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ACC > White Booklet - Anaesthetics > Flashcards

White Booklet - Anaesthetics Flashcards

1
Q

What is the importance of knowing if a px has had previous anaesthetic?

A
  1. Hx of difficult intubation.
  2. Perioperative problems = awareness, dreams, jaundice.
  3. PONV
  4. Enquire about: suxamethonium apnoea and malignant hyperthermia.
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2
Q

What is suxamethonium apnoea?

A

Some px lack the enzyme ‘plasma cholinesterase’ in the blood which metabolises suxamethonium. In a normal person - metabolism is usually complete in 5-10 mins.

Px with SA remain paralysed for many hours after a standard dose of suxamethonium - they must be kept anaesthetised + ventilated until it is eliminated.

Genetic = E1u (must ask in anaesthetic + family history).

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3
Q

What is malignant hyperthermia?

A

Rare autosomal dominant inherited disease of skeletal metabolism (1 : 10-40,000).

MH is due to the release of abnormally high levels of calcium from the sarcoplasmic reticulum = causing increased muscle activity + rapid generation of ATP. This results in a rise in core body temperature and release of K+ = hyperkalaemia + risk of arrhythmias.

MH = Ca+ release from sarcoplasmic reticulum = muscle activity + ATP generation = rise in body temp = release of K+ = hyperkalaemia + arrhythmias.

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4
Q

What are the common triggers for MH?

A

Halothane and suxamethonium.

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5
Q

What mutation is thought to cause MH?

A

RYR1 mutation (ryanodine receptor gene).

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6
Q

What is the Rx for MH?

A
  • Dantrolene 1mg/Kg (inhibits Ca2+ release)
  • Wet sponge + fanning
  • Hyperventilation (100% FiO2)
  • Treat acidosis = 8.4% sodium bicarbonate
  • Treat hyperkalaemia
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7
Q

What anaesthesia should be used for known MH?

A
  • Regional anaesthesia
  • Vapour free = propofol, thiopentone, opiods, atracurium, vecuronium
  • TIVA
  • Dantrolene = pretreatment
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8
Q

How long should an adult be fasted for prior to elective surgery?

A

Solids = 6 hours (milk is considered a solid).

Clear fluids = 2 hours

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9
Q

Is there a difference between children and adult fasting times before surgery?

A

With regards to solids - no. However breast milk = 4 hours (less fatty than normal milk).

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10
Q

Why are px fasted before surgery?

A

To avoid the risk of aspiration caused by vomit.

Silent regurgitation = neonates or neurological disorders.

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11
Q

What is Mendelson’s syndrome and which condition is this usually seen in?

A

Chemical pneumonitis caused by aspiration during anaesthesia - especially during pregnancy.

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12
Q

What are the effects of prolonged fasting?

A
  1. Hypoglycaemia - particularly a problem in children/ elderly/ diabetics.
  2. Hypovolaemia - due to dehydration.
  3. Increases organic response to trauma = increased insulin resistance, acute-phase response + loss of lean body mass.
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13
Q

What:

  1. Metabolic
  2. Anatomical
  3. Mechanical

Factors delay gastric emptying?

A
  1. DM, end-stage renal failure, obesity.
  2. Pyloric stenosis
  3. Increased IAP, pregnancy, obesity, trauma
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14
Q

Why is gastric emptying delayed in DM?

A

Peristalsis is delayed in diabetes.

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15
Q

Approximately how long does it take for:

  1. Gastric emptying
  2. Water to move through the stomach
A
  1. 4 hours

2. 10-20 minutes

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16
Q

How is the airway assessed and why is it important?

A
  1. Teeth = false or any missing?
  2. Mouth opening = less than 2 fingers breadth = difficult. (Wilson Score).
  3. Jaw protrusion = can lower incisors be brought anterior? (Calder Test).
  4. Neck = level of movement? (Wilson Score).
  5. Thyromental distance should be >6cm.
  6. Mallampati Score = I: soft palate + uvula + side pillars, II: soft palate + uvula, III: soft palate + base of uvula, IV: hard palate only. (III + IV = difficult intubation).

