anesthetics Flashcards
eliminate pain and other sensations in patients who undergo surgical manipulations
anesthesia
define general anaesthesia
Reversible state of CNS depression
What effects occur with general anaesthesia? (5)
- loss of consciousness: hypnosis
- loss of sensitivity: analgesia, anaesthesia
- loss of reflex activity: autonomic protection
- loss of motility: muscle relaxation.
Define local anesthesia
intervention is limited to a small area or limb
How does local anaesthesia work? (4)
- Reversibly nerve block
- ANS blocked (hypotension and vascular tone loss)
- block nociceptive receptors (sensory)
- no loss of consciousness
Which anaesthesia makes you lose consciousness?
general
Which anaesthesia doesnt make you lose consciousness?
local
The smaller the diameter of nerve fibers (C fibers) the _____ sensitive they are to anaesthetics.
more
How do we achieve differential blocking with local anesthesia? (2)
adjusting concentration and volume
Order the nerve fibers from largest to smallest: (3)
- A
- B
- C (smallest)
Order the nerve fibers from fastest to slowest conduction: (3)
- A
- B
- C (slowest)
Aα nerve fiber function
Motor function and proprioception
Aβ nerve fiber function
Touch-pressure
Aγ nerve fiber function
Muscle tone
Aδ nerve fiber function
Pain-temperature
B nerve fiber function
Vasoconstriction
C nerve fiber function
Pain-temperature
Blocking order of nerve fibres: (6)
- B
- C & Aδ
- Aβ
- Aγ
- Aα
Which nerve fibres are for pain-temperature?
C & Aδ
Sequence of nerve blocking effect wise? (5)
analgesia:
- sympathetic block (vasodilation)
- pain block
- thermal and pain fibers
Anaesthesia:
- touch and pressure sensitivity
- motor and proprioceptive
Anaesthesia mechanism of action (6)
decreased membrane permeability to sodium:
- inhibits Na+ voltage gated channels
- decreases action pot. porpagation
- incr. excitability threshold
- decr. conduction
- full conduction bloackade
Physico-chemical characteristics of Local Anaesthetics:
- Aromatic benzene ring: lipid solubility (potency)
- Amine portion: hydrophilic (pharmacological action)
- Ester or amide linkage: rate of metabolism and toxicity
if anaesthetics have high lipid solubility…
more potent
if anaesthetics have high protein binding…
high duration of action
if anaesthetics are less ionized… (2)
- faster entry
- lower latency period
all local anesthetics are _______ with a pKA of ______
- weak bases
- 7.5-9
At physiological pH, local anethesia is….
ionized in high proportion
What causes a low pKa LATENCY PERIOD? what does it mean?
low = if pKa and pH are closer, there is more non-ionized drug and it passes through the membrane faster
How does the non ionized fraction of local anesthetics work? (3)
passes through lipophilic nerve sheath
- then goes to the axon membrane
- then finally the neuronal membrane
How does the ionized fraction of local anesthetics work? (2)
- interacts with the channel to produce pharmacological action
- can only access the binding site from inside the cell, through the channel when it is open
The ionized fraction of local anesthetics is….
a charged cation
The ionized fraction of local anesthetics is….
a charged cation
What happens to the pKa latency period with local anaesthesia when there is a local infection?
acidosis retards diffusion by increasing the ionized fraction
CLASSIFICATION OF LOCAL ANAESTHETICS According to the linkage: (2)
- ester
- amide
What are the ester local anaesthetics? (4)
- COCAINE
- PROCAINE
- TETRACAINE
- BENZOCAINE
What are the amide local anaesthetics? (7)
ß LIDOCAINE ß MEPIVACAINE ß PRILOCAINE ß BUPIVACAINE ß LEVOBUPIVACAINE ß ROPIVACAINE ß ARTICAINE
What is the SHORT ACTION AND LOW POTENCY local anesthetics?
procaine
What are the INTERMEDIATE ACTION AND INTERMEDIATE POTENCY local anesthetics? How long is the action? (4)
- LIDOCAINE
- MEPIVACAINE
- PRILOCAINE
*150 min
What are the
LONG ACTION AND HIGH POTENCY local anesthetics? (4) how long?
- tetracaine
- bupivacaine
- L-bupivacaine
- ropivacaine
*6-8 hours
local anesthetic elimination?
renal
Which class of local anesthetics have less toxicity?
ester
Which class of local anesthetics are allergenic and have cross reactivity?
ester
Which class of local anesthetics have a very short half life?
ester
Which class of local anesthetics have an average half life?
amide
For general anesthesia what drugs cause analgesia?
opiates
For general anesthesia what drugs cause loss of relfexes?
neuroleptics
For general anesthesia what drugs cause muscle relaxation?
muscular blockers
For general anesthesia what drugs cause amnesia and loss of conciousness
anaesthetics
To get the effects of general anaesthesia various drugs are going to be administered _____ & ______
simultaneously and sequentially
What are the 3 phases of general anaesthesia?
