Anesthetics

Question 1

What is the chemical structure of an anesthetic?

Answer 1

lipophilic synthetic aromatic or heterocyclic residue, intermediate ester or amide linkage and a weakly basic tertiary amine terminal

Question 2

Why is lipophilicity of key component of anesthetics?

Answer 2

it can penetrate cells (corneal layers), skin, CNS, and blood brain barrier

Question 3

What does myelin do to anesthetics?

Answer 3

enhances its sensitivity independent of diameter (lipid myelin attracts lipophilicity)

Question 4

Are small diameter nerves more or less sensitive than large diameter nerves?

Answer 4

small (highly active) are more sensitive to anesthetics = fire more rapid and has repeated opportunity to bind drug (large = recover quicker - usually have life giving functions)

Question 5

What is the order of effects for anesthetic targets?

Answer 5

pain > cold > warmth > touch > deep pressure > motor

Question 6

what does the intermediate chain linkage on an anesthetic link?

Answer 6

a lipophilic aromatic residue with a hydrophilic amino group - longer linkage enhances potency

Question 7

Is the receptor on the nerve lipophilic or hydrophilic?

Answer 7

hydrophilic - the more lipophilic the more effective (potency)

Question 8

How are ester linkage anesthetics metabolized?

Answer 8

locally by pseudocholinesterase (PChE)

Question 9

What are the 3 parent structures in the ester group? and which anesthetics are in those groups?

Answer 9

PABA (tetracaine, procaine, benzocaine, and benoxinate), MABA (proparacine), and BA (cocaine)

Question 10

How are the amide linked anesthetics metabolized?

Answer 10

hepatic metabolism, urinary and biliary excretion

Question 11

What is the most common eye-care amide anesthetic?

Answer 11

lidocaine

Question 12

What is the difference in action between esters and amides?

Answer 12

amides are longer acting, have greater systemic effects and readily cross the blood brain barrier

Question 13

How do anesthetics increase absorption and intercellular permeability?

Answer 13

break the corneal epithelium tight junctions

Question 14

What is the schirmer I test?

Answer 14

without anesthetic = measures basal tearing + reflex tearing

with anesthetic = measures basal tearing (neurogenic reflex tearing is suppressed)

Question 15

What is the best anesthetic to use when collecting cultures?

Answer 15

Preservative free proparacine - least antibacterial/antifungal effects

Question 16

What are proparacine and tetracaine used for?

Answer 16

tonometry, gonio, sutures, nasolacrimal massage, ultrasound

Question 17

what is an advantage of proparacine over tetracaine?

Answer 17

proparacaine has less sting - but has potential to increase corneal thickness (cause swelling) and affects goldmann and pachymetry

Question 18

what is an advantage of tetracaine over proparacaine?

Answer 18

tetracaine has greater corneal toxicity but penetrates more than proparacaine

Question 19

Which ester anesthetic produces the least amount of corneal compromise but has the potential to increase thickness?

Answer 19

benoxinate

Question 20

what is the onset and duration for topical anesthetics?

Answer 20

(mainly esters) - 30sec onset and about 15min duration (procaine is longer)

Question 21

Why are amide anesthetics usually longer lasting and take longer to take effect?

Answer 21

they are not locally metabolized - need to go to liver

Question 22

How can you double lidocaine duration?

Answer 22

use with epinephrine for vasoconstriction

Question 23

If a patient has a red eye following anesthetic use - are they allergic to the drop?

Answer 23

not necessarily - vasodilation of lidocaine may relax nerves responsible for vascular tine and if it was a long half-life anesthetic they may have a red eye

Question 24

Why would you pair an anesthetic with a vasoconstrictor?

Answer 24

reduce absorption and systemic toxicity, reduce metabolism, keep effect localized, and reduce bleeding at injection site

Question 25

What is the only anesthetic that vasoconstricts instead of vasodilates?

Answer 25

cocaine

Question 26

what are the systemic adverse effects of cocaine?

Answer 26

excitement, convulsions, rapid palpitations, nausea, and delirium

Question 27

what are the ocular adverse effects of cocaine?

Answer 27

desquamation, mydriasis, lid retraction (unilateral)

Question 28

Why do TCADs, MAOIs, epinephrine, phenylephrine, Guanethidine, and Reserpine cause adverse reactions with cocaine?

Answer 28

these drugs also excite the sympathetic nervous system - amplify the effects of cocaine and cause serious damage

Question 29

what are some adverse effects of cocaine on ocular tissues?

Answer 29

desquamation, corneal edema, conjunctival hyperemia, allergic conjunctivitis, and lacrimation

Question 30

who is more susceptible to desquamation?

Answer 30

patients over age 50 - reduced blink rate (cells die), reduced tear production, and increased evaporation

Question 31

How do you determine if your patient has conjunctival hyperemia vs. allergic conjunctivitis from an anesthetic?

Answer 31

allergic conjunctivitis will itch (both will be red eyes)

Question 32

Why do you need to know what anesthetics your patient may have been on for surgeries or procedures?

Answer 32

they may have nystagmus or visual hallucinations from long lasting (long half-life) anesthetics

Question 33

what are the cardiovascular anesthetic adverse effects (except from cocaine)?

Answer 33

decreased excitability, decreased cardio force/conduction --> hypotension = cardio collapse

Question 34

what are some anesthetic cautions?

Answer 34

cholinesterase deficiency, hyperthyroidism, cardiac disease, allergy history, and sensitivity to similar drugs

Question 35

What is the primary sign of anesthetic abuse syndrome?

Answer 35

yellow-white stromal ring at the active site

Question 36

What are some signs and symptoms of anesthetic abuse syndrome?

Answer 36

corneal epithelium defect (stromal edema and descemet's folds), disciform stromal infiltrates, KP, hypopyon, hyphema, lid edema, neovascularization, discharge

Question 37

What are some non-anesthetic alternatives (allergy to amide/esters)?

Answer 37

``` Injectable = 1% Benadryl or saline Topicals = EMLA, lidoderm patch, or iontophoresis ```