General Anethsia Flashcards
What are the two types of anesthetics?
General
Local/regional
True or false: there is not total insensibility with general anesthesia
True–some sensory and even motor function are typically preserved
What is the major disadvantage of general anesthesia?
Disturbance of all organ systems
What are the responses of BP and respiration to general anesthesia?
Decreased
What is the triad of anesthesia?
asleep
Pain-free
Still
What are the six qualities of an ideal anesthetic agent?
Unconsciousness Amnesia Analgesia Muscle relaxation Areflexia Good control
What are the drugs that are administered prior to a procedure to relieve anxiety?
Benzodiazepines (e.g. midazolam)
What are the drugs that are administered prior to a procedure to prevent allergic reactions?
Antihistamines (e.g. diphenhydramine)
What are the drugs that are administered prior to a procedure to prevent n/v?
Antiemetics
e.g. dexamethasone, scopolamine
What are the drugs that are administered prior to a procedure to provide analgesia?
Opioids
e.g. fentanyl, morphine, hydromorphone
What are the drugs that are administered prior to a procedure to prevent bradycardia and secretion?
Atropine
Glycopyrrolate
What are the four phases of general anesthesia?
- Induction phase
- Maintenance phase
- Emergence phase
- Recovery period
What is involved in the induction phase of anesthesia?
Initial administration of a drug, until anesthesia acheieved
What is involved in the maintenance phase of general anesthesia?
Anesthetic concentration is maintained at or above minimum level
What is involved in the emergence phase of general anesthesia?
From sub-optimal concentration in the brain until it reaches zero
(“waking up” period)
What is the recovery phase of general anesthesia?
From discontinuance of anesthetic until full resolution of consciousness and normal function
What is the major hemodynamic response to general anesthesia?
Decreased BP via vasodilation, or decrease in sympathetic tone
What is the major respiratory effects of general anesthetics?
Decreased respirations via elimination of ventilatory drive
What is the cause of hypothermia seen in general anesthesia?
Lowering the core temperature set point at which the vasoconstrictie is activated to defend against heat loss
How do general anesthetics cause n/v?
Activation of the chemoreceptor trigger zone
What are the four stages of anesthesia?
Analgesia
Excitement
Surgical anesthesia
Medullary depression
What is involved in the analgesia stage of anesthesia?
analgesia and amnesia
What is involved in stage II (excitement) stage of anesthesia?
Excitement/delirium
Body is trying to counteract the anesthesia
What is involved in stage III (surgical anesthesia) stage of anesthesia?
Unconsciousness
Regular respiration
What is involved in stage IV (medullary depression stage) of general anesthesia?
Respiratory arrest
Cardiac depression/arrest
No eye movement
What are the two major subtypes of anesthetics?
Inhalable
IV
What type of anesthetic is used for neurosurgical cases?
IV
What is an induction agent? Maintenance agent?
Induction = getting asleep
Maintenance = staying asleep, but may not get to sleep fast
What is the beginning and end of stage III of anesthesia?
Beginning = regular respirations
End = Stopping of respirations
What is the beginning and end of stage IV of anesthesia?
Cessation of respiration
Cardiac arrest
Inhaled anesthetics are usually used as induction or maintenance?
maintenance
IV anesthetics are usually used as induction or maintenance?
Induction
What is balanced anesthesia/
The use of many different drug classes to produce an ideal state of anesthesia
What is anesthetic adjuncts?
Drugs used in addition fot eh anesthetic drug to compliment /supplement the anesthetic and produce a better anesthetic state
What are the four important history bits to obtain, prior to administering anesthesia?
H/o malignant hyperthermia
Cardiac problems
Respiratory disease
Allergies
When does stage 1 begin and end?
Analgesia to LOC
When does stage 2 begin and end
LOC to return of regular respiratory pattern
What are the three ways general anesthetics are thought to work?
- Induce neuronal hyperpolarization
- Increase firing threshold
- Inhibit synaptic transmission and response to released neurotransmitters
What are the three ion channels that general anesthetics are thought to work on, and what is the effect on them?
- Increase GABA-A receptor Cl channel activity
- Activate K channels
- Inhibit glutamate NMDA receptors
What is the effect of general anesthetics on GABA receptors?
Increase the Cl channel activity, causing hyperpolarization
What is the effect of general anesthetics on K channels?
Activates them, resulting in hyperpolarization of neurons
What is the effect of general anesthetics on Glutamate NMDA receptors?
Inhibits them, resulting in decrease excitatory neurotransmission
What is the MOA of ketamine?
Inhibits the glutamate NMDA receptors, resulting in decreased excitatory neurotransmission
What are the two types of inhalable anesthetics?
Volatile (halothane, fluranes)
Gaseous (N2O)
What are the advantages to inhalable anesthetic agents?
- easy to control the depth of anesthesia
- Readily reversible, minute to minute control
What is the main disadvantage to inhalable anesthetic agents?
Induction not as fast or smooth with fixed agents
The concentration of anesthetic in the air is proportional to what value?
The partial pressure it exerts
Partial pressure of an agent is related to what?
Ability to vaporize each agent
Increase what value increases the rate of rise in the alveoli
resulting in accelerated onset/induction?
Inspired partial pressure
What is the relationship of ventilation rate and anesthetic onset time?
positive
What affects the magnitude of the change in blood concentration of a given inhaled anesthetic, with an increase ventilation rate?
higher solubility will lower the increase in blood concentration
What is the ostwald coefficient? What does a lower number indicate?
