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Phase 3 > Anaesthetics > Flashcards

Anaesthetics Flashcards

1
Q

What is suxamethonium?

A

Depolarising muscle relaxant

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2
Q

How do you recover from suxamethonium?

A

Spontaneous, following metabolism by plasma cholinesterase which is synthesised in the liver

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3
Q

Why do pesticides prolong the activity of suxamethonium?

A

Inhibit cholinesterase activity so not broken down as rapidly

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4
Q

In what conditions should use of suxamethonium be with caution? Why?

A

Liver disease
Malnutrition
Pregnancy
Reduced levels of plasma cholinesterase

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5
Q

What is neostigmine?

A

Anticholinesterase

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6
Q

What is the American society of anaesthesiologists physical status classification system (ASA)?

A

ASA1: normal healthy patient
ASA2: mild systemic disease
ASA3: severe systemic disease
ASA4: severe systemic disease that is a constant threat to life
ASA5: moribund patient who is not expected to survive without the operation
ASA6: declared brain dead, organ removal for donor purposes

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7
Q

What is halothane hepatitis?

A

Appearance of liver damage within 28 days of halothane exposure when other known causes have been excluded

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8
Q

What antibodies do patients with halothane hepatitis have?

A

Antibodies against halothane altered antigens

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9
Q

When should halothane be avoided?

A

Previous exposure within 3 months
Known adverse reaction
Family history of adverse reaction
Pre existing liver disease

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10
Q

Why is a rapid sequence induction used?

A

In a patient who has not fasted to reduce the risk of GORD

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11
Q

A 22-year-old female is extubated following an uncomplicated laparoscopic appendicectomy. However, no respiratory effort is made and she is re-intubated and ventilated. She is monitored in the intensive care unit and all observations are normal. She is weaned from the ventilator 24 hours later successfully. What complication has occurred? Why?

A

Suxamethonium apnoea
Small subset of population has autosomal dominant mutation, lack of acetylcholinesterase in plasma which breaks down suxamethonium, terminating its muscle relaxant effect. So effects of suxamethonium are prolonged and patient needs to be mechanically ventilated and observed in ITU until the effects of suxamethonium wear off

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12
Q

What are some adverse effects of suxamethonium?

A

Hyperkalaemia, malignant hyperthermia and lack of acetylcholinesterase

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13
Q

What is the reversal agent of atracurium?

A

Neostigmine

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14
Q

What does a litre of Hartmanns contain?

A 
Sodium 131
Chloride 111
Potassium 5
Calcium 2
Lactate 29
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15
Q

How does pulse oximetry work?

A

Spectrophotometry - absorbance of light by haemoglobin

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16
Q

What factors may influence the reading of your pulse oximetry?

A 
Excessive movement
Dark pigmentation 
Vasoconstriction
Oedema
Poor arterial circulation
Low body temperature
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17
Q

What biochemical changes may make pulse oximetry levels inaccurate?

A

Severe anaemia
Elevated bilirubin levels
Elevated carboxyhaemoglobin levels
Elevated methylhaemoglobin levels

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18
Q

What regions are involved in the control of ventilation?

A

Senses: chemoreceptors, lung
Central: pons and medulla
Effectors: respiratory muscles

19
Q

What regions are involved in the central control of ventilation (central controller)? What does each area do?

A

Medullary respiratory centre: inspiration and expiration. Sets inherent rhythmicity of breathing. When all afferent stimuli have been abolished, rhythm becomes irregular
Apneustic centre in lower pons: inspiratory gasps occur if sectioned above this level
Pneumotaxic centre in upper pons: inhibits inspiration after a certain point, regulating respiratory rate
Cortex: allows voluntary hypoventilation and breath holding

20
Q

What do central chemoreceptors respond to?

A

Changes in hydrogen ion concentration

Rise in H+ stimulates ventilation

21
Q

Where are peripheral chemoreceptors located?

A

Carotid bodies at bifurcation of common carotid arteries

Aortic bodies above and below aortic arch

22
Q

What type of cells are located in peripheral chemoreceptors? What neurohormone do they contain?

