General Anesthetics Flashcards
How does general anesthesia work?
Work to suppress the CNS (prevent the signals from being sent)
Induces loss of consciousness, loss of feeling and loss of protective reflexes
This is contrast to local (peripheral) anesthetics where the signals are being sent, just the receptors for the signals are blocked
Why are IV anesthetics used more often in surgery?
Gets patients from stage 1 -> 3 quickly (10-40 seconds)
- does not put the patient in stage 4 however, but can if improper dosage.
Also allows for rapid recovery if the proper anesthetic is used
can use in combo w/ inhaled anesthetics to ensure better control over dose and recovery
What determines the amount of distribution and the pharmacokinetics of IV anesthetics?
Which body compartments have the highest blood flow = higher/faster distribution.
Highest blood flow
- brain
- heart
- kidney
- liver
Lowest blood flow
- skin
- skeletal muscle
- adipose tissue
what pharmacokinetics mediates recovery from anesthesia
The distribution out of the brain tissue -> muscle/adipose/skin
The faster this occurs, the faster the recovery
Thiopental/methohexital
Barbiturates
Ultra-short acting agents that are primarily used for the induction and maintenance of anesthesia
- by themselves, DO NOT produce and analgesic effect.
MOA: acts as pseudo GABA at GABAa receptors in high doses
- low doses acts as an agonist for GABA increasing GABA action
ADRs: respiratory depression, hypotension, cardiac arrhythmias, bronchospasm, shivering, tremor
can be abused
Propofol (diprivan)
Rapid onset similar to barbiturates but:
- has more rapid recover w/ hepatic metabolism
- can be used by itself in surgery
Most often used as a adjuvant to other anesthetics
- by itself DOES NOT produce analgesic effects
- Fospropofol is the prodrug form
MOA:
- acts as a NMDA antagonist
- acts as a GABAa agonist
- reduces CNS serotonin concentrations this is why it is least likely to induce vomiting of all anesthesics
ADRs:
- dose-dependent hypotension (most dangerous aspect)
- respiratory depression
- cardiac arrest
- apnea
- hypertriglycermia
can be used in patients with malignant hyperthermia (only one of the anesthetics)
Etomidate
Agonists of GABAa receptor and is used to induce and maintain general anesthesia WITHOUT analgesic effects
Unique features
- minimal CV and respiratory depression ADRs and promotes cardiovascular stability
- useful in patients with heart failure
ADRs:
- myoclonic muscle contractions
- nausea/vomiting
- adrenal suppression
- painful injection site
Ketamine
Agent that is used to induce and maintain general anesthesia WITH analgesic effects
MOA: reversible antagonist NMDA receptors
Unique features
- stimulates CV (useful in hypotensive patients)
- bronchodilator (useful in bronchospasm patients)
- can cause dissociative anesthesia w/ Catalonia, amnesia and conscious analgesics
ADRs:
- emergence phenomenon (post-operative disorientation/vivid dreams/hallucinations)
Is a horse tranquilizer in large doses
Common Adjunct agents
Benzo’s
A2 agonists
Opioids
Benzodiazepines (midazolam) tivity
Used as a pre-anesthetic sedative for anit-anxiety and “mind blocking” medication
DOES NOT produce anesthesia or analgesic effects
MOA: potentials GAGAa activity
ADRs:
- respiratory depression
- apnea
- hypotension
reversal agent is flumazenil
Dexmedetomidine (preceded)
A2 agonists
Does provide analgesic and sedative effects
MOA: agonism of a2 receptors and g(aio) portion coupled receptors
- reduces cAMP production and reduces activity of presynaptic calcium channels
- provides minimal respiratory effects
ADRs:
- hypotension
- bradycardia
Fentanyl and morphine
Produce a strong analgesic effect during and after surgeries
MOA: agonist for u-opioid receptors
ADRs:
- respiratory depression, constipation, nausea/vomiting
reversal agent is naloxone
