what are the four effects of nitrous oxide mixed with oxygen for the conscious analgesia?
pt remains conscious
protective relfexes are intact
relief of anxiety
analgesia
What combination of nitrous and oxygen is adequate, and what percent is recommended as the maximum nitrous limitation?
50% nitrous and 50% oxygen
60% nitrous and 40% oxygen
How long do you have the pt breath 100% O2 before adding nitrous in 10% increments?
2-3 minutes
At the termination of nitrous oxide sedation, the rapid movement of large amounts of nitrous oxide from the circulation into the lungs may dilute the oxygen in the lungs, resulting in a phenomenon known as what?
diffusion hypoxia
How do you prevent diffusion hypoxia?
administor oxygen for the amount of time needed to clear the nitrous from the lungs
Termination of nitrous oxide effects is by what?
exhalation
Why did surgery related mortality drop dramatically in 1864?
because of the introduction of diethyl ether
Who controls not only the depth of anesthesia, but also maintains homeostatic equilibrium with a combination of inhaled and intravenous anesthetics, and a number of adjuvant drugs?
the anesthesiologists
What type of anesthetic induces a generalized, reversible depression of the CNS charcterized by loss of consciousness, amnesia, and immobility, but not necessarily complete analgesia
general anesthetics
What is the primary site of action of anesthetics?
CNS
Loss of consciousness and amnesia from anesthesia appear to result from ________ action, while immobility in response to noxious stimuli is caused by the depression of both ________ and _________ and __________ pathways
supraspinal
supraspinal
spinal sensory
motor
What are supraspinal actions?
action in the brain stem, midbrain, and cerebral cortex
What are the 4 stages a pt goes through as they progress through stages of anesthesia?
consciousness is maintained, reflexes are present and respiration is regular, but reduction of sensation to pain begins
period of excitation characterized by autonomic activity, muscle twitching, vomiting and incontinene can occur, responses are abolished as more anesthesia is given
a decreasing loss of eyelash reflex and development of rhythmic respiration, muscles relax, and normal pulse rates are evident; most surgery is performed in this stage
this stage leads to respiratory depression, cardiac arrest and death can occur later in this stage, so it is avoided
who divided up the progress of anesthesia into 4 stages?
Arthur Guedel
The following things are part of which stage of general anesthesia?
analgesia
amnesia
euphoria
consciousness
stage I: anelgesia
The following things are part of which stage of general anesthesia?
excitement
delirium
combativeness
Stage II: excitement
The following things are part of which stage of general anesthesia?
unconsciousness
regular respiration resumes
decreasing eye movement
stage III: surgical anesthesia
The following things are part of which stage of general anesthesia?
respiratory arrest
cardiac depression and arrest
no eye movement
stage IV: medullary depression
A combination of agents is used to achieve surgical anesthesia, in clinical practice, this combination of agents is used to achieve what 6 things?
rapid loss of consciousness
amnesia of surgical events
minimal amount of time in the excitement phase (stage II)
stable plateau of surgical anesthesia
analgesia
appropriate levels of respiratory and cardiovascular responsiveness, and skeletal muscle relaxation
Inhalation anesthetics are useful for maintaining stable, long-term anesthesia, but why does it not provide rapid loss of consciousness or minimize the time of the excitation phase?
it doesn't raise their blood concentrations rapidly enough
general anesthesia is induced using what anesthetic agent, which can be injected directly into the circulation via IV and then maintained by inhalation anesthetics
highly lipid soluble anesthetic agents
What type of drugs are used to move the pt past stage II quikly?
short acting barbituates (thiopental, methohexital)
Why are the barbiturates thiopental and methohexital used to move the pt through stage II quickly?
because they are highly lipid soluble, which allows rapid penetration in the CNS
How fast can short acting barbituates enduce unconsciousness?
within 20 seconds
After using short acting barbiturates for general anesthesia, why do patients experience a long hanover period in which they will remain drowsy and more susceptible to CNS depressant drugs?
