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ANAESTHETICS Flashcards

1
Q

Broadly, what are the two types of airway management?

A

Simple airway

Advanced airway

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2
Q

Describe how a simple airway is maintained.

A
  1. Airway manoeuvre
  2. BVM
  3. OP/NP tube
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3
Q

Name two types of airway manoeuvre. What is the aim of airway manoeuvres?

A

Head tilt, chin lift
Jaw thrust

To lift the tongue and soft tissues of the pharynx anteriorly to open the airway.

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4
Q

When should you use a jaw thrust manoeuvre instead of head tilt?

A

Suspected trauma.

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5
Q

What is BMV?

A

Bag-mask-ventilation.

Facemask is used.

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6
Q

Which two airways can be used to aid BMV?

A

Oropharyngeal (OP) (guedel)

Nasopharyngeal (NP)

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7
Q

How do you insert an OP airway?

A
  1. Measure from the centre of the mouth to the angle of the jaw
  2. Insert into mouth and twist to advance
    DO NOT USE IF GAG REFLEX PRESENT
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8
Q

How do you insert a NP airway?

A
  1. Measure from the tip of the nose to the tragus of the ear
  2. Through the nose
  3. Advance straight
    DO NOT USE IN HEAD INJURY
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9
Q

Name two supraglottic airways?

A

LMA

iGel

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10
Q

How do you insert an LMA?

A

Insert blind

Inflate mask once situated

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11
Q

How do you insert an ET tube?

A
  • Visualise with laryngoscope
  • Sizing: 7 for women, 8 for men
  • Inflate cuff to protect the airway
  • 20-24cm markings should lie between the teeth
  • Used in theatre and ICU

Elastic bougies can be used to aid ET tube placement.

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12
Q

How do you insert a tracheostomy?

A

• Needle (emergency) or surgical cricothyroidotomy
• Inserted from front of the neck
• Cuff to protect airway
Used in ITU

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13
Q

Which interventions protect the airway?

A

ET
Fibreoptic intubation
Cricothyroidotomy

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14
Q

What is a definitive airway?

A

Cuffed tube below the vocal cords to create a seal and prevent aspiration.
ET tube or tracheostomy.

(NOT LMA as this may not protect the airway and there is still risk of gastric aspiration).

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15
Q

Broadly, what are the two types of ventilation?

A

Non-invasive airway (NIV)

Invasive airway

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16
Q

When do we use NIV?

A

When supplemental O2 is failing e.g. respiratory failure.

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17
Q

What are the two types of NIV?

A

CPAP

BiPAP

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18
Q

How do we decide which type of NIV to use?

A

Depends on the type of respiratory failure.

Type I = CPAP
Type II = BiPAP

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19
Q

How does CPAP work?

A

Maintains a minimum airway pressure.

In alveolar collapse (pneumonia) –> keeps alveoli open

In pulmonary oedema (heart failure) –> pushes the fluid out

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20
Q

How does BiPAP work?

A

During inspiration, BiPAP gives extra IPAP (inspiratory positive pressure).

Increases lung expansion and ventilation.

AND during expiration, maintains minimum airway pressure with EPAP (same as CPAP):

Keeps alveoli open and pushes fluid out.

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21
Q

Give two examples of invasive ventilation.

A

ET tube.

Tracheostomy.

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22
Q

What two types of ventilation can be achieved with invasive management?

A
  1. Volume control - theatres.

2. Pressure control - theatres and ITU, protects lungs from too much pressure (ITU/children).

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23
Q

How does invasive ventilation work in terms of volume-control and pressure-control?

A

Volume-control:

  • Pressure increases
  • Target volume reached
  • Ventilator stops
  • Expiration occurs

Pressure-control:

  • Pressure constant
  • Target time reached
  • Ventilator stops
  • Expiration occurs
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24
Q

What is FiO2?

A

Fraction of inspired O2.

Molar/volumetric content of O2 in an inhaled gas.

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25
Q

What is the FiO2 for patients on air?

How does increasing the flow rate change the FiO2?

A

21%

Increases - 10L = 60%

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26
Q

Name four different methods of delivery O2?

A

Nasal cannula
Hudson mask
Reservoir mask (non-rebreather)
Venturi

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27
Q 
What are the indications for the following type of O2 mask:
Nasal cannulae?
Hudson mask?
Reservoir mask?
Venturi mask?
A

NC - mild hypoxia.
Hudson mask - mild to moderate hypoxia
Reservoir mask - moderate to severe hypoxia
Venturi mask - COPD

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28
Q

What are some common issues with NC?

