Anaesthesia Flashcards
1
Q
What are the 3 types of anaesthesia?
A
- General (total loss of sensation)
- Regional (loss of sensation to a region or part of the body e.g. spinal anaesthesia or BP block)
- Local (topical, infiltration)
2
Q
What is amnesia?
A
A lack of response and recall to noxious stimuli - unconsciousness
3
Q
What is analgesia?
A
Pain relief
4
Q
What is akinesis?
A
Immobilisation/paralysis
5
Q
What is an induction agent?
A
Induce loss of consciousness in one/two arm-brain circulation time (intravenous)
10-20 seconds
duration of action: 4-10 minutes
6
Q
What are inhalation/volatile agents?
A
Used usually for maintenance of amnesia
7
Q
What are the 4 induction agents?
A
- Propofol
- Thiopentone
- Ketamine
- Etomidate
8
Q
Which induction agent is most commonly used? - and what is the dose per kg?
A
Propofol, 1.5-2.5 mg/kg (used in more than 95% of patients)
9
Q
Why is propofol most commonly used as an induction agent?
A
It has excellent suppression of airway reflexes and decreases the incidence of post-operative nausea and vomiting (PONV)
10
Q
Why did Michael Jackson call propofol milk?
A
Because it is lipid-based, hence a white emulsion
11
Q
What are the side effects/unwanted effects of using propofol? (3)
A
- Marked drop in HR and BP
- Pain on injection
- Involuntary movements
12
Q
What type of drug is thiopentone? and what is the usual dose per kg?
A
A barbiturate, 4-5mg/kg
13
Q
What are the benefits of using thiopentone?
A
It is faster acting than propofol, used mainly for rapid sequence induction (want to gain control of airway as quickly as possible as they are at risk of aspiration), it has anti-epileptic properties and protects the brain
14
Q
What are the unwanted effects of thiopentone? (4)
A
- Drops BP, but rise in HR
- Rash/bronchospasm
- Intra-arterial injection: thrombosis (it forms crystals)/gangrene
- Contraindicated in porphyria (porphyria is an inherited metabolic disorder that leads to the slow production of haem)
15
Q
What is the normal dose of ketamine given as an induction agent, per kg?
A
1-1.5mg/kg
16
Q
What are the characteristics/uses of ketamine as an induction agent?
A
It is a dissociative anaesthesia (amnesia prior to operation too - anterograde) causes catatonia, analgesia, amnesia
- Slow onset (90 seconds)
- Rise in HR/BP, bronchodilation
17
Q
What are the unwanted effects of ketamine as an induction agent? (2)
A
- Nausea and vomiting
2. Emergence phenomenon: vivid dreams, hallucinations
18
Q
What are the positives of using Etomidate as an induction agent, and what is the dose per kg? (3)
A
- Rapid onset (dose 0.3mg/kg)
- Haemodynamic stability
- Lowest incidence of hypersensitivity reactions
19
Q
What are the unwanted effects of etomidate? (4)
A
- Pain on injection
- Spontaneous movements
- Adreno-cortical suppression (blood loss, blood pressure continues to decrease)
- High incidence of PONV
20
Q
Which induction agent is best for a patient requiring a burn dressing change?
A
Ketamine
21
Q
Which induction agent is best for a patient undergoing arm operation under GA with an LMA (laryngeal mask airway)?
A
Propofol
22
Q
Which induction agent is best for a patient with a history of heart failure and requires a general anaesthetic?
A
Etomidate (keeps them haemodynamically stable)
23
Q
Which induction agent is best for a patient which requires an emergency laparotomy for intestinal obstruction?
A
Thiopentone
24
Q
Which induction agent is best, and which is contraindicated, for a patient with porphyria coming in for an inguinal hernia repair?
A
Propofol
thiopentone contraindicated
25
What are the inhalation agents used to maintain amnesia? (4)
1. Isoflurane
2. Sevoflurane
3. Desflurane
4. Enflurane
26
Which inhalation agent is used for long operations?
Desflurane
27
Which inhalation agent is best for children with no intravenous access? (and why?)
Sevoflurane as it is sweet smelling and is used for induction too (so no intravenous access required)
28
Which inhalation agent doesn't affect organ blood flow, and so it used for organ retrieval from a donor?