- (preanaesthesia)
- induction
- maintenance
- awakening
What drug do we use for general preanaesthesia?
anxyolitics - benzo
What drug do we use for induction of general anesthesia? (4)
- anticholinergic: atropine
- IV anaesthetic: (Thiopental-Barbiturate, Propofol, Etomidate, ketamine)
- muscle relaxant: succinylcholine
- opiate: fentanyl, remifentanyl, morphine
What drug do we use for maintenance of general anesthesia? (2)
- inhaled anaesthetic: enflurance
- muscle relaxant: Atracuronium, Venocuronium
What drug do we use for awakening after general anesthesia? (3)
- anti-achetylcholinesterase: neostigmine
- anti-opiates: naloxone
- anti-benzo: flumazenil
what IV opiates do we use for general anaesthesia? (3)
fentanyl
remifentanyl
morphine
what IV barbiturate do we use for general anaesthesia?
thiopental
what IV neuroleptic do we use for general anaesthesia?
droperidol
what IV anticholinergic do we use for general anaesthesia?
atropine
what IV benzos do we use for general anaesthesia? (2)
midazolam
diazepam
what IV anesthesia do we use for general anaesthesia? (3)
- ketamine
- propofol
- etomidate
What are the inhaled anesthetic classes and names? (4)
Volatile liquids:
- enuflurane
- halothane
- sio/sevoflurane
Gas:
-nitrous oxide
Mechanism of action for general anaesthesia? (4)
- alters synaptic transmission
- hyperpolarization of neuron membrane
- decreased ability of neuron to respond
- acts on ion channels
opioid bradycardia with general anesthesia can be controlled with this drug….
atropine
Which opioid do we prefer for general anesthesia?why?
fentanyl
-rapid onset and short duration
How long is the effect of ketamine?
short action
ketamine indications?
- children
- minor painful procedures
What effects do ketamine have? what effect does it not have (3)
- sedation
- analgesia
- NO respiratory depression
What are ketamines cardiovascular effects?
increased:
- sympathetic activity
- blood pressure
- HR
- intracranial pressure
Ketamine contraindications (3)
-hypertension
heart disease
stroke
Ketamine lipid solubility?
high
etomidate indication in anesthesia?
induction
etomidate effects?
hypnotic
etomidate theraputic index? side effects?
high
respiratory depression
does etomidate cross the BBB?
yes
etomidate cross the BBB?
yes
length of etomidate action? why?
short because of rapid redistribution
etomidate recovery time?
very fast
propofol pharmacological effects? (2)
- sedation vs anaesthesia
- hypnotic
propofol physiological effects? (3)
- hypotension
- bradycardia
- respiratory depression
propofol pharmacokinetic effects? (2)
Short duration of action, fast recovery
What drug has less laryngospasm than fluranes in children?
halothane
halothane indications? (2)
- maintence general anaesthesia
- children
halothane pharmacological actions? adverse effects? (4)
sensitizes myocardium to catecholamines:
- high risk of arrhythmias
- respiratory depression
- hepatotoxicity esp. after repeated exposure
nitrous oxide adverse reactions?
- megaloblastic anaemia
- leukopenia
to avoid hypoxia we use _____% of nitrous oxide
less than 70%
Effect and adverse effects of nitrous oxide?
- analgesic
- loss of consciousness
- myocardial depression
What concentration produces loss of consciousness with nitrous oxide?
-80%
What concentration of nitrous oxide do we use for analgesia?
- with 50% oxygen
What concentration of nitrous oxide do we use for sedation?
with 25% oxygen
-75%
What affect do vasoconstrictions have on local anaesthetics? how? (3)
increased duration of action
- slower absoprtion = prolonged effect
- reduces risk of systemic toxicity
vasoconstrictors used with local anaesthetics cannot be applied _______. why? (2)
in distal areas
risk of necrosis
What are the vasoconstrictors used with local anaesthetics ? (2)
- Epinephrine = adrenaline (the most used)
- Phenylephrine
Which anesthetics produce intense vasodilation?
- procaine
- bupivacaine
- lidocaine
systemic side effects due to local anaesthesia?
- CNS: b/c lipid solubility
- cardiovascular: tachycardia
- allergic reactions (mainly esters)
- vasovagal rxns
- vasoconstriction adverse reactions
cardiovascular adverse effects with local anaesthesia?
- therapeutic doses: tachycardia
- high doses: hypotension, bradycardia, decreased contractility
What does vasovagal mean?
droqp in blood pressure
Pregnancy and local anaesthesia?
caution when in first and third trimester
Risk of toxicity for local anesthesia is high for the… (2)
children and elderly
local anesthesia can cause _______ and _____ failure
renal
hepatic
in what type of drug addicts can vasoconstrictors for local anaesethia not be used?
cocaine addicts
Drug interactions with local anesthetics?
- ANTIARRHYTHMICS class I: Quinidine
- CNS depressants: increased toxicity
Mainly: antihistamines H1, antidepressants, sedative drugs - Beta blockers and cimetidine: decrease the hepatic metabolism of amide local anaesthetics
- Sulphonamides: local anaesthetics interfere with their antibacterial effects.
contradictions for local anaesthesia? (3)
- skin infection at injection site
- swollen/eroded areas
- large areas
topical local anaesthesia in dentistry? (2)
- LIDOCAINE: cream, aerosol, gel
- prilocaine
infiltrated local anaesthesia in dentistry? (5)
LIDOCAINE 2%
LIDOCAINE 2% (every ml - 0,0125mg adrenaline) MEPIVACAINE 3%
ARTICAINE 4% (every ml - 0,01mg adrenaline) BUPIVACAINE 0,5% (every ml 0,005mg adrenaline)