A

Irritate the nasal airway.

Don’t allow close control of FiO2.

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29
Q

What are some common issues with Hudson masks?

A

Risk of aspiration if the patient vomits whilst wearing the mask.
Don’t allow close control of FiO2.

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30
Q

What do you need to remember to do before fitting a reservoir mask?

A

Forgetting to fill the reservoir bag before attaching to the patient.
Doesn’t have a fixed seal so some air will leak out - it is not a fixed performance device.

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31
Q

What is humidified O2? Why is it used?

A

Oxygen is passed through a humidifying device producing a sterile vapour.
Reduces the drying effects of standard O2 and protects the airway mucosa.

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32
Q

What are the 3 components of anaesthesia?

A

Hypnosis
Muscle relaxation
Analgesia

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33
Q

What are the 3 levels of hypnosis? What class of drugs are used to achieve each level?

A
  1. Awake - local
  2. Sedated - sedatives
  3. Asleep - general
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34
Q

What types of local anaesthetic are there? What are they used for?

A
  1. Local - minor surgery, lacerations or wound repair.
  2. Regional - target specific nerves e.g. brachial plexus, usually for post-operative pain relief.
  3. Neuraxial - subarachnoid block (spinal) or epidural, for intra-operative and post-operative use.
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35
Q

What layers are found between the skin and CSF?

A

Skin –> fat –> supraspinous ligament –> Intraspinous ligament –> ligamentum flavum –> dura –> CSF

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36
Q

What is the difference between a spinal and epidural?

A

Spinal (subarachnoid block):
• Needle goes through ligament AND dura.
• Injected as a bolus, lasts about 2 hours.
• Smaller dose.
• Lumbar (below spinal cord) - same target as lumbar puncture.

Epidural:
	• Needle goes through ligament ONLY.
	• Catheter is passed. Local anaesthetic can be given as an infusion.
	• Larger doses can be given.
Thoracic or lumbar.
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37
Q

What other drug is commonly mixed with epidural infusions?

A

Opioids - be careful not to prescribe opioids for these patients via other routes.

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38
Q

Below which dermatome can an incision be made following a spinal/epidural?

A

T10 - umbilicus (below the highest nerve root affected by the block).

An incision above this level will require general anaesthesia.

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39
Q

How do local anaesthetics work?

A

Reversibly block Na+ channels and inhibit the generation of action potentials.
Small diameter fibres and unmyelinated neurones are affected first.

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40
Q

Why are some local anaesthetics mixed with adrenaline?

A

Adrenaline acts as a vasoconstrictor:
• Reduces bleeding
• Prolongs effect by reducing perfusion to other tissues

Do not use adrenaline on end arteries e.g. fingers.

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41
Q

Name two commonly used local anaesthetics. What are they used for?

A

Lidocaine:

  • Immediate onset, 15 mins duration
  • Small procedures - laceration, chest drains, big cannulae

Bupivacaine:

  • 10 mins onset, 2 hour duration (12-24 hour analgesia)
  • Regional, spinal epidural
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42
Q

Why are neuraxial blocks preferred over GA?

A

Reduced affect on endocrine system

Reduced incidence of DVTs

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43
Q

Name a short-term sedative. What are its uses?

A

Midazolam IV

Endoscopy, regional anaesthesia

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44
Q

Name a long-term sedative. What are its uses?

A

IV propofol +/- alfentanil

ITU, intubated patients for theatre or transfer

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45
Q

Name 3 hypnotic drugs that can be inhaled.

A
  1. Isoflurane - cheapest
  2. Desflurane - wears off quickly
  3. Sevoflurane - used for induction
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46
Q

Name 3 hypnotic drugs that can be used intravenously.

A
  1. Propofol - quick onset, also antiemetic, fast redistribution
  2. Thiopenthal - quick, emergency
  3. Ketamine - CVS instability and analgesia
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47
Q

Name two ways the airway can be managed once sedation is achieved.

A

Spontaneous breathing - BVM or laryngeal mask (e.g. iGel)

OR

Controlled ventilation - intubating the trachea (requires muscle relaxant)

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48
Q

Why are muscle relaxants used?