Isoflurane
29
What is needed for general anaesthesia?
1. Monitoring
2. IV access (to give anaesthetic poisons)
3. Start process: induction agents, analgesia, muscle relaxation
4. Maintain process:
30
What are the monitoring standards for anaesthesia? (7)
1. ECG
2. SpO2
3. NIBP
4. Airway gases e.g. oxygen, carbon dioxide and vapour
5. Airway pressure (how much pressure the machine has to use in order to ventilate the patient)
- if the pressure is high, an obstruction could have occurred, or the patient has aspirated, or anaphylaxis, any cause of bronchospasm)
6. Nerve stimulator
7. Temperature monitoring (if indicated)
31
What are the sizes of IV access?
14G to 24G
32
What is the minimum fasting time?
6 hours
33
Why is IV access important? (2)
1. To give induction agent
| 2. To give fluids (patient will be dehydrated due to fasting)
34
How are inhalation agents administered?
As vaporisers
35
What is MAC?
Minimum alveolar concentration of the anaesthetic
36
What does 1 MAC refer to?
100% of patients will be asleep, 50% will not feel anything
37
What does 1 MAC refer to in terms of the inhalation agents?
1. Sevoflurane is 2%
2. Isoflurane is 1.15%
3. Desflurane is 6%
4. Enflurane is 1.6%
38
What is analgesia required for during operations/pre/post? (5)
1. Insertion of airway
2. Laryngeal mask airway
3. Intubation
4. Intraoperative pain relief
5. Postoperative pain relief
39
Which are the short-acting drugs given as pain relief? (3)
1. Fentanyl
2. Remifentanil
3. Alfentanil
40
When are short-acting opioids used?
During the induction process, to suppress response to laryngoscopy and surgical pain
41
What are the long-acting opioids, used during the operation and post-operatively? (2)
1. Morphine
| 2. Oxycodone
42
Which other analgesic drugs are used?
1. Paracetamol (very commonly used)
2. NSAIDs; Diclofenac, Parecoxib*, Ketorolac*
3. Weaker opioids; tramadol, dihydrocodeine
*give IV
43
What are the advantages of using tramadol? (3)
1. Safe
2. Useful for different pain types
3. Can be used with morphine
44
What are the disadvantages of tramadol? (2)
1. Nausea and vomiting
| 2. Confusion
45
What are the advantages of using morphine?
1. Very effective
2. Cheap
3. Usually cheap
46
Which opioid can be given with morphine?
Tramadol
47
Name the two IV NSAIDs?
1. Ketorolac
| 2. Parecoxib
48
What are the two mechanisms of action for muscle relaxants?
1. Depolarising agents: act similar to acetylcholine on nicotinic receptors but very slowly hydrolysed by acetylcholinesterase. Therefore the muscle contracts then fatigues and relaxes
2. Non-depolarising: they block the nicotinic receptors therefore muscle relaxes
49
What is the depolarising muscle relaxant? and its dose per kg?
Suxamethonium 1-1.5mg/kg
50
What is the advantage of using suxamethonium?
It has a rapid onset and a rapid offset
51
What are the adverse effects of using suxamethonium?
1. Muscle pains
2. Fasciculations
3. Hyperkalaemia
4. Malignant hyperthermia
5. Rise in ICP, IOP (intra-occular pressure) and gastric pressure)
52
What are the advantages of using non-depolarising muscle relaxants?
1. Less side effects
53
Name two short-acting non-depolarising muscle relaxants?
1. Atracurium
| 2. Mivacurium
54
Name the two intermediate acting non-depolarising muscle relaxants?
1. Vecuronium
| 2. Rocuronium
55
Name the long acting non-depolarising muscle relaxant?
1. Pancuronium
56
Which agents can be used to reverse muscle relaxants?
1. Neostigmine
| 2. Glycopyrrolate
57
In addition to amnesics, analgesics and muscle relaxants, which other drugs are given?
1. Vaso-active drugs
2. Anti-emetics
3. Antibiotics (if indicated)
58
What are the commonly used drugs to treat hypotension? (3)
1. Ephedrine
2. Phenylephrine
3. Metaraminol
Ephedrine - used for low BP and low HR
Other two used for low BP but high HR
59
What are the commonly used drugs to treat severe hypotension? (3)
1. Noradrenaline
2 Adrenaline
3. Dobutamine
60
When is ephedrine used?
