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Anaesthetics Flashcards

1
Q

What is the effect of general anaesthetics?

A

Produces insensibility in the whole body, usually causing unconsciousness - centrally acting drugs (hypnotics/analgesics)

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2
Q

What is the effect of regional anaesthetics?

A

Produces insensibility in an area or region of the body - local anaesthetics applied to nerves supplying the area

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3
Q

What is the effect of local anaesthetic?

A

Produces insensibility in only the relevant part of the body - applied directly to the tissues

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4
Q

Which three components make up the triad of anaesthesia?

A

Analgesia, hypnosis and relaxation (skeletal muscle)

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5
Q

Which components of the triad do opiates do?

A

Analgesia and hypnosis

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6
Q

Which components of the triad do general anaesthetics do?

A

Hypnosis and relaxation (+ some anaesthesia)

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7
Q

Which components of the triad do muscle relaxants do?

A

Muscle relaxants

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8
Q

Which components of the triad do local anaesthetics do?

A

Analgesia and relaxation

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9
Q

How does balanced anaesthesia work?

A
  • Different drugs do different jobs
  • Titrate dose separately and therefore more accurately to requirements
  • Avoid overdose
  • Enormous flexibility
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10
Q

What are the potential problems of balanced anaesthesia?

A
  • Polypharmacy: increases chance of drug reactions/allergies
  • Muscle relaxation: needs artificial ventilation and airway control
  • Separation of relaxation and hypnosis: awareness
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11
Q

How do general anaesthetic agents work?

A
  • Interfere with neuronal ion channels
  • Hyperpolarise neurons making them less likely to fire
  • Inhalation agents dissolve in membranes
  • IV agents: allosteric binding to GABA receptors (opens chloride channels)
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12
Q

What effect does general anaethesia have on the body?

A
  • Cerebral function is lost from top to bottom (LOC first hearing later)
  • Reflexes relatively spared
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13
Q

How are those under general anaesthetic managed?

A
  • ABC (long drawn out resus)

- Airway management

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14
Q

What are the problems with general anaesthetics?

A
  • Impair resp function and control of breathing

- Impacts CVS function

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15
Q

What are the features of IV anaesthesia?

A
  • Rapid onset of LOC

- Rapid recovery (due to disappearance of drug from circulation)

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16
Q

In what order do tissues uptake anaesthesia?

A
  • Blood + vessels rich organs
  • Viscera
  • Muscle
  • Fat
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17
Q

What do inhalational anaesthetics consist of?

A

Halogenated hydrocarbons

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18
Q

How are inhaled anaesthetics uptaken and excreted?

A

Via the lungs

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19
Q

What is MAC?

A

Minimum alveolar conc.

  • Measure of potency
  • Low number = high potency
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20
Q

What are the main features of inhalational anaesthetics?

A
  • Slow induction
  • flexible maintenance
  • Awaken by stopping inhalation of the gas
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21
Q

What is the most common sequence of general anaesthesia?

A

Induction (Inhalational or IV) and maintenance (inhalational or IV) +/- additional regional analgesia/anaesthesia

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22
Q

What effect does GA have on the CVS centrally?

A

It depresses the CV centre:

  • reduces sympathetic output
  • negative inotrophic/ chronotrophic effect on the heart
  • reduces vasoconstrictor tone
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23
Q

What effect does GA have on the CVS directly?

A
  • Negatively inotropic
  • Vasodilation: decreased peripheral resistance
  • Venodilation: decreased venous return and decreased cardiac output
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24
Q

What effect does GA have on the respiratory system?

A
  • All anaesthetics are respiratory depressants
  • Reduce hypoxic and hypercarbic drive
  • Decrease tidal volume and increase rate
  • Paralyse cilia
  • Decrease FRC: lower lung volumes and cause VQ mismatch
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25
Q

What are the indications for the use of muscle relaxants?

A
  • Ventilation and intubation
  • When immobility is essential (microscopic and neuro surgery)
  • Body cavity surgery (access)
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26
Q

What are the problems with using muscle relaxants?

A
  • Awareness
  • Incomplete reversal (airway obstruction and ventilatory insufficiency post op)
  • Apnoea: dependence on airway and ventilatory support
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27
Q

Why give intraoperative analgesia?