A
  • To aid intubation (relax the glottis)
  • Muscles relaxed for surgery
  • Patients do not ‘fight’ the ventilator
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49
Q

What are the two types of relaxant? What are they used for?

A
  1. Non-depolarising - routine and emergency, 2-3 mins onset

2. Depolarising - emergency, 30 seconds

50
Q

Name three non-depolarising muscle relaxants.

A

Atracurium
Rocuronium - rapid onset
Vecuronium

51
Q

Name one depolarising muscle relaxants.

A

Suxamethonium (two ACh molecules bound together)

52
Q

What is the physiology of muscle contraction?

A 
ACh arrives released into NMJ.
Binds to (BOTH) ACh receptors.
Ca2+ crosses membrane to cause contraction.
53
Q

How do non-depolarising muscle relaxants work?

A

Competitively binds to ACh receptors.

Block binding site and prevent depolarisation.

54
Q

How do depolarising muscle relaxants work?

A

Block both binding sites simultaneously (non-competitive).
Causes depolarisation and contraction.
Keeps pores open and prevents further contraction.

55
Q

What can be used to reverse muscle blocks?

A

Neostigmine - cholinesterase inhibitor (prevents the breakdown of ACh). Facilitates the transmission of impulses across the NMJ.

56
Q

Describe the WHO pain ladder.

A

Mild: paracetamol & NSAIDs
Moderate: Codeine & tramadol
Severe: morphine

57
Q

What opioids might be used pre-operatively?

A

Codeine - weak
Tramadol - weak
Morphine - strong

58
Q

Which opioids might be used intraoperatively?

A

Fentanyl (potent)

Remifentanil (rapid onset)

59
Q

Name three types of antiemetic. Give an example for each group.

A

Serotonin receptor antagonist - ondansetron.
Dopamine receptor antagonist - metoclopramide, domperidone
Histamine receptor antagonist - cyclizine, cinnarizine, promethazine

60
Q

Where is the site of action for 5HT3 antagonists?

A

CTZ (chemoreceptor trigger zone)

GIT

61
Q

Where is the site of action for H1 antagonists?

A

Vomiting centre and vestibular system

62
Q

Name some causes of nausea that you might come across in surgical patients.

A 
Gut infection
Radiotherapy
Opioids
Diabetic gastroparesis
Motion sickness
Vertigo
63
Q

What are the most appropriate antiemetic to use for post-operative nausea and vomiting (PONV)? What is the best medication to use for prophylaxis of PONV?

A

Ondansetron OR Cyclizine.

Domperidone.

64
Q

What are the most appropriate antiemetic to use for motion sickness?

A

Cyclizine

65
Q

What are the most appropriate antiemetic to use for vomiting associated with long-term opioid use?

A

Metoclopramide (long-term opioid use causes gastric stasis which can be treated with a pro-kinetic).

66
Q

What are the most appropriate antiemetic to use for vertigo?

A

Prochlorperazine

67
Q

What is the formula for cardiac output?

A

CO = HR x SV

68
Q

Name two types of drug that can increase the heart rate?

A

Anticholinergics (muscarinic antagonists)

Beta-agonists (adrenergic agonist)

69
Q

How do anticholinergics lead to an increased heart rate?

A

Block ACh receptors
Inhibit the vagus nerve
Vagus nerve (X) is parasympathetic (slows the heart rate)
Heart rate increases

70
Q

How do beta-agonists lead to an increased heart rate? How else to they affect the heart?

A

Stimulate B-receptors on myocardial cells
Increased heart rate

AND increased contractility.

71
Q

Give two examples of anticholinergics. How are they used in anaesthetics?

A

Atropine
Glycopyrrolate

Used to treat bradycardia, common under anaesthetic.

72
Q

How do atropine and glycopyrrolate differ in their effects?

A 
Atropine = crosses the BBB, faster acting.
Glycopyrrolate = does not cross BBB, slower acting.
73
Q

What is the formula for blood pressure?

A

BP = CO x peripheral resistance

similar to voltage = current x resistance

74
Q

Name two types of vasoconstrictor. What drug group do they come under?

A

Peripheral (via cannula) OR central (via central line).

Alpha agonists.

75
Q

How do alpha-agonists work on blood vessels?

