general anesthetics Flashcards

1
Q

definition of GA

A

a medically induced coma and loss of protective reflexes resulting from the administration of one or more GA agents

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

ideal qualities of GA

A
  1. induce smooth and rapid loss of consciousness
  2. allow for prompt recovery after discontinuation
  3. wide safety margin and no adverse effects
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

definition of monitored anesthesia

A

pt continues to maintain a patent airway and respond to commands

LA w sedation and analgesia

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

stages of anesthesia

A

analgesia, amnesia, excitement (may vomit if stimulated), surgical anesthesia, medullary depression

stages obscured by rapid onset of GA and use of other drugs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

most reliable sign of surgical anesthesia

A

loss of motor and autonomic response to noxious stimuli

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

how is the effect of inhaled anesthesia produced? (A,D)

A

produced when we achieve the necessary BRAIN conc, depending on:
- solubility in blood (low solubility -> high arterial tension rapidly -> rapid equilibration w brain -> fast onset)
- anesthetic w moderate solubility can be given at higher conc initially to increase the rate of rise then reduced after adequate depth of anesthesia is achieved

  • anesthetic conc in inspired air (higher conc -> increase rate of transfer to blood)
  • rate and depth of pulm ventilation (increase absorption)
  • depression of respiration by opioid analgesics will reduce onset of anesthesia
  • pulm blood flow (increase blood flow -> less time for GA to diffuse into blood ->decrease rate of rise of anesthetic tension in blood)
  • ateriovenous conc gradient higher -> more go to tissue instead of brain -> more time to equilibrate w brain)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

determinants of rate of recovery (M,E)

A

excretion MAINLY through lungs (pulm blood flow, rate of ventilation impt), hepatic metab, bacteria in GI (NO)

  • insoluble in blood -> excrete faster
  • exposed longer -> accumulate in muscle, skin, fat -> eliminated slower
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

inhaled anesthetics mechanism of action

A

modify ion currents by direct interactions w ligand-gated ion channels

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

inhaled anesthetics actions on organ systems

A
  • CVS: decreased mean arterial P
  • Respi: decreased ventilation, response to hypercapnia, muco-ciliary function, bronchodilation
  • brain: increased cerebral blood flow –> undesirable in pt w increased intracranial P (NO least likely to increase cerebral blood flow)
  • renal: impairs renal autoregulation
  • liver: reduced hepatic blood flow
  • uterus: halogenated anesthetics –> potent uterine muscle relaxant
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

toxicity of inhaled anesthesia

A

repeated exposure of halothane may cause liver damage (develop hepatitis)

renal dysfunction following methoxyflurane (release of F- during metab)

malignant hyperthermia
- autosomal dominant skeletal muscle disorder (check fam history)
- increase in muscle cell Ca2+
- tx w dantrolene
- effects: hypertension, tachycardia, severe muscle rigidity, hyperthermia, acidosis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

inhaled anesthetics: halothane

A

standard for comparison for modern inhaled anesthetic
potent
maintain anesthesia
induction of anesthesia commonly in children
relax skeletal muscles, potentiates skeletal muscle relaxants
decrease BP, may cause bradycardia, arrhythmia
may rarely cause halothane hepatitis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

inhaled anesthetics: nitrous oxide

A

fast onset and recovery but LACKS potency
- cannot give surgical anesthesia even at max dose (80%)

used in adjunct w other inhaled anesthetics
analgesic agent for labour pain

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

limitation of inhaled anesthesia

A

require specialised vaporiser for delivery/equipment for disposal of exhaled gases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

properties of IV anesthetics

A

onset faster – commonly used for induction
rapid recovery
lack analgesic properties – combined use w inhaled/LA for short procedures

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

IV anesthetics: barbiturates

A

increases duration of GABA Cl- channel opening
AMPA receptor to depress glutamate mediated excitation

THIOPENTAL
- commonly used for induction as it rapidly crosses BBB
- high lipid solubility
- high dose/continuous infusion: decrease arterial BP, stroke vol, C/O
- potent respi depressant
- decrease cerebral metab, O2 consumption and blood flow – desirable for pt w ^ intracranial P

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

benzodiazepines (pre-medication, not GA)

A

potentiated GABA inhibition, increases freq of GABA Cl- channel openings

diazepam, larazepam, medazolam
- pre-anesthetic medication

may cause anterograde amnesia

17
Q

how to accelerate recovery from benzodiazepine

A

to accelerate recovery when large doses given (esp elderly), give benzodiazepine antagonist FLUMAZENIL

short duration of action (<90mins) – multiple doses

18
Q

IV anesthetics: propofol

A

potentiate GABA receptor activity, slowing channel closing time
sodium channel blocker

most popular IV A, rapid onset as barbiturates, more rapid recovery

rapidly metab by liver, excreted by kidney

decrease BP
potent respi depressant

19
Q

IV anesthetics: ketamine

A

dissociative anesthesia (no loss of consciousness)
only IV A w both analgesic + anesthetic properties
NMDA receptor antagonist

stimulates CVS
increase cerebral blood flow, O2 consumption, intracranial P
decrease respi rate
highly lipophilic
metab by liver, excreted by kidney + in bile

post op disorientation, illusions, dreams

20
Q

neurolept analgesia

A

fentanyl + droperidol

detached, pain-free state

21
Q

alternatives of GA

A

balanced anesthesia
- supervision by professional
- combination of inhaled/IV A, muscle relaxants, LA, cardiovascular drugs for control of transient autonomic responses to noxious surgical stimuli

monitored anesthesia care
- supervision by professional
- LA supplemented by IV anesthetics
- diagnostic, minor procedures
- midazolam for premedication, propofol infusion, opioid analgesics/ketamine

conscious sedation
- primarily by non-anesthesiologist
- pt maintain patent airway, responsive to commands
- benzodiazepine, propofol, opioid

22
Q

reverse opioid

A

naloxone, opioid antagonist