A
  • Prevention of arousal
  • Opiates contribute to hypnotic effect of GA
  • Suppression of reflex responses to painful stimuli e.g. tachycardia, hypertension
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28
Q

Why give regional anaesthesia intraoperatively?

A

Intense/complete analgesia with no hypnotic effect

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29
Q

What are the main features of local and regional analgesia?

A
  • Retain awareness/consciousness
  • Lack of global effects of GA
  • Derangement of CVS physiology (proportional to size of anaesthetised area)
  • Relative sparing of resp. function
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30
Q

What is the limiting factor in the use of local anaesthetics?

A

Toxicity

  • IV injection
  • Absorbtion> rate of metabolism = high plasma levels
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31
Q

What does the toxicity of local anaesthetics depend on?

A

Dose used
Rate of absorption
Patient Weight
Drug (bupivacaine > lignocaine >prilocaine

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32
Q

Name the signs and symptoms of LA toxicity

A 
Circumoral and lingual numbness and tingling
Light headedness
Tinnitus, visual disturbances
Muscular twitching
Drowsiness
CVS depression
Coma 
Cardio-respiratory arrest
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33
Q

How do LAs block pain fibres but not motor fibres?

A

Differential blockade: LAs penetrate into the different nerve types differently.
Motor fibres are relatively hard to block whilst pain fibres are much easier to block

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34
Q

How does a neuraxial block effect the CVS?

A

The sympathectomy causes veno and vasodilatation. Regional block effects are limited to the area covered by the block (opposite to GA)

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35
Q

List the examples of regional and local anaesthesia in increasing order of physiological impact

A 
Local anaesthesia
Field blocks
Plexus blocks
Limbs block
Central neural (neuraxial) block
(epidural and spinal)
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36
Q

How does a neuraxial block effect the respiratory system?

A 
Inspiratory function relatively spared
Expiratory function relatively impaired
Decrease FRC (airway closure similar to GA)
Increased V/Q mismatch
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37
Q

Name the steps in preparation of anaesthesia

A
  • Planning
  • Right patient, right operation
  • Right side
  • Pre-medication
  • Right equipment, right personnel
  • Drugs drawn up
  • IV access
  • Monitoring
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38
Q

Why should there be quiet when someone is being inducted?

A

Hearing is the last thing to go - want to make it easier to let them go over

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39
Q

What is the most common drug used for IV induction?

A

Propofol

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40
Q

What drugs might you add when inducting a frailer patient?

A

Drugs to maintain blood pressure etc.

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41
Q

What are the features of IV induction?

A
  • Rapid: one arm-brain circulation
  • No obvious planes
  • Easy to overdose
  • Generally rapid loss of airway reflexes
  • Apnoea is very common
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42
Q

Which gas is commonly used in gas induction?

A

Sevoflurane (can also use Halothane)

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43
Q

What are the features of gas induction?

A

Slow

  • More obvious planes of anaesthesia
  • Commonly used in children
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44
Q

Name the planes of anaesthesia

A
  • Analgesia
  • Excitation (note heightened reflexes)
  • Anaesthesia: light to deep
  • Overdose
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45
Q

How can conscious level be monitored whilst under anaesthesia?

A
  • Loss of verbal contact
  • Movement
  • Respiratory pattern
  • Processed EEG
  • Stages or planes of anaesthesia
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46
Q

What happens to the tongue in an unconscious patient?

A

It ends up resting on the posterior pharyngeal wall - can occlude airway

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47
Q

What is the “Triple Airway Manoeuvre”?

A

Head tilt/chin lift/jaw thrust

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48
Q

What apparatus can be used to maintain an airway?

A
  • Face mask
  • Oropharyngeal (Guedel) airway
  • Nasopharyngeal airway
  • Laryngeal mask airway
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49
Q

When can an oropharyngeal airway not be used and why?

A

When a patient is not fully unconscious - can cause vomiting or laryngospasm

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50
Q

When can i-gels be used?

A

Resuscitation (don’t protect from aspiration)

51
Q

List some of the causes of airway obstruction

A
  • Ineffective triple airway manoeuvre
  • Airway device malposition/kinking
  • Laryngospasm (forced reflex adduction of the vocal cords)
52
Q

Why is aspiration a possible complication of anaesthesia and surgery?

A
  • Anaesthesia causes loss of protective airway reflexes (gag, swallow, cough etc.)
  • Foreign material in the lower airway (gastric contents, blood and surgical debris)
53
Q

What is the difference between maintaining and protecting an airway?