A measure of the solubility of a gas in the blood
Lower coefficient = less soluble
Why is it that a less soluble gas will reach the brain quicker?
More quickly diffuse out of the blood once in
What agents are more readily absorbed by the CNS: polar or nonpolar?
nonpolar
What is the brain:blood partition coefficient related to?
Solubility in lipid
What is the effect of increased pulmonary blood flow on anesthetic concentration in the blood?
Lowers it
What is the effect of low pulmonary blood flow on anesthetic concentration in the blood?
Increases it
What is the relationship between alveolar and arterial concentration?
more soluble = less left in the alveoli/expire air
Which agents are eliminated faster: less soluble ones, or more soluble ones?
Less soluble ones
What is the difference between potency and induction speed?
Potency is how much drug need to produce an effect, whereas induction speed is just how long it take to get to the brain
What is the minimum alveolar concentration?
The concentration of anesthetic in the inspired air at equilibrium when there is no response to noxious stimulus in 50% of pts (similar to ED50)
A lower MAC translates to a more or less potent anesthetic?
more potent
What is the relationship between the MAC and lipid solubility?
More lipid soluble, more potent the drug (lower MAC)
true or false: MAC is greatly affects by sex, height, weight
False
What is the relationship between the MAC values of two or more agents added together?
Add MAC values
What are the major drugs that can decrease the MAC value of inhaled anesthetics?
CNS depressants
What is the relative blood/gas coefficient of Nitrous oxide? What is the significance of this?
Low, meaning that it is poorly soluble. It is quickly taken up, but also quickly eliminated.
What are the upsides of using N2O? (2)
Good analgesia
Safe/nontoxic
What are the major limitations of nitrous oxide? (2)
Incomplete anesthetic
Insufficient potency for surgical anesthesia
What is the major use of N2O?
Carrier gas to reduce the induction time for the primary agent
How does N2O work as a carrier gas?
Because N2O is taken up very quickly it has the effect of
concentrating the second agent (the primary anesthetic agent) that remains
in the lungs. The increased concentration of the second agent causes it to
move more quickly into the blood and then to the brain for a faster onset.
What are the three major effects N2O has on the agent it is administered with?
- Decreased induction time
- Decrease required amounts
- Decreased toxicity
What is the major side effect of N2O? MOA?
Diffuse hypoxia–It quickly diffuses out of the body into the alveoli, and dilute oxygen
Is N2O safe for prego?
No– can cause spontaneous abortion
true or false: N2O cannot be used as a sole anesthetic agent
true
What are the three effects of halogenating volatile agents?
- Non-explosive
- Increase potency
- Increased toxicity
What is halothane?
Volatile anesthetic
What are the systemic effect of halothane?
Decreased CO and hypotension
What is the toxicity concern with halothane?
Hepatitis
What is Enflurane?
Volatile Anesthetic
What are the major side effects of Enflurane
Respiratory depression
Reduced cardiac contractility
CNS stimulation
Patients with what conditions should not be given Enflurane?Why?
Seizures, since it is a CNS stimulant
What is Isoflurane? What is it typically used for?
Volatile anesthetic
used for maintenance
What limits the mask induction use of isoflurane?
Pungent odor
What is the duration of isoflurane? How toxic is it?
Very long duration d/t fat tissue
Low toxicity
What is desflurane? What are the advantages of using it?
halogenated volatile anesthetic
Has a fast onset and recovery
What is the major downside to using desflurane?
More irritating to the respiratory passages than others
What is sevoflurane? What are the advantages of using it?(2) What are the side effects? (2)
Newest halogenated volatile anesthetic
rapid onset and recovery. very potent.
Lower airway irritation. May cause renal/hepatic toxicity
What are the general adverse effects of inhalable anesthetics?
Depressed CO and respiratory
Decreased blood flow to liver and kidneys
Organ toxicity
What is malignant hyperthermia?
Ryanodine receptors located on the SR and function to sequester Ca are mutated, and open with administration of volatile anesthetics. The body tries to re sequester Ca, but produces heat doing so
What are the two main advantages of IV anaesthetics?
Quick, easy, and smooth induction
Rapid and complete recovery
What are the disadvantages of IV anesthetics?
cannot reverse the effects
What are the three main IV anesthetics?
Thiopental
Propofol
Ketamine
What is the MOA of thiopental?
barbiturate
How strong is the analgesic effect with thiopental?
None, in fact, hyperalgesia
What is the major issue with thiopental?
Redistributes to other tissues, meaning repeated dosing can accumulate in adipose, leading to longer duration of action and toxicity
What are the two major advantages of propofol?
Can be used as an IV drip
Excellent quality of recovery
What is the major disadvantage of propofol?
causes a significant decrease in BP
What is the use of ketamine?
Dissociative anesthesia
What is the MOA of ketamine?
Non-competitive glutamate NMDA receptor antagonist
What is the emergence phenomenon with ketamine?
Unpleasant dreams/hallucinations and disorientation during emergence
What patients should not be given ketamine?
Those with psychiatric history
Who is ketamine an excellent agent for (as opposed to other drugs)?
Those with compromised cardiac status
What is midazolam? What is it good for? MOA?
Benzo used for general anesthesia
Sedation, amnesia, and anxiolytic properties
Potentiation of GABA-A receptors