wk1- intro to LA

Question 1

uses for LA

Answer 1

1. diagnostic
2. therapeutic
3. surgery

Question 2

LAs that podiatrist can use

Answer 2

bupivocaine 0.5% or less

levobupivacaine of 0.5% or less

lidocaine of 2% or less

prilocaine 2% or less

Question 3

modes of delivery of LA

Answer 3

1. topical
2. infiltrative
3. ring block
4. peripheral nerve block
5. EMLA
6. iontophoresis

Question 4

podiatrists with ESM can do what with LAs

Answer 4

prescribe
give treatment dose
administer
purchase
possess
dispose

Question 5

what LAs do podiatrists with ESM have access to

Answer 5

methoxyflurane- more of an analagesic

tetracaine
bupivacaine
levobupivacaine
lidocaine with or without adrenaline
prilocaine
ropivacaine

Question 6

what LA does EMLA consist of

Answer 6

prilocaine

Question 7

what is iontophoresis

Answer 7

topical anaesthesia via an electric current

Question 8

what does LA do to the body

Answer 8

reversible loss of sensation in an area of the body

Question 9

how does LA work

Answer 9

they block sodium ion channels so sodium cannot flow into neurons
this inhibits the transmission of APs along individual neurons

Question 10

anatomy of LA (3 things and what do they determine?)

Answer 10

aromatic ring- confers lipid solubility

intermediate linkage- permits classification and mode of metabolism (amide or ester)

terminal amine- charged or uncharged to make it water or lipid soluble

Question 11

types of LA

Answer 11

amide
ester

Question 12

ester

metabolism, toxicity, allergy, stability, onset of action, pKa

Answer 12

M: rapid by protein cholinesterase
T: less likely
A: more likely
S: photo/temp labile
O: slower
pKa: higher (8.5-8.9)

Question 13

amide

metabolism, toxcity, allergy, stability, onset, pKa

Answer 13

M: slower, by the liver
T: more likely
A: less likely
S: very stable
O: moderate to fast
Pka: Close to 7.4

Question 14

types of esters

Answer 14

cocaine
chloroprocaine
tetracaine

Question 15

types of amides

Answer 15

bupivacaine
lidocaine
ropivacaine

Question 16

unpronated LA molecules can what

Answer 16

pass through cell membranes because theyre lipophilic

Question 17

define pKA

Answer 17

pH where drug is 50% ionised and unionised

Question 18

if the pka is low what does that mean for the LA drug in the body

Answer 18

lower the pKa, more drug present in unionised form, the faster the onset of drug

Question 19

what nerve fibers are effected by LA, what order is sensation lost

Answer 19

greatest effect is on automatic and small myelinated nerve fibers than large myelinated fibres

C-unmyelinated,
B-unmyelinated,
A delta (small myelinated)

order of nerve sensation loss

1. pain
2. temp
3. touch
4. deep pressure
5. motor

Question 20

how many nodes have to be blocked

Answer 20

more than 1 as AP can skip over a blocked node called saltatory conduction

Question 21

what makes onset of time faster?

Answer 21

the closer the pKa is to tissue pH (7.4), the more unionised form which causes a faster rate of onset

Question 22

LAs onset time, fastest to slowest

Answer 22

mepivacaine

lidocaine/prilocaine

bupivacaine/ropivacaine

Question 23

what speeds up onset?

Answer 23

alkalinisation (eg bicarbonate solution added to an LA)

Question 24

important characteristics of LAs

Answer 24

1. onset
2. duration
   3.toxicity
3. distribution
4. regression

Question 25

duration of LA depends on

Answer 25

1. lipid solubility (greater action)
2. molecular size (greater protein binding)
3. protein binding (greater action)

Question 26

injecting LA near vascular sites will result in

Answer 26

loss of LA as it is removed by systemic circulation too quickly

Question 27

maximum safe dose for lidocaine can be increased by the addition of what and why

Answer 27

adrenaline

delays the absorption of LA and prolongs its effects through vasocontriction in area of injection and confining LA to that region

Question 28

combining LA with adrenaline does what to the duration

Answer 28

increases the drugs duration

Question 29

when is adrenaline contraindicated

Answer 29

peripheral nerve block where there is no contralateral arterial supply (feet/digits) as it can cause prolonged ischaemia leading to necrosis of tissue

Question 30

complications of LA

Answer 30

-failure of LA
-infection
-allergy/anaphylaxis
-drug interactions
-toxicity
-needle breakage
-bruising
-soft tissue damage
-cardiac arrest
-seizure

Question 31

reasons for LA failure

Answer 31

-EDS/marfans
-infection
-technique
-anatomical variation

Question 32

what common drugs predispose someone to overdose

Answer 32

CNS depressants

alcohol
antidepressants
antihistamines
benzos
antiphychotics
LA
opioids
muscle relaxants

Question 33

difference between absolute and relative OD

Answer 33

absolute- dose too large, absorbed into CVS more rapidly than liver can remove it

relative- dose is fine, injection technique causes elevation

Question 34

signs of overdose (mild-mod)

Answer 34

lightheaded, restless, metallic taste, numbness, drowsiness, loss of consciousness, talkative, excitable, slurred speech, euphoria

Question 35

signs of overdose (mild to high)

Answer 35

1. tonic clonic siezure activity
2. generalised CNS depression
3. depressed BP, HR, resp rate

Question 36

common allergic reactions to LA

Answer 36

urticaria (wheals)
angioedema

typically occurs within 1 hour

Question 37

how long does it take for anaphylaxis to occur

Answer 37

within5-30mins

Question 38

signs of anaphylaxis

Answer 38

difficulty breathing
swelling of tongue/face/throat
wheeze/cough
cant talk
dizziness

Question 39

when is signed consent required for LA

Answer 39

not when given without surgical intervention

yes when being used as primary treatment (chronic neurological pain)

Question 40

documentation of LA includes

Answer 40

1. site of injection
2. time of injection
3. LA drug name and concentration
4. dose delivers- Mg
5. batch number
6. exp date
7. any adverse reaction noted

Question 41

minimum safety requirements

Answer 41

2 people in room
adrenaline
telephone

as well as clinical aprons/gloves