A
  • Maintained just means open and unobstructed

- Protected means the airway is protected from contaminants (only a cuffed tube in the trachea does this)

54
Q

Explain the method of endotracheal intubation

A
  • Placement of a cuffed tube in the trachea
  • Laryngeal reflexes must be abolished
  • Possible in awake patient using local anaesthesia and fibre-optic scope
55
Q

What are the indications for intubation?

A
  • Protect airway from gastric contents (e.g. full stomach in unfasted emergency patients)
  • Need for muscle relaxation
  • Shared airway with risk of blood contamination e.g. ENT surgey
  • Need for tight control of blood gases (esp. CO2 in neurosurgery
  • Restricted access to airway e.g. maxfax surgery
56
Q

What are the risks to an unconscious patient?

A
  • AIRWAY
  • Temp.
  • Loss of other protective reflexes e.g. corneal, joint position
  • DVT and PE risk
  • Consent and ID
  • Pressure areas
57
Q

How are patients under anaesthesia monitored?

A
  • Minimum: SpO2, ECG, NIBP, FiO2 and ETCO2
  • Resp. parameters
  • Agent monitoring
  • Temp., urine output and NMJ
  • Invasive venous/arterial monitoring
  • Processed EEG
  • Ventilator disconnect
58
Q

What are the risk factors for awareness?

A
  • Paralysed and ventilated
  • Previous episode
  • Chronic CNS depressant use
  • Cardiac surgery
  • Major trauma (need careful balancing of anaesthetic as too much may push them over the edge)
  • GA C/Section
59
Q

What are the steps of emergence/awakening?

A
  • Muscle relaxation reversed
  • Anaesthetics agent off
  • Resumption of spontaneous respiration
  • Return of airway reflexes/control
  • Extubation
60
Q

What are the two types of respiratory failure?

A

Type 1: oxygenation failure

Type 2: oxygenation + ventilation failure

61
Q

Which type of respiratory failure is best suited to non invasive ventilation?

A

Type 2

62
Q

Name the types of shock

A 
Septic/distributive
Hypovolaemic
Anaphylactic
Neurogenic
Cardiogenic
63
Q

Which types of drugs can be used to treat cardiovascular failure and how do they work?

A

Vasopressors: alpha 1 agonists

Inotropes: improve contractility

64
Q

Why is adrenaline not first line in the treatment of CV failure?

A

It causes vasoconstriction, contractility and HR - don’t know which of these is actually the problem so tend to avoid

65
Q

Give two examples of vasopressors

A

Metaraminol

Noradrenaline

66
Q

Give two examples of inotropes

A

Adrenaline and dobutamine

67
Q

What is the difference between colloid and crystalloid fluids?

A
  • Colloids: fluid with large molecules (e.g. albumin or starches)
  • Crystalloids: fluid that contains small molecules (e.g. sodium or plasmolyte)
68
Q

Why are most colloids no longer on the market?

A

Because they can cause anaphylactic shock and precipitate renal failure

69
Q

What is the maximum volume of fluids that can be given?

A

30ml/kg

70
Q

Name the causes of neurological failure

A
  • Metabolic e.g. DKA, hypoglycaemia
  • Trauma e.g head injuries
  • Infection e.g. meningitis, encephalitis and sepsis
  • Stroke
71
Q

At what GCS score are patients most likely to need to be ventilated?

A

<8

72
Q

What are some neuroprotective measures?

A
  • Avoid hyperthermia
  • Keep CO2 low
  • Avoid low O2
  • Keep glucose in normal range
  • Keep blood pressure stable
73
Q

How does the body react to the trauma of surgery?

A
  • Stress response
  • Fluid shifts
  • Blood loss
  • Cardiovascular, resp, renal and metabolic stress
74
Q

Which consideration are taken into account during the pre-op assessment?

A
  • Known co-morbidities
  • Unknown pathologies
  • Nature of surgery
  • Anaesthetic techniques
  • Post-op care
75
Q

What are the roles of the anaesthetist pre-op?

A 
Assess
Identify high risk
Optimise
Minimise risk
Inform and support patients decisions
Consent
76
Q

Why do anaesthetist do pre-op assessment?

