SC04 - General Anaesthesia Flashcards

1
Q

Types of anesthesia

A

General anaesthesia(GA):
Reduced level of consciousness and response to stimuli

Regional anaesthesia(RA):
Loss of sensation to a body part or region, Patient can be fully awake/sedated/unconscious

Combinations of general and regional

Monitored AnaestheticCare (MAC) or “Conscious Sedation”: Patient sedated and should be self ventilating

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2
Q

General anesthesia

  • ## Function
A

Function:
- Hypnosis, Amnesia, Analgesia, Areflexia, +/-Muscle relaxation

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3
Q

Pre-anesthetic preparations

A
  • Manage co-morbidities
  • Manage medications
  • Fasting instructions

Fasting: Minimize the chance of aspiration during induction of and emergence from anaesthesia
*Solids and non human milk: 6 hours
* Infant formula: 6 hours
*Breast Milk: 4 hours
*Clear fluids: 2 hours (Examples of clear liquids include, but are not limited to, water, and fruit juices without pulp, carbonated beverages, carbohydrate-rich nutritional drinks, clear tea, and black coffee)

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4
Q

Phases of general anesthesia

A

Induction: causing general anesthesia by the administration of pharmaceutics
- Intravenous agents: Propofol, thiopentone, etomidate, ketamine
- Volatile agents: Sevoflurane, Nitrous Oxide

Maintenance
* Ensure adequate delivery of pharmaceutics to
*Maintain physiological homeostasis
* Prevent of awareness
* Facilitate surgical activity

Emergence and Recovery
* process of return to baseline physiologic function of all organ systems after the cessation of administration of general anaestheticagent(s).

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5
Q

Types of monitoring during general anesthesia

A

Before induction *Pulse oximetry *Blood pressure *ECG

After induction *End tidal CO2Monitoring * EEG * Volatile agent conentration * Blood pressure

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6
Q

Muscle relaxants types

A

Muscle relaxants

Non depolarising
- Short acting: Mivacurium
- Intermediate acting: Atracurium, cis-atracurium Rocuronium, Vecuronium
- Long acting: Pancuronium

Depolarising
- suxamethonium

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7
Q

Sequence of General anesthesia **

A
  1. Establish monitoring of vitals
  2. Establish intravenous access: e.g. angiocath
  3. Induction of anesthesia: Induction agent (IV or Volatile), +/- opioids and muscle relaxants
  4. Airway intrumentation: intubation with laryngoscope or Video assisted intubation, endotracheal tube connected to anaesthetic circuit
  5. Maintenance agent: IV or inhaled anaesthetic
  6. Positioning and protection: pressure relief pads and bracing
  7. Monitoring, fluid and drug management
  8. Emergence +/- reversal agent:
  9. Recovery: Analgesic (oral, parenteral or regional block)
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8
Q

Maintenance agent types

Analgesics types

Reversal agent types

A

Maintenance:
Intravenous anaesthetic
- Propofol

Volatile anaesthetic
- Isoflurane
- Sevoflurane
- Desflurane
- Nitrous Oxide

Analgesia:
- Paracetamol: PO/IV/PR
- NSAIDs
- Opioids: Fentanyl, Morphine, Oxycodone, Pethidine
- Others: Gabapentin, Tramadol, Ketamine

Reversal agents:
- Neostigmine PLUS an anticholinergic
*Atropine
*Glycopyrrolate

  • Sugammadex
  • for reversing rocuronium only
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9
Q

Regional anesthesia
- Function
- Types

A

Function: reduced sensation from the anatomical area supplied by the blocked nerves

Types:
- Neuroaxial blocks: spinal or epidural
- Plexus blocks eg.brachial plexus for arm surgery
- Nerve blocks eg.Femoral nerve block
- Local infiltration
- Topical anaesthesiaeg.EMLA cream
- Intravenous regional technique

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10
Q

Neuroaxial block
Types
Differences

A

Spinal anaesthesia
- Local anaestheticagent (LA) injected into the CSF
- Block sensation supplied by spinal fibres below a certain level depending on the type and dose of LA used
- Achieve “Temporary paraplegia”: Dense block causing Motor and sensory block

Epidural anaesthesia
- LA agent deposited into the epidural space
- Varying degree of motor and sensory block

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11
Q

Reasons for extensive pre-anesthetic preparation even for RA

A
  1. May need conversion to GA immediately
  2. Total or partial failure of block
  3. Complications from the regional technique
    - Local anaesthetictoxicity
    - Severe haemodynamicdisturbances
    - Excessive block
  4. Prolonged surgery
    - Duration of surgery exceeds duration of block and return of feeling during surgery
    - Patients restless or becoming uncooperative
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12
Q

Causes of total or partial anesthetic failure

A

Operator factors
- Misplaced needle
- Incorrect dosage

Drug error (including expired drugs)

Patient factors
- Anatomical variants

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13
Q

Complications of RA

A

Local AnaestheticToxicity
- Inadvertent intravascular injection
- Overdose
- Adverse reaction to adjuvant: Epinephrine/ Preservatives
- Spectrum of systemic manifestations: Neurological symptoms/ Convulsions/ Cardiovascular collapse

Severe Haemodynamic disturbances
- Usually from neuroaxial block
- Hypotension: Sympathectomy/ Inadequate intravascular volumn/ Inappropriate patient choice e.g. Cardiac patients, Valvular heart disease
- Bradycardia: Blockade of cardiac sympathetic fibres

Excessive Block
- Excessive rostral spread of LA: high dose, head down position, wrong subdural injection
- Motor blockade of intercostal muscles causing respiratory distress
- “Total Spinal block”: Supraspinal neurons (brain, midbrain, pons medulla) blocked by the local anaesthetic

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