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Pain and Anxiety > L8 General Anaesthesia > Flashcards

L8 General Anaesthesia Flashcards

1
Q

Definition of GA

A

A controlled, reversible state of unconsciousness produced by anesthetic agents from which a patient cannot be aroused by an external stimuli

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2
Q

4 characteristics of GA

A
  1. Pt in a controlled state of unconscious
  2. Complete loss of protective reflexes
  3. Cannot maintain airway independently
  4. There is no purposeful response to verbal commands

Takes longer to come back from compared to IV sedation

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3
Q

4 stages of GA

A

Stage 1 - induction
Between initial administration of induction meds and loss of consciousness

Stage 2 - excitement
Period following loss of consciousness and marked by excited and delirious activity. Cannot work in this stage

Stage 3 - surgical anesthesia
Skeletal muscles relax, pt’s breathing becomes regular. Eye movements slow, then stop, surgery begins.

Stage 4 - overdose
Too much medication has been given and pt has severe medullary depression. Lethal without cardiovascular/resp support

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4
Q

Indications of GA

A
  1. Longer procedures
  2. Acute infections
  3. Allergy to LA
  4. Infants/children
  5. Learning disability
  6. Anxiety
  7. Pt’s difficult to do under IV sedation
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5
Q

Contraindications of GA

A
  1. Lack of training/equipment/facility
  2. Unescorted patient and patient eating!
  3. Pregnancy?
  4. ASA IV & certain ASA III
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6
Q

Advantages of GA

A
  1. Pt is unconscious
  2. Patient cooperation is not essential
  3. Analgesia, amnesia
  4. Muscle relaxation
  5. Airway is protected
  6. Rapid onset
  7. Can be titrated

LA is always safer, but it pt is very anxious this may be even safer

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7
Q

Disadvantages of GA

A
  1. Pt is unconscious
  2. Depressed protective reflexes/vital signs
  3. Advanced training needed
  4. Anesthesia team must be there
  5. Special equipments
  6. Recovery area is required
  7. Higher risk vs LA
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8
Q

3 types of GA

A
  1. Totally IV-GA (TIVA)
  2. Totally GA inhalation
  3. Mixed IV and inhalation
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9
Q

2 IV Agents

A
  1. Propofol

2. Ketamine

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10
Q

Inhalation Agents

A
  1. Halogenated ethers (common - especially in kids)
    ex. enflurane, isoflurane, desflurance, sevoflurane
  2. Halogenated ethane (uncommon)
    ex. Nitrous oxide (has to be combined with other gasses), halothane (less common from liver toxicity)
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11
Q

Out-patient GA (IV)

A 
Indication: short procedure
Requirement: fasting, escort, consent
ASA: I/II
Cost: cheaper 
Patients: lots of children

Other: reduced contact with hospital hazards, parental preference

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12
Q

MOA of propofol

A

Enhanced GABA, enhancing inhibition

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13
Q

Uses of propofol

A

Short acting GA & sedative

Weak analgesic & antiemetic

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14
Q

Constituents of propofol

A

10% soya beans oil
2.25% clycerol
1.2% egg phosphatide
1% isopropylephenol

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15
Q

Side effects of propofol

A

Inhibition of sympathetic vasoconstrictor nerve activity –> decreased vascular resistance

  1. hypotension
  2. lower brain metabolism
  3. decreased respiration
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16
Q

Onset of propofol, and duration

A

30s with quick recovery, duration <5-10 mn

17
Q

Location of metabolism and excretion of propofol

A

Metabolized: liver
Excreted: in urine

18
Q

Induction and maintenance doses of propofol

A

Induction: 1-2 mg/kg
Maintenance: 0.1 - 0.2 mg/kg/mn

19
Q

MOA of ketamine

A

Dissociation anesthesia - pt is in neuroleptic state by blocking NMDA receptors in nerve cells and other receptors

20
Q

Location of metabolism and excretion of propofol

A

Metabolized: liver
Excreted: in urine

21
Q

Side effects of ketamine

A
  1. Tachycardia
  2. hypertension
  3. hallucination on recovery
  4. bronchial secretions
22
Q

Induction doses of ketamine

A

IV 1-2 mg/kg (30-60s)
or
IM 5-10 mg/kg (5min)

23
Q

Results of ketamine

A
  1. Amnesia
  2. Analgesia
  3. Unconscious
  4. Open eyed and swallow un-purposefully
  5. Bronchodilation (with more secretions - useful for COPD pt)
24
Q

What are the uses of halogenated ethers vs ethanes?

A

Ethers: Induction and maintenance of anesthesia
- less liver toxicity and blood solubility

Ethane: induction only

  • liver toxicity is highest among GA gases (metabolized in liver)
  • sweet smelling drug, so good for induction
  • soluble in blood (slower induction & recovery)
25
Q

What about nitrous oxide in general anesthesia?

A

Has to be combined with other gases because it is a weak anesthetic
W/ other gasses –> induction & maintenance

Would never be used alone - has to be combined with other gases because it is too weak

26
Q

What is the benefit in terms of nitrous use as an inhalation agent?

A

it is excreted by lungs –> no liver toxicity

27
Q

How do we maintain the airway?

A
  1. Endotracheal intubation - oral/nasal
  2. laryngeal mask & fiber optic intubation are used in difficult intubation
  3. surgical airway are used in emergencies and impossible oro-naso-endotracheal intubation
28
Q

Muscle relaxants prior to intubation

A

Remove skeletal muscle responses to painful stimuli/tracheal intubation & reduce muscle tone

29
Q

What types of muscle relaxants are used?

A

Depolarising agents: suxamethonium, succenyl coline = short acting (3-5 mn)

Non-depolarising agents: recoronium, sistracurium, moderate and long acting (15-19)

30
Q

What is the sequence for tracheal intubation for GA?

A
  1. ventilation
  2. sedation
  3. IV GA induction
  4. Muscle relaxation
  5. Intubation

Opioids and steroids may also be used to blunt parasympathetic effects + reduce nausea and inflammation

LA used for hemostasis and pain control

Pain and Anxiety (7 decks)

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