Anaesthetics Flashcards
(153 cards)
1
Q
What do general anaesthetics do?
A
Produce insensibility in the whole body usually causing unconsciousness
Centrally acting drugs (analgesics/hypnotics)
2
Q
What do regional anaesthetics do?
A
Produce insensitivity in an area or region of the body
E.g. blocking central/peripheral nerves
3
Q
What do local anaesthetics do?
A
Produce insensibility in only the relevant part of the body
4
Q
What is the triad of anaesthesia?
A
Hypnosis
Analgesia
Relaxation
5
Q
Hypnosis
A
Sleepiness/unconsciousness
6
Q
Analgesia
A
Lack of pain
7
Q
Relaxation
A
Of skeletal muscle specifically
8
Q
What agents cause hypnosis?
A
GA
Opiates can cause a little bit
9
Q
What agents cause analgesia?
A
Opiates
10
Q
What agents cause relaxation?
A
Muscle relaxants
GA a little too
11
Q
Do you need to give analgesia even if the patient is unconscious?
A
Yes to prevent reflex autonomic responses to painful stimuli
12
Q
What is involved in balanced anaesthesia?
A
Different drugs do different jobs Titrate doses separately Avoid OD (can use lesser doses when using diff drugs for diff things)
13
Q
What are the problems with modern day anaesthetics?
A
Polypharmacy (DDIs/allergies)
Muscle relaxation - req. artificial ventilation and airway control
Separation of relaxation and hypnosis - awareness
14
Q
What is awareness?
A
Paralysis of someone with muscle relaxants but they are still awake
15
Q
How to GA work?
A
Interfere with neuronal ion channels
Open chloride channels –> hyperpolarise –> less likely to fire –> less action at synpases
(reversible)
16
Q
How do inhalational GA work?
A
Dissolve in membranes
Confirmation of chloride channel changes so it opens
17
Q
How do IV GA work?
A
Allosteric binding (binding to receptors at a place other than their active site)
18
Q
How does Propofol work?
A
Binds to and agnosises GABA receptors
GABA receptors are chloride channels that hyperpolarise neurons and function as inhibitory CNS receptors
19
Q
How is cerebral function lost with GA?
A
From top down - complex processes first, with relative sparing of primitive functions (reflexes/ANS)
Can still do reflexes on GA patient!
Loss of consciousness first, then hearing
20
Q
Why are reflexes spared in GA?
A
They are primitive and have a small no. of synapses
21
Q
What things must you do if you are giving GA?
A
Airway req.
Temp control
Avoid pressure sores
Keep them comfortable
22
Q
How quickly do IV anaesthetics work?
A
Rapidly - v. fat soluble - cross BBB
1 arm brain time (brain so well perfused)
ALSO clears quickly! - mainly due to drug leaving circulatory compartment and into vessel rich tissues, then skeletal muscle so conc. in blood falsl quickly)
After while goes into fat (fat poorly perfused so takes while to accumulate there)
Goes back into blood, metabolised by liver
23
Q
Giving IV anaesthetics requires…
A
Constant infusion
Target controlled infusion pump allows for v accurate infusion to achieve specific blood/brain concs.
24
Q
What are the inhaled anaesthetics?
A
Halogenated hydrocarbons
Breathed in and out of lungs
25
How do inhaled anaesthetics get to the brain?
Conc. gradients - lungs > blood > brain
| Cross alveolar BM easily
26
MAC
Minimal alveolar concentration (conc of drug in alveoli which is req. to produce anaesthesia)
Measure of potency
Low no = high potency
27
Inhalational anaesthetics
Induction slow
| Are used to extend/continue anaesthesia
28
How are the effects of inhalational anaesthetics reversed?
Washout - reversal in concentration gradient --> fall in alveolar concentration, followed by blood, brain and then consciousness returns
29
Most people have ____ induction and _____ maintenanc
IV
Inhalation
Rapid onset of IV induction, flexibility and more control with inhalation
30
What are the CVS effects of GA?
