General anesthesia Flashcards
what does general anesthesia do to respiration and BP?
lowers respiration and BP
what is the triad of anesthesia?
asleep, pain free, still
which anesthesia adjuvants relieve anxiety?
benzodiazepines (midolazam)
which anesthesia adjuvants prevent allergic reactions?
antihistamines (diphenhydramine, ranitidine)
which anesthesia adjuvants prevent nausea and vomiting?
antiemetics (dexamethasone, scopolamine)
which anesthesia adjuvants provide analgesia?
opiods (fentanyl, morphine, hydromorphone)
which anesthesia adjuvants prevent bradycardia and secretion?
atropine, glycopyrrolate
what kind of clinical conditions might be important to know about when a patient is to undergo anesthesia?
prior anesthetic history of patient and blood relatives:
malignant hyperthermia
CV problems
respiratory disease
allergies
what are the four phases of general anesthesia?
- induction
- maintenance
- emergence
- recovery
which route of anesthesia is usually used for maintenance?
inhalable
which route of anesthesia is usually used for induction in pediatric patients?
inhalable
which route of anesthesia is usually used for induction and short surgical procedures in adults?
IV
what are the general mechanisms of action for general anesthetics?
- depress spontaneous and evoked neuronal activity
2. alter ion channel function
how do general anesthetics depress spontaneous and evoked neuronal activity?
- induce neuronal hyperpolarization
- increase firing threshold (lessen activity)
- inhibit synaptic transmission and response to released NTs
which ion channels are altered under general anesthetics?
- increase GABAa receptor chloride activity
- activate voltage gated potassium channels
- inhibit glutamate NMDA receptors
what are the stages of general anesthesia with respect to effects on the brain?
- analgesia
- excitement
- surgical anesthesia
- medullary depression
which stage of general anesthesia do anesthesiologists want to avoid?
stage 2 (excitement)
what does ketamine do?
inhibits glutamate NMDA receptors - decreases excitatory neurotransmission
what are the advantages to inhalable anesthetic agents?
- easy to control depth of anesthesia
- readily reversible
- minute to minute control
what are the disadvantages to inhalable anesthetic agents?
induction not as fast or smooth as with fixed agents
which pharmacokinetic factors affect the rate of anesthetic onset and recovery?
- concentration in inspired air
- ventilation rate
- solubility in blood and lipid
- lung blood flow
- arteriovenous concentration gradient
- elimination
the partial pressure of anesthetic with higher solubility are affected by what physiological process?
ventilation rate
what is the ostwald coefficient?
blood - gas partition coefficient - solubility in blood
lower coefficient means lower solubility
how does low solubility in blood affect equilibration with brain and induction?
less solubility leads to a rapid rise in partial pressure in blood and a faster equilibration with brain and induction
what does the brain-blood partition coefficient describe? what is it related to?
solubility in lipid
related to anesthetic potency
which solubility factor relates to anesthetic potency?
solubility in lipid
how does high blood flow affect onset? low flow?
high flow - slow onset
low flow - fast onset
how does alveolar and arterial concentration affect onset?
the greater the uptake of agent, the difference between inspired and alveolar concentrations - slower rate of induction
elimination is dependent on what solubility coefficient? why?
blood - gas partition coefficient: ostwald
less soluble - faster elimination
what is the minimum alveolar concentration? what does a low MAC value mean? high MAC value?
concentration of anesthetic (%) in inspired air at equilibrium when there is no response to noxious stimulus in 50% of patients
low MAC - more potent
high MAC - less potent
how does lipid solubility related to minimum alveolar concentration (MAC)?
high lipid solubility - more potent (lower MAC)
when is anesthesia produced, as related to partial pressure in brain and MAC?
when partial pressure of drug is equal to or exceeds the MAC
is MAC affected by age, height, sex, or weight?
no
MAC values for inhaled anesthetics have what property?
additive
what is the gaseous inhalable anesthetic?
nitrous oxide
what is the major limitation of nitrous oxide?
incomplete anesthetic
insufficient potency for surgical anesthesia due to low potency (110% MAC value)
what is the second gas effect?
reduces induction time for primary agents - carrier agent
reduced induction time
reduced requirement concentration of primary agent
reduced toxicity of primary agent
what are the advantages of nitrous oxide?
- 2nd gas effect
- minimal effects on CVS, respiratory, liver, kidney, GI
- minimal toxicity
what are the disadvantages of nitrous oxide?
- lack of potency
- diffuse hypoxia
- increased risk of spontaneous abortion
what are the uses for nitrous oxide?
- general anesthesia
2. analgesic for minor procedures
can nitrous oxide be used as sole anesthetic agent?
no
what is the general use for halogenated agents?
maintenance of anesthesia
what are the properties of halothane?
- complete anesthetic
- poor analgesia
- muscle relaxant
what is the toxicity of halothane?
post-op hepatitis
what are the systemic effects of halothane?
decreased CO and hypotension
why is enflurane not as popular?
CNS stimulation effects - EEG convulsion pattern, jerking, twitching
isoflurane is used for what phase of anesthesia?
maintenance
what are the primary advantages of desflurane?
fastest onset and recovery, excellent minute to minute control
what are the advantages of sevoflurane?
- rapid onset and recovery
- very potent
- excellent controllability due to low solubility and high potency
- low airway irritation - USED FOR MASK INDUCTION AND THOSE WITH AIRWAY IRRITATION
thiopental is used for what phase of anesthesia?
induction
propofol is what class of anesthetic?
barbiturate
what are the advantages of propofol?
- can be used as IV drip
2. excellent quality of recovery
propofol is used for what phase of anesthesia?
induction
ketamine produces what type of anesthesia?
dissociative anesthesia
what is dissociative anesthesia?
intense analgesia, catalepsy, and amnesia
what is the MOA of ketamine?
NMDA receptor antagonist
what is an adverse effect of ketamine?
emergence phenomenon
what is emergence phenomenon?
unpleasant dreams, hallucinations, disorientation
ketamine is ideal for what situation?
compromised cardiac status - tamponade, bleeding GSW, GI bleed
midazolam is used for what adjunctive purposes?
sedation for painful procedures, induction
