Anesthesia Flashcards
-from administration to loss of consciousness, decreased awareness of pain, may have some amnesia and decreased consciousness
stage1 - analgesia stage
- from loss of consciousness to regular respiration
- excitation and delirium may occur
- amnesia occurs
- vomiting and incontinence possible
stage 2 - disinhibition
- from regular respiration to respiratory arrest
- patient unconscious, no pain reflexes
- respiration and blood pressure maintained
stage 3 -surgical
- from respiratory arrest to death
- requires mechanical and pharmacological support
stage 4 - medullary paralysis stage
- very controllable, readily reversible
- induction not as fact or smooth as with fixed agents
- depress spontaneous and evoked neuronal activity
- act at voltage gated K channels, GABAa receptor chloride channels resulting in hyperpolarization
inhalable anesthetics
- insufficient potency for surgical anesthesia
- has analgesic activity
- can be used as carrier for volatile anesthetics
- decreases methionine synthetase with chronic exposure and can cause megaloblastic anemia
nitrous oxide
halothan, enflurance, desflurane, isoflurane, sevoflurane
volatile inhaled anesthetics
anesthetic concentration in the inspired air is proportional to _________, with higher resulting in more rapid achievement of anesthetic concentrations in blood
partial pressure
blood:gas partition coefficient?
Otswald
lower Otswald coefficient leads to _______ equilibrium with the rbain
faster
the partial pressure of anesthetics with _______ solubility in blood are more affected by ventilation rate
higher
the concentration of anesthetic in the inspired air at equilibrium when there is no response to a skin incision in 50% of patients
minimum alveolar concentration (MAC)
higher MAC = ______ potent
less
inhaled anesthetic that depresses myocardium, has liver toxicity
halothane
- barbiturates, IV/fixed anesthetics
- rapid induction
- no analgesia*, pain on injection
- decrease in respiration, difficult to control level of anesthesia
- redistributes, accumulates in adipose
thiopental, methohexital
- IV/fixed anesthetic
- acts at GABAa receptors, increase channel open time
- more rapid recovery than barbiturates, 10X faster hepatic metabolism
- maintenance and induction anesthesia
- used for OP procedures
- significant decrease in BP and blunts baroreceptor reflex, decreases respiration
propofol
- used for induction and balanced anesthesia, esp in patients at risk for hypotension
- minimal CV/resp depression
- no analgesic activity
- not recommended for long term infusion
- high incidence of nausea, vomiting, pain on injection, myoclonus
etomidate
- dissociative anesthesia, catatonia, analgesia, amnesia w/o loss of consciousness
- blocks NMDA glutamate receptor ion channel
- short duration of action
- excellent analgesia and amnesia
- mydriasis, salivation, lacrimation, spontaneous limb movements
- cardiac stimulation
- increases cerebral blood flow
- emergence phenomenon - hallucinations and disorientation, can decrease w/ benzodiazepines
- use limited mainly to small children, patients at risk for hypotension and bronchospasm
ketamine
- shortest acting benzo, least irritating for IV admin
- used in combo with inhaled agent or IV opioids
- can be used for maintenance of anesthesia with other agents as part of general or conscious sedation
- rapid onset and recovery
- good amnestic effects
- antagonist flumazenil can accelerate recovery
- induction too slow to induce anesthesia
midazolam
- opioid, can achieve anesthesia with sufficient dose or in combo with benzodiazepines
- useful in patients with compromised CV function
- provides excellent post op analgesia
- can cause truncal rigidity, impair ventilation
fentanyl
- minimize anesthetic use
- good for ortho procedures
- short acting good for intubations, ECT
- should never be used as substitute for inadequate anesthesia
neuromuscular blocking agents (paralytics)
- d-tobucurarine, mivacarium, rocuronium
- potency altered by pH, increases in histamine release
competitive nicotinic antagonists
- depolarizing nicotinic agonist
- short duration of action
- desensitization follows with long term exposure
succinylcholine
- no effect on motor end plate depolarization
- no effect on striated muscle
- small muscles affected first
- additive w/ d-tobucurarine
- reversal of block with physostigmine
- increased potency w/ inhaled anesthetics and antibiotics
competitive neuromuscular blockers
- partial persistent depolarization at motor end plate
- fasciculations of striated muscle
- skeletal muscle affected first
- antagonistic effect with d-tobucurarine
- no antagonism w/ physostigmine
- no effect with inhaled anesthetics or antibiotics
depolarizing neuromuscular blockers
-most paralytics cause _______ release leading to hypotension and bronchospasm, most pronounced with d-tobucurarine
histamine
succinylcholine cause muscle pain due to ________
fasciculations
- opioids
- local anesthetics - increase potency of both competitive and depolarizing agents
- anticonvulsants
- CV drugs
- antibiotics (esp. aminoglycosides, increase potency and duration of competitive antagonists)
- inhalable anesthetics esp isoflurance increase potency and duration
drug interactions with neuromuscular blockers
- block nerve conduction by blocking voltage gated sodium channels, thus preventing depolarization and conduction of the cation potential
- charged anesthetic molecules gain access to the channel when it is open
- efficacy is use dependent,
- also block K channels at higher concentrations
local anesthetics
local anesthetics order of block?
pain –> cold/warm/touch/deep pressure –> muscle tone/proprioception/motor function
- penetrates membranes, vasoconstrictor, medium acting
- ester, used topically for nasal and opthalmic procedures
cocaine
- ester, surface use only, very lipophilic
- burns, bites, hemorrhoids, cather, endoscope placement
benzocaine
-amide, most widely used, medium acting
lidocaine
- amide, medium acting
- vasoconstricts, slightly longer lasting
mepivicaine
long acting amides
bupivicaine, ropivicaine
potency of local anesthetics affected by ______
pH
local anesthetics are weak bases, the _______ form is required to penetrate the membrane to gain access to the channel inside the cell membrane
-potency decreased at low pH (infected tissues)
unprotonated
- duration of action of local anesthetics proportional to time drug is in contact with the nerve
- more ________ leads to shorter action, greater systemic absorptin
- use epi to increase duration
vascularization
- CNS: sleepiness, lightheaded, restlessness, nystagmus and myoclonus, tonic clonic seizures with esters, direct neurotoxicity with spinal admin due to pooling in cauda equina
- CV: depression, hypotension, cocaine can cause HTN, arrythmias, myocardial failure
- allergic rxns with esters
local anesthetic adverse effects
______ syndrome tends to occur with continuous spinal anesthesia
cauda equina
