Anaesthetics Flashcards
(114 cards)
1
Q
State and explain the main categories of anaesthesia:
A
- General anaesthesia: making the patient unconscious
- Regional anaesthesia: blocking feeling to an isolated area of the body (e.g. a limb)
2
Q
Outline what is involved when a patient has general anaesthesia:
A
- Involves putting the patient in a state of controlled unconsciousness
- The patient will be intubated or have a supraglottic airway device, and their breathing will be supported and controlled by a ventilator
- The patient is continuously monitored
3
Q
Why should a patient fast before having a general anaesthetic?
A
- To reduce the risk of the stomach contents refluxing into the oropharynx (throat), then being aspirated into the trachea (airway) leading to pneumonitis
4
Q
When is the risk of aspiration highest?
A
- Before and during intubation, and when they are extubated
- (Once the endotracheal tube is correctly fitted, the airway is blocked and protected from aspiration)
5
Q
How long should a patient fast before having a general anaesthetic?
A
- 6 hours of no food/feeds
- 2 hours of no clear fluids (nil by mouth)
6
Q
Before being put under a general anaesthetic, why will the patient have a period of several minutes where they breathe 100% (preoxygenation)?
A
- This gives them a reserve of oxygen for the period between when they lose consciousness and are successfully intubated and ventilated (in case the anaesthetist has difficulty establishing the airway)
7
Q
Why are medications given to a patient before they are put under general anaesthesia (premedication)?
A
- To relax them, reduce anxiety, reduce pain and make intubation easier
8
Q
State 3 classes of medications that may be given to a patient before they are put under general anaesthesia:
A
- Benzodiazepines (e.g. midazolam) to relax the muscles and reduce anxiety
- Opiates (e.g. fentanyl) to reduce pain and reduce the hypertensive response to the laryngoscope
- Alpha-2-adrenergic agonists (e.g. clonidine), helps with sedation and pain
9
Q
What is Rapid Sequence Induction/Intubation (RSI)?
A
- RSI is used to ensure successful intubation with an endotracheal tube as soon as possible after induction (when the patient is unconscious) to protect the airway
10
Q
Why is RSI considerably more risky than pre-planned intubation?
A
- The patient has often not been fasted (risk of aspiration)
- The anaesthetist has not had the chance to plan for potential problems
11
Q
Define intubation:
A
- The insertion of a tube into a patient’s body, especially that of an artificial ventilation tube into the trachea
12
Q
Other than in emergency situations, when is RSI used?
A
- In non-emergency situations where the airway needs to be secured quickly to avoid aspiration, such as in patients with gastro-oesophageal reflux or pregnancy
13
Q
The biggest concern during RSI is the aspiration of stomach contents into the lungs. State 2 methods that can be used to reduce this risk:
A
- The bed can be positioned so the patient is more upright
- Cricoid pressure may be used to compress the oesophagus
14
Q
What makes up the triad of general anaesthesia?
A
- Hypnosis (unconscious)
- Muscle relaxation (relaxed)
- Analgesia (without pain)
15
Q
Hypnotic agents are used to make the patient unconscious. They can be either given intravenously or by inhalation. State 4 IV hypnotic agents:
A
- Propofol (the most commonly used)
- Ketamine
- Thiopental sodium (less common)
- Etomidate (rarely used)
16
Q
Hypnotic agents are used to make the patient unconscious. They can be either given intravenously or by inhalation. State 4 inhaled hypnotic agents:
A
- Sevoflurane (the most commonly used)
- Desflurane (less favourable as bad for the environment)
- Isoflurane (very rarely used)
- Nitrous oxide (combined with other anaesthetic medications – may be used for gas induction in children)
17
Q
Sevoflurane, desflurane and isoflurane are volatile anaesthetic agents. What does this mean?
A
- Volatile agents are liquid at room temperature and need to be vaporised into a gas to be inhaled (by a vaporiser)
18
Q
What are vaporisers used for and how do they work?
A
- Used for inhaled volatile agents
- Liquid medication put into the machine
- The machine then turns it into vapour and mixes it with air in a controlled way
- During the anaesthesia, the concentration of the vaporised anaesthetic medication can be altered to control the depth of anaesthesia
19
Q
Why are IV agents often used as induction agents and inhaled agents used for maintenance?