A

Stimulate alpha receptors which are found on peripheral vessels
Cause vasoconstriction
Increases blood pressure (BP = CO x peripheral resistance)

However, they can lead to bradycardia as the body compensates to reduce CO (HR x SV).

76
Q

Give an example of a peripheral vasoconstrictor.

A

Phenylephrine

Metaraminol

77
Q

Give an example of a central vasoconstrictor.

A

Adrenaline (has combined alpha and beta effects but is very potent and should only be used in ITU).

78
Q

What actions/drugs can reduce heart rate/BP during surgery?

A

• Low resting heart rate
• Regular medications e.g. propranolol
• Vagal stimulation - especially laparoscopic surgery
Drugs - propofol & opioids

79
Q

What actions/drugs can increase heart rate/BP during surgery?

A

• Anxiety
• Pain
Drugs - alpha/beta agonists, anticholinergics

80
Q

What should be given if heart rate AND blood pressure are low?

A

Give a combined alpha and beta agonist e.g. ephedrine.

81
Q

What can you use to check if a low blood pressure reading is accurate?

A 
Perfusion trace (SATS monitor) - in hypoperfusion the trace will be flat, but sats can initially be normal.
CO2 - CO2 will be retained due to hypoperfusion of the lungs.
82
Q

How would you manage the cardiovascular status of a patient with aortic regurgitation?

A

Most important thing is to maintain cardiac output (prevent shock).

^HR and decrease peripheral resistance.

83
Q

How would you manage the cardiovascular status of a patient with aortic stenosis?

A

Most important thing is to maintain coronary perfusion (prevent cardiac arrest).

Reduce HR (don’t want the heart to be working too fast) and increase peripheral resistance.

84
Q

At what point in the cardiac cycle does blood flow into the coronary arteries?

A

Diastole - when the ventricles are relaxed.

85
Q

How does a spinal anaesthetic affect the patient’s blood pressure and heart rate?

A

Anaesthetic blocks sympathetic nerve roots which leads to vasodilation below the level of the spinal. Blood pressure will drop and heart rate will decrease.

86
Q

What percentage of total body weight is water?

A

60%

87
Q

In a 70kg adult, what is the total body water (in litres)?

A

42L

88
Q

How is total body water divided?

A 
2/3 = intracellular fluid
1/3 = extracellular fluid
89
Q

How is extracellular fluid divided?

A 
2/3 = interstitial
1/3 = intravascular
90
Q

Describe the sodium and potassium distribution in extracellular and intracellular fluid? Why is this maintained?

A

ECF - ^Na, low K (140 mmol/L Na+, 4 mmol/L - K+)
ICF - low Na, ^K (8 mmol/L - Na+, 151 mmol/L - K+)

Maintains electrochemical gradient across the membrane - allows nerves to work (for excitable membranes).

91
Q

What are the two main types of fluid?

A

Crystalloid

Colloid

92
Q

Describe the composition of crystalloid fluids and give some examples.

A

Water + electrolytes.

Can be hyper/hypotonic.

0.9% Saline, Hartmann’s, Plasmalyte, dextrose-saline, dextrose (5, 10, 50%).

93
Q

Describe the composition of colloid fluids and give some examples.

A

Contains large insoluble molecules.

Stays in the intravascular space.

Blood products, human albumin, gelatins and starch.

94
Q

What is the goal of fluid replacement?

A

To maintain adequate perfusion of the tissues.

95
Q

What three factors determine oxygen delivery to the tissues?

A

• CO
• Hb concentration
Oxygen saturation

96
Q

What is maintenance fluid?

A

30ml/kg/day

97
Q

What is the best fluid to use for volume replacement?

A

Saline OR Hartmann’s (anaesthetists like this).

98
Q

What is the best fluid to use for blood loss?

A

Blood

99
Q

What is the specific danger of giving too much saline in resuscitation?

A

Hyperchloremic alkalosis - if someone needs a large amount of resuscitation fluid, then you need to be careful about giving exclusively saline.

100
Q

If a patient is on maintenance fluids, how often should U&Es be taken?

A

Daily

101
Q

How can you establish the risk of major complications preoperatively?

A

Need to assess the degree of impairment from cardiovascular, cerebrovascular and renovascular impairment.

• U&Es
• Exercise testing
• ECHO - cardiac ischaemic may be silent due to autonomic neuropathy Carotid duplex doppler
102
Q

Where should diabetic patients be placed on the theatre list? Why?

