IV Anesthetics Flashcards
Anesthetic action (2)
1) Enhance inhibitory synaptic activity
2) Diminish excitatory activity
Glutamate
Excitatory (NMDA/AMPA/Kainate)
Glycine
Inhibitory (increase Cl conductance)
GABA
A: Inhibitory (increase Cl conductance)
B: Inhibitory (decrease Ca++ conductance: presynaptic) Inhibitory (increase K+ conductance: postsynaptic)
Where do barbiturates act?
GABA A receptors (enhance) and depress glutamate binding to AMPA receptor
Where does propofol act?
GABA A and Glycine receptors (enhance)
Where does Etomidate act?
GABA A receptors enhance)
Where does ketamine act?
NMDA and nACh (inhibits)
Where do Benzodiazepine’s act?
GABA A and Glycine (enhance)
Where do Inhaled agents act?
GABA A and K+ channels (enhance);
N2O on NMDA receptors (inhibit)
Explain sedation.
Calming/drowsiness/ decreased activity of excitement/anxiolytic
Explain Hypnosis.
Facilitates the onset and being of a state of sleep.
Explain Anesthesia.
Global but reversible CNS depression. Results in loss of response to and perception of external stimuli.
- amnesia
- immobility to noxious stimuli
- analgesia
- unconsciousness
Which channels, pre or post, are important in setting the resting membrane potential of neurons?
Post-synaptic channels.
Explain the GABA receptor complex.
Pentameric structure with alpha(2)/beta(2) and gamma(1) subunits.
Where does GABA bind?
between alpha and beta subunits
Where do Benzodiazepines/Flumazenil bind?
between the alpha and gamma subunit
After an IV dose, where do drugs accumulate first? (3)
First to last:
1) Brain/Viscera
2) Lean Tissues
3) Fat
What is context sensitivity?
The time is takes for blood concentrations of a drug to reach 50% after infusion has discontinued.
Where are barbiturates derived from?
Barbituric Acid
What makes Thiamylal and Thiopental more potent?
Replacing the oxygen at C2 with a sulfur atom. –> more potent/shorter duration of action (THIObarbiturates)
What is special about the barbiturate methohexital?
The methyl group prevents the drug from being anti-convulsive. Used in ECT.
What is special about the barbiturate phenobarbital?
The phenyl group makes the drug an anti-convulsive.
Explain barbiturate pharmacodynamics.
- onset 10-20 secs; lasts 8-20 mins
- constrict cerebral vasculature
- decreased cerebral oxygen
- lowers pain threshold (anti-analgesic)
Thiopental and Methohexital effects on CV
- peripheral vasodilation (decrease in BP)
- Venous vasodilation; peripheral pooling, decreased venous return
- Vagolytic compensatory responses (HR and contractility increase)
Barbiturate’s on Respiratory system
- Depression; decreasing response to CO2 and O2 –> could lead to increased rate to compensate
- Histamine release (not methohexital/only sulfur containing)
Do barbiturates contain muscle relaxation or analgesia?
No; neither.
The rate limiting step in Haem synthesis.
ALA synthetase
Barbiturates + ALA synthetase =
Porphyrias leading to abdominal pain, psychosis, LMN palsies.
What seems to be replacing barbiturates?
Propofol
