Anaesthetics Flashcards
1
Q
What is the triad of anaesthesia?
A
Hypnosis
Analgesia
Relaxation
2
Q
In relation to the triad of anaesthesia, what do opiates do?
A
Hypnosis and analgesia
3
Q
In relation to the triad of anaesthesia, what do GAs do?
A
Hypnosis, analgesia (little except ketamine) and relaxation
4
Q
In relation to the triad of anaesthesia, what do LAs do?
A
Analgesia and muscle relaxation
5
Q
In relation to the triad of anaesthesia, what do muscle relaxants do?
A
Relaxation
6
Q
Why is balanced anaesthesia required?
A
Increased control over individual components of triad and helps avoid overdosage
7
Q
What are disadvantages of balanced anaesthesia?
A
Polypharmacy
Increased ADRs
Airway control needed
8
Q
How can GAs be administered?
A
Inhaled or IV
9
Q
How do GAs work?
A
Open Cl- channels -> hyperpolarise (less likely to fire) or suppress excitatory synaptic activity
10
Q
How do inhaled GAs work?
A
Halogenated hydrocarbons that dissolve in membranes
Slow
Flexible maintenance
11
Q
Discus the arterial and alveolar partial pressures of inhaled GAs.
A
Equal to each other
12
Q
What is the MAC?
A
Minimum alveolar concentration
- measures potency of drug
- if low MAC then increased potency
13
Q
How do you stop inhaled GAs?
A
stop agent, give gas, reduce alveolar concentration and then blood and then brain, consciousness will then return
14
Q
Discuss uptake and excretion of inhaled GA.
A
Uptake and excretion both by lungs
lungs > blood > brain
15
Q
How does IV GA work?
A
allosteric binding to GABA receptors
rapid onset and recovery
16
Q
What are spared under GA?
A
Reflexes and some autonomic functions
17
Q
What is vital to consider when using GA?
A
ABC Resuscitation
Airway management
18
Q
How is IV GA redistributed around body?
A
Blood > viscera > muscle > fat (slowed uptake but larger stores therefore lipid soluble drugs important)
19
Q
What is TCI?
A
Targeted controlled infusion pump used to achieve accurate infusions of blood or brain concentrations
20
Q
What is the most common sequence of administration of GA?
A
IV induction then inhalation maintenance
nb: alternative IV maintenance with propofol or remifentanyl
21
Q
What is the most common drug used for IV induction?
A
Propofol
others e.g thiopentone
22
Q
How fast is IV induction?
A
Rapid - one “arm-brain” circulation approx 20s
23
Q
Give an example of a drug used for gas induction.
A
Devoflurane (halothane)
24
Q
What are planes of anaesthesia?
A
Analgesia/sedation
Excitation
Anaesthesia (light –> deep)
Overdose
25
What type of GA induction is slower with more obvious "planes" of anaesthesia?
Inhaled
26
What is needed during induction of anaesthesia?
Quietness
Administer Gas or IV agent
Careful monitoring of conscious level
Airway maintenance
27
How do you monitor consciousness?
```
Loss of verbal contact
Movement
Respiratory pattern (can sometime hyperventilate first)
Processed EEG
"Planes" of anaesthesia
```
28
What is the triple airway manoeuvre?
Head tilt/chin lift/jaw thrust
29
Why is the triple airway manoeuvre always required in GA?
Airway maintenance since loss of muscle tone and tongue rests on pharyngeal wall
30
What simple apparatus is used after the triple airway manoeuvre?
Face mask
Oropharyngeal (guedel) airway
NPA
31
What happens when you insert a guedel into a "light" patient?
Vomiting or larngospasm
32
What does an LMA do?
Maintains but doesn't protect airway
33
What does an I-gel not protect from?
Aspiration
34
What are causes of airway obstruction?
Ineffective triple airway manoeuvre
Airway device apposition or kinking
Laryngospasm
35
What is laryngospasm?
Reflex adduction of vocal cords in semi-conscious state
36
What is the management of larnygospasm?
Avoidance
| Timing of extubation and airway manoeuvre
37
Why can aspiration occur?
