Induction Agents Flashcards
what are the names of the stages of anesthesia according to unit 2
analgesia, delirium, surgical anesthesia, and medullary paralysis
a patient in stage 1 of anesthesia should be able to
open their eyes on command, breathe normally, maintain airway, and tolerate mild stimuli
what might you see during stage 2: delirium of anesthesia
cv instability, rapid ocular movements, laryngospasm, emesis
how long does stage 2 of anesthesia typically last
30s-1 min
5 components of surgical anesthesia
hypnosis, analgesia, muscle relaxation, sympatholysis, and amnesia
in stage 4 of anesthesia the patient is experiencing
loss of all reflexes, marked hypotension and flaccid paralysis
what is the gold standard induction agent
barbiturates
MOA of barbiturates
potentiate GABA A activity; mimics GABA with activity on glutamine, adenosine, and neuronal nach receptors
barbiturates do what to CBF and CMRO2
decreases by 55%
cerebral vasoconstriction is a positive attribute of barbs because
it decreases CBF and CMRO2 and has anticonvulsant properties
barbiturates have no
analgesic properties
barbiturates have a rapid onset and awakening due to
rapid redistribution
with prolonged infusion, barbs have
a long context sensitive half time
at 30 minutes, how much barbiturate is left in the brain
10%
what is the site of initial redistribution of barbs
skeletal muscle
we dose barbiturates on
ibw
excretion of barbiturates is through
kidneys
where are barbs metabolized
hepatocytes
what do barbiturates preferentially bind
albumin 70-85%
a non ionized drug favors an
acidic environment
an ionized drug favors an
alkalotic environment
what is the fat/blood coefficient for thiopental
11
E 1/2 time of thiopental is longer than
prop and etom
methohexital has a ______ lipid solubility than pentothal despite having a _____ non ionized form
lower; 76%
What excitatory phenomena is methohexital associated with
hiccoughs and myoclonus
a continuous infusion of methohexital could cause
post op sz activity
methohexital causes seizures in patients undergoing temporal lobe resections d/t lowering the seizure threshold; but during this procedure, it may decrease sz duration
ECT
list the most important CV side effects of methohexital and the dose associated with it
when given 5 mg/kg, we can see a decrease in sbp 10-20 mmhg, a decrease in hr 15-20 bpm; we can see histamine release and may need to have vasopressin ready; and we can see lack of baroreceptor response in patients with CHF, hypovolemia, and beta blockade
list the most important pulmonary effects of methohexital
depresses medulla and pontine causing apnea; makes patient less sensitive to CO2 causing slow return to spontaneous ventilation
in someone who has a decreased ventilatory drive, how would we prepare for extubation
slow the frequency of the vent, decrease tidal volume, and let CO2 build up to trigger spontaneous respiration
what kind of monitoring is required for administration of barbiturates
somatosensory evoke potential or SSEP
what is one side effect to be wary of that may occur days after the administration of barbs
enzyme induction appx 2-7 days post infusion; especially can deactivate anticoagulants
rapid injection of propofol will can unconsiousness in
30s
lecithen is associated with
egg yolk
MOA of propofol
modulator of GABA A receptor causing transmembrane chloride conductance to increase
where is propofol cleared the most
the lungs
main metabolism of prop is
cyp450
e 1/2 time of propofol
30 mins to 1 1/2 hours
context sensitive half time of an 8 hour propofol infusion
40 minutes
the context sensitive half time of prop is shorter than
barbiturates
what are props’ metabolites
glucuronide and sulphate
what is cleared the fastest between ketamine, propofol, and etomidate
propofol
propofol will do what to blood pressure and heart rate
decrease it
etomidate will do what to blood pressure and heart rate
have no effect
ketmine will do what to blood pressure and heart rate
increase it
are we concerned about giving propofol to people with renal disease, liver disease, or pregnancy? why?
