C5
This receptor is considered the primary inhibitory receptor involved in the action of most intravenous and inhaled anesthetics.
What is the GABAA receptor?
Potentiation of inhibitory GABAA receptors is considered a primary mechanism of action for many IV and inhaled anesthetics. Activation increases chloride influx through membrane channels, producing neuronal inhibition and CNS depression.
This route of administration provides 100% bioavailability because the drug enters systemic circulation directly.
What is the intravenous route?
Intravenous administration bypasses absorption barriers and first-pass metabolism, delivering the entire dose directly into circulation immediately.
This inhalation anesthetic has the highest oil/gas coefficient and is the most potent volatile agent listed.
What is isoflurane?
Isoflurane has the highest oil/gas coefficient (99), indicating high lipid solubility and greater anesthetic potency.
This term describes the alveolar concentration of anesthetic that prevents movement in 50% of patients exposed to surgical incision.
What is Minimum Alveolar Concentration (MAC)?
MAC is the standard measurement of inhaled anesthetic potency. Lower MAC values indicate more potent anesthetics.
A potent NMDA receptor antagonist that reduces excitatory neurotransmission.
What is ketamine?
Ketamine:
Noncompetitive NMDA antagonist
Meaning:
Result:
Ketamine is a potent NMDA receptor antagonist that reduces excitatory neurotransmission.
Ketamine is a noncompetitive NMDA receptor antagonist.
Ketamine binds at the phencyclidine site within the NMDA receptor channel and prevents ion conduction despite glutamate binding.
This reversal agent is an example of chemical antagonism because it encapsulates the muscle relaxant molecule rather than blocking receptors.
What is sugammadex?
Sugammadex is a selective relaxant binding agent that encapsulates the muscle relaxant molecule and renders it inactive. No receptor interaction occurs, making this chemical antagonism.
This form of a drug is lipid soluble and crosses biologic membranes most easily.
What is the nonionized form?
Nonionized drugs are uncharged and lipid soluble, allowing them to diffuse across cell membranes such as the blood-brain barrier and placenta. Ionized drugs are water soluble and cross poorly.
This volatile anesthetic has the lowest blood/gas solubility coefficient and therefore the fastest emergence.
What is desflurane?
Desflurane has the lowest blood/gas solubility coefficient (0.42). It is the least soluble volatile anesthetic and makes it the fastest volatile anesthetic for induction and recovery.
This volatile anesthetic is preferred for pediatric mask inductions because it is minimally irritating to the airway.
What is sevoflurane?
Sevoflurane is non-pungent and well tolerated during inhalation induction, especially in children.
Activation of background potassium leak channels by volatile anesthetics causes:
Depolarization, Repolarization, or Hyperpolarization?
What is hyperpolarization?
Activation of leak K+ channels increases potassium efflux, making the neuron more negative.
TREK-1 and TASK are members of the 2P/4TM background potassium channel family.
Activation of 2P/4TM leak potassium channels is an important anesthetic mechanism.
This type of antagonism occurs when an antagonist binds a different site on the receptor or permanently disables receptor function, so increasing agonist concentration cannot restore maximal effect.
What is noncompetitive antagonism?
Noncompetitive antagonists are drugs that impair receptor function without being displaced by the agonist. Ketamine blocks NMDA channel activity despite glutamate binding, preventing excitatory calcium influx.
Propofol patients awaken quickly after a bolus dose because of this pharmacokinetic process.
What is redistribution?
Propofol is highly lipid soluble and rapidly redistributes from the brain (central compartment) to muscle and fat (peripheral compartments), causing rapid awakening long before the drug is fully eliminated from the body.
This inhaled anesthetic has a MAC greater than 100%
What is nitrous oxide?
Nitrous oxide has a MAC of approximately 105%, reflecting extremely low anesthetic potency.
Higher Mac = less potent agent
Lower MAC = more potent agent.
Lipid solubility is directly proportional to potency (name the rule).
What is the Meyer-Overton rule?
The higher lipid solubility corresponds to greater anesthetic potency and lower MAC.
The potency of general anesthetics correlates with their solubility in oil, which is expressed as the oil/gas solubility coefficient of the anesthetic (Meyer-Overton rule). The more lipid-soluble the anesthetic, the higher the potency.
This phenomenon describes why more anesthetic is needed for induction than for emergence.
What is neural inertia?
Neural inertia refers to hysteresis between induction and emergence anesthetic concentrations.
This happens to the dose-response curve when a competitive antagonist is present because more agonist is needed to achieve the same effect.
What is a rightward shift?
Competitive antagonists reversibly occupy receptors and reduce agonist affinity, requiring larger agonist doses to achieve the same response. Antagonists cause a rightward shift in the dose-response curve.
This enzyme system is primarily responsible for oxidation reactions during Phase I metabolism.
What is the Cytochrome P450 system?
Phase I oxidation reactions are catalyzed primarily by cytochrome P450 enzymes in the liver. These reactions increase drug polarity to facilitate elimination.
This volatile anesthetic undergoes the greatest metabolism.
Sevoflurane
Sevoflurane undergoes approximately 5–8% metabolism, greater than the other modern inhaled anesthetics.
Ranked: MOST → LEAST Metabolized
This area of the nervous system is primarily responsible for the immobilizing effects of inhaled anesthetics.
What is the spinal cord?
Immobility mediated primarily at spinal cord. Immobility from volatile anesthetics is mediated primarily at the spinal cord through effects on ion channels and inhibitory neurotransmission.
This CYP enzyme is responsible for the metabolism of the greatest number of drug
What is CYP3A4?
Important CYP isoenzyme in drug metabolism. CYP3A4 accounts for approximately 40–45% of all CYP-mediated drug metabolism.
This phenomenon occurs when chronic agonist exposure causes receptors to decrease in number and responsiveness.
What is down-regulation?
Continued stimulation with agonists results in receptor desensitization or down-regulation, producing diminished response and clinical tolerance.
This phenomenon occurs when a weak base enters a more acidic environment and becomes trapped in its ionized form.
What is ion trapping?
Weak bases become more ionized in acidic environments. Once ionized, they cannot easily cross lipid membranes and therefore accumulate or become “trapped,” such as local anesthetics in fetal circulation or acidic CNS tissue during toxicity.
2 PART QUESTION:
1. This anesthetic property determines how quickly induction and emergence occur.
2. This measurement reflects the lipid solubility and potency of inhaled anesthetics.
1. What is the blood/gas solubility coefficient?
The blood/gas coefficient reflects how much anesthetic dissolves in blood. Lower solubility means faster rise in alveolar and brain concentration, producing faster induction and emergence.
2. What is the oil/gas solubility coefficient?
Higher oil/gas solubility correlates with greater potency because lipid-soluble drugs more readily penetrate the CNS.
Unlike other volatile anesthetics, this inhaled agent increases cerebral metabolic rate and cerebral blood flow.
What is nitrous oxide (N₂O)?
N₂O increases both CMRO2 (Cerebral Metabolic Rate of Oxygen) and CBF (Cerebral Blood Flow) which may increase intracranial pressure in susceptible patients.
2 Part:
1. Clearance depends mainly on hepatic blood flow
Examples: fentanyl, propofol, ketamine, morphine
2. Clearance depends mainly on liver enzyme activity (intrinsic clearance)
Examples: diazepam, thiopental, methadone
1. What is high-extraction drugs?
2. What is low-extraction drugs?