A
- Inhaled medications need to diffuse across the lung tissue and into the blood, where it takes a while for them to reach an effective concentration
- IV agents have a head start, as they are infused directly into the blood and so can quickly reach an effective concentration
20
Q
What is total intravenous anaesthesia (TIVA)? What medication is most commonly used for it? What are the benefits?
A
- TIVA involves using an intravenous medication for induction and maintenance of the general anaesthetic
- Propofol is the most commonly used
- This can give a nicer recovery (as they wake up) compared with inhaled options
21
Q
What is the drug class of propofol?
A
- GABA receptor agonist
22
Q
Muscle relaxants are given to relax and paralyse the muscles. This makes intubation and surgery easier. Outline their mechanism of action:
A
- Muscle relaxants block the neuromuscular junction from working
- Acetylcholine (the neurotransmitter) is released by the axon but is blocked from stimulating a response from the muscle
23
Q
What are the 2 categories of muscle relaxants?
A
- Depolarising (e.g. suxamethonium)
- Non depolarising (e.g. rocuronium and atracurium)
24
Q
What drug class can reverse the effects of neuromuscular blocking medications?
A
- Cholinesterase inhibitors (e.g. neostigmine)
25
Which drug is used specifically to reverse the effects of certain non-depolarising muscle relaxants (rocuronium and vecuronium)?
- Sugammadex
26
Opiates are the most frequently used medication for analgesia. State 4 examples:
- Fentanyl
- Alfentanil
- Remifentanil
- Morphine
27
Antiemetics are often given at the end of a procedure to prevent post-operative nausea and vomiting. State 3 antiemetics:
- Ondansetron (5HT3 receptor antagonist): avoided in patients at risk of prolonged QT interval
- Dexamethasone (corticosteroid: used with caution in diabetic or immunocompromised patients
- Cyclizine (histamine (H1) receptor antagonist): caution with heart failure and elderly patients
28
Before waking the patient, the muscle relaxant needs to have worn off. Explain 2 methods by which this can be tested:
- A nerve stimulator may be used to test the muscle responses to stimulation, to ensure the muscle relaxant effects have ended
- (This is often tested on the ulnar nerve at the wrist, watching for thumb twitches)
- Alternatively, the facial nerve can be stimulated at the temple while watching for movement in the orbiculares oculi muscle at the eye.
- This involves a train of four (TOF) stimulation, where the nerve is stimulated four times to see if the muscle responses remain strong (indicating it has worn off) or whether they get weaker with additional stimulation (indicating it hasn't fully worn off)
29
After the muscle relaxant has worn off, when is the patient extubated?
- Once the muscle relaxant has worn off, the inhaled anaesthetic is stopped
- The concentration of the anaesthetic in the body will fall, and the patient will regain consciousness
- They are extubated at the point where they are breathing for themselves
30
State 6 risks of general anaesthesia:
- Accidental awareness (waking during the anaesthetic)
- Aspiration
- Dental injury, mainly when the laryngoscope is used for intubation
- Anaphylaxis
- Cardiovascular events (e.g. myocardial infarction, stroke and arrhythmias)
- Malignant hyperthermia (rare)
31
What is malignant hyperthermia?
- A rare but potentially fatal hypermetabolic response to anaesthesia mainly associated with volatile anaesthetics (isoflurane, sevoflurane and desflurane) and suxamethonium
32
There are genetic mutations that increase the risk of malignant hyperthermia. What pattern are these inherited in?