When there is a low BP and low HR
61
When is phenylephrine and metaraminol used?
When there is a low BP but a high HR - so causes a rise in BP by vasoconstriction and a drop in HR
62
Which receptors do phenylephrine and metaraminol act on?
Alpha receptors
63
Which receptors does ephedrine act on?
Alpha and beta receptors
64
Which vaso-actiev agent is best used for someone in intensive care with severe sepsis?
Noradrenaline or adrenaline
65
Which three anti-emetics are most commonly used during surgery?
1. Ondansetron
2. Cyclizine
3. Dexamethasone
66
How is the general anaesthetic reversed to wake the patient up?
1. Give oxygen (as they will be respiratory suppressed due to opioids etc)
67
What does neostigmine do?
It is an anti-cholinesterase which prevents breakdown of acetylcholine
68
Which drug is best used to reverse anaesthesia, but is not commonly used due to it being very expensive?
Sugammadex
69
What happens on the post-anaesthesia care unit?
1. Administer O2
2. Handover the patient e.g. brief history, any problems anticipated, intraoperative analgesia and PONV anaphylaxis
3. Prescribe:
- Rescue analgesia
- Rescue anti-emetics
- Fluids
- Other medications as indicated
70
What is the sequence of general anaesthesia?
1. Oxygenation
2. Opioid (fentanyl/alfentanyl)
3. Induction agen (propofol)
4. Turn on volatile agent (sevoflurane/isoflurane)
5. Bag valve mask ventilation
6. Inset LMA
71
What are the sequences of intubation?
1. Oxygenation
2. Opioid
3. Induction agent (propofol)
4. Turn on volatile agent (sevoflurane/isoflurane)
5. Bag valve mask ventilation
6. Muscle relaxant
7. Endotracheal intubation
72
In terms of fasting guidelines before an operation, what are the various time slots for food and fluids?
6 hours fasting for solid foods (light meal) and milk
4 hours fasting for breast milk and fluids with pulp
2 hours fasting for water and clear fluids like black coffee and black tea
73
If someone needs to take tablets with water 30 minutes before their operation, how much are they allowed?
30ml
74
What are the metabolic causes of gastric emptying? (2)
1. Diabetes mellitus
| 2. End stage renal failure
75
What is the anatomical cause of delayed gastric emptying?
Pyloric stenosis
76
What is the mechanical cause for delayed gastric emptying?
Anything that causes a raised intra-abdominal pressure - pregnancy, obesity
77
What are the others causes of delayed gastric emptying?
1. Head injury
2. High fat content
3. Anxiety
4. GORD
78
When is rapid sequence induction performed?
Normally in an emergency, when the patient has a full stomach for any reason
79
What is the initial step of rapid sequence induction?
Pre-oxygenation; three minutes, 5 full vital capacity breaths, EtO2 concentration >90 (rationale for this is to replace FRC with oxygen)
80
Which drugs are given in rapid sequence induction? - dose, onset and duration of action? (3)
1. Thiopentone: 4-5mg/kg, onset 15-30 seconds and duration is 4-8 minutes
2. Propofol: 1.5-2.5mg/kg, onset 30 seconds and duration of action is 2-6 minutes
3. Suxamethonium: 1-1.5mg/kg, duration of action is 6 minutes
81
What is the dose of lignocaine without adrenaline in mg/kg?
3mg/kg
82
What is the dose of lignocaine with adrenaline in mg/kg?
7mg/kg
83
What is the dose of bupivacaine/levobupivacaine, and why is it different to prilocaine and lignocaine?
Dose is 2mg/kg and this is different as it does not change if it is with or without adrenaline
84
What is the dose of prilocaine in mg/kg?
6mg/kg
85
What is the dose of prilocaine with adrenaline?
8mg/kg
86
What does 1% lignocaine mean in terms of mg/ml?
1% is 1gram/100ml (or 1000mg/100ml) (or 10mg/ml)
87
So what is 2% lignocaine in terms of mg/ml?
2 x 10 = 20mg/ml
88
So what is 0.25% lignocaine in terms of mg/ml?
