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Oncology, pharmacology, anaesthetics (IHD DEN303) > Anaesthesia > Flashcards

Anaesthesia Flashcards

1
Q

Why are there so many anaesthetic drugs?

A

No single perfect agent
Combinations of anaesthetics sometimes used for synerstic and additive therapeutic effects
Risk of > adverse effects
Drug prescription much about minimising adverse effects as achieving therapeutic goals

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2
Q

Why sedation?

A 
< pt anxiety
> acceptability of prolonged/ extensive procedures
-still effective time limit < 2 hrs
Looking for
-anxiolysis
-cooperation
-street fitness
Not sedation???
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3
Q

Why GA

A 
Extensive/ prolonged procedures
Brief painful procedures
-extractions
Total lack of pt cooperation
-intellectual impairment
-children
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4
Q

Drugs available for sedation

A 
Alcohol
Tetrahydrocannabinol
Opiates
Major tranquilisers
Minor tranquilisers
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5
Q

Alcohol for sedation

A

Disinhibition, nausea, slow recovery

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6
Q

THC for sedation

A

Nausea, illegal

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7
Q

Opiates for sedation

A

Euphoria, nausea, respiratory depression

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8
Q

Major tranquilisers for sedation

A

Chloropromazine, haloperidol

Profound anxiety, hypotension

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9
Q

Minor tranquilisers for sedation

A

Benzodiazepines

Drowsiness, prolonged effect

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10
Q

Oral benzodiazepines

A 
Long interval, variable, small effect
-although often enough for many pts
IV
-competence in IV cannulation
-limited duration of action (repeat doses)
-need for monitoring (SpO2 mandatory)
-written record (pulse, BP, SpO2)
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11
Q

Benzodiazepines mechanism of action

A

Barbiturates / benzodiazepines –> bind to GABAa receptor at different allosteric sites –> facilitates GABA action –> Barbiturates > duration and frequency, benzodiazepines > frequency of opening of Cl- channel –> membrane hyperpolarisation –> CNS depression
At higher dose barbiturates can act as GABA mimetic

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12
Q

Types of benzodiazepams

A 
Diazepam
-irritant
-skin necrosis
Diazemuls
-rapid onset
-brief duration of action
-psychoactive metabolites with long half life
Midazolam
-slow(er) onset
-less predictable effect
-rapid metabolism
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13
Q

Sedation with propofol

A

Believed to work at least partly via GABA receptor
Short acting and fast recovery
Can be used in subanaesthetic doses - good amnesia
BUT
-no algesia
-continuous infusion (secure IV access)
-expensive delivery system

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14
Q

Difference between sleep and unconsciousness

A 
Unrousability
Loss of protective reflexes: potential for
-aspiration
-obstruction
-nerve damage due to prolonged pressure
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15
Q

Process of GA

A 
Induction: rapid pleasant production of unconsciousness 
-IV or gaseous/ volatile
Secure airway
-optimum head position, LMA, ETT
Maintenace
-gaseous/ volatile or IV
-analgesia
-+/- muscle relaxant
Emergence
-reversal of muscle relaxation
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16
Q

Induction

A

IV
-Propofol, thiopentone, katime, etomidate
Volatile
-sevoflurane

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17
Q

Characteristic of IV anaesthetics: propofol

A

Rapid pleasant onset
Non cumulative
Hypotension (Vasodilation)
Painful on injection

18
Q

Characteristic of IV anaesthetics: Thiopentone

A 
Rapid onset	
Offset due to redistribution
Slow metabolism
Cumulative
Hypotension (myocardial depression)
Odd complications
-arterial spasm
-porphyria
-anaphylaxis rare but serious
19
Q

Characteristic of IV anaesthetics: ketamine

A 
Rapid onset
Hypertension
Powerful analgesic
Non cumulative
Muscle rigidity
Unpleasant hallucinations
20
Q

