block (in CSF/subarachnoid space) can cause (increase/decrease) BP because..

Answer 51

Decrease; block of the preganglionic sympathetic fibers, causing vasodilation

Question 52

Epidural nerve block differs from spinal nerve block in that:

Answer 52

Injection into epidural space outside dura (as opposed to subarachnoid space in spinal block)