ANESTHESIA Flashcards
why are general anesthetics typically given via inhalational & intravenous route?
offer more immediate control over dose & hence duration of action
term for the concentration in the inspired gas required to render half of a group of pts unconscious, that is unresponsive to painful stimulus
minimum alveolar concentration (MAC)
what is the oil gas partition coefficient?
describes relationship b/w lipid solubility & potency of the drug in producing unconsciousness (the larger the number the more lipid soluble the drug)
what is the meyer-overton hypothesis?
states that anesthetic activity is directly linked to lipid solubility
which inhaled anesthetic has the highest min. alveolar concentration?
N2O
what is the general mechanism of action for the inhaled anesthetics?
reinforce of GABA & glycine inhibitor signaling, reinforcement of two more potassium channel activity & inhibition of glutamatergic signaling
Remember that loss of memory and perceptive awareness can precede the production of what?
analgesia (customary in anesthesia to rely upon analgesics to make sure the pt is pain free)
why do you add a fluorine molecule to the inhaled anesthetics?
removes the explosive nature of the drug product
the volatile anesthetics are most commonly administered in conjunction w/ what and oxygen?
nitrous oxide
which inhaled anesthetic has the highest blood:gas partition coefficient?
isoflurane
which inhaled anesthetic has the lowest blood gas partition coefficient?
nitrous oxide
which inhaled anesthetic drug has has very low hepatic metabolism?
nitrous oxide
the newer agents like (name the two) equilibrate more rapidly into the brain and produce a faster onset of unconsciousness than does halothane.
desflurane & sevoflurane (also when turned off these re-equilibrate from the brain to blood and then to alveoli flooding back into lungs and permitting a more rapid recovery of consciousness)
equilibration occurs most rapidly with high flow organs like the ___________ and less rapidly into skeletal muscle and adipose tissue
brain
once the anesthetic is turned off, elimination of drug is most rapid again in high flow organs, but overall duration of elimination is governed by the rate of release from __________tissue
adipose
what are the two factors that the anesthesiologist can control to adjust the speed of onset of unconsciousness?
can increase the percentage of anesthetic delivered with each breath
can adjust RR (more profound effect on N2O, which doesn’t block the reflex response to PaCO2)
with increasing delivery of anesthetic and thus depth of unconsciousness, there is both a loss of _______________ & reduction in tidal volume
loss of responsiveness to rising carbon dioxide levels
what are the two main respiratory effects of inhaled agents?
increased RR
decreased tidal volume
reflex response to PaCO2 is blocked by all inhaled agents except what?
N2O
when used alone which inhaled agent has no effects on the CV system?
N2O
what are some of the effects of CV depression by inhaled agents?
direct depression -decreased symp. outflow Peripheral ganglion blockade -decreased adrenal catecholamine release Baroreceptor attenuation -decreased Ca2+ flux Vagal stimualation
name two inhaled agents that have irritating odor?
desflurane
isoflurane
none of the inhaled agents except for which drug produce analgesia?
N2O
none of the inhaled agents have effects on muscle relaxation except?
isoflurane
which inhaled agent is protective in that reflexes are maintained if this agent is used alone?
nitrous oxide
which inhaled agent is teratogenic?
N2O (spontaneous abortions)
N2O is an inhibitor of what vitamin?
vitamin B12
what is the second gas effect for N2O?
high volume of N2O + relative insolubility = rapid uptake of gas from alveoli including any accompanying anesthetic agent for O2
what is diffusional hypoxia with N2O?
that brief period of time when the anesthetic is turned off and large quantities of anesthetic gas exit the body by being exhaled (important that anesthesiologist applies oxygen by mask during this critical period)
increase pressure with N2O could give rise to what adverse outcome?
eardrum perf. (N2O has 34x solubility that of nitrogen)
why do we use N2O?
vapor sparing effect (reduced requirement for expensive volatile agent) reduced inspired volatile concentration -reduced resp. depression -reduced CV effects -smoothens the anesthetic procedure cheap
the need to accomodate such a high volume of nitrous oxide compromises the ability to provide high levels of what?
oxygen
which two drugs have actions on NMDA receptor system for glutamate?
propofol
ketamine
which IV anesthetic is unusual in that it can function like GABA itself?
propofol
propofol blocks the binding of glutamate to what receptor?
