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Gwen - Anaesthetics > Induction and Maintenance > Flashcards

Induction and Maintenance Flashcards

1
Q

What is the triad of anaesthesia?

A
  • Hypnosis- unconsciousness (necessary component of GA)
  • Analgesia- pain relief (removal of perception of unpleasant stimulus)
  • Relaxation- muscle relaxation (provides immobility during surgery)

General anaesthetics (hypnotic, relaxant and analgesic)

Muscle relaxant (relaxants)

Analgesia (local, opiates)

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2
Q

What is a balanced anaesthesia?

A

Allows a great degree of control over the individual components of the triad of anaesthesia.

Various componentes: awake, analgesia, muscle relaxation, airway management

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3
Q

Why should ACEi be stopeped prior to surgery

A

Can cause severe hypotension after induction of GA

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4
Q

What are examples of intravenous anaesthetics?

A
  • Propofol
  • Thiopental sodium
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5
Q

What are adverse reactions to intravenous anaesthetics?

A
  • Rapid onset of upper airway obstruction due to loss of muscle tone
  • Respiratory depression and apnoea
  • Bradycardia (propofol)
  • Hypotension
  • Propofol infusion syndrome (<16 years)
  • Anaesthetic hangover - long period of drowsiness post anaesthetic
  • Nausea, vomiting, headache
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6
Q

What are examples of inhaled anaesthetics?

A
  • Isoflurane
  • Sevoflurane
  • Desflurane
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7
Q

What is an important contraindication to inhaled anaesthetic use?

A

Susceptibility to malignant hypertermia

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8
Q

What are adverse reactions to inhaled anaesthetics?

A
  • Respiratory depression
  • Hypotension
  • Arrhythmias
  • Mucous membrane irritation leading to cough, breath-holding and laryngospasm (Isoflurane/Desflurane)
  • Increased intracranial pressure - cerebral vasodilatation
  • Uterine hypotonia
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9
Q

What are examples of non-depolarising neuromuscular blocking drugs?

A
  • Atracurium
  • Mivacurium
  • Rocuronium
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10
Q

What is an example of a depolarising neuromuscular drug?

A

Suxamethonium

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11
Q

When are non-depolarising neuromuscular blocks contraindicated for use?

A

Allergy

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12
Q

When are depolarising neuromuscular blocks contraindicated for use?

A
  • Family history of malignant hyperthermia
  • Severe burns
  • Numerous neuromuscular contraindications including spinal cord injury and dystrophia myotonica
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13
Q

How do non-depolarising NM blocks work?

A

Act as competitive antagonists of the acetycholine channels of the motor end plate. The drugs bind the channel and stop ACh from binding and opening the channel to Na+, preventing action potentials in the muscle fibres

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14
Q

How do depolarising NM blocks work?

A

Act as acetylcholine agonists on the ACh channels of the motor end-plate. Their binding results in the continuous production of action potentials until exhaustion of the cell’s ability to repolarise occurs, causing neuromuscular paralysis

Suxamethonium is rapidly broken down by plasma cholinesterase, once this has happened repolarisation again becomes possible and neuromuscular function returns.

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15
Q

What are adverse reactions to non-depolarising NM blocks?

A
  • Histamine release (atracurium / mivacurium)
  • Allergy
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16
Q

What are adverse reactions to suxamethonium?

A
  • Hyperkalaemia
  • Malignant hyperthermia
  • Prolonged paralysis (cholinesterase deficiency)
  • Post-operative muscle pains
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17
Q

What are the general levels of sedation?

A
  • Minimal sedation
  • Moderate sedation
  • Deep sedation
  • General anaesthesia
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18
Q

What does minimal sedation mean?

A

Drug-induced state where the patient is still able to respond to speech. Cognitive function and coordination are impaired but ABC are unaffected

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19
Q

What does moderate sedation mean?

A

Conscious sedation

Drug-induced reduction of consciousness during which the patient is able to make a purposeful response to voice or light touch. At this level of sedation, no airway adjuncts are required, and B and CVS function should be adequate

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20
Q

What does deep sedation mean?

A

Drug-induced reduction in consciousness to a point where the paitent cannot be easily roused but does respond purposefully to painful stimuli. At this level, airway intervention may be required, with spontaneous ventilation becoming inadequate

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21
Q

What does general anaesthesia mean?

A

Drug-induced LOC during which pateitns are not able to be roused, even by painful stimuli. Airway typically needs intervention, spontaneous ventilation is frequently inadequate, and CVS function may be impaired.

They provide: hypnosis, muscle relaxation (small degree), analgesia (to different extents)

22
Q

What steps would you take for intravenous induction of anaesthesia?

A
  • Establish IV access
  • Pre-oxygenate
  • Give co-induction agents - fentanyl, midazolam
  • Give sleep inducing dose - propofol
23
Q

What steps are involved in gaseous induction of anaesthesia?

A
  • Either
    • Sevoflurane in oxygen
    • Nitrous oxide + sevoflurane
  • Establish IV access as soon as asleep
24
Q

What are indications for gaseous induction of anaesthesia?

A
  • Patient request
  • Difficult IV access
  • Children
  • Patients with partially obstructed airway - awake fibre optic intubation often needed
25
Q

When is intrubation in anaesthesia often needed?

