pain 2 Flashcards
what is anesthesia
loss of sensation
do all general anesthesias do analgesia
no
what are 5 things that lots of general anesthetics try to achieve
- analgesia
- amnesia
- loss of consciousness
- inhibit sensory &autonomic reflexes
- skeletal muscle relaxation
what are 3 things that are sought after in an ideal general anesthetic
- smooth and rapid anesthetic induction, but permits rapid recovery when administration ceases (balanced anaesthesia)
- wide margin of safety
- devoid of adverse effects
what does balanced amnesia mean
induce anesthesia smooth and rapidly, but permits rapid recovery when administration ceases
what are 5 common adverse effects of anesthesias
- vomiting
- cadiovasc depresion
- resp depression
- toxicity
- respiratory irritant effevts of volatile anesthetics
how do they try to achieve balanced anesthesia
by combining drugs to maximize favorable effects and minimize untowards effects
what is the therapeutic index for general anesthetics
low
what do doctors do for minor procedures (2 things)
oral sedatives and regional local anesthetic
what do doctors do for conscious sedation (2 drugs)
benzos (IV) + opioid analgesics
what is conscious sedation
when patients can respond to verbal commands + open airway
what do they often give patients preoperatively (3)
- sedatives (anxiolytic, amnesia)
- muscle relaxants (d-tubocurarine like drugs)
- atropine (limit mucous secretion)
why do they give atropine preoperatively
because anesthetics are irritating so lungs secrete fluid and mucous, so this stops that
what are some drugs that are used to induce anaesthesia
thiopental propofol etomidate benzos (midazolam)
what do doctors use for deep anesthesia (2 types)
inhaled anaesthetics and maybe IV anesthetics
what are 3 examples of inhaled anesthetics
N2O
isoflurane
methoxyflurane
what is N2O
inhaled general anesthetic
what is isoflurane
inhaled general anesthetic
what is methoxyflurane
inhaled general anesthetic
what are inhaled general anesthetic (2 properties / descriptions)
volatile liquids, halogenated hydrocarbons
what is an example of a intravenous barbiturate used for general anesthetic
thiopental
what is an example of a intravenous benzodiazepine (2) used for general anesthetic
midazolam, diazepam
what is an example of a intravenous opioid agonist used for general anesthetic
fentanyl
what is the “dissociative” intravenous drug used for general anesthetic
KETAMINE
what is the “neurolept” intravenous drug used for general anesthetic
droperidol
what is thiopental
intravenous barbiturate used for general anesthetic (fast acting)
what is midazolam
intravenous benzo used for general anesthetic
what is diazepam
intravenous benzo used for general anesthetic
what is fentanyl
intravenous opioid agonist used for general anesthetic
what is ketamine
intravenous dissociative used for general anesthetic
what is droperidole
intravenous neurolept used for general anesthetic
what is propofol
intravenous general anesthetic
what is etomidate
intravenous general anesthetic
what are 8 examples intravenous general anesthetics
thiopental midazolam diazepam fentanyl propofol etomidate ketamine droperidol
what are the 4 stages of anesthesia
- analgesia
- excitement
- surgical anesthesia
- medullary depression
what is in the first stage of anesthesia
analgesia without amnesia –> analgesia with amnesia
what is in the second stage of anesthesia
excitement: delirium, amnesia, retching, vomiting, irregular respiration
what is in the third stage of anesthesia
irrecular respiration –> regular breathing –> cessation of breathing
what is in the fourth stage of anesthesia
medullary depression: cessation of spontaneous breathing, severe depression of medullary vasomotor center (hypotension) and resp center, DEATH
which stage do they want you in
third stage
which stage do they want to limit your time in
second
what stage kills you
fourth
how do local anesthetics work (generally)
impair nerve conduction
how do general anesthetics work (generally)
primary effects on synaptic processes to decrease neuronal activity
what is the mechanism of action of inhaled anesthetics
block α7 nAChR, 5-HT3 receptor/ ion channel, open TASK channels (2 pore K+ channels), activate thalamic “extrasynaptic” GABA A R to cause polarizations
where are 4 targets for inhaled anesthetics
α7 nAChR, 5-HT3, TASK (K+), GABA A R
what do inhaled anesthetics do to α7 nAChR
block
what do inhaled anesthetics do to 5-HT3
block
what do inhaled anesthetics do to TASK channels
activate
what are TASK channels
2 pore domain K+ channels
what do inhaled anesthetics do to GABA A receptors and what does it cause
activate to cause hyperpolarization
where are the GABA A receptors that inhaled anesthetics activate
thalamic extrasynaptic
why is the dose-response relationship difficult to determine
minimal response=pain
maximal response=death
what is minimum alveolar anesthetic concentration
concentration (ex:% of alveolar gas mix) that results in immobility in 50% of patients when exposed to noxious stimulus (like surgical insertion)
what does minimum alveolar anesthetic concentration (MAC) represent
ED50
what is ED50
the dose of drug that produces an effect in 50% of the population
what is minimum alveolar anesthetic concentration (MAC) used for
representing anesthetic dosages (expressed in multiples of MAC)
how is anesthetic dosage expressed
in multiples of minimum alveolar anesthetic concentration (MAC)
can minimum alveolar anesthetic concentration (MAC) exceed 100% and why
yes, for a weak anesthetic like N2O, it may not be enough to prevent immobility in patients
what are 2 main organs that are affected by volatile inhaled anaesthetics
cardiovascular system and respiratory system
what do volatile inhaled anaesthetics do to BP
lower
what do volatile inhaled anaesthetics do to peripheral resistance
some will lower
what do volatile inhaled anaesthetics do to cardiac output