blood brain barriers decline rapidly as the drugs diffues into tissues with a lower blood supply, skeletal muscles, skeletal muscle and adipose tissue act as a reservior of the drug
What are 4 types of IV general anesthetics?
short acting barbiturates
etomidate
propofol
ketamine
Which type of IV GA is being described?
it resembles barbiturates pharamcologically and orivudes fir rapid induction and recovery, it also metabolizes rapidly in the liver and dangers with a long hangovers are lessened.
egomidate
What is the negative side of using etomidate IV GA?
it can cause adrenal suppression after repeated exposure
What IV GA resembles the hallucinogen drug phencyclidine (PCP or angel dust) which produce a state of functional and electroencephalographic anesthesia, but w/persistent eye and skeletal movement? It causes dissociative anesthesia, and is accompanied by marked analgesia.
ketamine
A state where pts have their eyes open and are able to make some voluntary movement, but they appear unaware or dissociated from their surroundings.
dissociative anesthesia
Which IV drug is one of the safest general anesthetics, and why?
ketamine
it causes minimal cardiopulmonary depression
When is ketamine good to be used? And where is it usually used?
valuable when hospital facilities are not available
used by oral surgeons
gases or volatile liquieds that are administered by inhalation in air or with oxygen at a sufficient gasious partial pressure to achive the appropriate concentrations in the brain
inhlation anesthetics
Inhalation anesthetics appear to interact with lipphilic sites on key cellular proteins mainly where?
the medullary reticular activating system involved with the regulation of sleep and wakefulness
What might explain the effects of amnesia from inhalation anesthetics?
anesthetics inhibitory effects on the hippocampus of the brain, affecting the release of and sensitivity to acetylcholine
What inhalation anesthetic provides for fast onset of action and rapid recovery because of its low solubility in blood?
nitrous oxide
What prevents nitrous oxide from achieving the concentrations to reach full anesthesia?
the requirement to maintain an acceptable partial pressure of oxygen
What are 2 major concerns of the use of nitrous oxide?
hypoxia during recovery
repeated use can disrupt methionine synthesis (for vitamin-B), which can disturb DNA synthesis and lead to severe anemia on prolonged exposure
What is the recommended dosage of nitrous oxide for induction, and what is the recommended dosage for maintenance?
60% nitrous 40% oxygen
30% nitrous 70% oxygen
true or false. Nitrous is excreted 100% unchanged through the lungs by exhalation
true
How did the adverse effect happen in the past that led to too much nitrous being delivered to the client?
the hoses on the oxygen and nitrogen tanks were swithced
true or false. On the new oxygen and nitrous tanks, the fitting for the blue nitrous tank will not fit the green oxygen tank, and vice versa
true
What are the most noteable side effects of nitrous oxide?
nausea
vomiting
delirium
no known drug interactions
When might a headache occur from using nitrous oxide?
if 100% oxygen is not breathed for 5 minutes at the end of the procedure
When is the use of nitrous oxide contraindicated?
pts who have had ocular surgery within the last 3 months
if pts have repeatedly abused the use of it
in pregnant pts
an increased risk for fetal exposure to nitrous oxide and spontaneous abortion exists for pregnant who? presenting as what type of hazard?
oral health care workers
occupational hazard
self administering nitrous oxide on a regular basis can lead to what?
numbness of hands and legs (neuropathy)
a new induction agent that is a widely used GA in hujans, although it is only a weak analgesic; it produces hypotension and cardiac depression and sensitizes the heart to catcholamines leading to arrhythmias. it is eliminated through the lungs, 15% is metabolized in the liver, but rare hepatotoxicity has been reported
halothane
less potent halogenated hydrocarbons that resemble halothane, most of the gas is eliminated through exhalation, but 2% is metabolized in the liver with the production of fluoride ions which are believed to account for a greater risk for renal toxicity
enflurane and isoflurane
newer anesthetics that are much more potent than nitrous oxide, but provide fast induction and similar recovery times, but is a poor induction agent because of bad odor, and laryngospasm. Major side effects include cardiovascular and repiratory depression