- Autosomal dominant
33
State 6 physiological effects of malignant hyperthermia:
- Increased body temperature (hyperthermia)
- Increased carbon dioxide production
- Tachycardia
- Muscle rigidity
- Acidosis
- Hyperkalaemia
34
State and explain 1 treatment for malignant hyperthermia:
- Dantrolene (skeletal muscle relaxant)
- Interrupts the muscle rigidity and hypermetabolism by interfering with the movement of calcium ions in skeletal muscle
35
Where possible, it is desirable to keep the patient awake and only anaesthetise the area required for the operation. State 3 types of regional anaesthesia:
- Peripheral nerve blocks
- Central neuraxial (spinal) anaesthesia
- Epidural anaesthesia
36
Outline how peripheral nerve blocks are used to anaesthetise the patient:
- Patient remains awake during procedure
- Local anaesthetic is injected (with ultrasound guidance) around specific nerves, causing the area distal to the nerves to be anaesthetised
- This usually involves making a limb numb so that a surgeon can operate without causing any pain
- A screen is put up between the patient and the operating site so that they cannot see the operation taking place
- (Sedation may be given to help the patient relax)
37
Outline how central neuraxial (spinal) anaesthesia is used to anaesthetise the patient:
- Patient remains awake during procedure
- Local anaesthetic injected into the cerebrospinal fluid, within the subarachnoid space
- It is only used in the lumbar spine, after the point where the spinal cord ends, to avoid damaging the spinal cord (in practice, the needle is usually inserted into the L3/4 or L4/5 spaces)
- Neuraxial anaesthesia will cause numbness and paralysis of the areas innervated by the spinal nerves below the level of the injection
- Cold spray applied to the skin is often used to test whether the anaesthetic has worked (it takes around 1 to 3 hours for the anaesthetic to wear off)
38
State 3 examples of procedures where central neuraxial (spinal) anaesthesia is commonly used:
- Caesarean sections
- Transurethral resection of the prostate (TURP)
- Hip fracture repairs
39
Outline how epidural anaesthesia is used to anaesthetise the patient:
- Involves inserting a small tube (catheter) into the epidural space in the lower back
- This is outside the dura mater, separate from the spinal cord and CSF
- Local anaesthetic medications are infused through the catheter into the epidural space, where they diffuse to the surrounding tissues and spinal nerve roots, where they have an analgesic effect
40
How is an epidural different from a neuraxial/spinal block?
- Epidural: local anaesthetic injected into the epidural space, where they diffuse to the surrounding tissues
- Neuraxial/spinal: local anaesthetic is injected into the cerebrospinal fluid, within the subarachnoid space
41
Give an example of a common combination of medications given in an epidural:
- Combination of local anaesthetic and opioid (e.g. levobupivacaine and fentanyl)
42
State 2 scenarios where epidurals are commonly used:
- Analgesia in pregnant women in labour
- Post operatively after a laparotomy
43
State 6 potential adverse effects of an epidural:
- Headache if dura is punctured, creating a hole for CSF to leak from (dural tap)
- Hypotension
- Motor weakness in the legs
- Nerve damage (rare)
- Infection, including meningitis
- Haematoma (may cause spinal cord compression)
44
When used for analgesia in labour, state 2 potential adverse effects of an epidural:
- Prolonged second stage
- Increased probability of instrumental delivery
45
Why do patients need an urgent anaesthetic review if they develop significant motor weakness (unable to straight leg raise) during an epidural?
- The catheter may be incorrectly sited in the subarachnoid space (and cerebrospinal fluid) rather than the epidural space
46
What is local anaesthetic (e.g. lidocaine) commonly used for?
- Used to numb a very specific area where a procedure is being performed
- Usually used for smaller operations and procedures
47
What is an endotracheal tube (ETT)?
- A flexible tube, with an inflatable cuff on one end and a connector at the other end, inserted into the trachea to maintain an open airway and facilitate breathing
48
Regarding the ETT, what is the pilot line?
- A tube that is used with a syringe to inflate the inflatable cuff
49
Regarding the ETT, what is the pilot balloon?
- Lies towards the end of the pilot line and inflates along with the cuff
- Allows the anaesthetist to roughly assess how inflated the cuff is (while it is out of sight in the trachea)
50
Regarding the ETT, what equipment can be used to check the pressure of the cuff?
- Manometer
51
Regarding the ETT, what is Murphy's eye?
- An extra hole on the side of the tip that gas can flow through in the event that the main opening at the tip of the ETT becomes occluded
52
What is a laryngoscope and how can it be used with an ETT?
- A metal blade attached to a handle, with a light attached
- It is inserted through the mouth and into the pharynx to visualise the vocal cords
- An ETT can be guided along the blade into position in the trachea
53
What is a McGrath laryngoscope?