Loss of protective airway reflexes e.g gag swallow
Foreign material in lower airway e.g gastric contents, blood, surgical debris
38
Compare airway maintenance and airway protection.
Maintained if opened and unobstructed
Protected only when conscious and in charge of own reflexes or if cuffed tube below vocal cords.
39
What is endotracheal intubation?
Placement of a cuffed tube in trachea
Oral route most common
Laryngeal reflexes must be abolished
Can be carried out in awake patient using LA and fibre-optic scope
40
Why intubate?
Protect airway from gastric contents
Need for muscle relaxant e.g laparotomy
Shared airway with risk of blood contamination
Need for tight control of blood gases esp CO2 levels in neurosurgery
Restricted airway access e.g maxfax
41
What are risks to the unconscious patient?
```
Airways
Temperature
Loss of other protective reflexes e.g corneal, joint position
VTE
Consent and identification
Pressure areas
```
42
What are potential positions of a patient under GA?
```
Supine
Lithotomy
Prone
Lying on side
Sitting
```
43
What is the basic "minimum" monitoring during anaesthesia?
```
SpO2
ECG
NIBP
FiO2
ETCO2
```
44
What a potential complications with anaesthesia?
Airway, Breathing, Circulation, Related to technique or position, awareness
45
What are risk factors of awareness while under GA?
```
GA C-section
Major trauma
Cardiac surgery
Chronic CNS depressant use
Previous episode of awareness
Paralysed and ventilated
```
46
What are the steps for awakening?
```
Reverse muscle relaxant
Anaesthetic agents off
Resume spontaneous respiration
Return of airway reflexes
Extubation
```
47
What else is controlled post-op?
Pain
Airway
N&V
48
What is critical care?
Initial assessment and management of respiratory failure and CVS failure or neurological failure
and fluid management
49
Describe the two types of respiratory failure.
1 - oxygenation failure
2 - oxygenation and ventilation failure
50
What type of respiratory failure is a high flow nasal cannula used for?
Type 1
Can be given in HDU
51
What type of respiratory failure is NIV given to?
Type 2 respiratory failure
52
What is shock?
Acute circulatory failure with inadequate or inappropriately distributed tissue perfusion resulting in cellular hypoxia
53
Name types of shock
```
Distributive (Septic)
Hypovolaemic
Anaphylactic
Neurogenic
Cardiogenic
```
54
What does SV equal?
Preload/contractility/afterload
55
What is given for cardiovascular failure?
- Vasopressors - metaraminol, noradrenaline
| - Inotropes - adrenaline, dobutamine
56
How do we measure cardiovascular failure?
Arterial line or central line
57
What are benefits of a central line in critical care?
stay in for a week and allow administration of strong meds e.g noradrenaline
58
What are central lines not useful for?
Fluid resuscitation
59
What are vasopressors used for?
Alpha Cause vasoconstriction
| if enough fluid in vascular tree but not in correct place
60
What are inotropes?
Given if pump failure and cardiogenic shock to improve contractility of heart.
61
What is a colloid?
A fluid with large molecules in it
62
What is a crystalloid?
A fluid with small molecules e.g sodium chloride, plasmalite
63
How much fluid should be given?
30ml/kg is sensible limit
64
What are causes of neurological failure?
Metabolic
Trauma
Infection
Stroke
65
What is the physiological impact on the CVS of anaesthetics?
Depress CVS centre
| - decrease sympathetic outflow, -ve inotropic/chronotropic effect on heart, increased vasodilation
66
What does the negative inotropic effect of anaesthetics have on CO?
Reduces CO
67
What does increased venodilation from anaesthetics do to the CVS?
Reduced venous return and CO
68
What anaesthetic does not depress the CVS and respiratory system?
Ketamine
69
What does MAP equal?
CO x SVR
70
What do anaesthetics do to the respiratory system?
Reduce hypoxic and hypercapnia drive
Reduced TV
Increased RR
Decreased FRC (VQ mismatch, reduced lung volumes)
71
What happens to the respiratory system with opiates?
Preserves TV but reduced RR
72
What are indications for muscle relaxants?
