Anaesthetics Flashcards

1
Q

What are the 2 main categories of anaesthesia?

A

General- Unconscious, requires support of ventilator
Regional- Block feeling to isolated area (eg: Limb)

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2
Q

What is the purpose of fasting before a general anaesthetic?

A

Empties stomach
Reduces risk of reflux stomach contents into oropharynx and being aspirated

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3
Q

What are the risks of aspiration in administering a general anaesthetic?

A

Can lead to aspiration pneumonitis and pneumonia

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4
Q

What are the fasting guidelines related to general anaesthetic?

A

6h no food/feeds before operation
2h no clear fluids (nil by mouth)

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5
Q

Outline preoxygenation in general anaesthetic

A

Several minutes before general anaesthetic breathing 100% oxygen
Gives reserve of oxygen between losing consciousness and successful intubation and ventilation

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6
Q

Outline premedication before general anaesthetic

A

Given to relax patient, reduce anxiety, reduce pain and make intubation easier

Benzo (midazolam)- Relax muscle, reduce anxiety (also causes amnesia)
Opiate (fentanyl)- Reduce pain and hypertensive response to laryngoscope
Alpha-2-adrenergic agonist (clonidine)- Sedation and pain

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7
Q

What is the purpose of cricoid pressure in an RSI?

A

Compresses oesophagus and prevents stomach contents refluxing into pharynx

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8
Q

What is the triad of general anaesthesia?

A

Hypnosis
Muscle relaxation
Analgesia

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9
Q

List IV options for hypnotic agents in general anaesthesia

A

Propofol (most common)
Ketamine
Thiopental sodium (less common)
Etomidate (rarely used)

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10
Q

List inhaled options for hypnotic agents in general anaesthesia

A

Sevoflurane (most common)
Desflurane (bad for environment)
Isoflurane (rarely used)
NO- Combined with others- May be used for children

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11
Q

What is a common way to administer hypnotic agents for general anaesthesia?

A

IV meds for induction agent, inhaled meds for maintenance

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12
Q

What is Total IV anaesthesia?

A

Uses IV meds for induction and maintenance of GA
Propofol most common
Give nicer recovery than inhaled options

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13
Q

Outline use of muscle relaxants in GA

A

Block NMJ
ACh released by axon but is blocked from stimulating response from muscle
Relax and paralyse muscles

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14
Q

What are the 2 categories of muscle relaxants used in GA?

A

Depolarising (eg: Suxamethonium)
Non-depolarising (eg: Rocuronium and atracurium)

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15
Q

What reverses the effects of NMJ blocking meds in GA?

A

Cholinesterase inhibitors- Neostigmine

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16
Q

Which med is used specifically to reverse effects of non-depolarising muscle relaxants following GA?

A

Sugammadex

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17
Q

What are the options for analgesia in GA?

A

Opiates most common:
Fentanyl
Alfentanil
Remifentanil
Morphine

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18
Q

What is given for symptoms control at the end of a procedure requiring GA?

A

Antiemetics:
Ondansetron
Dexamethasone
Cyclizine

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19
Q

What is the MoA of ondansetron and its CIs?

A

5HT3 receptor antagonist
Avoid in risk of prolonged QT interval

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20
Q

What is the MoA of cyclizine and which patients is caution given?

A

H1 receptor antagonist
Caution- HF and elderly

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21
Q

Outline emergence from GA

A

Before waking:
Muscle relaxant needs to wear off- Use nerve stimulator on ulnar nerve and watch for thumb movement

After waking:
Stop inhaled anaesthetic
Extubate when breathing for themselves

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22
Q

What are the risks of GA?

A

Sore throat
Post-operative N+V
Accidental awareness
Aspiration
Dental injury
Anaphylaxis
CV events- MI, stroke, arrhythmias
Malignant hyperthermia
Death

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23
Q

What is malignant hyperthermia?

A

Rare potentially fatal hypermetabolic response to anaesthesia
Certain medications and genetic mutations (autosomal dominant) increase risk

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24
Q

Which medications increase risk of malignant hyperthermia?

