Anesthetics Flashcards
Amnesia is mediated through what loci?
Hippocampus
Immobility is mediated through what loci?
Thalamus
Unconsciousness is mediated through what loci?
RAS (reticular activating system)
What do we use to induce analgesia before maintaining it with gas?
Propofol, thiopental (both IV)
What drug is used as an anti-emetic before surgery?
Promethazine po
What drug is used to decrease secretions before surgery?
Antihistamines po
What oral drugs are used for analgesia/sedation before surgery?
Clonidine, dexmetetomidine
What IV anxiolytic/amnestic is used prior to surgery?
Midazolam
What IV analgesic is used during surgery?
Fentanyl
What muscle relaxant is used during surgery?
Atracurarium
What drugs are used for maintenance of anesthesia?
N2O and isoflurane
What indicates need for more fentanyl or gas during surgery?
Increases in HR or BP
What is used after surgery to reverse blockade?
Neostigmine and atropine
What are the inhalation anesthetics?
Ether
Nitrous oxide (N2O)
Halothane
What are the IV anesthetics?
Barbiturates
Ketamine
Propofol
What are the molecular targets of general anesthetics? (6)
- Enhance Gaba-A receptor sensitivity (enhance affinity for GABA, prolong channel opening time and increase frequency of opening)
- Enhance glycine-gated Cl- channels (Increase receptor’s affinity for glycine)
- Inhibit neuronal nicotinic ACh receptors, inhibiting excitation (produce analgesia and amnesia; does not affect neuromuscular junction)
- Inhibit NMDA receptors (Inhibit long-term potentiation, produce unconsciousness)
- Activate two-pore domain K+ channels (Hyperpolarization causes inhibition of action potentials, produces unconsciousness)
- Neurotransmitter release (inhibit NT release in hippocampus, contributes to amnesia)
What kind of therapeutic index do anesthetics have?
Very low
What CNS effects do anesthetics have? (5)
Increase cerebral blood flow
Stimulate CTZ (nausea and vomiting)
Decrease or eliminate ventilatory drive
Decrease ventilatory reflexes (ie response to high CO2)
Lower temperature setpoint –> Hypothermia (worse with cold iv fluids, exposed organs, vasodilation)
What CV effects to anesthetics have? (6)
Decrease sympathetic tone Increase vasodilation Myocardial depression Blunt baroreceptors Decreased blood pressure Decreased cardiac output (Worse with volume depletion and worsened myocardial dysfunction)
Besides CNS and CV effects, what other 3 effects do anesthetics have?
Decrease renal blood flow and filtration
Muscle relaxation
Decrease esophageal sphincter tone
What is MAC?
Mean Alveolar Concentration: concentration (%) at 1 atm required to prevent reflex responses to skin incision of 1 cm in 50% of patients
What is MAC-WAKE?
concentration (%) at 1 atm where 50% of patients will respond to verbal commands
Lower MAC value – more potent the agent
MAC over 100 means hyperbaric condition is needed
Which anesthetic has the highest MAC? Lowest MAC?
Lowest MAC: Halothane (0.75%)
Highest MAC: Nitrous oxide (105%)
What does a low partition coefficient mean?
Less in the blood, more in the brain
What determines induction rate?
B/GPC
What anesthetic has the highest Blood/Gas Partition Coefficient? Lowest?
Lowest: Desflurane (0.42)
Highest: Halothane (2.30)
Lowest = fastest into the brain (fastest induction)
Fat/blood ratio affects what?
Recovery time and residual effects
Which anesthetic has the fastest recovery time?
Nitric oxide