A

It reduces:

  • Anxiety
  • Delays
  • Cancellations
  • Complications
  • Length of stay
  • Mortality
77
Q

What things would you ask in a pre-op history?

A
  • Known co-morbidities: severity and control
  • Unknown co-morbidities: systemic enquiry and clinical exam.
  • Ability to withstand stress: exercise tolerance, reason for limitation and cardio-respiratory disease
  • Drugs and allergies
  • Previous surgery and anaesthesia
  • Potential anaesthetic problems: airway, spine, reflux, obesity and rarities/FH (malignant hyperpyrexia and cholinesterase deficiency)
78
Q

What are the pre-op investigations looking for?

A
  • Detect unknown conditions
  • Diagnoses suspected conditions
  • Severity of known disease
  • Establishing a baseline
  • Detecting complications
  • Assessing risk
  • Guiding management
  • Documenting improvement
79
Q

Which investigations might you do if someone has cardiovascular problems?

A

ECG, exercise tolerance, ECHO, myocardial perfusion scan, stress ECHO, cardiac catheterisation, and CT coronary angiogram (don’t necessarily need all of these)

80
Q

Which investigations might you do in a patient with resp. problems?

A

Sats, ABG, CXR, peak flow, FVC/FEV, gas transfer and CT chest (don’t necessarily need all of these)

81
Q

List the ASA grading scale points

A 
ASA1 : Otherwise healthy patient
ASA2: Mild to moderate systemic disturbance
ASA3: Severe systemic disturbance
ASA4: Life threatening disease
ASA5: Moribund patient
ASA6: Organ retrieval
82
Q

Name 3 examples of medications that are continued right up to surgery

A

Inhalers, anti-anginals and anti-epileptics

83
Q

Name two examples of medications which must be stopped before surgery?

A

Anti-diabetic medication (oral anti-hyperglycaemics and insulin)

Anticoagulants

84
Q

What is the definition of pain?

A

“an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage

85
Q

What are the benefits of treating pain?

A

Physical: improved sleep, better appetite and fewer medical complications
Psychological: reduced suffering, less depression and less anxiety
For the family: improved functioning and able to keep working
-Society: lower health costs and able to contribute to society

86
Q

What are the features of nociceptive pain?

A
  • Obvious tissue injury or illness
  • AKA physiological of inflamm pain
  • Protective function
  • Sharp +/- dull and well localised
87
Q

What are the features of neuropathic pain?

A
  • Nervous system damage or abnormality
  • Tissue injury may not be obvious
  • No protective function
  • Burning, shooting pain +/- numbness and pins and needles
  • Not well localised
88
Q

What happens in the periphery in nociceptive pain?

A
  • Tissue injury
  • Release of chemicals = prostaglandins and substance P
  • Stimulation of pain receptors
  • Signals travel in Adelta or C nerves to the spinal cord
89
Q

What happens in the spinal cord in nociceptive pain?

A
  • Dorsal horn is the first relay station
  • Adelta or C nerve synapses with second nerve
  • This nerve travels up the spinothalamic tract on the opposite side of the spinal cord
90
Q

What happens in the brain during nociceptive pain?

A

Thalamus is the secondary relay station which connects to other parts of the brain:

  • Cortex: pain perception
  • Limbic system: emotional side to pain
  • Brainstem: CVS response to pain
91
Q

How is pain modulated?

A

Descending pathway from brain to dorsal horn - usually decreases pain signal

92
Q

What is the Gate theory?

A

Distractive stimulus: rubbing, massaging, application of heat etc. create a distraction signal which can reduce the perception of pain

93
Q

Name some examples of neuropathic pain

A

Nerve trauma, diabetic pain, fibromyalgia and chronic tension headache

94
Q

Describe the pathophysiology of neuropathic pain

A
  • Increased receptor numbers
  • Abnormal sensitisation of nerves (peripheral and central)
  • Chemical changes in the dorsal horn
  • Loss of normal inhibitory modulation
95
Q

Give two examples of simple analgesics

A

Paracetamol

NSAIDs

96
Q

Give examples of mild and strong opioids

A

Mild: codeine, dihydrocodeine
Strong: morphine, oxycodone and fentanyl

97
Q

Name other analgesics used for pain (other than paracetamol, NSAIDs and opioids)

A 
Tramadol
Nefopam
Antidepressants
Anticonvulsants
Ketamine
Local anaesthetics
Topical agents
98
Q

Which pain treatments work on the periphery?

