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Pharmaco Ca2 > General Anaesthesia > Flashcards

General Anaesthesia Flashcards

1
Q

General anaesthesia results in

A

Medically induced coma and loss of protective reflexes

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2
Q

Should general anaesthesia result in amnesia

A

Yes

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3
Q

What is monitored anaesthesia

A

Minor procedures where patient maintains patient airway and responds to commands

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4
Q

What are the 4 stages of general anaesthesia

A
  1. Analgesia (first without amnesia then with)
  2. Excitement (amnestic, delirious, irregular respiration)
  3. Surgical anaesthesia (loss of motor and autonomic response to noxious stimuli, loss of eye movements)
  4. Medullary depression
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5
Q

How is general anaesthesic thiopentone administered

A

Intravenously (inducing agent)

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6
Q

What is propofol

A

Intravenous inducing agent, general anaesthesia

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7
Q

How are inhaled anaesthetics distributed to the brain

A

Transferred from alveolar air to the blood, transfer from blood to brain

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8
Q

What are the 5 factors affecting rate of inhaled general anaesthesia reaching brain concentration

A

Solubility, concentration in inspired air, rate and depth of pulmonary ventilation, pulmonary blood flow, arteriovenous concentration gradient

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9
Q

How does solubility of general anaesthesia affect rate of onset

A

Low blood solubility, able to saturate in blood faster and reach high arterial tension more quickly. This allows for more rapid equilbration with the brain and faster onset

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10
Q

How does concentration in inspired air affect rate of onset of general anaesthesia

A

Increase concentration, increase rate of transfer into blood and brain

Higher concentration, higher onset

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11
Q

How does rate and depth of pulmonary ventilation affect onset of general anaesthesia

A

Increased pulmonary ventilation, increased onset rate

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12
Q

How does pulmonary blood flow affect rate of onset of inhaled general anaesthesia

A

Increase blood flow, decrease rate of rise of anesthetic tension between blood and brain (keep carrying to tissues)

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13
Q

How does arteriovenous concentration gradient affect inhaled general anaesthesia onset

A

High concentration gradient between artery and vein means increased uptake by tissues, more time needed to achieve equilibrium with brain

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14
Q

How is inhaled general anaesthesia eliminated

A

Mainly excreted through the lungs

Hepatic metabolism
Bacteria in gut can break down nitrous oxide

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15
Q

How does solubility affect metabolism of inhaled general anaesthesia

A

Low solubility, eliminated faster

More soluble, accumulate in muscle, skin, fat, more slowly eliminated

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16
Q

What is the mechanism of action of general anaesthesia

A

Modifies ion currents. Directly interact with ligand gated ion channels eg activates GABA receptor and glycine receptor, inhibits nicotinic receptor

It acts at multiple levels of CNS, affect sensitivity of specific neurons and pathways

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17
Q

How does inhaled general anaesthesia affect cardiovascular function

A

Decrease mean arterial pressure by reducing cardiac output, reducing systemic resistance, reducing myocardial function

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18
Q

How does inhaled general anaesthesia affect respiratory function

A

Decreased minute ventilation

Decreased response to hypercapnia, increased apneic threshold

Depress mucociliary function, bronchodilation

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19
Q

How do inhaled general anaesthesia affect the brain

A

Increases cerebral blood flow by decreasing cerebral vascular resistance. Undesirable in patients with increased intracranial pressure

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20
Q

Patient with high intracranial pressure. Which inhaled general anaesthesia should i use

A

Nitrous oxide as it is least likely to increase cerebral blood flow

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21
Q

How does inhaled general anaesthesia affect the kidney

A

Decreases renal blood flow

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22
Q

How do inhaled general anaesthesia affect the uterus

A

Halogenated general anaesthesia are uterine muscle relaxants

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23
Q

What is the side effect of repeated exposure to halothane (inhaled ga)

A

Hepatitis. Formation of reactive metabolites that directly damage liver or initiate immune mediated response

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24
Q

Which inhaled general anaesthesia can cause renal dysfunction and how

A

Methoxyfluorane via release of fluoride during metabolism

25
Q

What is malignant hyperthermia in response to general anaesthesia

A

Autosomal dominant skeletal disease that results in inherited susceptibility for adverse reaction to GA. GA in susceptible individual triggers hypertension, tachycardia, severe muscle rigidity, hypothermia, acidosis. Increase in muscle cell calcium.

26
Q

How do you treat malignant hyperthermia

A

general anaesthesia rxn.