Ventilation and intubation
Immobility essential
Body cavity surgery e.g laparotomy
73
What are problems from muscle relaxants?
Awareness
Incomplete reversal
Apnoea
74
Why is intraoperative analgesia given?
Prevent arousal
Opiates contribute to hypnotic effect of GA
Suppress reflex response
75
Give examples of local anaesthetics.
Lignocaine
Bupivicaine
Ropivacaine
76
What type of anaesthetic does not cause hypnosis and patient retains consciousness/awareness?
Local anaesthetic
77
How do local anaesthetics work?
Block Na+ channels (prevent AP firing)
78
What system is not usually affected by local anaesthetic?
Respiratory
79
Name a risk of local anaesthetic use.
Local anaesthetic toxicity.
80
What is TIVA?
Total Intravenous Anaesthesia
- General anaesthesia using a combination of agents given solely by the intravenous route and in the absence of all inhalation agents
81
Why is pre-op assessment important?
Trauma associated with surgery --> stress response, fluid shifts, blood loss, CVS, Resp and metabolic stress
82
What are important considerations in pre-op assessments?
- Known co-morbidities
- Unknown pathologies
- Nature of surgery
- Anaesthetic techniques
- Post-op care
83
What is the role of the anaesthetics pre-op?
```
Assess
Identify high risk
Optimise
Minimise risk
Inform and support patient decisions
Consent
```
84
What are the levels of post-op care?
1 - monitor every 1/2 hours on ward
2 - HDU suppor
3 - still ventilated, ICU support
85
Why is pre-op assessment important?
Reduces anxiety, delays, complications, length of stay, mortality
86
When can you do a pre-op assesment?
Elective planned surgery (primary care, pre-assessment clinic), urgent surgery, emergency surgery
87
What is involved in a pre-op assessment?
Hx
Ex
Ix
88
What is important in a pre-op history?
- Severity and control of known co-morbidities (especially heart and lung function)
- Systematic enquiry of unknown co-morbidities
- Ability to withstand stress
- Drugs/allergies
- Previous surgery/anaesthesia
- Potential problems e.g obesity, reflux, airway, malignant hyperpyrexia
89
What do the NICE guidelines suggest for pre-op assessment?
ASA grade
Surgery grade
Co-morbidities
90
What Ix could be carried out pre-op?
LINK WITH CO-MORBIDITIES:
CVS: ECG, exercise intolerance, echo, stress echo, cardiac catheterisation, CT coronary angiogram
Resp: Sats, ABG, CXR, Peak flow, FVC/FEC, CXR, Gas transfer, CT chest
91
Describe the ASA grading score.
1: healthy
2: mild to moderate systemic disturbance
3: severe systemic disturbance
4: Life threatening
5: Moribund patient
6: Organ retrieval
92
Is ASA useful?
Not all the time, e.g patient with MS would be ASA 3 but could be a Paralympian
93
What scores can be used pre-op?
Cardiac risk index
Exercise tolerance - METS
Surgical outcomes risk tool (SORT)
94
What are the 6 factors considered in a cardiac risk index?
```
High risk surgery
IHD
CHF
Cerebrovascular disease
DM
Renal failure
```
95
What lifestyle factors are considered pre-op?
Smoking, alcohol, cannabis, obesity, exercise
96
What is pre-habilitation?
Encouraged by anaesthetists pre-op - prescribed exercise
| --> improved outcomes
97
What medications would you continue pre-op?
```
anti-diabetics
anticoagulants
Inhalers
Anti-anginals
Anti-epileptics
```
Inhalers
Anti-anginals
Anti-epileptics
98
What are benefits of treating pain?
Physical
Psychological
For family
For society (lower health costs)
99
How is pain classified?
Duration (Acute, chronic or acute on chronic), cause (cancer or non-cancer), mechanism (nociceptive or neuropathic)
100
What is nociceptive pain?
Obvious tissue injury or illness
Described as sharp or dull and is well localised
101
What is neuropathic pain?
Nervous system damage or abnormality
Tissue injury may not be obvious
No protective function
102
How is neuropathic pain described?