Central - depression of CNS, CV centres & nuclei --> reduced SNS ouflow, negative inotrophic/chronotrophic effect on heart (dec. HR), reduced vasomotor tone --> vasodilation
Direct - anaesthesia on vascular smooth muscle & myocardium - negatively inotropic, vasodilation --> decreased peripheral resistance, venodilation --> reduced venous return, decreased CO
31
MAP = ?
CO x SVR
32
What are the respiratory effects of GA?
Resp depression
Reduce hypoxic and hypercarbic drive via depression of brainstem resp centres --> decreased TV and increased rate
Paralysis of cilia
Decreased FRC - lower lung volumes --> VQ mismatch
May req. O2 post op
33
When are muscle relaxants indicated?
```
When ventilation and intubation req.
Immobility essential (e.g. microscopic surgery, neurosurgery, body cavity surgery
```
34
What are the problems with muscle relaxants?
Awareness
Incomplete reversal - airway obstruction/ventilatory insufficiency in immediate post-op period
Apnoea - dependence on airway and ventilatory support
35
Why do you give intraoperative analgesia?
Prevention of arousal
Opiates contribute to hypnotic effect
Suppression of reflex responses to painful stimuli - tachycardia, HTN --> more bleeding in an op
36
In regional/local anaesthesia - derangement of CVS physiology is proportional to what?
Size of anaesthetised area
There is relative sparing of aresp function
37
How do regional anaesthetics usually provide muscle relaxation?
Blocking motor nerves so spinal or epidural anaesthesia may not req. muscle relaxants
38
What is the limiting factor in the use of local anaesthetics?
Toxicity (high plasma levels, e.g. absorption > rate of metabolism)
39
What does toxicity of LA depend on?
Dose used
Rate of absorption (site dependent)
Patient wt
Drugs (bupivacaine > lignocaine > prilocaine)
40
What are the ssx of LA toxicity?
Circumoral/inguinal numbness/tingling, light headedness, tinnitus, visual disturbances, muscular twitching, drowsiness, CV depression, convulsions, coma, cardiorespiratory arrest
41
LA: differential blockage
Diff penetration into diff nerve types
Myelinated, thick fibres relatively spared --> motor fibres relatively spared, pain fibres blocked easily --> anaesthesia without paralysis
42
What are the CVS effects of RA?
All due to symphathectomy due to LA blockage of mixed spinal nerves --> veno and vasodilation
43
Give e.g.s of RA
Field blocks, e.g. hernia repair
Plexus block
Limb blocks, e.g. femoral/sciatic
Central neural block, e.g. epidural, spinal
44
What is the physiology of a neuroaxial block?
Inspiratory function spared (insp muscles served by higher roots)
Expiratory function impaired (cough dependent on abdo muscle function)
Decreased FRC
Increased VQ mismatch
45
Conduct of GA
```
Pre-op assessment
Preparation
Induction
Maintenance
Emergence
Recovery
Post-op care and pain manage
```
46
What is involved in preparation?
```
Planning
Right patient, side, operation
Pre-meds (analgesia e.g.)
Right equipment, personnel
Drugs drawn up
IV access
Monitoring
```
47
What is involved in induction?
Gas/IV
Monitor consciousness
Airway maintenance
48
What drugs are used for IV induction?
Propofol (most used), thiopentone (barbiturate), others
May also give benzodiazepine, muscle relaxants, analgesia
49
What drugs are used in gas induction?
Halothane
More common in kids/IVDA where venous access difficult
50
What are the planes of anaesthesia?
Analgesia/sedation - light headed, giggly, eyes may close
Excitation (disinhibited)
Anaesthesia (deep --> light)
Overdose (too deep, serious cardio and resp depression)
51
How do you monitor conscious level?
```
Loss of verbal contact
Movement
Resp pattern
Processed EEG
Stage/plane
```
52
What is involved in airway management in anaesthesia?
