General Anesthetics Flashcards
(68 cards)
what are the 4 original stages of Anesthesia based on Ether?
- Analgesia (Loss of Pain Sensation)
- Excitement (Delirium & Disinhibition) – Most Dangerous Stage
- Surgical Anesthesia (Ideal Stage for Surgery)
- Medullary Depression (Dangerous Overdose Stage)
what happens during Stage 1:Analgesia (Loss of Pain Sensation)?
- patient is conscious but has decreased awareness of pain
- impaired consciousness begins, but the patient can still respond to stimuli.
- may experience amnesia, but reflexes and breathing remain normal
what happens during Stage 2: Excitement (Delirium & Disinhibition) – Most Dangerous Stage
- patient becomes delirious, excited, and uncoordinated
- amnesia is present, but reflexes are hyperactive
- irregular breathing, enhanced reflexes, and uncontrolled movements occur
- retching, vomiting, and incontinence may happen
- patients are prone to laryngospasm
what happens during Stage 3: Surgical Anesthesia (Ideal Stage for Surgery)
- patient is unconscious and does not perceive pain
- reflexes to pain may still be present, but the brain is not processing pain perception
- spinal cord responses cause increased blood pressure and tachycardia when pain is applied
- breathing is regular, and blood pressure is stable
what happens during Stage 4: Medullary Depression (Dangerous Overdose Stage)
- severe respiratory depression (or complete respiratory arrest)
- cardiovascular collapse (severe hypotension, bradycardia)
- loss of all reflexes
- patient requires immediate respiratory and cardiovascular support (mechanical ventilation and vasopressors) to prevent death
Goals of General Anesthesia?
- unconsciousness
- analgesia
- immobility, skeletal muscle relaxation without impairing breathing
- inhibition of autonomic reflexes that causes bronchospasm, excess salivation, arrhythmias
- amnesia
an ideal anesthetic drug should?
induce rapid and smooth induction, be rapidly reversible upon discontinuation, and possess a wide margin of safety.
what is balanced anesthesia?
combination of agents and techniques (e.g., premedication, regional anesthesia, and general anesthesia with one or more agents) is used to produce the different components of anesthesia
what are the two MOA for general anesthetics?
- altering ligand gated ion channel activity in neurons
- activate sleep-promoting neurons in the hypothalamus
how do Anesthetics increase inhibitory synaptic activity?
enhance the function of inhibitory neurotransmitters, particularly GABA (gamma-aminobutyric acid) to allow hyperpolarization of neurons through Cl- channels
or
activate potassium channels, leading to neuron hyperpolarization
what are the Anesthetics that enhance GABA-A activity?
- Inhaled anesthetics (e.g., isoflurane, sevoflurane)
- Barbiturates (e.g., thiopental)
- Etomidate
- Propofol (widely used for IV anesthesia).
how do Anesthetics reduce excitatory synaptic activity?
suppress excitatory neurotransmission, particularly by blocking glutamate activity through its ionotropic glutamate receptors (AMPA, Kainate, NMDA)
or
blocking acetylcholine activity through its nicotinic acetylcholine receptors
what are the Anesthetics that reduce excitatory synaptic activity?
- Ketamine blocks NMDA receptors
- Nitrous oxide inhibits glutamate activity
- Most inhaled anesthetics inhibit nicotinic acetylcholine receptors at moderate to high concentrations
General anesthetics cause direct activation of (Anesthetic hypnosis)?
sleep-promoting neurons in the ventrolateral preoptic nucleus of the hypothalamus.
- these neurons preferentially fire during natural sleep
what are the inhaled general anesthetics?
- Nitrous Oxide
- Sevoflurane
- Desflurane
- Isoflurane
- Halothane
what are the intravenous general anesthetics?
- Propofol
- Ketamine
- Etomidate
- Fospropofol
- **Methohexital
what is special about Methohexital?
an ultrashort-acting barbiturate that is primarily used for inducing anesthesia by exciting the brain, which helps facilitate seizure induction during electroconvulsive therapy (ECT)
what is the main advantage of Anesthetic Gases?
can be rapidly adjusted by changing the gas mixture which allows for fast induction, maintenance, and recovery from anesthesia and quick elimination via the lungs reduces systemic toxicity
what are three anesthetic gasses no longer used?
Ether, cyclopropane and enfluorane
what is Minimum Alveolar Concentration (MAC)?
the “dose” (potency) of an inhaled anesthetic needed to keep half of the patients completely unconscious and unresponsive to pain
**the lower the MAC the more potent the drug
what would increasing the ventilation rate due to the rate of induction for inhaled general anesthetics?
increase the rate of induction
the lower the blood:gas partition coefficient (decreased solubility) the
faster the induction rate
- less soluble anesthetics cause effects faster
the lower the solubility of a drug (blood:gas partition coefficient), the faster the
rate of elimination
how do inhaled general anesthetics affect the liver?
- reduce hepatic (liver) blood flow by 15–45% (usually reversible)
- Most inhaled anesthetics undergo minimal liver metabolism, meaning they are primarily eliminated through the lungs (Halothane is an exception)