it can be effected
what are 4 things that volatile inhaled anaesthetics do to the cardiovascular system
- lower BP
- may influence cardiac output
- may lower peripheral resistance
- sensitize myocardium to catecholamines
what do volatile inhaled anaesthetics do to myocardium
sensitize them to actions of catecholamines
how can volatile inhaled anaesthetics cause ventricular dysrhythmias
they sensitize myocardium to actions of catecholamines, so now even endogenous NA can cause dysrhymia
what do volatile inhaled anaesthetics do to respiratory system (3)
- decrease minute respiration
- decrease ventilatory reponse to hypoxia
- decrease mucoliliary function (mucous pooling)
which inhaled anesthetic doesnt effect the respiratory system
N2O
what do volatile inhaled anaesthetics do to minute respiration
decrease
what do volatile inhaled anaesthetics do to response to hypoxia
decreases ventilatory response
what do volatile inhaled anaesthetics do to mucociliary function and what does thiscause
decreases function so there is mucous pooling
What are 2 types of anesthetic toxicity
- nephrotoxicity
- malignant hyperthermia
what causes nephrotoxicity
from hepatic metabolism - fluoride ions from the anesthetics
what causes malignant hyperthermia
genetic disorders where Ca++ handling by skeletal muscle is altered
what is the mechanism of action of IV anesthetics
potentiate movement of Cl- ions through GABA A receptor channels
what is the mechanism of action of barbiturates
potentiate Cl- movement through GABA A channel and increase duration of channel opening
what is the mechanism of action of benzos
potentiate Cl- movement through GABA A channel and increase frequency of channel opening
what is the mechanism of action of propofol
potentiate movement of Cl- ions through GABA A receptor channels
what is the mechanism of action of etodimate
potentiate movement of Cl- ions through GABA A receptor channels
what is the mechanism of action of ethanol
potentiate movement of Cl- ions through GABA A receptor channels
where do benzos and barbs bind
at different sites of the GABA A receptor channel
do benzos or barbs increase frequency of channel opening
benzos
do benzos or barbs increase duration of channel opening
barbs
what does GABA potentiation do to neuronal activity
decreases
what is the rate of onset of thiopental
rapid
what kind of solubility is thiopental
lipid soluble
does thiopental cross the BBB and why
yes because its lipid soluble so it can enter brain
what is a downside to thiopental
it is redistributed to other tissues like body fat, so its tough for obese people to have offset (like come-down or whatever)
can you use thiopental alone and why
yes for short procedures because it is potent and has a rapid onset of action
does thiopental have analgesic effect
no
what happens with large doses of thiopental
hypotension and resp depression
what is thiopental often combined with
inhalation agent
what is an example of a ultra-short acting barb
thiopental
can midazolam and diazepam be used in induction of anesthesia and why
no because its onset is too slow
what is midazolam and diazepam often given with and when
a mix of anesthetic mixtures as a premedication
what is a useful use for midazolam and diazepam
producing anterograde amnesia (patient wont remember they’re about to have surgery)
can midazolam and diazepam produce surgical anesthesia
no not alone, but good for amnesia
what is flumazenil
benzo antagonist
why do you use flumazenil
to speed up recovery from midazolam and diazepam
can flumazenil work on midazolam and diazepam
yes thats what its for
can flumazenil work on thiopental
no its a bard not a benzo
what is the rate of onset for propofol
rapid
what is the rate of offset for propofol
rapid
where is propofol metabolized
in liver
what happens with large doses of propofol
hypotension, respiratory depression
what does propofol cause in children
acidosis
what is a good thing about propofol
doesnt cause vomiting and patients feel better post operative
what is the rate of onset for etomidate
rapid
what is the use for etomidate and why
for induction because it causes a loss of consciousness within seconds
does etomidate cause analgesia
no
what are the pros of etomidate
it has minimal cardiovascular and resp depression
what is a con for etomidate
causes nausea and vomiting
why is etomidate good for old geisers
it doesnt cause much cardio and resp depression
what are advantages to fentanyl (3)
cardio stability, sedative, analgesia
what are disadvantages to fentanyl (3)
resp. depression, hypotension, postoperative recall
what does fentanyl do to the cardio system
not much, keeps stable
what does fentanyl do to the resp system
depression
what does fentanyl do to the BP
lowers
does fentanyl cause analgesia
yes
What is naloxone and naltrexone
opioid antagonists
why do they use naloxone and naltrexone
to speed up recovery phase
what drugs do they use to speed up recovery phase from opioids
naloxone and naltrexone
what is a common combination of drugs for sugery
fentanyl + benzo or barb +N2O
what is in neuroleptanaesthesia
fentanyl + droperidol + N2O
what is droperidol
D2 receptor antagonist
what do all D2 antagonists do that is good for surgery
prevent vomiting
what are 3 good things about droperidol
- anti-emetic
- reduce motor activity
- reduce anxiety
what are 2 things that ketamine does
catatonia, cardio stimulation
are people conscious with ketamine
yes but they dont move
what are some procedures that ketamine is good for
geriatrics, children and burn dressing
what is the mechanism of action of ketamine
blocks glutamate NMDA receptors/ channels
what are the untoward effects of ketamine
hallucinations and nightmares
what is the mechanism of action of ethanol
blocks NMDA receptors and activates GABA A receptor (including extra synaptic receptors)
is thiopental a strong analgesic
no
does ketamine produce neurolept anesthesia
no
