Local Anesthetics - the drugs Flashcards
Its metabolite interferes with efficacy of sulfonamide antibiotics
Procaine
what LAs have significant 1st pass effect by the lungs
Bupivicaine
Lidoicaine
Prilocaine
Chloroprocaine duration after infiltration
30 min to 1 hr
LAs that come as pure enantiometrs
Ropivacaine
Levobupivacaine
*advantage = less toxic, easier to resuscitate in case of toxicity
What is the dose of Lidocaine for epidural placement?
It depends on the level of blockade required and the density of blockade required. If you want profound motor blockade at T4 for example and the epidural is placed at the L2-3 interspace that is about 10 segments. Say this person is average size – I would give 1.5ml per segments I wanted blocked – so I would give 15cc of 2% lidocaine. 15cc X 20mg/cc = 300mg of lidocaine. I would need to make sure that this amount did not exceed the maximum dose allowed which is 5mg/kg for plain lidocaine. If the patient was 70kg that is 350mg – so 15cc is O.K. If I wanted to give more I might add epi which would increase my maximum dose to 7mg/kg or 490mg.
Chloroprocaine Max Dose
12 mg/kg
Lidocaine uses?
- Regional/ neuraxial block
- Cough suppression
- Attenuate ICP/BP raise during laryngoscopy
- Attenuate reflex bronchospasm that may occur with airway instrumentation
- Suppress ventricular dysrhythmias
Tetracaine Max Dose
3 mg/kg
Cocaine toxicity sxs
cocaine ↓ reuptake of NE → leads to ↑ concentrations of NE
- restlessness, tremors, seizures & euphoria
- tachycardia/MI
LAs that come in racemic mixtures
Bupivacaine
Mepivacaine
Arrange LAs in the order of non-ionization %
cocaine, lidocaine, mepivacaine, chloroprocaine, prilocaine, ropivacaine, tetracaine, procaine
Procaine 3%
Chloroprocaine 5%
Tetracaine 7%
Cocaine 7%
Bupivacaine/Levobupivacaine 17%
Ropivacaine 17%
Lidocaine 24%
Prilocaine 24 %
Mepivacaine 39%
Bupivacaine E½t
3.5 hrs
LA great for differential nerve block (sensory>motor)
great for OB
Bupivacaine
when do you redose lidocaine (epidural)?
lidocaine lasts about 1.5-2 hours etc
Ropivacaine max spinal dose
15-20
Bupivacaine DOA after spinal
1.5 to 3.5 hr
List max doses of LAs
Bupivacaine, cocaine, tetracaine, ropivacaine, etidocaine, lidocaine, mepivacaine, choroprocaine
Bupivacaine 2.5 mg/kg
Cocaine 3 mg/kg
Tetracaine 3 mg/kg
Ropivacaine 3 mg/kg (3.5 w epi)
Etidocaine 4 mg/kg
Lidocaine 4 mg/kg (7 w epi)
Mepivacaine 4 mg/kg (7 w epi)
Chloroprocaine 12 mg/kg
Prilocaine duration after infiltration
1 -2 hrs
Mepivacaine duration after infiltration
1.5 - 3 hr
LAs with pKa in the ≈ 8s
Bupivacaine/Levobupivacaine 8.1
Ropivacaine 8.1
Cocaine 8.5
Tetracaine 8.5
Chloroprocaine 8.7
Procaine 8.9
which has more CNS toxicity poptential
lidocaine or mepivacaine
mepivacaine
Does lidocaine have an active metabolite?
YES.
2 Monoethylglycinexylidide (80% activity)
(Mono-ethyl-glycine-xylidide)
xylidide (10% activity)
Bupivacaine (Levobupivacaine)
duration after infiltration
4-8 hrs
LAs with pKa in the ≈7s
Mepivacaine 7.6
Etidocaine 7.7
Lidocaine 7.9
Prilocaine 7.9
Shortest DOA for epidural
Chloroprocaine
Ropivacaine duration after infiltration
4-8 hrs
LA toxicity s/s?
