1
Q
3 components of anaesthesia and sedation
A
hypnosis
analgesia
muscle relaxant
2
Q
3 types of local anaesthetic technique
A
- local
- regional - target specific nerves
- neuraxial - spinal/epidural
3
Q
spinal anaesthesia - subarachnoid block
A
- needle into CSF
- bolus injected
- lasts ~ 2h
- rapid onset
4
Q
layers a spinal goes through
A
- skin - supraspinous ligament - interspinous ligament - ligamentum flavum - dura
5
Q
epidural
A
- catheter into extradural space
- continuous infusion
- larger doses and slower onset
- anaesthesia or analgesia
- thoracic or lumbar
6
Q
mechanism of local anaesthetics
A
- reversibly block Na channels so inhibit action potential
- affect smaller, unmyelinated nerves first
7
Q
order of block and affects of nerves affected by local anaesthetics
A
o B fibres - autonomic (vasodilatation)
o C and Aδ fibres - pain and temperature
o Aβ fibres - light touch and pressure
o A⍺ and Aγ fibres - motor and proprioception
8
Q
use of adrenaline with local
A
- causes vasoconstriction which reduces bleeding and prolongs local (reduces tissue uptake)
- don’t use adrenaline in end arteries
9
Q
lidocaine
A
- Immediate onset|15 minutes duration
- Small procedures
10
Q
bupivacaine
A
- Regional, spinal & epidural
- 10 minute onset
- 2 hours anaesthesia|12-24 analgesia
11
Q
opioids and local
A
used in epidurals alongside local anaesthetic for pain relief and improves the effect of locals
12
Q
what is sedation
A
drugs given to reduce anxiety, reduce consciousness, reduce airway irritability, induce amnesia
13
Q
short term sedation
A
- IV Midazolam
- Endoscopy
- Regional anaesthesia
14
Q
long term sedation
A
IV propofol +/- alfentanil
15
Q
IV vs inhaled hypnotic drugs
A
-IV has rapid onset and depresses airway reflexes, apnoea common
- inhaled has slower onset but may irritate airway (normally keep breathing)
16
Q
3 inhaled hypnotics
A
- Isoflurane – cheapest, used for maintenance
- Desflurane – maintenance, wears off quickly
- Sevoflurane – induction and maintenance
17
Q
3 IV hypnotics
A
- Propofol – quick, most common, also an antiemetic, fast redistribution and recovery of consciousness
- Thiopental – quick, emergency anaesthetic
- Ketamine – used in CVS instability, also analgesic
18
Q
simple airways
A
- Airway manoeuvres – head tilt, chin lift, jaw thrust
- Facemask – basic, for bag-mask-ventilation (BMV)
- Oropharyngeal – Guedel airway device in mouth to aid BMV
- Nasopharyngeal – aids BMV, used in seizures
19
Q
advances airway
A
- Laryngeal mask – sits above laryngeal inlet, iGel, spontaneous breathing, insert blind
- Endotracheal – insert with laryngoscope, enters trachea, cuff inflated to protect the airway
- Tracheostomy
20
Q
T1RF
A
- Inadequate oxygenation due to alveolar collapse (eg pneumonia) or fluid in the alveoli (eg left HF)
21
Q
CPAP
A
- T1RF
- maintains minimum airway pressure to keep lungs open and force fluid out.