2.5mg/ml
89
What is a local anaesthetic?
A drug which reversibly prevents transmission of the nerve impulse in the region to which it is applied, without affecting consciousness
90
What is a local anaesthetic composed of?
Two groups; lipid-soluble hydrophobic aromatic group and a charged hydrophilic amide group
91
How is a local anaesthetic classified?
According to whether it has an ester or amide link:
- esters
- amides
92
Which classification of local anaesthetic rarely causes an allergic reaction?
Amides
93
Which ester local anaesthetics have a short duration of action? (3)
1. Procaine
2. Benzocaine
3. Cocaine
94
Which ester local anaesthetic have a medium duration of action?
Prilocaine
95
Which ester local anaesthetic has a long duration of action?
Amethocaine
96
Which amide local anaesthetic have a medium duration of action?
1. Lidocaine (lignocaine)
| 2. Mepivacaine
97
Which amide local anaesthetics have a long duration of action?
1. Bupivacaine
2. Levobupivacaine
3. Ropivacaine
98
Which receptor channels for does local anaesthetic act upon?
Sodium channels
99
How does blocking the sodium channels work to anaesthetise?
Causes inhibition of voltage sensitive sodium channel in axon, preventing action potential. This prevents pain by causing a reversible block of conduction along nerve fibres
100
What are the 5 types/techniques of local anaesthetics?
1. Topical
2. Infiltration
3. Conduction
4. Extradural
5. Spinal
101
Which type of local anaesthetic is used for infiltration anaesthesia?
This is for minor surgical procedures and commonly amides are used.
102
What does conduction anaesthesia refer to?
Minor or major nerve blockade e.g. single nerve block like ulnar nerve, or brachial plexus block
103
What are the signs of local anaesthetic toxicity? (In order of development) (12)
1. Tongue paraesthesia
2. Metallic taste
3. Dizziness
4. Slurred speech
5. Diplopia
6. Tinnitus
7. Confusion
8. Restlessness
9. Muscle twitching/convulsions
10. Coma
11. Respiratory arrest
12. CVS depression
104
What is the treatment for local anaesthetic toxicity? (8)
1. Stop injecting the LA
2. Call for help
3. A : Maintain the airway and if necessary secure it with a tracheal tube
4. B : Give 100% oxygen and ensure adequate lung ventilation
5. C : Confirm or establish IV access
6. D : Control seizures - benzodiazepine, thiopental or propofol
7. Give IV lipid emulsion
8. Consider drawing blood for analysis, in circulatory arrest start CPR
105
What is the safe dose of prilocaine with adrenaline?
8mg/kg
106
How much 1% lignocaine can a 70kg man have?
Lignocaine safe dose is 3mg/kg
- So 70x3 = 210mg
- 1% lignocaine = 10mg/ml
- 210/10 - 21mls
107
What is the safe dose of 2% lignocaine with adrenaline for a 60kg woman?
Lignocaine with adrenaline is 7mg/kg
-So 60x7 = 420mg
-2% lignocaine = 20mg/ml
420/20 = 21mls
108
What is the safe dose of 0.25% bupivacaine for a 60kg woman?
Bupivacaine is 2mg/kg (with or without adrenaline)
- So 60x2 = 120mg
-0.25% = 2.5mg/ml
120/2.5 = 48ml
109
What is the safe dose of 0.5% bupivacaine with adrenaline for a 60kg woman?
Bupivacaine with adrenaline is still 2mg/kg
- So 60x2 = 120mg
-0.5% x 10 = 5mg/ml
120/5 = 24ml
110
What is the safe dose in mLs of 1% prilocaine for a 60kg woman?
Prilocaine without adrenaline is 6mg/kg
-So 60x6 = 360mg
-1% x 10 = 10mg/ml
360/10 = 36mls
111
What is the mechanism of action of paracetamol?
It inhibits prostaglandin production and acts centrally on COX-3. This helps to increase the pain threshold and reduced prostaglandin concentrations in the thermoregulatory region of the hypothalamus, controlling fever.
112
What is the maximum dose of paracetamol in 24 hours?
Max 4g in 24 hours
113
How does paracetamol produce toxicity in overdose?
