Local Anaesthetic Agents

Question 1

LA agents refers to drugs which (reversibly or irreversibly ?) block the transmission of __________ nerve impulses.

Some others also ß-blockers, antihistamines.

Answer 1

reversibly

peripheral

Question 2

A reversible block may also be produced by __________ factors; __________, _______.

Answer 2

physical

pressure, cold.

Question 3

All LA originates from __________ , an __________ found in Erythroxylum coca in 1860.

Its fisrt LA action was demonstrated by Koller ,1864. limited use owing to __________.
In 1904, __________ synthesized

Answer 3

cocaine ; alkaloid

allergic reactions.

procaine

Question 4

In North America, the __________ {A,C,P} are popularly used but its use is limited by potential __________

Answer 4

esters{A,C,P}

allergic reactions

Question 5

Classification/structure
Based on the physical structure: ________ and ________.

The ________ chain allows either an ________ OR ________ linkage.

Answer 5

esters and amides.

intermediate chain

ester[ESTER LA}

amide {AMIDE LA}

Question 6

Esters; examples???

Amide ; list 6.

Answer 6

Esters; cocaine,procaine,amethocaine, chloroprocaine.
Amide ; lidocaine,mepivacaine, prilocaine, bupivacaine, ropivacaine, levobupivacaine.

Question 7

Classification of LA

Based on potency/duration of action

Short duration of action +low anaesthetic potency; _______,__________

Intermediate duration of action/anaesthetic potency;
__________, __________, __________, __________.

Long duration of action and high potency;
__________, __________, __________

Answer 7

procaine, chloroprocaine.

lidocaine, mepivacaine, prilocaine, cocaine.

bupivacaine, tetracaine, etidocaine

Question 8

Classification of LA

Esters tend to _________ spontaneously in storage and should only be _________ once.

Amides are (more or less?) stable in solution. H/v the heavy preparations is (more or less?) stable with heat changes, it is allowed to be heat sterilized once.

Answer 8

hydrolyse ; heat sterilized

more ;less

Question 9

Pharmacology of LA

Duration of action; increases with ______ solubility, affinity for ____________ , type of ____________ fibre.

Potency; related to __________

Rate of onset; _______ of the LA , this will increase the proportion of the drug in the non-ionised form.
The __________ the pka, the faster the the onset of action of the LA.
__________ of the LA to a lesser extent also affect the rate of onset.

Answer 9

lipid

binding to protein

peripheral nerve fibre.

lipid solubility

pka ; lower

Lipid solubility

Question 10

Pharmacokinetics of LA
— Site of injection is influenced by _____________

Answer 10

rate of blood flow

Question 11

Pharmacokinetics of LA

IVRA; ___________ release will result in ————————————- directly into the circulation if released within _______ of application.

Answer 11

premature tourniquet

rapid entry of large dose

20 mins

Question 12

Pharmacokinetics of LA

LA gets into the systemic circulation
____________ {no effect}
Lungs{some _________ and ____________ }
Tissues depending on blood flow{ brain, heart, liver, spleen, muscle, fat}

Answer 12

Right heart

sequestered and metabolized

Question 13

Pharmacokinetics of LA

Metabolism of LA; generally the ester LA undergo __________ by __________. This is a very (slow or rapid?) process hence the blood concentration difficult to measure in blood after RA. Hence _____________ with them is very rare.

Amide LA are metabolised in the _______. __________ however undergo some extra-hepatic metabolism. Severe ___________ damage will affect metabolism of amide LA

Answer 13

hydrolysis by plasma cholinesterase

Rapid; systemic toxicity

liver; Prilocaine

hepatocellular

Question 14

Pharmacokinetics of LA
—
Protein binding; LA bind to plasma protein to some degree. 2 plasma proteins; ——————- and _______________ .
—
— Placental transfer; LA present in maternal blood will equilibrate through the ______________ and then________________ {α1-acid}. .

Answer 14

α1- acid glycoprotein and albumin

placental membrane

fetal circulation

Question 15

Pharmacokinetics of LA

α1-acid glycoprotein has ________ capacity but binds ______ while albumin has ____ affinity but _______ capacity.

___________ is least bound and yet the least toxic amide LA.

Answer 15

lesser; avidly

low; large

Prilocaine

Question 16

Pharmacodynamics of LA
During the resting phase, the interior of a peripheral nerve axon has a potential difference of about -70mV relative to the outside. With nerve stimulation, it rises to +20mV then repolarization until resting potential is restored. {Na/K}

The ___________ portion of LA that enters and ________ the __________ channels, and prevents _________ of _______ ions. As a result, no action potential is generated or transmitted, and ______________ occurs.

Answer 16

re-ionized

blocks ; sodium; influx; sodium

conduction blockade

Question 17

Additives to LA

List 8

AIM: To adjust the pH, tonicity, baricity, preservative, pharmacologic reasons

Answer 17

Adrenaline
Dextran
Clonidine
Sodium bicarbonate
Felypressin
Neostigmine
Hyaluronidase
EMLA

Question 18

EMLA {__________________________________}

Answer 18

Eutectic Mixture of Local Anaesthetics

Question 19

LA Toxicity

If significant amounts of LA reach the tissues, heart and brain, they exert the same membrane-stabilizing effect
as on peripheral nerve, resulting in ________________________.

