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BCN EXAM 4 > General anesthetics > Flashcards

General anesthetics Flashcards

1
Q

what are the desirable components of general anesthesia?

A

reversible immobility in response to noxious stimulus

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2
Q

Examples of inhalational, volatile agents?

A

isoflurane, sevoflutran, desflurane, halothane, enflurane, diethyl ether, chloroform, cyclopropane,

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3
Q

Examples of inhalational, gas agents?

A

nitric oxide

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4
Q

Examples of Intravenous agents?

A

barbiturates, benzodiazepines, etomidate, ketamine, propofol,

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5
Q

Midazolam, diazepam

A

benzos that reduce anxiety

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6
Q

Pentobarbital

A

barbiturates, sedation

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7
Q

Diphenhydramine

A

Antihistamines, prevent of allergic reactions

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8
Q

Ondansetron

A

antiemetic, prevents aspiration of stomach contents, reduces postsurgical nausea and vomiting

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9
Q

Fentanyl

A

opioid, provides analgesia

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10
Q

Scopolamine

A

anticholinergic, amniesia, prevents bradycardia and fluid secretion

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11
Q

Muscle relaxant

A

Facilitation of intubation

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12
Q

Examples of preanesthetics

A

Midazolam, diazepamPentobarbital, diphenhydramine, ondansetronFentanyl, Scopolamine, muscle relaxants

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13
Q

Ideal Physicochemical anesthetic

A

water soluble, stable on shelf, lipophilic, small injection volume

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14
Q

Ideal Pharmacokinetic anesthetic

A

rapid onset, short duration, nontoxic metabolites

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15
Q

Ideal Pharmacodynamic anesthetic

A

wide margin of safety, no interpatient variability in effects, nonallergenic, nontoxic to tissues

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16
Q

Parenteral anesthetics

A

barbiturates - thippental opioids - fentanyl benzos - midazolam others - etomidate, propofol

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17
Q

Mechanisms of Action

A

Enhanced GABA effect on GABAa receptors Block nicotinic receptor subtypes (analgesia) Activate Tandem pore-domain K channels (hyperpolarize Vm) Inhibit NMDA (glutamate) receptors Inhibit synaptic proteins (decrease NT release) (amnesia) enhance glycine effect on glycine R’s (immobility) alpha2A adrenergic receptor agonist - dexmedetomidineVoltage gated ion channels - Ca and Na - impaired function

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18
Q

Enhanced GABA effect on GABAa receptors

A

inhaled anesthetics BarbituratesBenzos Etomidate Propofol

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19
Q

block nicotinic receptor subtypes (analgesia)

A

moderate to high conc’s of inhaled anesthetics

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20
Q

Activate tandem pore-domain K channels (hyperpolarize Vm)

A

inhaled anesthetics, NO, ketamine, xenon

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21
Q

Inhibit NMDA (glutamate) receptors

A

NO, ketamine, xenon, high dose barbiturates

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22
Q

how do you measure amount of inhaled anesthetics?

A

partial pressure or “tension” in inspired air

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23
Q

Speed of induction of anesthesia depends on?

A

inspired gas partial pressure (GA concentration) Ventilation GA solubility (less soluble GAs equilibrate more quickly with blood and into tissues such as the brain)

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24
Q

Name some major nuclei involved in arousal and respiration

A

Lateral hypothalamus - orexin Locus ceruleus - NorEpi Basal forebrain - Ach Tuberomammillary nucleus - Histamine Pedunculopontine tegmental area - Ach Laterodorsal tegmental area - Ach PAG - dopamine Preoptic area - Galanin, GABADR- serotonin

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25
Q

solubility effects arterial anesthetic levels

A

most = desflurane, NO, sevoflurane, isoflurane, halothane

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26
Q

Modern agents are

A

Ethers

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27
Q

Measures of Anesthetic potency

A

MAC: Minimum alveolar concentration equilibrium concnetration required to prevent the response to a painful stumulus in 50% of patients OR conc at 1 atm that produces immobility in 50% of pts or animals exposed to a noxious stimulus like an EC50 useful for comparison of drugs b/c are consistent and reproducible