A

First - to shorten fasting time and prevent the risk of hypoglycaemia and ketoacidosis.

103
Q

Why can diabetic patients be difficult to intubate?

A

Glycosylation of collagen in the cervical vertebrae and temporomandibular joints.

104
Q

Why might diabetic patients require intubation?

A

Gastroparesis can lead to delayed gastric emptying due to autonomic neuropathy.

105
Q

Why are the associated risks with regional vs general anaesthetics in diabetic patients?

A

Regional - quicker return to normal diet, but may compensate poorly to sympathetic blockade and infection risk is increased.

106
Q

Why might patients with NIDDM require insulin for major surgery?

A

Insulin resistance and stress response.

107
Q

How should diabetic medication be managed for minor surgery (expected to eat/drink <4 hours)?

A

Oral hypoglycaemics should be omitted on the day of surgery.

Half dose of soluble insulin given if blood glucose >10mmol/L.
No insulin given if blood glucose <10mmol/L.

Resume normal diet and medication as soon as possible post-operatively.

108
Q

How should medication be managed for major surgery?

A

Omit oral hypoglycaemics and SC insulin.

VRII with 5% dextrose and KCl 20mmol in 1L at 100mL/h.

109
Q

Which patients will require VRII?

A

• Surgery requiring a long fasting period (missing more than one meal)
• Poorly controlled diabetes
High risk of AKI e.g. low eGFR

110
Q

How should metformin be adjusted in surgery?

A

Take as normal

111
Q

When can oral diabetic medications be started again post surgery?

A

When the patient is eating normally again.

Metformin should only be started if eGFR >60.

112
Q

Name 3 complications of poor diabetic control during surgery.

A

• Wound/respiratory infection
• Postoperative AKI
Long stay in hospital

113
Q

What is the most common classification system used to determine the urgency of a surgery?

A

NCEPOD (National Classification Enquiry into Patient Outcome and Death).

114
Q

What is the most common scoring system used to assess general risk before surgery?

A

ASA grading (American Society of Anaesthesiologists).

115
Q

What is the purpose of preoperative assessment clinic?

A

• Assess risk - conduct tests
• Manage risk factors/control chronic disease
Reduce cancellations

116
Q

What are the important aspects of a preoperative history?

A 
1. Anaesthetic history:
	• Previous anaesthetic
	• Airway - previous difficulties with the airway, spinal surgery, previous trauma or infection, scarring of the head/neck
2. Systems review:
	• Cardiac disease
	• Respiratory disease
	• GI disease
	• Renal disease
	• CNS disease
	• MSK disease
3. Medications:
	• Current
	• Allergies
4. Lifestyle:
	• Smoking
	• Alcohol
	• Recreational drugs
5. Family history: ask specifically about malignant hyperthermia
Any preoperative concerns
117
Q

Which three classes of drugs are likely to be changed preoperatively?

A

• Anti-hypertensives
• Hypoglycaemics
Anti-coagulants

118
Q

List some procedures that require special preparation.

A

• Thyroid surgery; vocal cord check.
• Parathyroid surgery; consider methylene blue to identify gland.
• Sentinel node biopsy; radioactive marker/ patent blue dye.
• Surgery involving the thoracic duct; consider administration of cream.
• Pheochromocytoma surgery; will need alpha and beta blockade.
• Surgery for carcinoid tumours; will need covering with octreotide.
• Colorectal cases; bowel preparation (especially left sided surgery)
Thyrotoxicosis; lugols iodine/ medical therapy.

119
Q

How and why should patients fast before anaesthesia?

A

To prevent gastric juices entering the tracheobronchial tree and causing aspiration pneumonia. Food particulates can also cause airway obstruction.

For elective surgery:
• > 2 hours since clear fluids
• > 4 hours since milk
> 6 hours since food

120
Q

Which patients are at risk of gastric aspiration even after fasting? How should they be managed?

A
  • Opioid use
  • Hiatus hernia
  • Acute abdomen
  • GI obstruction
  • Pregnancy (2nd and 3rd trimester)
  • Severe trauma

Early endotracheal intubation.

121
Q

What is the WHO checklist? When is it used? What does it check?

A

Checks the patient, procedure and specific concerns such as blood loss, glycaemia control and antibiotic prophylaxis.
Check that everyone is happy with their responsibilities.

FINALS (26 decks)

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