General Anesthetics

Question 1

Intravenous anesthetics?

Answer 1

Etomidate, ketamine, propofol, thiopental

Question 2

Etomidate: Side Effects

Answer 2

Induction agent known for its
cardiovascular stability.
Contraindicated in septic shock.

Question 3

Metabolism of IV general anesthetics?

Answer 3

Metabolism:
hepatic
Excretion:
renal
clearance

Question 4

Ketamine: MOA

Answer 4

Antagonizes the NMDA receptor.
- Causes some areas of the brain to be
tonically excited → this central stimulation
of the sympathetic nervous system allows
for CV stability, maintained ventilation,
and increased cerebral blood flow,
intracranial pressure, and cardiac output.

Question 5

Propofol: MOA

Answer 5

- Possesses high lipid solubility and a
redistribution phase with a short half-life
(t1/2α)
- Powerful respiratory depressant.
- Available for IV administration only.

Question 6

Thiopental: MOA

Answer 6

• Belongs to the barbiturate drug class.
• Suppresses transmission of excitatory
  NTs (e.g., acetylcholine) and enhances
  inhibitory NTs (e.g., GABA).
• Can create a loss of consciousness in
  30 seconds.

Question 7

Ketamine: Indications

Answer 7

- Blocks polysynaptic reflexes in
spinal cord.
- Inhibits excitatory NT effects in parts
of the brain.
- Disassociates thalamus from limbic
cortex → “dissociative” anesthetic,
Pt appears conscious but can’t
process sensory input.

Question 8

Propofol: Indications

Answer 8

• Rapid onset and recovery
• One of the most well-known and
  highly utilized general anesthetics.
• Approved for mod-deep sedation
  and general anesthesia (induction +
  maint.).

Question 9

Thiopental: Indications

Answer 9

Decreases ICP
- Acts as resp. and CV depressants.
Decreases both CBF and ICP →
reduces brain O2 consumption →
helpful in neurosurgical patients.
- Most used as induction agent.

Question 10

Ketamine: Side Effects

Answer 10

Hallucinations,

nightmares

Question 11

Propofol: Side Effects

Answer 11

Respiratory
depression,
bradycardia

Question 12

Thiopental: Side Effects

Answer 12

Respiratory
depression,
bradycardia

Question 13

Inhaled general anesthetics?

Answer 13

Desflurane, halothane, isoflurane, nitrous oxide, sevoflurane

Question 14

Treatment for malignant hyperthermia?

Answer 14

Dantrolene

Question 15

Dantrolene: MOA

Answer 15

Dantrolene is a muscle relaxant that
depresses excitation-contraction coupling
in skeletal muscle by binding to the
ryanodine receptor and decreasing
intracellular calcium concentration.

Question 16

Inhaled general anesthetics: MOA

Answer 16

Although inhalation anesthetics are widely
used, their mechanism of action is
largely unknown. It is presumed that
their primary mechanism is through the
inhibition of glutamate receptors and
enhancement of GABA
neurotransmission. The site of action for
these drugs likely occurs at multiple
locations within the CNS. Specific brain
areas including the reticular activating
system (RAS), cerebral cortex,
hippocampus, and spinal cord are all
impacted by anesthetic agents,
contributing to these drugs’ various
physiologic effects.

Question 17

Inhaled anesthetics: Indications

Answer 17

Inhalation anesthetics are used for
the induction and maintenance
phase of general anesthesia. These
gases are administered by breathing
through an anesthesia mask or
endotracheal (ET) tube connected to
an anesthetic machine.

Question 18

What factors affect inhaled anesthetics?

Answer 18

The ultimate clinical effect of
inhalation anesthetics depends on
delivery of a therapeutic partial
pressure of an agent to the CNS. This
delivery is affected by properties of
the agents themselves and by
physiologic variables including
regional blood flow, cardiac output,
and ventilation.

Question 19

Side effects of inhaled anesthetics?

Answer 19

Myocardial
depression
- Decreased SVR
and SBP.
- Volatile anesthetics
create classic
respiratory pattern:
increased RR,
decreased TV, and
decreased
ventilatory response
to CO2
(hypercarbia). All
agents cause
reduced RBF and
GFR.
Malignant
hyperthermia (MH)
is a potential
complication shared
by all of the volatile
anesthetics (and
succinylcholine).

Question 20

Inhaled anesthetics: Metabolism

Answer 20

Inhalation
anesthetics
undergo
limited
metabolism.
The recovery
(emergence)
from these
drugs is
achieved by
lowering the
anesthetic’s
concentration
at the site of
action (the
brain). The
majority of
elimination
occurs at the
alveolus and is
dependent
upon same
principles that
facilitate
induction of
anesthesia.