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28
Q

MAC awake

A

MAC at which response to commands are lost

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29
Q

MAC bar

A

blunt autonomic response

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30
Q

MAC intubation

A

response to intubation

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31
Q

1.3 MAC

A

conc. more than 99% will not respond to stimuli

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32
Q

when several GAs are mixed, the MAC values

A

are additive

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33
Q

MAC is increased by

A

Hyperthermia, elevated CNS catecholamine NT release, chronic alcohol use, acute cocaine use, hypernatremia

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34
Q

MAC is decreased by

A

Hypothermia, pregnancy, shock, increasing age, acute alcohol ingestion, CNS-depressant drugs, decreased CNS NT release

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35
Q

Inhaled anesthetics from less to most potent

A

NO, Desflurane, Sevoflurane, Ether, Enflurane, Isoflurane, Halothane

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36
Q

all agents result in predictable and dose dependent

A

Hypnosis, amnesia, analgesia, inhibition of autonomic reflexes, muscle relaxation (except N2O)

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37
Q

Induction speed is affected by

A

Solubility Ventilation rate cardiac output

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38
Q

Vessel Rich group Uptake and distribution

A

CNS and visceral organs high blood flow (75%) and low capacity

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39
Q

Muscle Group Uptake and distribution

A

skin and muscle moderate flow and high capacity

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40
Q

Fat group uptake and distribution

A

low flow and high capacity

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41
Q

Vessel poor group uptake and distribution

A

bone, cartilage, ligamentslow flow and low capacity

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42
Q

What terminates anesthetic activity

A

commonly by redistribution of drug from brain to the blood and out through the lungs

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43
Q

What GAs can lead to liver toxicity

A

halothane and methoxyflurane

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44
Q

properties of NO

A

MAC > 100%: incomplete anesthetic good analgesia No metabolism rapid onset and recovery used along with other anesthetic fast induction and recovery

45
Q

properties of Halothane

A

first halogenated inhalational anesthetic not pungent (used for induction w/ children, few side effects in childern) Medium rate of onset and recovery although inexpensive, its use has declined sensitizes the heart to epi-induced arrhythmias rare halothane induced hepatitis

46
Q

properties of Desflurane

A

most rapid onset of action and recovery of halogenated GAs (low PC) widely used for outpatient surgery irritating to the airway in awake patients and causes coughing, salivation, and bronchospasm (poor induction agent) used for maintenance of anesthesia

47
Q

properties of Sevoflurane

A

very low blood: gas partition coefficient w/ relatively rapid onset of action and recovery widely used for outpatient surgery not irritating to the airway useful induction agent, particularly in childern

48
Q

properties of Isoflurane

A

medium rate of onset and recovery used for induction and maintenance of anesthesia isoflurane “was” the most commonly used inhalational GA in the US. Largely replaced by Desflurane damages mitochondria

49
Q

properties of Methoxyflurane

A

widely considered obsolete slow onset and recovery extensive hepatic/renal metabolism, w/ release of F- ion causing renal dysfunction

50
Q

Malignant Hyperthermia

A

esp. when halogenated GA used with succinlycholineRx: dantrolene (immediately)

51
Q

Halothane toxicity

A

halothane undergoes >40% hepatic metabolism rare cases of postoperative hepatitis occur Halothane can sensitize the heart to Epi (arrhythmias)

52
Q

Methoxyflurane toxicity

A

Fluoride release during metabolism (>70%) may cause renal insufficiency after prolonged exposure

53
Q

NO toxicity

A

megaloblastic anemia may occur after prolonged exposure due to decreases in methionine synthase activity (vit B12 def)

54
Q

N&V toxicity

A

GA effect the chemoreceptor trigger zone and brainstem vomiting center RX: ondansetron (5HT antagonist) to prevent, avoidance of N2O, ketorolac vs. opioid for analgesia, droperidol, metaclopromide and dexamethasone asso with intravenous anesthetics N2O greatest culprit

55
Q

Drug disposition affect on toxicity

A

Absorption, distribution, metabolism and elimination Distribution - results in termination of effects of most anesthetics, alteration in physiology (hemodynamics, disease states) Metabolism & elimination - plays a small role in termination of effects