CNS
circumoral numbness, tinnitus, vision changes, dizzy, slurred speech, restless, muscle twitching (especially in the face), seizures (which cause CNS depression, apnea, hypotension)
CV
hypotension, myocardial depression, AV block
Note: bupivacaine is most CV toxic
Lidocaine max spinal dose
30-100 mg
Bupivacaine pros and cons?
Pro
highly protein bound
- low incidence of neuro complications with spinal
- longer DOA (good for post-op pain and labor)
Also, A alpha, beta, and gamma fibers are not completely blocked, so sensory is blocked and motor is not completely blocked.
Con
TOXICITY! very cardio toxic; pressure is still felt, that can freak people out
metabolism of prilocaine.
Rapid metabolism
TOXIC metabolite ortho-toluidine
Must be avoided in OB due to metabolite
Big doses will convert hgb to methemoglobin (treated with methylene blue)
Bupivacaine solution concentration
Spinal 0.5 - 0.75%
Epidural 0.0625 - 0.5%
Peripheral nerve block 0.25 - 0.5%
LAs that cannot be give epidurally
Procaine
Tetracaine
Lidocaine onset and DOA w/ epidural
onset 5-15 min
DOA 90-130 min
what LAs are highly lipid soluble
Bupivicaine
Etidocaine
Tetracaine
BET
Lidocaine Max Dose
4 mg/kg
7 mg/kg with epi
Chloroprocaine onset and DOA w/ epidural
onset 5-15 min
DOA 30-90 min
most cardiotoxic LA
Bupivacaine
LAs that cannot be given in aperipheral block
Tetracaine
Lidocaine solution concentrations
topical
regional IV
PNB
Spinal
Epidural
topical 4%
regional IV 0.25-0.5%
PNB 1-2 %
Spinal 1.5 - 5%
Epidural 1.5 - 2%
Mepivacaine onset and DOA w/ epidural
onset 2-15 min
DOA 1 - 3 hrs
Mepivacaine Max Dose
4 mg/kg
7 mg/kg with epi
What is chloroprocaine used for?
OB epidurals
it has an ultra rapid serum hydrolysis (metabolism) which reduces toxicity risk to mom and baby
LAs that can be given IV
Lidocaine
Prilocaine
How is cocaine metabolized?
Liver, plasma esterases, and about 10-12% eliminated by kidney
careful with renal disease
NOT PAVA like the other esters
Long DOA for an ester
Tetracaine
1.5 - 3.5hrs
Mepivacaine max spinal dose
40-80 mg
Bupivicaine max spinal dose
15-20 mg
pt cannot have epi
what LA is best alternative
Mepivacaine
it doesn’t vasodilate like lidocaine so can be used when avoiding epi
Bupivacaine Max Dose
2.5 mg/kg
Cocaine Max Dose
3 mg/kg
Which LAs have slow, moderate, and fast onsets?
Slow: procaine, tetracaine (esters)
Intermediate: bupivacaine
Fast: chloroprocaine, lidocaine, etidocaine, mepivacaine
Etidocaine Max Dose
4 mg/kg
LA not effective topically
Mepivacaine
Tetracaine max spinal dose
5-20 mg
Ropivacaine Max Dose
3 mg/kg
3.5 mg/kg with epi
Procaine duration after infiltration
45 min - 1 hr
Why is lidocaine avoided in spinals?
Linked to caudal equina syndrome
Epidural ok to use
LAs that are still questionable for a spinal block
Chloroprocaine
Lidocaine
Mepivacaine
Prilocaine
Procaine max spinal dose
100-200 mg
Bupivacaine onset and DOA w/ epidural
onset 15-20 min
DOA 3 - 6 hrs
LAs used topically
tetracaine
Lidocaine
S (or levo) enantiomer of bupivacaine
Ropivacaine
less cardio-toxic