A

Glomus cells

Contain dopamine

23
Q

What do peripheral chemoreceptors respond to?

A

Decreases in arterial PO2 and pH and increases in arterial PCO2

24
Q

What post op problems might you encounter in a patient with muscular dystrophy?

A 
Plasma creatinine kinase raised
Chest infections
Sensitive to opioid and other resp depressant drugs
Hyperkalaemia 
Myoglobulinuria
25
Q

A 24 year old previously well male gives a hx of right iliac fossa pain associated with anorexia and vomiting. Acute appendicitis is suspected and he is booked for an appendectomy. What type of anaesthesia should be used?

A

Rapid sequence induction with cricoid pressure - risk of regurgitation and aspiration

26
Q

Why is cricoid pressure applied during a rapid sequence induction?

A

Occlude the oesophagus to reduce risk of gastric contents being aspirated

27
Q

What is a Biers block?

A

Intravenous regional anaesthesia - can provide anaesthesia for minor surgery to distal ends of both upper and lower limbs
Tourniquet and local anaesthesia used

28
Q

Why is a subclavian perivasicular block contraindicated in day case surgery?

A

Risk of pneumothorax

29
Q

A 28 year old female is scheduled for knee arthroscopy and anterior cruciate ligament reconstruction. She smokes 20 cigarettes per day and has asthma. She never uses her inhalers. What type of anaesthesia should be used?

A

Spontaneous ventilation through LMA - risk of coughing and bronchospasm reduced

30
Q

What is the safest approach to anaesthesia in a patient with a fractured mandible with restricted mouth opening?

A

Awake fibre optic intubation via the nose

31
Q

A 52 year old male in post op ICU with a central line catheter develops spikes of fever. What is the likely causative organism?

A

Coagulase negative staphylococci - staph epidermidis

32
Q

Why does post op atelectasis occur?

A

Patient not breathing properly due to postoperative pain
Small plugs of mucus block small airways
Alveoli collapse due to inadequate ventilation
Normally patient is able to cough to expectorate small plugs

33
Q

Which are the shortest and longest acting muscle relaxants out of atracurium, suxamethonium, pancuronium? How long does each last?

A

Suxamethonium: 10 mins
Atracurium: 15 to 35 mins
Pancuronium: 100 mins

34
Q

When should suxamethonium be used for muscle relaxation in anaesthesia?

A

Rapid sequence induction

If patient has not fasted or is high risk of aspiration - hiatus hernia

35
Q

What is thiopentone and when should it be used?

A

Barbiturate
Has anticonvulsant properties
Can be used as IV induction agent in patients with epilepsy

36
Q

What is suxamethonium apnoea?

A

Pseudocholinesterase deficiency
Abnormality in production of plasma cholinesterases leading to increased duration of action of muscle relaxants in anaesthesia
Respiratory arrest is inevitable unless patient can be mechanically ventilated while waiting for muscle relaxants to degrade

37
Q

When does warfarin need to be stopped pre op?

A

At least 72 hours before and replaced with LMWH

38
Q

What needs to happen with oral steroids pre operatively?

A

Hydrocortisone dose needs to be escalated prior to surgery with a bolus IV of 50-100mg at induction

39
Q

When should clopidogrel be stopped pre op?

A

One week before surgery

40
Q

What is malignant hyperthermia?

A

Autosomal dominant condition where intracellular calcium transport is deranged and generalised muscular contractions generating heat are precipitated by anaesthetic agents

41
Q

How is malignant hyperthermia treated?

A

Dantrolene

42
Q

Which commonly used anaesthetic agent cannot be used in myasthenia gravis?

A

Suxamethonium - depolarising neuromuscular blocker

Will be resistant to its effects and would need significantly higher doses

43
Q

To which anaesthetic agents would patients with myasthenia gravis be more susceptible?

A

Non depolarising neuromuscular blockers eg rocuronium

Phase 3 (23 decks)

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