56
Q

Metabolism as % of administered dose

A

Halothane - 20% Sevoflurane - 2-5% Isoflurane - 0.2% Desflurane - 0.02%

57
Q

Intravenous anaesthetic properties

A

rapid onset (sec), rapid awakening (mins), danger of overdose due to irrevocability of iv injection redistribution determines duration of action

58
Q

Biotransformation and elimination of most anesthetics is

A

slow long elimination half lives, but short effects duration of effects is dose-dependent - anesthetic doses result in brief effects, redosing used to prolong effects

59
Q

Thiopental

A

“Truth serum”, most frequently used barbiturate, ultra short acting drug, BUT has a long elimination half life duration of action is dose-related anesthetic induction dose lasts 5 minutes

60
Q

Properties of Thiopental

A

rapid unconsciousnessgood amnesia, poor analgesia, poor muscle relaxation pleasant induction for the patient

61
Q

Thiopental Mechanism of action

A

Binds to GABAa receptor - increases chloride ion flux into cell and stimulates inhibitory neuronal systems

62
Q

Thiopental CNS effects

A

reduces cerebral metabolism and oxygen utilization reduces cerebral blood flow, oxygen consumption, blood volume, intracranial pressure, not cerebral perfusion pressure protects brain against hypoxic/ischemic injury

63
Q

Thiopental Cardiovascular Direct effects

A

peripheral vasculature: BP, vascualr resistance and cardiac output may decrease it transiently, venodilation may result due to increased venous capacitance and in hypotension in pts in shock,

64
Q

Thiopental Cardiovascular Indirect effects

A

Heart rate increased via barostatic reflex

65
Q

Additional Thiopental organ effects

A

pts with high sympathetic tone will experience large drop in blood pressure
ex. hypovolemia and heart failure
due to redistribution of cardiac output

66
Q

Thiopental Respiratory effects

A

depresses respiration in dose dep fashion - depresses response to hypoxemia and hypercapnia
muscle relaxants required due to retention of tracheal/laryngeal reflexes - hiccups
Thiopental depresses mucociliary clearance

67
Q

midalozam and lorazepam

A

benzos
Best amnestic agents
excellent anxiolytics, anti-convulsants, muscle relaxants
bind to distinct sites on GABAa receptor

68
Q

Midazolam in vial: pH = 3.5

A

allows the imidazole ring to remain open

maintains water solubility

69
Q

Midazolam in plasma: pKa = 6.2

A

on injection, the ring closes and the basic drug becomes 94% unionized
increases lipid solubility, which decreases time to onset on action

70
Q

Midalozam CNS effects

A

dose related effects on cerebral metabolism and blood flow
raises seizure threshold - good anticonvulsant
EEG: beta activity
antegrade, not retrograde amnesia

71
Q

Midazolam CV effects

A

hypotensive effect similar to thiopental
hypotension exaggerated in hypovolemia
synergistic sedative effect exists with opioids

72
Q

Midazolam Respiratory effects

A

hypnotic dose causes apnea

amnestic dose gives minimal depression

73
Q

Opioid actions

A

analgesic action via mu receptors
-ones with some hypnotic action, not reliable for amnesia
used for premedication, induction and maintenance of anesthesia and postoperative pain control

74
Q

Opioid side effects

A

nose and whole body - Pruritis
chest wall rigidity
Patients forget to breathe

75
Q

Ketamine mechanism of action

A

arylcyclohexylamine - like PCP
Non competitive NMDA antagonist
-only IV agent that works mostly via inhibition of stimulatory neuronal systems
-acts on Cortex, limbic system, hippocampus, spinal cord

76
Q

‘Dissociative’ anesthetic

A

individuals cognitive function is separated from his physical being

77
Q

Ketamine CNS effects

A

Fast acting antidepressant
unpleasant dreams, hallucinations and delirium
incidence higher in adults, females, habitual dreamers, psychological problems
Benzos, barbs, N2O reduce incidence of these effects
increases intracranial pressure 1-60 mmHg
Nystagmus