NMDA
which IV anesthetic works to physically occlude the NMDA channel?
ketamine
name the 4 induction agents?
thiopental
propofol
etomidate
also Ketamine
it is very difficult for a patient to overdose on what class of drugs?
benzodiazepines
what is the rate limiting step in the final elimination of IV anesthetics following surgery?
ultimate release of drug from adipose tissue
awakening of the pt who has undergone IV anesthesia is due only to what?
drug-redistribution
after extended periods of administration the elimination half-lives of IV anesthetics become governed by what?
become governed by processes of accumulation & release from fat, metabolism and elimination
which IV anesthetic causes increased cerebral blood flow & intracranial pressure?
ketamine
which drug has no inhibitor effect upon cardiac output and MAP, which makes it useful for surgery with cardiac pts?
etomidate
most of the IV anesthetics have what effect on respiratory function?
depressive
which IV anesthetic does not have a negative effect on respiratory function?
ketamine
which drug can cause like porphyria?
thiopental
which IV anesthetic has analgesic action and can cause hallucinations (hint: structurally related to angel dust)?
ketamine
which IV anesthetic has inhibition of steroidogenesis?
etomidate
what are the adverse effects of propofol?
antiemetic
propofol infusion syndrome
which benzo- has the shortest duration of effect?
midazolam
which benzodiazpine has the longest duration of effect?
diazepam
name the class of drugs: anticonvulsant, amnesia, wide therapeutic safety margin, minimal CV & respiratory depression if used alone
benzodiazepines
anesthetics reduce the normal ventilation response to what?
PaCO2
name the 20 minute drug for a 20 minute procedure
fentanyl (N/V are rare in contrast to morphine)
which class of drugs can have malignant hyperthermia?
all volatile anesthetic agents (including desflurane, sevoflurane)
what are the amide type local anesthetics?
lidocaine
prilocaine
bupivacaine
what are the ester type local anesthetics?
procaine
tetracaine
which local anesthetic is used for topical use only?
benzocaine
what is the mechanism of action of the local anesthetics?
lipophilic drug that passes through neuronal membrane and binds inner surface of the sodium channel causing it to block the ability of an action potential to produce threshold depolarization
the local anesthetic produces a differential blockade, what is that?
larger diameter nerves require more local anesthetic, and the time it takes to impact fibers in the center of the bundle
the __ is longer for a myelinated nerve than for a non-myelinated nerve because in the former the action potential actually skips along the sufrace of the nerve
zone of anesethetic
the local anesthetic usually binds to receptor during which phase of sodium channel activation?
the majority of drug binding takes place with inactivated sodium channels
the component of overall local anesthetic drug in the neutral form is dependent on what?
local pH (the majority of local anesthetics are weak bases w/ pKa around 8)
application of local anesethetic is discouraged in what areas?
areas of inflammation (b/c very low proportion of drug can access teh nerve and won’t cause blockade)
which part of the nerve fibers is the last part to experience blockade by a local anesthetic?
-nerve fibers in the center (which serve distant anatomic locations) are the last to be blocked
loss of sensation by local anesthetic begins from what to what?
proximal to distal
-note recovery happens from proximal to distal
caines are considered what local anesthetic structure?
amide “caine contains I” (lidocaine, prilocaine, bupivacaine)
-note if local doesn’t have an I then it’s an ester
why do we use vasoconstrictors with local anesthetics?
removes gradient b/w drug and vasculature, permitting a larger portion of drug to pass down gradient into the adjacent nerve bundle
what is the longest acting local anesthetic?
bupivacaine
what is the shortest acting local anesthetic?
procaine
name the drug: anti-dopamine/cholinergic/histaminergic effects
given IM, PO to lower threshold for seizures
promethazine
which 1st gen. antihistamine is used as a bronchodilator, sedative, anxiolytic and analgesic with preop ?
diphenhydramine
what is the purpose of using 1st. gen. antihistamines in the preoperative period?
have sedative effect and anticholinergic effect which dries secretions & provides prophylaxis of emesis
return of the function of what must return before the pt can be discharged following hopsitilization (following opiate therapy)?
gastrointestinal motility
why do we prophylactically treat all pts with neutralization of stomach acid before going into surgery?
reduces the risk of aspiration
name one of the H2 blockers used to reduce the incidence of aspiration pneumonitis, also works rapidly to reduce the rate of acid secretion?
ranitidine
what do bicitra & polycitra do?
neutralize stomach pH (sodium & potassium citrate + citric acid)
the effectiveness of agents like metoclopramide (in gastric emptying) is compromised by the pharmacologic antagonism by what two classes of drugs?
anticholinergics & narcotics
name inhaled anesthetic that is considered proemetic?
nitrous oxide
Which anticholinergic is most potent in reducing tracheobronchial secretions?
glycopyrrolate
what is the typical sequence of drug delivery for rapid sequence intubation?
IV push of sedative, then NMB, usually succinylcholine
what is the most common reason for delayed awakening?
residual anesthetics & ancillary drugs
what are some of the respiratory components to anaphylaxis in anesthesia?
cyanosis, wheezing, increased peak airway pressure, acute pulmonary edema, bronchospasm
what are some of the CV components to anaphylaxis in anesthesia?
tachycardia, dysrhythmias, pulmonary htn, CV collapse
what are two common aspects of anesthetic agents (ancillary) which can cause anaphylaxis?
bone cement
radio contrast dye
what is the MCC of compression of the optic chiasm?
pituitary adenoma