Burning, shooting +/- numbness, pins and needles
103
What causes cardiovascular response to pain?
Brainstem
104
What is the first and second relay system of pain?
```
1st = dorsal horn
2nd = thalamus
```
105
Give examples of neuropathic pain.
Nerve trauma
Diabetic pain
Fibromyalgia
106
How do you treat neuropathic pain?
Hard to treat, patients have to live with a certain degree of pain
107
What are the pathological mechanisms of neuropathic pain?
Increased receptor numbers
Abnormal sensitisation of central and peripheral nerves
Chemical changes in dorsal horn
Loss of normal inhibitory modulation
108
What are simple analgesics?
Paracetamol
| NSAIDS
109
Name mild and strong opioids.
Mild = codeine
Strong = morphine, fentanyl
110
What is tramadol?
analgesic - mixed opiate and 5HT/NA reuptake inhibitor
111
What is ketamine?
Analgesic NMDA receptor antagonist
112
What types of analgesias work at the periphery?
NSAIDS
Local anaesthetics
Non drugs - RICE
113
What analgesia works at spinal cord level?
Non drug: Acupuncture, massage, TENS
LAs
Opioids
Ketamine
114
What analgesia works at the brain level?
Non-drug: psychological
Drug treatments: paracetamol, opioids, amitriptyline, clonidine
115
What is a disadvantage of paracetamol?
Liver damage in overdose
116
What routes can paracetamol be given?
Orally, rectally or IV
117
What is the best treatment option for nociceptive pain?
NSAIDs given with paracetamol (synergism)
118
What are potential side effects of NSAIDS?
GI and renal SEs and bronchospasm in sensitive asthmatics
119
What should you do when giving paracetamol IV?
Reduce dose, especially for under 50kg patients (can cause liver failure)
120
What are disadvantages of tramadol?
Nausea and vomiting
121
What are advantages of tramadol?
Less respiratory depression
| Can be used with opioids and simple analgesics
122
What is morphine good for?
Mild-severe acute nociceptive pain (e.g post-op pain)
| Chronic cancer pain
123
How can morphine be given?
IV, IM, SC
124
What are disadvantages of morphine?
Constipation
Respiratory depression in high dose
Misunderstanding about addiction
125
Compare the oral dose of morphine with IV/IM/SC dose.
Oral dose = 2/3x IV/IM/SC dose
126
How does amitriptyline work?
Modulate pain, increase noradrenaline in spinal cord
127
What are advantages of amitriptyline?
Good for neuropathic pain
| Treats depression and poor sleep
128
What are disadvantages of amitriptyline?
Anti-cholinergic side effects e.g glaucoma and urinary retention
129
What are anticonvulsants such as carbamazepine useful for with regards to pain?
Reduce abnormal firing of nerves
--> good for neuropathic pain
130
How do you work out what drugs to give for nociceptive pain?
WHO Pain ladder
131
How do you work out what drugs to give for neuropathic pain?
use alternative alagesics and/or psychological and non drug treatments. Not WHO pain ladder
132
What is the RAT model for management of pain?
Recognise (ask patient or family etc, look)
Assess (Severity, type, other factors)
Treat (drugs, non drugs)
133
How do you assess pain?
```
Verbal rating score
Numerical rating score
Smiling faces
Visual analogue scale
Abbey pain scale (if confused)
```
134
What should you consider when assessing pain?
Pain score at rest and with movement
How does pain affect patient?
Type? Acute, chronic, cancer/non-cancer, nociceptive, neuropathic
Other factors e.g physical, psychological, social
135
What are non-drug treatments for pain?
```
RICE
Nursing care
Surgery
Acupuncture
Massage
TENS
Psychological
```
136
What are drug treatments for nociceptive pain based on pain ladder?
Mild --> paracetamol (+/- NSAIDS)
Moderate --> ) + codeine/alternative
Severe --> + morphine
137
What should you do as nociceptive pain resolves ?
Move down WHO pain ladder
138
As pain ladder isn't usually used for neuropathic pain. What drugs could you prescribe?
Amitriptyline
Gabapentin
Duloxetine
