Slides 6 Flashcards
What is general anesthesia?
A state of:
1) Analgesia
2) Amnesia
3) Loss of consciousness
4) Inhibition of sensory and autonomic reflexes
5) Skeletal muscle relaxation
How is general anesthesia achieved?
By a combination of
intravenous and inhaled drugs.
What are IV general anesthetic agents used for?
To achieve an anesthetic state or sedation.
What are the IV general anesthetic agents?
1) Barbiturates: Thiopental, methohexital
2) Benzodiazepines: Midazolam, diazepam
3) Propofol
4) Ketamine
5) Opioid analgesics: Morphine, fentanyl,
sufentanil, alfentanil, remifentanil.
6) Miscellaneous sedative-hypnotics: Etomidate,
dexmedetomidine.
What are the inhaled general anesthetic agents?
1) Volatile liquids: Halothane, isoflurane, desflurane, enflurane, methoxyflurane, and sevoflurane.
2) Gases: Nitrous oxide
What is balanced anesthesia?
Employs multiple drugs
(inhaled anesthetics, sedative-hypnotics, opioids,
neuromuscular blocking drugs) to minimize unwanted effects
Modern anesthesia typically involves a combination
of:
1) IV agents for induction of anesthesia.
2) Inhaled agents for maintenance of anesthesia.
3) Muscle relaxants.
4) Analgesics.
5) Cardiovascular drugs to control autonomic
responses.
What are IV anesthetics commonly used for?
1) Induction of general anesthesia because of more rapid onset than inhaled agents.
2) Provide sedation for
patients in ICU settings.
What causes the rapid onset of IV anesthetics?
Their lipophilicity = preferentially partition into highly perfused lipophilic tissues (brain, spinal cord).
IV anesthetics recovery is __ and they are used for __ procedures.
Rapid; short
What is the termination of the effect of a single IV bolus determined by?
Redistribution of the drug into less perfused and inactive tissues such as
skeletal muscle and fat. (NOT related to their metabolism)
What is the most popular IV anesthetic? Which drugs did it replace?
Propofol; barbiturates
How does Propofol exert its effects?
1) Interacts with GABAA receptor-chloride channels 2) Potentiates glycine-gated currents
Propofol acts as a __ but does not have __.
Hypnotic; analgesic properties
What is the rate of onset and recovery of Propofol?
Its rate of onset of action is similar to IV barbiturates, but recovery is more rapid and
patient ambulation is earlier.
What is the agent of choice for ambulatory surgery?
Propofol
What can Propofol be used for?
Both induction and maintenance of anesthesia
What does Propofol reduce?
The required concentration of inhaled anesthetics
When used during maintenance of anesthesia,
Propofol infusion can be combined with __ to completely avoid the use of inhaled anesthetics.
IV opioids and neuromuscular blockers
Propofol is effective in producing __ in patients in critical care setting, but
cumulative effect can lead to __.
Prolonged sedation; delayed arousal
Which recovery is more complete (with less “hangover” effects):
Propofol or Thiopental?
Propofol
What can raise serum lipids?
Prolonged administration of conventional emulsion formulation
What happens if you give Propofol to critically ill young children?
1) Severe acidosis in the
presence of respiratory infection
2) Neurologic sequelae upon withdrawal
What are some adverse effects of Propofol?
1) Depression of central ventilatory drive and apnea
2) Profound bradycardia and asystole
Which effects are occasionally observed during induction of anesthesia (Propofol)?
Excitatory effects such as twitching or spontaneous movement (can be confused with seizures)
Which effects are observed during induction of anesthesia through
arterial and veno dilation?
Marked decrease in blood
pressure
Which IV drug has the greatest direct negative inotropic effect?
Propofol
What is the most common adverse effect of Propofol?
Pain at the site of injection after IV bolus administration
reduced by admixture with lidocaine
Which adverse effect happens after prolonged use of Propofol?