Hence the features; ___________ or __________
of the tongue and circumoral area; ____________, anxious, drowsy and/or complain of ________. ___________ is lost, convulsions.

Answer 19

progressive depression of function

numbness or tingling

light-headed; tinnitus

consciousness

Question 20

Mgt of LA Toxicity
No matter how careful the anaesthetist is with regard to prevention, facilities for treatment must always be available.

The _________ is maintained and _______ administered by _________ , using ______________ , if apnoea occurs.

Convulsions ; small increments of either ___________ (___ mg) , _________ or __________ (____ mg).

Answer 20

airway; oxygen

face mask; artificial ventilation

Midazolam;2

diazepam or thiopental; 50

Question 21

Mgt of LA Toxicity

Excessive doses should not be given to control convulsions, as ____________ may be exacerbated. If cardiovascular collapse occurs despite ________________ (and this is (common or rare?)), it should be treated with an __________ drug with α and β effects e.g. __________ in ______ mg increments.

Answer 21

cardiorespiratory depression

adequate oxygenation; rare

adrenergic; ephedrine

3-5

Question 22

Choice of LA

___________ of the solution
______ of injection/ _____of absorption

Expected _________ of surgery
___________ of the drug

Answer 22

Strength

Site; rate

duration; Availability

Question 23

Site of injection and rate of absorption when choosing an LA

Lidocaine ____% for infiltration/IVRA, ____% for minor nerve block, _____ % brachial plexus and sciatic /femoral nerves, _____% for epidural, _____% for spinal.

Answer 23

0.5

1

1-1.5

1.5-2

2.5

Question 24

Role of Cocaine in modern anaesthetic practice?

Answer 24

Cocaine has no role in modern anaesthetic practice,

Question 25

Cocaine

used in _______________ surgery for its vaso__________ action.

Because of its use as a drug of __________, it is increasingly difficult to obtain cocaine legitimately at a reasonable price.

Causes systemic ________ and _______ reactions

Answer 25

ear, nose and throat

constrictor; addiction

toxicity; allergic

Question 26

Benzocaine
An ester LA, does not ionize easily hence readily form _____________ and can only be used ___________.
It is hydrolysed very rapidly to ______________ , hence _____ toxicity but may cause _______ reactions.

Mode of mech is the classical effect on the Na/K but thought to diffuse directly into the cell membrane.

Answer 26

water soluble salts

topically; ρ- aminobenzoic acid

Low ; allergic

Question 27

Procaine & Chloroprocaine

Ester LA, ______ shelf life, ______ duration of action, relatively ______ incidence of allergic reactions .

_______________ is hydrolysed faster than _________ and more potent.

Answer 27

short; brief; high

Chloroprocaine

procaine

Question 28

Most potent and longest acting ester LA in clinical use ???

Answer 28

Amethocaine/tetracaine

Question 29

Amethocaine/tetracaine

Hydrolysed by ________________, (slowly or rapidly?) hence quite _______

In small doses, used for ______ anaesthetic

Answer 29

plasma cholinesterase

Slowly ; toxic

spinal

Question 30

Lidocaine
Lidocaine (previously ___________ )

Having been used safely and effectively for ___________ type of local anaesthetic procedure

Answer 30

lignocaine

every possible

Question 31

Local Anaesthethic

__________ is currently the standardagent. It has no unusual features and is also a standard __________.

Answer 31

lidocaine

Question 32

Lidocaine is used commonly for _________ , for peripheral nerve blocks if __________ duration is required. It can be used for intravenous regional anaesthesia, although ___________ is preferred.

Answer 32

infiltration

an intermediate

Prilocaine

Question 33

Lidocaine can be used for intravenous regional anaesthesia

T/F

Answer 33

T

although prilocaine is preferred.

Question 34

lidocaine
Lidocaine 5% has been used for _______ anaesthesia, although the ___________ is unpredictable, the duration of action is relatively ________. However there are relatively new concerns about its __________ in such high concentrations.

Answer 34

subarachnoid

degree of spread

short; neurotoxicity

Question 35

1-2%, lidocaine produces _______ anaesthesia with a ______ onset time.

Lidocaine 2—4% is used by many anaesthetists as a _______ solution for anaesthesia of the ____________ before awake fibreoptic intubation.

Answer 35

epidural

Short

topical

upper airway

Question 36

Bupivacaine
The introduction represented a significant advance in anaesthesia.

Relative to potency, its acute central nervous system toxicity is __________ than that of lidocaine, but its (shorter or longer ?) duration of action reduces the need for ___________ , and thus the risks of ____________ .

Answer 36

only slightly lower

longer

repeated doses

cumulative toxicity

Question 37

Several deaths have occurred after accidental intravenous administrationof large doses of bupivacaine

T/F

Answer 37

T

Question 38

Uses of bupivacaine
Bupivacaine, for _________ , frequently for ______________ blockade and for __________ and _________ anaesthesia because of its ____________________.

Answer 38

infiltration; peripheral nerve

subarachnoid and epidural

prolonged duration of action

Question 39

Uses of bupivacaine

________ —-% is the most commonly used drug for subarachnoid anaesthesia in the UK.
It may be used in a _____ solution or in a ________ formulation

Answer 39

Bupivacaine 0.5

plain; hyperbaric