- A high-tech version of a standard laryngoscope, which has a camera and screen attached so that the vocal cords can be visualised via a live video feed
54
What is a bougie?
- A device to help with intubation, notably when the vocal cords cannot be visualised
- The bougie is inserted into the trachea
- The endotracheal tube slides along the bougie into the correct position in the airway
- The bougie is then removed, and the endotracheal tube remains in place
55
What is a stylet?
- A stiff metal wire (with a plastic coating) that is inserted into the endotracheal tube before intubation is attempted
- It can be bent to hold the endotracheal tube in a specific shape
- It is usually used to bend the tip of the endotracheal tube anteriorly towards the trachea (to avoid going posteriorly into the oesophagus
56
What is awake fibre-optic intubation?
- A special procedure where the endotracheal tube is inserted with the patient awake, under the guidance of an endoscope
57
When might awake fibre-optic intubation be used?
- Where there is restricted mouth opening or difficult anatomy (e.g. after radiotherapy to the neck)
- Trismus
58
What is trismus?
- Pain and restriction when opening the jaw
- This can make intubation more difficult and might need awake fibre-optic intubation
59
What is a supraglottic airway device (SAD)?
- A medical tool used to keep the upper airway open for ventilation, especially when tracheal intubation is not possible or desired
60
Explain how SADs differ from ETTs:
- SAD: sit above the vocal cords and seal around the laryngeal inlet
- ETT: passed through the vocal cords and into the trachea
61
The tip of an SAD will be located at the top of the oesophagus, with the cuff around the opening of the larynx. State 1 example of a SAD with an inflatable cuff and 1 example of a SAD with a non inflatable cuff:
- Inflatable cuff: laryngeal mask airways (LMA)
- Non inflatable cuff: I-gel, has a gel like cuff that moulds to the larynx
62
What are guedels?
- Rigid oropharyngeal airways that create an air passage between in front of the teeth and the base of the tongue, maintaining a patent upper airway
63
Explain how guedels are inserted:
- Inserted upside down, then rotated into position once the tip is past the tongue
- (The size is measured from the centre of the mouth to the angle of the jaw)
64
When are guedels most commonly used?
- When ventilating the patient via a face mask and bag prior to inserting an SAD or ETT
65
What are nasopharyngeal airways?
- Slightly flexible tubes inserted through the nose that create an air passage from outside the nostril to the pharynx
66
State 1 contraindication for inserting a nasopharyngeal airway:
- A base of skull fracture
67
What is a tracheostomy?
- A hole/opening is made in the front of the neck with direct access to the trachea
- A tracheostomy tube is inserted through the hole into the trachea and held in place with stitches or soft tie around the neck
68
Tracheostomies can be planned or emergency. State 5 indications for a tracheostomy:
- Respiratory failure where long-term ventilation may be required (e.g. after an acquired brain injury)
- Prolonged weaning from mechanical ventilation (e.g. ICU patients that are weak after critical illness)
- Upper airway obstruction (e.g. by a tumour or head and neck surgery)
- Management of respiratory secretions (e.g. in patients with paralysis)
- Reducing the risk of aspiration (e.g. in patients with an unsafe swallow or absent cough reflex)
69
What are the 4 stages of action (from the Difficult Airway Society) to take in the case of unanticipated difficulty intubating a patient?
- Plan A: laryngoscopy with tracheal intubation
- Plan B: supraglottic airway device
- Plan C: face mask ventilation and wake the patient up
- Plan D: cricothyroidotomy
70
What is an arterial line?
- A special type of cannula inserted into an artery (e.g. the radial artery)
71
State 2 uses for an arterial line:
- The blood pressure can be accurately monitored in real-time
- Arterial blood samples (for ABG monitoring) can be taken
72
Why must medications never be given through an arterial line?
- Injecting medications directly into an artery can expose tissues (e.g. fingers, brain) to very high concentrations of drug
- Can cause vasospasm, thrombosis
73
What is a central line?