Treat with dantrolene to reduce release of calcium

27
Q

Compare rate of onset and recovery for halothane and nitrous oxide

A

Halothane has medium rate of onset and recovery while nitrous oxide has rapid onset and recovery

28
Q

Is halothane volatile

A

Yes

29
Q

Which is more potent — halothane or nitrous oxide

A

Halothane is more potent

Nitrous oxide is not potent, unable to induce complete unconsciousness and surgical anaesthesia

30
Q

What is halothane used for

A

Induction and maintenance of anesthesia

Able to relax skeletal muscles and dose dependent respiratory depression

31
Q

What is nitrous oxide used for

A

Labour pains. Good for analgesia as higher doses will not render the woman unconsciousness. Adjunct with other inhaled anesthetics

[stronger analgesic properties, analgesia sets in way before full anesthesia]

32
Q

Why are intravenous general anaesthesics commonly used for induction

A

Onset of anesthetic action faster

33
Q

Are intravenous general anaesthesics appropriate to use for short outpatient procedures

A

Yes, recovery is sufficiently rapid

34
Q

Mechanism of action of barbiturate

A

Bind to GABA receptor to increase duration of GABA gated chloride channel opening

Bind to AMPA receptor to depress glutamate mediated excitation

35
Q

What is thiopental

A

Thiopental is a barbiturate (GABA and AMPA receptor)

Used for induction of anesthesia because it rapidly crosses BBB. Has high lipid solubility hence rapidly distributes out of blood and brain to muscle and fat, allowing for rapid recovery

36
Q

Is thiopental appropriate to use in patients with high intracranial pressure

A

Yes. It is desirable. It decreases cerebral metabolism, decreases O2 consumption and blood flow

37
Q

Effect of Thiopental on cardiovascular system

A

Decrease cardiac output, decrease stroke volume, decrease arterial bp

38
Q

What is the mechanism of benzodiazepine

A

intravenous general anaesthesics

Increase frequency of gaba gated chloride channel openings. Does not directly activate GABA, but increases efficiency of GABA. Potentiates GABAergic inhibition

39
Q

Name some benzodiazepines

A

Diazepam, lorazepam, midazolam

40
Q

What are benzodiazepines used for

A

Sedative, anxiolytic, amnestic properties

Use for pre anesthetic and adjuvants during procedures under LA

41
Q

Can benzodiazepine be used for surgical anaesthesia?

A

No. Reaches plateau inadequate for surgical anesthesia. Slower onset of CNS depressant effects compared to barbiturate

42
Q

What are the disadvantages of using benzodiazepine for deep sedation and how to overcome them

A

High dose is required. This will prolong post anesthetic recovery and may cause anterograde amnesia

Accelerate recovery with high doses by using antagonist flumazenil (req multiple doses, patient may lapse back into deeper sedation)

43
Q

Can benzodiazepines be used in pregnancy

A

Avoid in first trimester due to increased risk of cleft palate formation

44
Q

Mechanism of propofol

A

Slow channel closing time by potentiating GABA receptor activity. Also a sodium channel blocker

45
Q

How is the rate of onset and recover of propofol

A

As rapid as barbiturates but recovery is more rapid ie patient can ambulated sooner and less nausea

46
Q

What s propofol used for

A

Induction, maintenance of anesthesia

Sedation

Monitored anesthesia

Causes potent respiratory depression

47
Q

How it propofol cleared

A

Rapidly metabolised by liver and excreted by kidney

48
Q

What is the mechanism of action of ketamine

A

NMDA receptor antagonist

49
Q

What are some effects of ketamine

A

Dissociative amnesia, catatonia, analgesia without loss of consciousness

Decrease respiratory rate

Stimulate cardiovascular system by stimulating sympathetic system and inhibiting noradrenaline uptake

Increase cerebral blood flow and oxygen consumption, increasing intracranial pressure

50
Q

Is ketamine rapidly distributed to brain

A

Yes

51
Q

What is unique about ketamine

A

Only iv anaesthetic with analgesic and anesthetic property

52
Q

Do intravenous general anaesthesics have analgesic property

A

Only ketamine

53
Q

Which intravenous general anaesthesic can result in post operative disorientation, illusions, dreams

A

Ketamine

54
Q

What is balanced anesthesia

A

Combination of inhaled and IV anesthesia

IV used to induce and inhaled to maintain.

May also have muscle relaxants to facilitate traceable intubation, LA for pre/post op analgesia, cardiovascular drugs to control transient autonomic responses to noxious surgical stimuli

55
Q

What are the steps to monitored anaesthesia care

A

Regional or local anesthesia supplemented by IV.

  1. Midazolam used as premeds for anxiolytic and mild sedation
  2. Titrated variable propofol infusion such that preserves spontaneous breathing and airway reflexes
  3. Opioid analgesics/ketamine

Patient is aware throughout but very relaxed

56
Q

How to reverse opioid analgesics

A

Nalaxone

57
Q

How does increased lipid solubility affect onset of intravenous general anaesthesics

A

Increased lipid solubility crosses BBB to go to brain more quickly (vs inhaled greater lipid solubility go to tissues greater av gradient onset slower)

58
Q

How does general anaesthesia affect TURP

A

Positive pressure ventilation in general anaesthesia increases venous resistance, reducing absorption of irrigation fluid, decreasing risk of TURP syndrome

Pharmaco Ca2 (11 decks)

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