A

Volatile anaesthetics- Isoflurane, sevoflurane, desflurane
Suxamethonium

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25
How does malignant hyperthermia present?
Hyperthermia Increased CO2 production Tachycardia Muscle rigidity Acidosis Hyperkalaemia
26
How is malignant hyperthermia managed?
Dantrolene- Interrupts muscle rigidity and hypermetabolism- Interferes with movement of calcium ions in skeletal muscle
27
Outline peripheral nerve blocks
Regional anaesthesia Patient remains awake Local anaesthesia injected around specific nerves- Area distal anaesthetised Injection under US guidance with nerve stimulator
28
When is central neuroaxial anaesthesia used?
C section Transurethral resection of prostate (TURP) Hip fracture repair
29
What is central neuraxial anaesthesia?
Spinal anaesthetic/spinal block Type of regional anaesthesia Local anaesthetic injected into CSF within subarachnoid space Only used in lumbar spine (L3/4 or L4/5) Takes 1-3h to wear off
30
What are the adverse effects of epidural?
Headache if dura punctured- Creates hole for CSF to leak from (dural tap) Hypotension Motor weakness in legs Nerve damage (rare) Infection- Meningitis Haematoma (may cause spinal cord compression)
31
When is epidural used?
Labour Post-op after a laparotomy
32
Outline epidural anaesthesia
Catheter in epidural space in lower back Outside dura mater, separate from SC and CSF Local anaesthetics infused through catheter
33
Give an example of an epidural
Levobupivacaine with or w/o fentanyl
34
What are the risks of using an epidural in labour?
Prolonged 2nd stage Increased probability of instrumental delivery
35
When do patients need an urgent anaesthetic review with an epidural?
Develop significant motor weakness (unable to straight leg raise) Catheter may be incorrectly sited in subarachnoid space
36
What is this us and how can it affect intubation?
Pain and constriction when opening jaw Makes intubation more difficult- May need awake fibre-optic intubation
37
What do you use to check the pressure in the cuff of the endotracheal tube?
Manometer
38
What is the Murphy’s eye?
Extra hole on side tip that gas can flow through in case main opening tip of ETT becomes occluded
39
What is a McGrath laryngoscope?
High tech version of standard laryngoscope- Camera and screen attached to visualise vocal cords
40
Outline awake fibre-optic intubation
ETT inserted under guidance of endoscope (camera) through nose
41
What is a CI for nasopharyngeal airway?
Basal skull fracture
42
List indications for tracheostomy
Respiratory failure where long term ventilation may be required Prolonged weaning from mechanical ventilation Upper airway obstruction Management of respiratory secretions (eg: Paralysis) Reducing risk of aspiration- Unsafe swallow, absent cough reflex
43
Outline the stages of a difficult airway
Plan A- Laryngoscopy with tracheal intubation Plan B- Supraglottic airway device Plan C- Face mask ventilation and wake patient up Plan D- Cricothyroidotomy
44
Outline arterial lines
Cannula in artery Accurate BP recording Arterial blood samples NEVER give meds through line
45
Outline central lines
Central venous catheter Inserted into large vein with tip in vena cava Have separate lumens- Can be used for giving meds/taking blood Last longer and more reliable than cannulas
46
What are common locations for insertion of a central line?
Internal jugular Subclavian vein Femoral vein
47
Which meds would be too irritating to give through a peripheral cannula?
Give through central venous line instead Inotropes Amiodarone Fluids with high potassium conc.
48
What is a Vas Cath?
Central venous catheter inserted on temporary basis Usually in internal jugular vein or femoral vein Has 2 or 3 lumens Used short term for haemodialysis
49
Outline Portacath
Type of central venous catheter Small port under skin on top of chest used to access device- Connected to catheter that travels through SC tissue and into SC vein, with tip in SVC or RA When catheter needed to be accessed- Needle inserted through skin into port Used long term- Chemotherapy
50
Outline Pulmonary Artery Catheter
Swan-Ganz catheter Pulmonary artery catheter inserted into IJV through central venous system/RA/RV into pulmonary artery Inflate balloon- Gives pulmonary artery wedge pressure- Gives indication of pressures in LA Rarely used- Mostly cardiac
51
What is a PICC line?
Peripherally inserted central catheter Type of central venous catheter Long, thin tube inserted into peripheral vein and fed into central vein Contain 1 or 2 lumens Narrower than standard central line Low risk of infection- Stay in for longer
52
Outline Tunnelled Central Venous Catheter
Hickman line Long, thin catheter- Enters skin on chest, travels through SC tissue and enters subclavian or jugular vein with tip that sits in SVC Stay in long term Used for regular IV treatment (eg: Chemotherapy or haemodialysis)
53
What is the definition of chronic pain?
Pain present >3mths
54
What are the 2 aspects to the experience of pain?
Sensory- Signal transmitted from pain receptor Affective- Unpleasant emotional reaction to pain
55
What is pain threshold?
The point at which sensory input is reported as painful
56
What is allodynia?
Pain experienced with sensory inputs that don’t normally cause pain (eg: Light touch)
57
What is pain tolerance?
Person’s individual response to pain
58
Outline the basic pathway of pain signals
Nociceptors detect damage/potential damage- Along afferent nerves- Spinal cord- Up spinothalamic tract and spine reticular tract- Brain- Interpreted as pain in thalamus and cortex
59
Outline afferent sensory nerves associated with pain
Transmit pain signals Peripheral nervous system Called primary afferent nociceptors
60
What are C fibres?
Unmyelinated and small diameter Transmit signals slowly and produce dull and diffuse pain sensations
61
What are A-delta fibres?
Myelinated and larger diameter Transmit signals fast Produce sharp and localised pain sensations
62
What are the main sensory inputs that generate a pain signal?
Mechanical (eg: pressure) Heat Chemical (eg: prostaglandins)
63
Outline referred pain
Pain in location away from site of tissue damage Nerves may share innervation of multiple parts of body Pain in one area amplifies sensitivity in SC to signals coming from other areas Activation from SNS in response to pain results in pain in other areas
64
What are the typical features of neuropathic pain?
Burning Tingling Pins and needles Electric shocks Loss of sensation to touch of affected area
65
Outline neuropathic pain
Abnormal functioning or damage of sensory nerves, resulting in pain signals transmitted to brain
66
Outline the steps of the analgesic ladder
Step 1: Paracetamol and NSAIDs Step 2: Weak opioids- Codeine and tramadol Step 3: Strong opioids- Morphine, oxycodone, fentanyl, buprenorphine
67
List drugs used to manage neuropathic pain
Amitriptyline- TCA Duloxetine- SNRI Gabapentin- Anticonvulsant Pregabalin- Anticonvulsant Capsaicin cream- Chilli
68
What is a common SE of long term use of analgesic meds?
Medication overuse headache
69
What are the SEs of NSAIDs?
Gastritis with dyspepsia Stomach ulcers Exacerbation of asthma HTN Renal impairment CAD, HF and strokes
70
What are NSAIDs CI in?
Asthma Renal impairment Heart disease Uncontrolled HTN Stomach ulcers
71
What are the SEs of opioids?
Constipation Skin itching (pruritis) Nausea Altered mental state (sedation/cognitive impairment/confusion) Respiratory depression
71
What is often co-prescribed with NSAIDs?
PPI (omeprazole or lansoprazole) Reduce risk of GI SEs (acid reflux, gastritis and stomach ulcers)
72
What is the antidote to opioids?
Naloxone
73