A

Non-drug treatments: rest, ice, compression and elevation
NSAIDs
Local anaethetics

99
Q

Which pain treatments work on the spinal cord?

A

Non drug treatments: acupuncture, massage and TENS
Local anaesthetics
Opioids
Ketamine

100
Q

Which pain treatments work on the brain?

A 
Psychological
Paracetamol
Opioids
Amitriptyline
Clonidine
101
Q

What are the advantages and disadvantages of paracetamol?

A

Advantages: cheap, safe, multiple modes of administration, good for mild pain and in combination for mod-severe pain
Disadvantages: liver damage in overdose

102
Q

What are the advantages and disadvantages of NSAIDs?

A

Advantages: cheap, safe (generally) and good for nociceptive pain
Disadvantages: GI and renal side effects and bronchospasm in some asthmatics

103
Q

What are the advantages and disadvantages of codeine?

A

Advantages: cheap, safe and good for mild-moderate acute nociceptive pain
Disadvantages: constipation and not good for chronic pain

104
Q

What are the advantages and disadvantages of tramadol?

A

Advantages: less resp. depression, can be used with opioids and simple analgesics and is not a controlled drug
Disadvantages: nausea and vomiting

105
Q

What are the advantages and disadvantages of morphine?

A

-Advantages: cheap, generally safe, can be given orally and IV/IM/SC and effective if given regularly (for most acute pain and also chronic cancer pain)
Disadvantages: constipation, resp. depression in high dose, addiction and controlled drug

106
Q

What are the advantages and disadvantages of amitriptyline?

A

Advantages: cheap, safe in low dose, good for neuropathic pain and also treats depression/poor sleep
Disadvantages: anti-cholinergic side effects (e.g. glaucoma and urinary retention)

107
Q

Which type of pain are anticonvulsant drugs good for?

A

Neuropathic pain

108
Q

Which type of pain does the WHO pain ladder work for?

A

Nociceptive pain

109
Q

What are the steps in the RAT approach to pain?

A

Recognise
Assess
Treat

110
Q

List the different pain assessment tools?

A 
Verbal rating score
Numerical rating score
Visual analogue scale
Smiling faces
Abbey pain scale (confused patients)
Functional pain
111
Q

Which non drug treatments are available for the treatment for pain?

A
  • Rest, ice, compression and elevation
  • Nursing care
  • Surgery, acupuncture, massage and TENS
  • Psychological
112
Q

How is the total body water distributed in the body?

A
  • TBW: 42:
  • ICF: 28L
  • ECF: 14L (11L ISF + 3L plasma)
113
Q

Which fluids in the body make up the ECF?

A
  • ISF
  • Intravascular fluid
  • Water in connective tissue
  • Transcellular fluid
114
Q

What is osmolality?

A

Number of osmoles of solute/kg

115
Q

What is osmolarity?

A

Number of osmoles of solute/litre

116
Q

What is the normal plasma osmolarity

A

298 (280-300mOs/L)

117
Q

What is tonicity?

A
  • Effective osmolality
  • Not all particles will effect osmolality
  • Na and accompanying ionsin ECF and K and macromolecules in ICF are the main particles which effect osmolality
118
Q

What are the symptoms of tonicity changes?

A
  • Swelling: raised ICP, compromised CBF and herniation

- Shrinkage: ICH venous sinuous thrombosis

119
Q

Name the common crystalloid solutions

A
  • 5% dextrose
  • 0.9% saline
  • Hartmann’s solution
  • Plasma-lyte
  • 5th normal saline in 4% dextrose
  • 0.18% saline/4% dextrose
120
Q

Name the common coloids

A
  • Gelatins
  • Starches
  • Dextrans
  • Albumin
  • Blood products
121
Q

What are the pros and cons of crystalloids?

A
  • Pros: cheap and non allergenic

- Cons: ECF expansion, oedema and increased vascular pressure

122
Q

What are the potentional problems with colloids?

A
  • Anaphylaxis
  • Coagulopathy
  • Renal failure
  • Rheology
123
Q

What are the daily fluid and electrolyte requirements?

A
  • 25-30ml/kg/day of water
  • 1mmol/kg/day potassium, sodium, chloride
  • 50-100g/day of glucose

Specialities (4 decks)

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