Important to assess how difficult it will be to intubate px.

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17
Q

What are the criteria for the Wilson Score?

A
  1. Fat
  2. Reduced head + neck movement
  3. Reduced mouth opening
  4. Receding mandible
  5. Buck teeth

= difficult intubation

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18
Q

Describe the Calder Test and what it suggests as difficult intubation?

A

Px asked to protrude mandible as far as possible = lower incisors can either progress anterior, in line with upper or posterior to upper.

In line + posterior to upper = difficult intubation.

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19
Q

Which conditions lead to difficult intubation?

A

Achondroplasia (dwarfism), Marfan’s syndrome, Noonan’s syndrome (no neck), obesity, rheumatoid arthritis.

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20
Q

What are the aims of pre-operative assessment?

A
  1. Check right px for surgery
  2. Plan appropriate anaesthesia
  3. Check they are optimised for surgery (identify co-morbidities)
  4. Assess airway

= all to prevent cancellation of surgeries due to the px not being fit for operation.

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21
Q

What risks should be considered in pregnancy anaesthesia?

A
  1. Increases risk of spontaneous abortion in early pregnancy.
  2. Increases risk of aspiration.
  3. Consider X-ray risk
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22
Q

What problems may smokers suffer through GA?

A
  1. Carbon monoxide in cigarette smoke + Hb = carboxyhaemoglobin. This reduces the oxygen carrying capacity of RBC = hypoxia, HTN.
  2. Nicotine stimulates sympathetic nervous system (fight or flight) = tachycardia.
  3. More likely to have broncho- / laryngo- spasm.
  4. More prone to post-operative atelectasis (lung collapse) = reduced FRC + increase mucus secretion. This also increases risk of pneumonia.
  5. V/Q (ventilation:perfusion) mismatch + pulmonary shunt.
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23
Q

Are smokers more likely or less likely to suffer PONV?

A

Less likely!

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24
Q

How long should you advise a px to stop smoking before surgery?

A

4-6 weeks - reduces the risk of peri-operative complications.

8 weeks = improves airway
2 weeks = reduces irritability - less chance of bronchospasm
24 hours = decreases carboxyhaemoglobin levels!

25
Q

What needs to be considered in alcoholics with regards to GA?

A

> 50 units a week = induces liver enzymes - greater tolerance to anaesthetic drugs, therefore will require more.

Must consider physiological withdrawal effects - can give chlordiazepoxide.

26
Q

How can these anti-hypertensives affect the px and the anaesthetic?

  1. ACEi
  2. Beta-blockers
  3. CCB
  4. Diuretics
  5. Anti-coagulants
A

ACEi

  • Okay to take before + on the day of surgery + IV dose during.
  • Some anaesthetists stop on the day as causes drop in BP.

Beta-blockers

  • Okay to take before + on the day of surgery + IV dose during.
  • Abrupt withdrawal may adversely affect HR + BP and precipitate MI.

CCB

  • Okay to take before + on the day of surgery + IV dose during.
  • BUT may exaggerate myocardial depressant effects of volatile agents + prolong non-depolarising muscle relaxants.

Diuretics

  • Stop the day before surgery
  • Check U+E before surgery = hypokalaemia? - lead to arrhythmias.
  • Potentially cause diuretic-induced volume depletion (hypovolaemia) + hypokalaemia.
27
Q

What considerations should be taken with regards to px taking anti-coagulants and anaesthetics?

A
  • Why are they taking them and what surgery are they having?
  • Check their INR
  • Swap warfarin to heparin pre-operatively = allow INR to reach <1.5
28
Q

What should be the INR of px having an epidural / spinal?

A

<1.3 = can result in bleeding into the spinal cord (epidural haematoma) + causing cord compression.

29
Q

Which antibiotics prolong neuromuscular blockade?