the drug can be metabolized elsewhere besides the liver; there is no influence on the kidneys for clearance; the fetus can rapidly clear propofol
TIVA stands for
total IV anesthesia or balanced anesthesia
children require higher doses of propofol because
they have a larger distribution volume and clearance rate
what % would we consider lowering the dose of prop for elderly patients
25-50%
propfol has these unconventional benefits
anti itch, antiemetic, antioxidant properties
list the CNS side effects of propofol
decreases CMRO2 , CBF, and ICP; large doses may decrease CPP; myoclonus; no SSEP suppression
list the CV side effects of propofol
decreased SBP, SVR, SNS response, intracellular calcium, and baroreceptor reflexes - may have profound bradycardia and asystole with healthy adult patients; some s/e can be modulated by DL stimulus
list pulm side effects of propofol
dose dependent suppression of ventilation; lungs maintain hypoxic drive; painful surgical stimulation counteracts ventilatory depressant effects
surigcal infusions of propofol don’t cause any hepatic or renal issues; however, prolonged infusions may cause
hepatocellular injurt, PRIS, green urine from phenols, and cloudy urine
what is PRIS and what elements are involved
propofol infusion syndrome; > 75 mcg/kg/min doses; can cause fatal bradycardia in children; lactic acidosis, bradydysrhythmias, and rhabdo
name some miscellaneous s/e of propofol
decrease IOP, pain on injection, inhibition of platelet aggregation, allergic reactions, prolonged myoclonus
Oxybarbituates such as methohexital have an oxygen in their second position; thiopental has what element in its second position that makes it more lipid soluble
sulfur
what ring is present in etom
imidazole
etom is ___ soluble in acid and ____ soluble in physiologic pH
water; lipid
what percent of etom is propylene glycol
35%
etom has a high incidence of
myoclonus
etom onset
1 minute
what percent bound is etom to albumin
76%
how is etom metabolized
hydrolized by hepatic microsomal enzymes
e 1/2 time of etom
2-5 hours
how is etom eliminated
in the urine
etom is cleared 5x faster than
thiopental
etom is best for patients with an
unstable cv system
does etom have analgesic properties
no
from greatest to least, list some induction agents by myoclonus incidence
etom, thiopental, methohexital, propofol
how can we offset the incidence of myoclonus with admin of etom
give 1-2 mcg/kg fentanyl
adrenocortical suppression is common in what drug? what does it cause
etom; severe HPN and increase in mechanical ventilation time
enzyme inhibition of etom can last
4-8 hours after initial dose
caution in giving etom to
sepsis and hemorrhaging patients; sz patients d/t myoclonic effect
list the most significant cns effects of etom
decreases cbf and cmro2 by 35-45%; decreases ICP; more frequent excitatory spikes on eeg; may activate sz foci and increase amplitude of SSEP
list the most significant cv effects of etom
minimal changes in hr, sv, co, and contractility; at high doses, may cause sudden hpn with hypovolemia
list the most significant pulm effects of etom
less potent ventilatory depressant than thiopental; rapid iv injection will cause apnea; decreases in Vt are offset by compensatory increase in respiratory rate; stimulates co2 medullary centers
ketamine is a derivative of
pcp - phenylcyclidine
ketamine has both ____ and ____ properties
analgesic and amnestic
what would you expect to see in a pt after administration of ketamine
slow nystagmus; wakefulness, but noncommunicative; hypertonus and purposeful skeletal muscle movement
etom has no ____ __ _______ like propofol does
no pain on injection
what is the preservative behind ketamine
benzothonium chloride
S-ketamine has what better analgesic effects
2x greater than racemic and 4x greater than r-ketamine
racemic ketamine acts like which illicit drug? in what way?
cocaine in that it blocks reuptake of catecholamines
primary excitatory nt in the cns
glutamate
which kind of binding does ketamine do and where does it bind
non competitive to the nmda receptor and opioid receptors
ketamine has weak action here
gaba and sigma receptors
peak plasma concentration of ketamine in
1 minute
duration of action of ketamine
10-20 mins
ketamine is _x more lipid soluble than thiopental
5-10
Vd of ketamine
3 L
e 1/2 time of ketamine
2-3 hours
ketamine is cleared and metabolized by
the liver
active metabolite of ketamine
norketamine
ketamine is excreted by
the kidneys
tolerance to ketamine is most likely to develop in
burn patients
5 different dosages of ketamine are for
induction, maintenance, subanesthetic (analgesic), neuraxial, post op pedi hearts
ketamine increases salivation; what can we give to combat this
glycopyrrolate
full consciousness returns after how many minutes after admin of ketamine
60-90 mins
clinical uses for ketamine
asthmatics, MH, hypovolemia; CAD cocktail; burn dressing changes; psychiatry; restless leg syndrome; reversal of opioid tolerance;
avoid using ketamine in
pulm and systemic htn and patients at risk for high icp
list the cns effects of ketamine
potent cerebral vasodilator –> increased icp, and increases cbf by 60%; myoclonus; increased amplitude of SSEP
list the cv effects of ketamine
resembles sns stimulation; unexpected drops in sbp due to depleted catecholamine stores
list the pulm effects of ketamine
no sig depression of ventilation; ventilatory response to co2 is maintained; upper airway skeletal muscle tone and reflexes remain intact; bronchodilator activity
psychedelic effects of ketamine are? due to? how long might they last?
morbid vivid colored dreams and hallucinations; due to depression of the inferior colliculus and medial geniculate nucleus; may last 24 hours
we can prevent emergence delirium by giving
benzos before ketamine
name some miscellaneous s/e of ketamine
inhibition of plt aggregation, free ca, and plasma cholinesterase
ketamine may enhance the effects of these drugs
succs - prolonged apnea; nmdbs - prolonged paralysis; volatile anesthetics - decrease sns stimulus
we can blunt the effects of ketamine on the sns by
administering benzos, volatiles, or n20 (nitrous)
ketamine may be good for osa because
it maintains upper airway reflexes