A
  • Increased vomiting risk/aspiration
  • Difficult airway
  • Inaccessible/shared airway - head and neck surgery
  • Paralysis indicated in surgery - e.g. abdominal surgery
26
Q

What options are available for maintianing anaesthesia?

A
  • Volatile agent
  • IV infusion - propofol +/- opiates
  • High dose opiates with mechanical ventilation
27
Q

How would you gauge the depth of general anaesthesia?

A
  • HP
  • BP
  • Signs of sympathetic stimulation
28
Q

What signs may indicate a lack of appropriate anaesthesia?

A
  • HR increase
  • BP increase
  • Lacrimation
  • Dilated pupils
  • Movement or laryngospasm
29
Q

What monitoring is normally conducted when somoene is under GA?

A
  • Respiration - depth and RR
  • BP
  • Temperature
  • Pulse oximetry
  • ECG
  • CVP - helps differentiate between hypovolaemi and decreased cardiac function so if large blood loss anticipated helps guid fluid replacement
  • Capnogrophy
  • Inspired O2 concentration
  • Urine output
  • Ventilator pressures
  • Neuromuscular status
30
Q

Why is capnogrophy essential in surgery?

A

A low end tidal CO2 can indicate a displaced ET tube, emboli and more

31
Q

What are features which indicate intubation could be difficult?

A
  • Obese
  • Short neck
  • Limited neck movement
  • Receding chin/mandible
  • Protruding Teeth
  • Limited mouth opening
32
Q

What classification system is used to assess difficulty of intubation?

A

Mallampati classification

33
Q

What mallampati classification is the following?

A

Class I - soft palate and uvula visible

34
Q

What mallampati classification is the following?

A

Class II - Uvula tip masked by base of tongue

35
Q

What mallampati classification is the following?

A

Class III - Only soft palate visible

36
Q

What mallampati classifcation is the following?

A

Class IV - Soft palate not visible

37
Q

How would you subjectively assess if someone might have a difficult airway?

A
  • Mallampati classification
  • Thyromental and sternomental distances
38
Q

What are the main anaesthetic complications that can occur in surgery?

A
  • Failure to intubate
  • Atelectasis and penumonia
  • Awareness
  • Bronchospasm
  • Laryngospasm
  • Malignant hypertemia
  • Teeth damage
  • Suxamethonium apnoea
  • Shivering
  • Aspiration
39
Q

How would you manage someone with laryngospasm?

A
  • 100 % oxygen
  • Deepen anaesthesia + attempt to ventilate
  • May be necessary to paralyse and intubate
40
Q

What is malignant hyperthermia?

A

Causes a fast rise in body temperature and severe muscle contractions when someone with the MH gets general anesthesia.

41
Q

How is malignant hyperthermia inherited?

A

Autosomal dominant

42
Q

How is malignant hyperthermia triggered?

A

Exposure to suxamethonium or other volatile agents

43
Q

What are features of malignant hyperthermia?

A
  • Increased O2 consumption
  • Hypercapnia
  • Tachycardia
  • Metabolic acidosis
  • Raised temperature - late sign (>1 degree every 30 minutes)

Masseter spasm may be an early sign

44
Q

How would you manage someone with Malignant hyperthermia?

A
  • Hyperventilate with 100%
  • Maintain anaesthesia with IV agent
  • Abandon surgery
  • Non-depolarising muscle block
  • Give dantrolene IV (muscle relaxant)
  • Active cooling
  • Check for hyperkalaemia, arrythmias, acidosis, myoglobinaemia, coagulopathy
45
Q

What is sux apnoea?

A

Abnormal cholinesterase leads to prolonged drug effect lasting 2-24 hrs.

46
Q

What is rapid sequence induction?

A

Method of ET intubation used in emergency setting of an acutely unwell patient and suspected risk of aspiration is high

47
Q

What is the sequence of steps the occur in RSI?

A
  • Pre-oxygenate with 100% O2 for 3 minutes
  • Apply cricoid pressure and give induction agent (propofol) + muscle relaxant (sux)
  • Wait 60 seconds for relaxant to work
  • Intubate the trachea and release cricoid pressure
  • Add volatile agent to mainatin anaesthesia
48
Q

Why is suxamethonium used in RSI?

A

Fast acting muscle relaxant

49
Q

How is airway maintained?

A
  • Triple airway manoeuvre
  • Simple apparatus
    • Face mask
    • Oropharyngeal (Guedel) airway
    • Nasopharyngeal airway
  • Advanced apparatus
    • Laryngeal mask airway (LMA) - cuffed tube with “mask
50
Q

Why would you intubate?

A
  • Requires muscle relaxation with a depolarising/non depolarasing NABs
  • Protects airway from gastric contents
  • Shared airways with risk of blood contamination (tonsillectom in ENT surgery)
  • Need for tight control of blood gases
  • Restricted aaccess to airway (Max-Fax surgery)
51
Q

Complications of airway maintenance

A
  • Obstruction - usually caused by loss of airway tone
  • Laryngospasm - forced reflex adduction of the vocal cords
  • Aspiration - foreign material in the lower airway (gastric content or blood)
52
Q

How can a patient be woken in an emergency?

A
  • Anaesthetic agents off an change inspired gases to 100% O2
  • Discontinue any anaesthetic agent and reverse muscle aparlysis
  • Put patient in recovery position once patient is spontaneously breathing.

Gwen - Anaesthetics (16 decks)

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