Muscle movements, hypotonus, and rarely
tremors
Propofol decreases cerebral blood flow, leading to what?
1) Decreased intracranial pressure (ICP)
2) Decreased intraocular pressure
3) Decreased cerebral perfusion pressure
What is Fospropofol?
A water-soluble prodrug of
propofol
What are the differences between Fospropofol and Propofol?
1) Onset and recovery of Fospropofol are prolonged compared with propofol because the prodrug
must first be converted into an active form.
2) Fospropofol does NOT produce injection site pain
3) Fospropofol can produce paresthesia in the perianal region
What effects does Etomidate have?
Hypnotic but NO analgesic effects
How does Etomidate act?
Through potentiation of
GABAA-mediated chloride current
What is Etomidate used for?
Induction of anesthesia in patients with limited cardiovascular reserve, because it causes minimal cardiovascular and respiratory depression and minimal hypotension.
Which recovery is more rapid: Propofol or Etomidate?
Propofol
True or false:
Etomidate produces rapid loss of consciousness
True
Distribution of Etomidate is __(slow/rapid).
Rapid
What is responsible for Etomidate’s short duration of action?
Redistribution of the drug from the brain to highly perfused tissues
Etomidate causes potent cerebral vasoconstrictor, leading to:
Decreased cerebral blood flow and ICP
What are the adverse effects of Etomidate?
1) Pain upon injection
2) Myoclonic activity
3) Postoperative nausea and vomiting
4) It may activate seizure foci
5) Inhibition of steroidogenesis (inhibition of 11βhydroxylase) with decreased plasma levels of
cortisol and hypoadrenalism = hypotension, electrolyte imbalance, and oliguria.
True or false:
Etomidate is used as continuous infusion
False; it is not
What kind of state does Ketamine produce?
A “dissociative anesthetic state” characterized by catatonia, amnesia, and
analgesia, with or without loss of consciousness.
Ketamine is chemically related to:
Phencyclidine, a psychoactive drug with high abuse potential.
What is Ketamine’s mechanism of action?
It blocks glutamic acid NMDA receptor subtype.
What are the pharmacokinetics of Ketamine?
Highly lipid soluble and rapidly distributed
into well-perfused organs, including brain, then
it redistributes to less well perfused tissues.
Ketamine is the ONLY IV anesthetic that has what?
1) Analgesic properties
2) The ability to produce
dose-related cardiovascular stimulation
How can ketamine be administered?
Multiple routes (intravenous, intramuscular, oral, rectal, epidural)
What does Ketamine stimulate?
The central sympathetic nervous system and inhibits the reuptake of norepinephrine at sympathetic nerve terminals.
What does Ketamine do?
1) Increases heart rate
2) Increases cardiac output
3) Increases arterial blood pressure (transient)
4) Increases cerebral blood flow
5) Increases oxygen
consumption
6) Increases intracranial pressure (ICP)
7) Decreases respiratory rate (tone and reflexes are preserved)
8) Relaxes bronchial smooth muscle
9) Increases lacrimation and salivation
Ketamine is dangerous in people with:
Elevated intracranial pressure
Ketamine may cause __ especially in children.
Laryngospasm
What can we use to premedicate someone to decrease lacrimation and salivation?
An anticholinergic drug
What has the use of Ketamine been associated with?
Emergence phenomena:
1) Postoperative disorientation
2) Sensory and perceptual illusions
3) Vivid colorful dreams
4) Out-of body experiences
5) Increased and distorted visual, tactile, and auditory sensitivity.
Emergence phenomena can be associated with:
Fear and confusion
Why can Ketamine be abused?
Because a euphoric state may be induced
How can we reduce emergence phenomena effects?
Premedication with a benzodiazepine (diazepam, midazolam).
When is Ketamine most useful?
In patients undergoing painful procedures such as burn dressing.
What does Ketamine do in regards to opioids?
Reduces opioid tolerance and opioid-induced hyperalgesia.