- A thin, flexible tube inserted into a large vein, typically in the neck, chest, or groin that leads directly to the vena cava
74
State 3 veins where central lines are commonly inserted:
- Internal jugular vein
- Subclavian vein
- Femoral vein
75
State 3 benefits of central lines:
- They have separate lumens (tubes), which can be used for giving medications or taking blood samples
- They last longer and are more reliable than peripheral cannulas
- They can also be used for medications that would be too irritating to be given through a peripheral cannula (e.g. inotropes, amiodarone or fluids with a high potassium concentration)
76
What is a Vas Cath?
- A type of central venous catheter inserted on a temporary basis, usually into the internal jugular or femoral vein
- It has two or three lumens
- It may be used for short-term haemodialysis (in renal failure)
77
What is a peripherally inserted central catheter (PICC line)?
- A type of central venous catheter inserted into a peripheral vein (e.g. in the arm) and fed through the venous system until the tip is in a central vein (the vena cava or right atrium)
78
State 1 benefit of a PICC line:
- They have a low risk of infection, meaning they can stay in for a prolonged period and are useful as medium-term IV access
79
What is a Hickman line (Tunnelled Central Venous Catheter)?
- A long, thin catheter that enters the skin on the chest, travels through the subcutaneous tissue (“tunnelled”), then enters into the subclavian or jugular vein, with a tip that sits in the superior vena cava
- There is a cuff (sleeve) that surrounds the catheter near the skin insertion that promotes adhesion of tissue to the cuff, making the catheter more permanent and providing a barrier to bacterial infection
80
What is a pulmonary artery catheter (Swan-Ganz catheter)?
- A catheter inserted into the internal jugular vein, through the central venous system, right atrium, right ventricle and into a pulmonary artery
- It has a balloon on the end that can be inflated to “wedge” the catheter in a branch of the pulmonary artery
81
Explain how pulmonary artery catheters can be used to measure the pressure of the left atrium:
- They have a balloon on the end that can be inflated to “wedge” the catheter in a branch of the pulmonary artery
- The pressure distal to the wedged balloon can be measured
- This gives the pulmonary artery wedge pressure, which gives an indication of the pressures in the left atrium
82
What is a portacath?
- A type of central venous catheter
- There is a small chamber (port) under the skin at the top of the chest that is used to access the device
- This chamber is connected to a catheter that travels through the subcutaneous tissue and into the subclavian vein, with a tip that sits in the superior vena cava or right atrium
83
State 1 benefit of a portacath:
- They are fully internalised under the skin, reducing the chance of infection, meaning they last the longest of the options for central venous access
84
Define pain:
- An unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or potential tissue damage
85
State and explain the 2 categories of pain:
- Acute pain: new onset of pain
- Chronic pain: pain present for 3 months or more
86
State and explain the 2 aspects to the experience of pain:
- Sensory: the sensory signal transmitted from the pain receptor (“it is a sharp sensation, likely a needle”)
- Affective: the unpleasant emotional reaction to the pain (“it is excruciating, I can’t bear it”)
87
What is allodynia?
- When pain is experienced with sensory inputs that do not normally cause pain (e.g. light touch)
88
What are the 2 groups of nerve fibres that transmit pain?
- C fibres (unmyelinated and small diameter): transmit signals slowly and produce dull and diffuse pain sensations
- A-delta fibres (myelinated and larger diameter): transmit signals fast and produce sharp and localised pain sensations
89
What major ascending sensory pathway is responsible for carrying pain sensation?
- The spinothalamic tract
90
What is referred pain?
- Pain that is experienced in a location away from the site of tissue damage
91
What is neuropathic pain?
- Pain that is caused by abnormal functioning or damage of the sensory nerves, resulting in pain signals being transmitted to the brain
92
State 2 methods by which pain can be measured:
- The visual analogue scale (VAS): involves asking the patient to rate their pain along a horizontal line
- The numerical rating scale (NRS): involves asking the patient to rate their pain on a numerical scale of 0 to 10
93
What are the 3 steps of the World Health Organisation (WHO) analgesic ladder?
