2. Sedative, Hypnotics, IV Anesthetics Flashcards
sedation
calming and drowsiness
decreases activity
moderates excitement
calms pt
hypnosis
produces drowsiness
facilitates the onset/mx of sleep
anesthesia
global but reversible CNS depression results in loss of response to and perception of external stimuli
“deafferentation”
changes in behavior and perception
anesthetic effects
amnesia
decreased/diminished pain response
immobility to noxious stimuli
analgesia
unconsciousness
anesthetic drugs can
enhance inhibitory synaptic activity
(GABA/Glycine)
or
diminish excitatory activity
(Glutamate)
glutamate anatomy
relay neurons all levels and some interneurons
glutamate receptors
NMDA
AMPA
Kainate
metabotropic
NMDA (gultamate)
excitatory
increase cation conductance
(esp Ca++)
AMPA (glutamate)
excitatory
increase cation conductance
Kainate (glutamate)
excitatory
increase cation conductance
metabotropic (glutamate)
inhibitory (presynaptic)
- decrease Ca conductance
- decrease cAMP
excitatory
- decrease K+ conductance
- increase IP3
- increase DAG
glycine anatomy
spinal interneurons and some brainstem interneurons
glycine receptors
glycine
glycine receptor MOA
inhibitory
increase Cl conductance
GABA anatomy
spuraspinal and spinal interneurons
pre and postsynaptic
GABA receptors
GABAa
GABAb
GABAa
inhibitory
increase Cl conductance
GABAb
inhibitory
presynaptic:
- decrease Ca conductance
postsynaptic:
- increase K conductance
drug catetogies
sedatives
hypnotics
anesthetics
potential drug effects
amnesia
analgesia
anticonvulsant
muscle relaxation
respiratory
depression
drug classes
benzodiazepines
non-bz sedative hypnotics (Z drugs)
barbituates
melatonin congeners
IV anesthetics
inhaled anesthetics
balanced anesthesia
combination of agents to limit dose and toxicity of each agent
triad of general anesthesia
unconsciousness
analgesia
muscle relaxation
IV agent uses:
- sedation-based
- monitored anesthesia care
- regional anesthesia
- conscious sedation
- deep sedation
- light general anesthesia
monitored anesthesia care (MAC)
regional or local anesthesia delivered with supplemental sedation
conscious sedation
small doses
pt mxs airway
pt responds to commands
ICU for prolonged mechanical ventil
light state of general anesthesia
loss of protective reflexes
inability to mx airway
lack responsiveness to sx stimuli
IV induction side effects
(non-anesthetic)
CV (?)
pain at injection site
movement
hiccups
apnea
IV recovery side effects
(non-anesthetic)
restlessness
nausea
vomiting
GABA type
inhibitory CNS neurotransmitter
GABAa receptor
pentameric structure
- subunits: aby
major isoform has
- 2 alpha 1
- 2 beta 2
- 1 gamma 2
GABA binding site (GABAa)
2 sites (one on each lobe)
located between a1 and b2
BZ binding site (GABAa)
between a1 and y2
BZ binding is
allosteric modulation
BZ effects GABAa by
attracting more GABA to the receptor to bind
barbituates effect GABAa by
increasing the duration the channel is open
allosteric agonist
different binding site
enhance effect
allosteric antagnoist
different binding site
inhibit effect
onset time
how quickly the drug takes to get from blood to tgt organ
(brain/viscera)
continuous infusion half life
pt may take longer to recover from a continuous infusion compared to a single dose due to a prolonged half life
barbiturates
methohexital (Brevital)
thiopental (Pentothal)
thiamylal
barbituates MOA
-allosteric modulation
-enhance Cl conductance
-increased duration of GABA-gated Cl channel opening
barbituates structure
derived from barbituric acid
methohexital will elicit
epilectiform activity
used in electroconvulsive therapy or surgeries where seizures are desired
barbituates admin
- IV
- rectally (peds)
barbituates lipid solubility
high
barbituates distribution
plasma:brain equilibrium rapidly
- onset within 30 sec
rapid diffusion to other tissues
- limited duration of induction
(20 min)
barbituates and elderly
reduce induction dose
slower redistribution
longer duration of action
barbituates repeated doses
(or continuous infusion)
saturates peripheral compartments
minimize redistribution effect
increases duration of action
barbituates metabolism
metabolized by CYP enzymes
no active metabolites
barbituates elimination
some renal elim of metabolites
some excretion in feces
methohexital cleared rapidly by liver
barbituates formulations
alkaline solution for solubility
will precipitate when mixed w/weak bases
- roc, lidocane, labetalol, morphine
barbituates site of action
CNS
barbituates CNS onset
10-20 sec
bolus lasts 8-20 min
half life: 3-12 hrs
barbituates CNS impacts
constrict cerebral vasculature
-decrease BF/ICP
-decrease cerebral O2 consumption
anticonvulsant (except methohexital)
-decreases EEG
decrease pain threshold
involuntary muscle movements
-hiccups, myoclonus
barbituates cardiovascular impacts
peripheral vasodilation: BP decreas
neg ionotropic effects (CO decrease) venous vasodilation
- (decrease BP/CO)
vagolytic compensatory responses
- HR and contractility
barbituates contraindications
Pt w/o adequate baroreceptor response
- hypovolemia
- beta blocker therapy
- congestive heart failure
asthma pt (histamine response)
acute intermittent porphyria
barbituates respiratory impacts
dose related respiratory depression
incomplete suppress of airway reflex
apnea
bronchospasm
hiccup
laryngospasm
barbituates histamine release
may cause hypotension/tachycardia
rare allergic reactions
barbituates pharmacodynamics
no muscle relaxation
injection pain
no analgesia
no renal/hepatic toxicity
induce ALA-S (may trigger porphyrins)
acute intermittent porphyria
neurological disease cause by inadequate porphyrin metabolism
porphyrins
highly reactive oxudants
cause toxic neurological seueqlae
porphyrias symptoms
nausea
vomiting
abdominal pain
psychosis
lower motor neuron palsies
barbituates status
being replaced by propofol
methohexital used for ECT
thiopental not used in US
barbituates interactions req dose reduction
opioid
alpha 2 adrenergic agonist
benzodiazepine
acute ethanol
barbituate dose reduction for pts w/
anemia
low protein
decreased cardiac output
shock
elderly
benzodiazepines (BZ)
diazepam
lorazepam
midazolam
BZ mechanism of action
potentiate GABA inhibition
increase efficiency of GABA
increase freq of Cl channel openings
GABA must be present
binds to BZ receptor
flumazenil
BZ receptor antagonist
BZ structure
3 ring structure
water soluble
- affects parenteral prep
BZ lipid solubility
high
speeds up CNS onset
diazepam absorption/admin
oral
- 1-2 hr onset
IM
- painful/erratic absorption
lorazepam absoprtion/admin
oral
- 1-2 hr onset
IM
- well absorbed
- 90 min peak
midazolam absorption/admin
oral
IM
- well absorbed
- 30 min peak
IV
- short onset (minutes)
BZ lipid solubility
M>D>L
BZ distibution to brain
time to onset:
M<D<L
BZ redistribution
rapid
3-10 min
short duration of effect