Characteristic of IV anaesthetics: etomidate

A 
CV stability
Noncumulative
Odd (major) complication
-inhibition of steroid synthesis
-death due to induced Addison's
21
Q

Airway maintenance

A

Optimum head position
-neck flexed, head extended
Laryngeal mask (does not prevent aspiration)
Tracheal intubation largely eliminates danger of aspiration but use muscle relaxant to overcome laryngeal reflexes
-suxamethonium, atracurium, cisatracurium, rocuronium, pancurocium

22
Q

Characteristics of suxamethonium

A 
\+:
Rapid onset and usually rapid offset
-:
Depolarising
Muscle pain
Occasional prolonged paralysis
Malignant hyperthermia
23
Q

Characteristics of atracurium

A

+: reliable spontaneous hydrolysis
-:
Histamine release
Hypotension

24
Q

Characteristics of cisatracurium

A

+:Not so much histamine release

-:slow onset

25
Q

Characteristics of rocuronium

A

+:
Long duration
Specific reversal agent
-: histamine release

26
Q

Characteristics of pancuronium

A

+: medium duration
-:
Tachycardia
Renally excreted unchanged

27
Q

Maintenance of anaesthesia

A

Gaseous/ volatile
-nitrous oxide
-isoflurance, sevoflurane, desflurane
IV: propofol

28
Q

MAC

A

minimum alveolar conc at which 50% of pts do not react to initial surgical incision

29
Q

Characteristics of nitrous oxide

A 
MAC 104%
Strong analgesia
0 pugency
Isses:
-dysphoria
-association with miscarriage
30
Q

Characteristics of isoflurane

A

MAC 1.2% (strong potency)
+/- analgesia
++ pungency

31
Q

Characteristics of sevoflurane

A

MAC 1.8% (+++ potency)
+/- analgesia
+ pungency
Issues: acceptable for volatile induction

32
Q

Characteristics of desflurane

A

MAC 6.6% (++ potency)
+/- analgesia
++++ pungency
Issues: rapid onset/ offset

33
Q

Characteristics of propofol

A 
\++++ potency
0 analgesia
NA pungency
Issues:
-IV agent - access required
-microprocessor controlled infusion pump - expensive
-can be used for sedation
34
Q

Preoperative assessment - why?

A

Perfect Preparation Prevents Poor Performance
Maximise pt safety
-optimise pt’s condition
-postpone procedure if necessary
Toxic drugs with significant side effects
-all have life threatening effects at therapeutic doses
-CV depressant
-respiratory depressant

35
Q

Complications encountered during an operation

A

Pt
Anaesthesia
Surgeon

36
Q

Patient complications

A

Pre-existing disease

  • cardiac (aortic stensosis; coronary artery disease)
  • respiratory (COPD; asthma)
  • diabetes (common; associated with renal, CV pathology)
37
Q

An anaesthetic history

A

Proposed procedure
PMH
-drugs/ allergies
-surgical: previous GA, problems (pt/ family)
-medical
–cardiac: IHD, valvular, other
–respiratory: obstructive/ restrictive diesases
-GI: aspiration risk - hiatus hernia
–renal: impairment affects drug handling
–diabetes
-airway assessment

38
Q

Anaesthetic complications and ways of reducing them

A

Awareness/Overdose (Agent monitoring; Brain function monitors; Neuromuscular blockade)
Anaphylaxis (Learn the drill)
Hypoxia (SpO2)
Respiratory Depression (CO2 monitoring)
Aspiration (Preop starvation; Intubation)
Peripheral Nerve Damage (Careful positioning)

39
Q

Haemorrhage signs

A

Falling BP
Rising HR
Suction container full of blood
Loads of wet swabs being piled in a corner

40
Q

Treatment for haemorrhage

A

Permissive loss of haemoglobin (to Hb ~80)
Restore circulation with crystalloid
Chloride is current unfashionable anion

Oncology, pharmacology, anaesthetics (IHD DEN303) (6 decks)

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