Tongue normally held by tone --> anaesthesia --> falls back and obstructs airway
HEAD TILT/CHIN LIFT/JAW THRUST
Simple apparatus - face mask, oropharyngeal (Guedel) airway, nasopharyngeal airway
53
Anaesthetic face mask
Gas tight seal
54
Oropharyngeal airway
Rigid plastic
ONLY when unconscious
In light plane insertion may --> vomiting, laryngospasms
55
Laryngeal mask airway
Cuffed tube with mask sitting over glotting
| Maintains but does not protect airway
56
What is the standard airway device kept on the red trolley?
I-gel
2nd gen LMA
57
What are airway complications in GA use?
Obstruction - ineffective triple airway manoeuvre most common cause, airway device/kinking/laryngospasm
Aspiration - loss of protective airway reflexes, foreign material in lower airway (blood, gastric contents, surgical debris)
58
Distinguish between airway maintenance and airway protection
Maintenance - open and patent
Protection - cuff tube in trachea protects airway from contamination
59
What is the only protected airway maintenance?
Endotracheal intubation
Laryngeal reflexes must be abolished
Laryngoscope, muscle relaxant, sniffing the morning air position
Or LA, fibre optic scope
60
Why intubate?
Protect from gastric contents in non-fasted patient
Need for muscle relaxant & artificial ventilation
Shared airway with risk of contamination, e.g. tonsillectomy
Need for tight control of BG (e.g. CO2 levels in neurosurgery)
Restricted access to airway, e.g. MaxFax
61
What are risks to an unconscious patient?
```
Airway
Temperature
Loss of other protective reflexes
VTE risk
Consent and identification
Pressure areas
```
62
What are the different positions patients can be in?
```
Supine
Lithotomy
Prone
Lying on side
Sitting
```
63
What is involving in continuing anaesthesia?
```
Care of unconscious person
Analgesia, muscle relaxants
Fluid management
Monitoring and physiological support
Documentation
Maintenance (IV/inhalation/both)
Self/artificial ventilation
Analgesia
Gas supply from anaesthetic machine
```
64
What is involving in monitoring when someone is under anaesthesia?
Basic minimum - SpO2, CG, NIBP, FiO2, ETCO2
Respiratory parameters
Agent monitoring
Temp, UO, NMJ with nerve stimulator
Invasive venous/arterial monitoring to measure pressure
Processed EEG
Ventilator disconnect alarm
65
What are the anaesthetic complications?
```
Airway
Breathing
Circulation
Related to technique/position
Awareness
```
66
How common is awareness?
1 in 42, 000
67
What are risk factors for awareness?
Paralysed and ventilated, prev. episode of awareness, chronic CNS depressant use, cardiac surgery, major trauma, GA C-section
68
What happens in emergence?
```
Muscle relaxant reversed
Anaesthetics ware of
Resumption of spontaneous respiration
Return of airway reflexes/control
Extubation (if removed prematurely risk of laryngospasm)
```
Can be v. quick of slow (depends on dose, inter-individual variation)
Worry if prolonged emergence
69
What is involved in recovery?
May have not regained consciousness/airway control
ABC problems
Pain control
Post op NV
70
What are your Na requirements?
1-2mmol/kg/day
71
What are your K requirements?
0.5-1mmol/kg/day
72
What are your fluid req.?
25-30ml/kg/day
73
What are your glucose req.?
50-100g/kg/day
74
What are the levels of critical care?
```
Levels of care:
0 - primary care
1 - ward care
2 - HDU
3 - ITU
```
HDU = single organ support
ITU = multi-organ support
Both of these are critical care
75
Under what circumstance with single organ failure would you come to ITU?
If you req. invasive ventilation
76
What is your plan with a compromised airway?
Head tilt, chin lift, jaw thrust
Oropharyngeal airway
Then get anaesthetics to intubate
77
Distinguish between type 1 and type 2 respiratory failure
type 1 - one problem, low O2 in the blood
Type 2 - 2 problems - low O2 high CO2
Because CO2 passes out the blood easily type 1 most common
78
What is your approach to tachypnoea/respiratory distress?