A

Aminoglycosides + tetracyclines

30
Q

What information do these investigations provide and when are they necessary?

  1. FBC
  2. U+Es
  3. LFTs
  4. Coagulation screen
  5. Group & save
  6. ECG
  7. CXR
  8. Echo
A
  1. Hx of bleeding loss, major surgery, cardioresp disease, men >50 years.
  2. Renal function = If on diuretics, digoxin, steroids, major trauma, burns, hepatic / renal disease, severe diarrhoea / vomiting.
  3. If jaundiced, malignancy, alcoholic.
  4. Liver disease, hx bleeding, on warfarin / heparin.
  5. All major surgery
  6. For cardiopulmonary disease, diabetes, age >50
  7. Known cardiopulmonary disease, pathology/symptoms i.e. pneumonia, thoracic surgery.
  8. Cardiac disease (LV function, valves).
31
Q

What drug is given to carry out a ‘stress echo’ and what is its MOA?

A

Dobutamine (acts on B receptors in the heart) is given to increase HR and myocardial work and can assess the body’s response - type of CPX.

32
Q

How long does it take for induction agents to induce loss of consciousness? What is the duration of action?

A

10-20 seconds.

Duration of action = 4-10 minutes.

33
Q

What px can etomidate be used on and why?

A

Px with heart conditions - etomidate has haemodynamic stability therefore no rise in BP/HR.

34
Q

What condition should etomidate NOT be used for and why?

A

Septic shock = continuous IV etomidate leads to adreno-cortical suppression (72 hours after a single bolus). Increased mortality in px with septic shock.

35
Q

Which inducing agents:

  1. Px requiring a burn dressing change?
  2. Px undergoing arm operation under GA with an LMA?
  3. Px with a history of HF requires a GA?
  4. Px with intestinal obstruction requires emergency laparotomy?
  5. Px with porphyria comes for an inguinal hernia repair?
A
  1. Ketamine (used for single short procedures).
  2. Propofol (excellent airway suppression).
  3. Etomidate (haemodynamically stable).
  4. Thiopentone (for rapid sequence induction - emergency).
  5. Propofol (NOT thiopentone).
36
Q

What is TIVA and what drug is used for this?

Why are these drugs NOT used?

  1. Ketamine
  2. Thiopentone
  3. Etomidate
A

‘Total IV Anaesthesia’ = IV drugs alone given for induction and maintenance anaesthesia.

Drug used = Propofol

  1. Hallucinogenic effect (“emergence phenomenon”).
  2. Hangover effects.
  3. Adreno-cortical suppression.
37
Q

What are the disadvantages of induction agents?

A
  • Px become apnoeic = need manual ventilation.
  • Varying effects on BP (hypotension).
  • May lose airway patency.
38
Q

What are inhalation agents?

A
  • Halogenated hydrocarbons

- Used to maintain amnesia + administered via vaporisers.

39
Q

Which inhalation agents are INSOLUBLE? What are their advantages?

A

Sevoflurane and desflurane.

  • Rapid onset of action
  • Less hangover effect
  • Faster emergence from anaesthesia
  • Small blood-gas partition co-efficient

= lower blood-gas partition coefficient, faster onset and quicker recovery.

40
Q

What is the only SOLUBLE anaesthetic and what is its disadvantage?

A

Halothene

  • Require higher blood-gas partition co-efficient = larger amount of gas needed to be taken up in the blood before passing onto brain = more needed to take effect.
41
Q
  1. Low MAC means that a higher/lower concentration will be needed for maintenance induction.
  2. Compound with low potency with have high/low MAC? - name a compound.
  3. Compound with high potency will have high/low MAC? - name a compound.
A
  1. LOWER
  2. High = Desflurane, Sevoflurane
  3. Low = Haloflurane
42
Q

Halothane and Enflurane are older inhalation agents - therefore have high/low solubility?

A

High = higher blood:gas partition coefficient - need more to take effect.