The metabolite of paracetamol is called NAPQI (N-acetyl-p-benzoquinone imine). NAPQI damages hepatocytes. Our body's contain glutathione which is able to conjugate NAPQI and excrete it, however our glutathione reserves are limited, and excess paracetamol leads to excess NAPQI which inevitable damages the liver.
114
How long do stores of glutathione in the body normally last? - and why does this matter?
8-10 hours, so the symptoms/signs of toxicity won't develop until the store of depleted, go after 8 hours.
115
What is the treatment for paracetamol overdose?
NAC - n-acetylcysteine. NAC is a precursor of glutathione, and thus does the same job by conjugating/binding to the NAPQI to form cysteine which is non-toxic.
116
Which receptors do opioids act on?
mu receptors
117
What is clonidine?
Clonidine is an alpha 2 agonist; acting on the brain and dorsal horn causing sedation and analgesia.
118
What is the concentration of sodium in NaCl?
0.9%
119
What is the definition of a solute?
a dissolved substance e.g. glucose
120
What is a solvent?
A liquid which is able to dissolve a solute to form a solution e.g. water
121
What is a semipermeable membrane?
Freely permeable to the solvent but not the solute
122
What is the modified mallampati scoring system?
There are 4 groups, and the scoring system predicts how difficult an intubation may be. It is based upon the visibility of the pharyngeal structures with the mouth open as wide as possible.
123
In 10% of patients an LMA is inserted incorrectly and airway obstruction occurs. What has normally happened when this occurs?
When inserting the LMA the epiglottis is folded back and pushed down by the mask.
124
What is the average size for tracheal tubes in men and women- and what does the size refer to?
8.0mm tube for females
9.0mm tube for males
Size refers to the internal diameter of the tube
125
What clinical signs are used to confirm tracheal intubation? (6)
1. Direct visualisation of the tracheal tube through vocal cords
2. Palpation of tube movements within the trachea
3. Chest movements
4. Breath sounds
5. Reservoir bag compliance and refill
6. Condensation of water vapour on clear tracheal tubes
126
What are the technical tests to confirm intubation?
1. End-tidal CO2 monitoring (six breaths)
| 2. Fibreoptic observation of the trachea
127
Why is it important to test six breaths for CO2 in expired air after intubation?
Alveolar CO2 may have been ventilated into the upper GI tract before intubation and then will be excreted.
Also if the individual has drank a carbonated drink, this may give false reading
128
Which muscle relaxant has the fastest onset and shortest duration, and is often used in emergency operations or in patients with full stomachs?
Suxamethonium
129
Which new drug is used to reverse the effects of long-acting muscle relaxants?
Sugammadex
130
What are the two local anaesthetics in EMLA cream?
Lignocaine/Prolicaine
131
What is the maximum dose of 0.5% lignocaine with adrenaline for a 75kg patient?
75 x 7 = 525
0.5% = 5
525/5 = 105mls
132
How do local anaesthetics work?
By blocking voltage-gated Na+ channels, preventing depolarisation
133
What is the equation for calculating pH of blood? (Henderson-Hasselbach equation)
pH = 6.1 + log10 (conc. HCO3 / 0.0307 x pCO2)
134
How many litres of oxygen are comfortably delivered in a nasal cannula, and therefore what % of oxygen is being delivered?
2-3 litres at 24-28%
135
How many litres of oxygen are delivered in a hudson face mask and therefore what % of oxygen?
6 litres, generally about 30-40%
136
In the non-rebreathe mask, how many litres are delivered, at what % of oxygen?
15L high flow oxygen at close to 100%
137
How do you measure a guedel/oropharyngeal airway appropriately?
From the corner of the mouth to the tracheal ear, or from the mandible to the centre of the teeth
138
How do you measure the correct diameter of the nasopharyngeal airway?
Diameter of the patients little finger
139
When is a nasopharyngeal airway contraindicated?
In patients with a basal skull fracture
140
What is the normal size of endotracheal tube used for males and females respectively?
Males 8-9mm
| Females 7-8mm
141
How do you check the endotracheal tube has been fitted properly?
1. Misting of the tube
2. CO2 expiration
3. Equal chest rising
4. Visually watched the tube enter
5. Auscultate lungs and stomach