Blood gas to see if hypercapnic
If issue with oxygenation - high flow nasal cannula, CPAP, intubation and invasive ventilation, ECMO
If problem also involves CO2 removal then invasive ventilation tends to be req.
79
CO = ?
HR x SV
80
SV = ?
Preload/contractility/afterload
81
What do vasopressors do?
Increase afterload
82
What do inotropes do?
Drive contractility
83
What do chronotropes do?
Speed up HR
84
What do beta blockers do?
Slow HR
85
How much fluids should you give in sepsis?
30ml/kg before switching to vasopressors
86
What kind of drugs are vasopressors?
Alpha-1-agnosts
They constrict BVs
Mostly veins
87
What kind of drugs are inotropes?
Beta-1-agonists --> improved contractility
88
How can you measure the result of giving vasopressors/intropes etc. to improve circulation?
Better BP
UO - kidneys better perfused
Conscious level - brain perfused
Lactate reduced - less hypoperfusion
89
What level of lactate is abnormal?
>2
90
What is involved in disability of ABCD?
Look at all the other organs, e.g. dialysis, TPN,
91
GCS below what = intubation?
8
92
GENERAL ANAESTHESIA
Drug induced reversible coma
CNS, cardiac and respiratory depression
DDIs
93
REGIONAL ANAESTHESIA
Profound sympathectomy - obliterating BP and normal mechanisms to control BP
Neurological sequalae
94
What is involved in pre-op care?
```
Assess
High risk mortality/morbidity?
Minimise risk
Inform and support patient decisions
Consent
```
95
Why is pre-op care important?
Reduces anxiety, delays, cancellations, complications, mortality, length of stay
Identifies comorbs, limitations, red flags
96
When is pre-op care done?
Elective: GP, pre-assessment clinic
Urgent less time
Emergency less time but must identify risks still
97
What is done in pre-op assessment?
Hx - co-morbs, systemic enq for unknown comorbs, clinical Ex, ability to withstand stress (ETT, reasons for limitation, CR dx), DA, prev surgery/anaesthesia, potential issues - airway, spine, reflux, obesity, malignant hyperpyrexia, cholinesterase deficiency
Ix
98
What is involved in Ix in pre-op assessment?
Detect unknown conditions, diagnose suspected conditions, severity of known disease, getting a baseline, assessing risk etc.
99
What cardio Ix might you do in pre-op care?
ECG, ETT, echo, myocardial perfusion scans, stress echo, cardiac catheterisation, CTCA
100
What resp Ix might you do in pre-op assessment?
Sats, ABG, CXR, peak flow measurements, FVC, FEV, gas transfer, CT chest
101
What is ASA grading?
```
ASA 1 - otherwise healthy patient
ASA 2 - mild to moderate systemic disturbance
ASA 3 - severe systemic disturbance
ASA 4 - life-threatening dx
ASA 5 - moribund patient
ASA - organ retrieval
```
102
What is cardiac risk index?
Estimates likelihood of perioperative cardiac events
```
1 point for each of:
High risk surgery
Ischaemic heart dx
Congestive heart failure
CV dx
Diabetes
Renal failure
```
0/1 point = 0.4-0.9&
2 points = 6 points
3+ = 11%
103
What are the ETT METs?
Can you do the following without getting breathless:
walk around house - 2 METs
do light housework - 3 METs
walk 100-200m on flat - 4 METs
Climb a flight of stairs/walk uphill - 5 METs
Walk on flat at brisk pace - 6 METs
Play golf, mountain walk, dance/other exercise - 7 METs
Run a short distance - 8 METs
Do strenuous exercise/heavy physical work - 9 METs
5 or more - likely to have better outcomes than if less than 5
104
What does cardiopulmonary exercise testing measure?
Expired/inspired O2 (strength and capacity of lungs), ECG, BP before, during and after exercise
Can predict outcomes of durgery
105
What things do we want to optimise pre-operatively?