43
Q

Describe Sevo/Desflurane with regards to:

  1. Potency
  2. Solubility
  3. MAC
  4. Recovery time
A
  1. Low potency
  2. Low solubility
  3. High MAC
  4. Rapid recovery (doesn’t stay in tissues for long)
44
Q

Why does the ‘hangover effect’ occur?

A

GA that is highly fat soluble accumulates in fat, slowly diffuses out, thus the effects carry on.

45
Q

Why is Desflurane NOT recommended in children?

A

Very irritant = cough, breath holding, apnoea, laryngospasm + increased secretions.

46
Q

What are the advantages and disadvantages of Isoflurane?

A

Advantages = Medium potency (low MAC), stable HR (least effect on organ blood flow), enhancement of muscle relaxation, less incidence of arrhythmias than halothane, CHEAP.

Disadvantages =
hypoxia/hypercapnia, initial respiratory irritation, hepatotoxicity (small chance - less than Halothane).

47
Q

What are the indications for muscle relaxant use?

A
  1. If surgery requires it (e.g. open abdo surgery).
  2. RSI
  3. Endotracheal tube insertion
  4. Endoscopic examinations
  5. Ortho procedures
48
Q

How can we assess the adequacy of neuromuscular blockade?

A

Electrode stimulator = on tragus (VII nerve) or wrist (Ulnar nerve).

Train-of-four stimulation.

49
Q

What are the problems with using Suxamethonium?

What is suxamethonium also known as?

A

Muscle pains, suxamethonium apnoea, hyperkaemia = arrhythmia, malignant hyperthermia, histamine release (anaphylaxis).

  1. Succinylcholine
50
Q

How are muscle relaxants reversed?

A

Neostigmine (2.5mg IV) + Glycopyrrolate

51
Q
  1. Name 3 commonly used vaso-active drugs.

Fall in BP

  1. Px HR low give?
  2. Px HR high give?
A
  1. Ephedrine
    - ^HR + ^contractility = ^BP
    - acts on alpha and beta receptors
    - indirect + direct action
  2. Phenylephrine
    - Vasoconstriction = ^BP
    - direct action on alpha receptors
    - drops HR
  3. Metaraminol
    - Vasoconstriction = ^BP
    - most alpha receptors
    - direct and indirect action
  4. HR low = ephedrine
  5. HR high = metaraminol (longer acting than phenylephrine)
52
Q

What vasopressors are used in severe hypotension / ICU?

A
  1. Noradrenaline
  2. Adrenaline
  3. Dobutamine
53
Q

How does Dobutamine work and what conditions is it used for?

A
  • Directly stimulates beta-1 adrenoreceptors = increases HR and force of contractions.
  • HF due to reversible causes + Congestive HF (positive inotropic action).
54
Q

Best vaso-active agent:

  1. Low BP, low HR
  2. Low BP, high HR
  3. Intensive care / severe sepsis
A
  1. Ephedrine.
  2. Metaraminol or Phenylephrine (only via vasoconstriction - smaller effect on heart).
  3. Adrenaline / noradrenaline / dobutamine.
55
Q

What type of drug is adrenaline and what is its method of action?

A
  1. Endogenous catecholamine

2. Alpha receptors in BV to increase SVR + beta receptors in the heart to increase contractility + rate (SV).

56
Q

Why is adrenaline used with LA? Where should it not be used?

A
  1. Reduce toxicity
  2. Reduce blood flow
  3. Extends duration

(Prolonged duration of anaesthetic action because less blood flow to remove LA from the area).

DO NOT use at extremities.

57
Q

What 2 categories do LA fall under and name them.

A
  1. Esters
    - Tetracaine (amethocaine) = AmeTop
    - Cocaine
    - Procaine
  2. Amides
    - Lidocaine
    - Bupivacaine
    - Prilocaine
    - Ropivacaine
    - Mepivacaine

Two ‘i’ = Amides

58
Q

Which of the 2 LA groups are more likely to cause allergic reactions?

A

Esters

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