78
Q

Ketamine organ side effects

A

salivary and tracheobronchial secretions are markedly increased
reduced with atropine

79
Q

Ketamine CV side effects

A

central sympathetic stimulation results in increased HR, BP, epi and nor epi levels

  • offers advantage over thiobarbs when sympathetic stimulation is helpful
  • direct myocardial depressant
80
Q

Ketamine Ventilation side effects

A

small doses given slowly result in minimal ventilatory depression - profound analgesia reduces airway reflexes
rapid infusion, or combination with benzos potentiates depressant effects
sympathetic stimulation results in bronchdilation via direct smooth muscle effects

81
Q

Etomidate is a _______ derivative

A

imidazole

82
Q

Etomidate CNS side effects

A

lowers cerebral blood flow and thus intracranial pressure

lowers cerebral metabolic rate for oxygen

83
Q

Etomidate respiration side effects

A

minimal ventilatory depressant

lower incidence of apnea - good for short procedures

84
Q

Etomidate CV side effects

A

minimal changes in all parameters

85
Q

Etomidate Musculoskeletal side effects

A

myoclonus

86
Q

Propofol mechanism of action

A

diisopropyl phenol
some action at GABAa complex - binds to a distinct site
may enhance Cl- conductance at glycine receptors

87
Q

Propofol CNS side effects

A

reduces cerebral blood flow and meatbolism

autoregulation is maintained in animal studies, along with response to changes in cardiac output

88
Q

Propofol CV side effects

A

decreased mean BP, vascular resistance, HR and cardiac output
central venous pressure unchanged

89
Q

What burns on injection?

A

Propofol

phenol component

90
Q

Propofol pharma properties

A

extremely fast acting - conversation resumed in recovery, clearance exceeds hepatic blood flow
Euphoric - pts feel better the next day
“milk of amnesia”: Fospropofol - prodrug faster onset

91
Q

Dexmedetomidine site of action

A

brain (locus ceruleus), spinal cord and autonomic nerves
CNS effects - sedation/hyponsis, anxiolysis and analgesia
Autonomic nerves - decrease in sympathetic activity, BP and HR

92
Q

selectivity of alpha2/1

A

Dexmedetomidine > medetomidine > clonidine > I-medetomidine

93
Q

Prolonged recovery with

A

Midazolam

opiates

94
Q

Respiratory depression

A

midazolam
propofol
opiates

95
Q

Significant hypotension

A

midazolam
propofol
dexmedetomidine

96
Q

Cumulative effects seen with

A

midazolam

opiates

97
Q

Constipation

A

opiates

98
Q

Lack of orientation and cooperation seen with

A

midazolam
propofol
opiates

99
Q

Desflurane

A

must be delivered using a special vaporizer

100
Q

NO, nitrous oxide

A 
good analgesia 
rapid onset/recovery 
safe, nonirritating 
incomplete anesthesia
no muscle relaxation 
must be used with other anesthetics for surgical anesthesia
101
Q

Halothane

A 
reduces hepatic and renal blood flow 
lowers BP 
sensitizes myocardium to actions of catecholamine 
hepatic toxicity 
arrhythmias
102
Q

Isoflurane

A 
good muscle relaxant 
rapid recovery 
stability of cardiac output 
does not raise intracranial pressure 
no sensitization of heart to Epi
103
Q

Sevoflurane

A

potential renal toxicity at low flows
bronchial smooth muscle relaxation good for patients with asthma
rapid onset/recovery
not irritating; useful in childern

104
Q

Thiopental advantages and disadvantages

A 
poor analgesia 
causes significant nausea 
little muscle relaxation 
laryngospasm 
rapid onset of action 
potent anesthesia
105
Q

Propofol

A

poor analgesia
not likely to cause nausea
rapid onset
lowers intracranial pressure

106
Q

Dexmedetomidine

A

no respiratory depression

blunts undesirable CV reflexes

107
Q

where are opioid receptors and peptides located ?

A

CNS, PNS, and GI tract

108
Q

Opioid receptors are inhibitory, they

A

inhibit release of some NT (5HT, GABA, glutamate, Ach)

and enable the release of dopamine (contributes to dependence potential of opiates)

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