HTN, IHD, HF, asthma, COPD, DM, epilepsy
106
What is poor diabetic control assoc with post-operatively?
Inc. risk of infections, cardiac and resp complications
107
What lifestyle factors do you want to address in your pre-op assessment?
Smoking - less post-op resp complications if they stop
Alcohol - reduce and reduce risk of infection and septic shock
Obesity
Exercise - better outcomes
108
High risk emergency patient pre-op care
Informed consent
Anaesthetic plan
Invasive monitoring more likely to be req.
109
Pre-op medication
Continue as normal for most (esp inhalers, anti-anginals/epileptics)
Exceptions: oral hypoglycaemics, anticoagulants
110
Define pain
Unpleasant sensory and emotional experience assoc with actual/potential tissue damaged
111
How common is persistent pain?
1 in 4
Assoc. w v. poor QoL
112
What is the most common cause of pain?
Lower back pain
113
What are the benefits of treating pain for the patient?
Physical - improved sleep, better appetite, less medical complications (e.g. heart attack)
Psychological - less suffering, less depression/anxiety
114
What are the benefits of treating pain for the family of the patient?
Improved functioning as family member
| Able to keep working
115
What are the benefits of treating pain for society?
Lower health costs
| Able to contribute to community
116
How is pain classified?
Duration - acute, chronic (>3m, after normal healing), acute on chronic
Cause - cancer/non-caner
Mechanism - nociceptive/neuropathic/mix
117
What is nociceptive pain?
Pain due to damage to nociceptive afferents in tissue/skin
Obvious tissue damage
Aka physiological/inflammatory pain serves a protective function
Rx with WHO pain ladder
118
What is neuropathic pain?
May not see obvious tissue damage
No protective function
Abnormality of nervous system (e.g. slipped disc)
119
What is the character of nociceptive pain?
```
Sharp +/- dull
Well localised (ab pain may be less localised if visceral)
```
120
What is the character of neuropathic pain?
Burning, shooting +/- numbness, pins, needles
| Not well localised
121
Physiology of pain
PERIPHERY - tissue injury, release of chemicals (prostaglandins, substance P --> pain) - accentuate pain pathway (amplifying the signal), inflammatory pathway worsens sensation of pain by release of chemical markers
Stimulation of pain receptors (nociceptors)
Signals travel in Adelta or C nerves to spinal cord
SPINAL CORD - first relay - Adelta/C nerve synapses with second nerve which travels up to spinal cord via spinothalamic tracts
BRAIN - thalamus is second delay station - connects to thalamus, limbic system, brainstem (inc. BP, tachycardia)
Pain perception in cortex
MODULATION - descending pathway from brain to dorsal horn, usually descreases pain signal
Genetic difference in modulation - some better at descending inhibition (less sore)
Done through NA/5HT reuptake
122
What is the gate theory of pain?
Noxious stimuli can be reduced by distractive stimuli (rubbing, massaging etc.) by Ab/a neurones creating a negative inhibition loop to switch off pain fibres
123
What fibres carry noxious stimuli?
Adelta
| C
124
What fibres carry normal sensation?
Aalpha
| Abeta
125
What is neuropathic pain due to?
Abnormal processing of a pain signal due to NS damage/dysfunction
e.g. diabetic neuropathy, nerve trauma, fibromyalgia, chronic tension headache, common after thoracic surgery/mastectomy as intercostal nerves damaged
126
What are the pathological mechanisms behind neuropathic pain?
Increased receptor numbers
Abnormal sensatisation of nerves (peripheral/central)
Things that do not normally cause pain (e.g. cold air) will
Damage to thalamic pathways after stroke --> chronic pain
Chemical changes in dorsal horn
Loss of inhibitory modulation, e.g. NA/5HT
127
What are the classification of drugs for pain?
Simple anaglesics (paracetamol/NSAIDs)
Opioids (mild - codeine, dihydrocodeine, strong - morphine, fentanyl)
Others
128
What are the adverse effects of NSAIDs?