- Step 1: non-opioid medications such as paracetamol and NSAIDs
- Step 2: weak opioids such as codeine and tramadol (tramadol has multiple mechanisms of action, including being an SNRI and agonist of opioid receptors)
- Step 3: strong opioids such as morphine, oxycodone, fentanyl and buprenorphine
94
State 4 side effects of NSAIDs:
- Stomach ulcers
- Exacerbation of asthma
- Hypertension
- Renal impairment
95
State 4 side effects of opioids:
- Constipation
- Pruritus
- Altered mental state
- Respiratory depression
96
What drug is used to reverse the effects of opioids in a life-threatening overdose?
- Naloxone
97
10mg of oral morphine is equivalent to how much: oral codeine, oral tramadol, oral oxycodone, IV morphine and IV diamorphine?
- 100mg oral codeine
- 100mg oral tramadol
- 6.6mg oral oxycodone
- 5mg IV morphine
- 3mg IV diamorphine
98
What is the difference between a level 1, level 2 and a level 3 patient?
- Level 1 patients can be managed on a general acute ward
- Level 2 patients can be managed on the high dependency unit
- Level 3 patients can be managed on the intensive care unit
99
Why is total parenteral nutrition (TPN) normally given through a central line rather than a peripheral cannula?
- TPN is very irritant to veins and can cause thrombophlebitis
100
Explain how ICU admission could cause ventilator-associated lung injury:
- A complication of mechanical ventilation
- Forcefully blowing air into the lungs can cause volutrauma (damage from over-inflating the alveoli), barotrauma (damage from pressure changes) and inflammation
- Long-term, it can lead to lung fibrosis
101
Explain how ICU admission could cause ventilator-associated pneumonia:
- A complication of mechanical ventilation
- Being ventilated increases the risk of bacteria being aspirated into the lungs
102
State 2 ways to reduce the risk of ventilator associated pneumonia:
- Positioning the bed at a 30-degree angle with the patient’s head elevated reduces the risk of aspirating secretions from the stomach
- Good oral care with regular mouth cleaning
103
State 2 ways to reduce the risk of catheter-related bloodstream infections:
- By using antibiotic-impregnated or silver-impregnated catheters
- Keeping them in for the shortest time possible
104
What is stress-related mucosal disease?
- Common in critically unwell patients
- Damage to the stomach mucosa occurs mainly due to impaired blood flow
- It increases the risk of upper gastrointestinal bleeding, which can be life-threatening
105
State 2 ways to reduce the risk of stress-related mucosal disease:
- By suppressing acid secretion in the stomach using proton pump inhibitors (e.g. omeprazole) or H2 receptor antagonists
- Starting NG feeding early in patients that cannot eat normally
106
State 1 medication used in the intensive care unit to sedate agitated patients:
- Dexmedetomidine
107
State 2 ways to reduce the risk of VTE in ICU:
- Low molecular weight heparin (e.g. enoxaparin)
- Intermittent pneumatic compression devices (e.g. flowtrons) that regularly inflate to squeeze the legs, promoting blood flow
108
What is critical illness myopathy?
- Muscle wasting and weakness during critical illness and treatment in the ICU
- Short-term, it can lead to difficulty weaning off mechanical ventilation
- Long-term, it can result in reduced exercise capacity and quality of life
109
What is critical illness polyneuropathy?
- Degeneration of the sensory and motor nerve axons during critical illness and treatment in the ICU
110
State 1 way to reduce the risk of critical illness polyneuropathy:
- Having optimal glycaemic control
111
State 2 pathologies that commonly cause a respiratory alkalosis:
- Hyperventilation syndrome (e.g. due to anxiety, high PaO2)
- Pulmonary embolism (low PaO2)
112
State 4 electrolyte imbalances that may contribute to metabolic acidosis:
- Raised lactate – lactate is released during anaerobic respiration (indicating tissue hypoxia)
- Raised ketones – typically in diabetic ketoacidosis
- Increased hydrogen ions – due to renal failure, type 1 renal tubular acidosis or rhabdomyolysis
- Reduced bicarbonate – due to diarrhoea (stools contain bicarbonate), renal failure or type 2 renal tubular acidosis
113
Low PaO2 indicates hypoxia and respiratory failure. What would high CO2 and low CO2 indicate?
- Normal pCO2 with low PaO2 indicates type 1 respiratory failure
- Raised pCO2 with low PaO2 indicates type 2 respiratory failure
114