Renal function, DDIs
129
What are the other analgesics?
Tramadol
Antidepressants (amitryptilline, duloxetine for neuropathic pain)
Anticonvulsants (gabapentin)
Ketamine (NMDA receptor antagonist - works centrally in spinal cord)
LAs
Topical agents, e.g. capsaicin
130
What are your Rx for pain working in the periphery?
RICE
NSAIDs
Local anaesthetics
131
How do LAs work?
Switch of adelta/C fibres
132
What are your Rx for pain working at the spinal cord?
Acupuncture, TENS, massage
LA
Opioids
Ketamine
133
What are your Rx or pain working in the brain?
Psychological/CBT
Pain management programmes
Paracetamol, opioids, amitryptilline, clonidine
134
Paracetamol - adv and disadv
Adv - cheap, safe, oral/rectal/IV administration
Good for mild pain or in combo with other drugs for more severe pain
Disadv - liver damage in OD
135
NSAIDs - advs and disadvs
Adv - cheap, generally safe, nociceptive pain (best given with paracetamol - synergism)
Disadv - GI/renal SEs, plus sensitive asthmatics
136
Give e.g.s of NSAIDs
Aspirin, ibuprofen, diclofenac
137
Codeine - advs and disadv
Adv - cheap, safe, mild-mod nociceptive pain (best given with paracetamol)
Disadv - constipation, nausea, not good for chronic pain
138
Tramadol - adv and disadv
Adv - less resp depression, can be used with opoids and single analgesics
Disadv - NV
139
How does tramadol work?
Weak opioid effect plus inhibitor of serotonin/NA reuptake (modulation)
140
Morphine - adv & disadv
Adv - cheap, safe, antedote if take too much, IM, IV, PO, SC
Good for mod-severe nociceptive pain, chronic cancer pain
Disadv - constipation, resp depression in high dose, oral dose 2-3x IV/IM/SC (lot taken away by first pass met)
141
How does amitryptilline decrease pain?
Increases descending inhibitory signals
142
Amitryptiline adv and disadv
Adv - cheap, safe, good for neuropathic pain
Also Rx depression, poor sleep
Disadv - anticholingeric SEs
143
How do anticonvulsants reduce pain?
Reduce abnormal firing of nerves
| Good for neuropathic pain
144
What are the ways you can administer pain relief?
```
Oral
Rectal
Sublingual
Subcutaneous
Transdermal
IM
IV
```
145
What are delivery routes for local anaesthetics?
```
Epidural
Intrathecal
Wound catheters
Nerve plexus catheters
Local infiltration of wounds
```
146
What are the ways you can assess pain?
Verbal rating score (no pain, mild, mod, severe, excruitiating - 1 to 5)
Numerical rating score (0-10)
Visual analogue - 10cm line mark where pain is
Smiling faces in paeds (happy smiling child --> screaming)
Abbey pain scale (confused patients) - pain behaviour scoring, bad behaviour in dementia is largely down to them being sore
147
What are non-drug Rx for pain?
RICE, surgery, acupuncture, massage, physio, changing their posture
Psychological - explanation, reassurance, counselling
148
For what kind of pain do you use the WHO pain ladder?
Nociceptive acute pain
149
How do you Rx neuropathic pain?
Alternative analgesics/psychological/non-drug Rx
150
What is the WHO pain ladder?
Mild-mod pain - non-opioids (NSAIDs, paracetamol)
Mod-severe - mild opioids (codeine) +/- non-opioids
Severe - strong opioids (morphine) +/- non-opoids
151
As pain resolves what do you with their pain relief?
Move down the ladder - passing middle rung first
Stop NSAIDs before paracetamol
152
What is the RAT approach to pain management?
Recognise - are they in pain?
Assess - severity, type, other factors (depression, anxiety, substance misuse, social factors)
Treat
Reassess after
153
What drugs should you use to Rx neuropathic pain?
Amitryptilline
Gabapentin
Duloxetine