22
Q
T2RF
A
inadequate ventilation due to limited alveolar expansion
23
Q
BiPAP
A
- Biphasic/Bilevel positive airway pressure
- Used for insufficient alveolar expansion T2RF
- Has a base expiratory pressure (CPAP) then increases for an inspiratory pressure to help expand the lungs
24
Q
non-polarising muscle relaxants
A
o Routine and emergency anaesthesia
o 120-180s onset
o Atracurium, rocuronium (rapid onset), vecuronium
o Competitively inhibit Ach preventing depolarisation and contraction
25
depolarising muscle relaxants
o Emergencies
o 30s onset
o Suxamethonium – is 2 Ach molecules bolted together so binds to two sites simultaneously (non-competitive) causing contraction then keeps pore open so prevents further contraction
26
drugs used to increase HR
- anticholinergics - inhibit ACH (vagus nerve)
- beta adrenoceptor agonists - increase HR and contractility by stimulating beta receptor in myocardia cells (dobutamine using in ITU for HF)
27
anticholinergics used to increase HR
o Atropine – crossed BBB, quick acting
o Glycopyrrolate – doesn’t cross BBB, slower acting, commonly used under anaesthesia for bradycardia
28
managing low BP with vasoconstrictors
* Alpha agonists – increase BP by causing vasoconstriction in peripheral vessels
* Vasoconstrictors may be peripheral vi cannula (phenylephrine, metaraminol) or central via central line (noradrenaline)
29
managing low BP and HR
- combined beta and alpha agonist (ephedrine)
o Adrenaline also has both effects but is very potent so only used in arrests/ITU
30
fluid distribution
– 60% of body weight, 70kg adult has 42L
o Intracellular fluid – 2/3 TBW
o Extracellular fluid – 1/3 TBW
- Interstitial fluid – 2/3 ECF
- Intravascular fluid – 1/3 ECF
31
fluid composition
o ICF – Na 8mmol/l, K 151mmol/l
o ECF – Na 140mmol/l, K 4 mmol/l
32
crystalloid fluid
o Water + electrolytes
o Rapidly moves from intravascular space
o Hypertonic – draws fluid into the intravascular compartment
o Hypotonic – shifts fluid out of the intravascular compartment
o e.g. 0.9% saline (can cause hyperchloraemia), Hartmann’s (contains K+ , do not use in renal failure), Plasmalyte, dextrose-saline, dextrose (5, 10, 50%)
33
colloid fluid
o Contains large insoluble molecules e.g. proteins
o Stays in intravascular space
o Attract water from cells into blood vessels - short term effect
o e.g. all blood products, human albumin solution, gelatins and starches (no longer used)
34
fluid used t manage volume replacement
Hartmann's
Saline
35
pain management ladder
* mild – paracetamol, NSAIDS
* moderate – codeine, tramadol
* severe – morphine
36
NSAIDS
- inhibit COX
- COX 1 makes protective prostaglandins (gastric mucosa, platelet aggregation)
- COX2 makes inflammatory prostaglandins
- reduces prostaglandin synthesis but increase leukotrienes so can't use in asthma
- SE - peptic ulcers, AKI, blood thinning (especially aspirin which inhibits thromboxane A2)
37
opioids vs opiates
* Opioids are synthetic, opiates are natural opioids
38
pre-op opioids
o Weak – codeine, tramadol
o Strong – morphine, oxycodone, methadone, buprenorphine
o Modified release – fentanyl patch, morphine sulphate tablets, oxycontin
39
intra-op opioids
o Rapid onset/offset
o Fentanyl/alfentanil – injections or infusions, fentanyl more potent but slower acting
o Remifentanil – ultrashort acting with rapid onset/offset, metabolised differently to other opioids, wide therapeutic index, infusion only
40
post-op opioids
o Codeine – prodrug (metabolised into morphine in liver), contraindicated in children, oral/IM
o Tramadol – acts on noradrenaline/opioid/serotonin receptors, oral/IV
o Morphine – oral
41
critical care opioids
o Alfentanil – infused drugs accumulate over time, alfentanil best for low accumulation
o Morphine – for ongoing pain, will accumulate, often used as PCA (patient controlled analgesia)
42
triggers of vomit centre
* Higher centres – emotion (fear, anxiety)
* Cerebellum – vestibular system
* Solitary tract nucleus – pharynx, GI tract
* Chemoreceptor trigger zone – blood-borne emetic
43
Serotonin (5HT-3) receptor antagonists for antiemetics
- ondansetron
- acts on CTZ and GIT for drugs and visceral stimuli
- avoid in QT prolonging drugs (SSRI, antipsychotics)
44
D2 receptor antagonists for antiemetics
* Metoclopramide, domperidone
* Site of action – CTZ, upper GIT
* Mechanism – prokinetic: relaxes the pylorus, reduces lower oesophageal sphincter tone, increases gastric peristalsis
* Side effects – diarrhoea, extrapyramidal side effects with metoclopramide e.g. acute dystonia. Domperidone does not cross BBB so no effect
- don't use in GI obstruction/perforation
45
H1 receptor antagonists for antiemetics
* Cyclizine, cinnarizine, promethazine
* Site of action – vomiting centre, vestibular system
- use in motion sickness and vertigo
- avoid in prostatic hypertrophy as can cause urinary retention
46
rough guide to antiemetic use
* Ondansetron – post op N/V, after acute opioid administration
* Cyclizine – post op, motion sickness, after acute opioid admin
* Metoclopramide – long term opioid use (can reduce constipation aswell)
* Domperidone – premedication for patients at risk of POST OP n/v
* Prochlorperazine – vertigo
47
post-op N+V risk factors
* Patient Factors - Female, Previous PONV, History of travel sickness, Non-smoker
* Surgical factors - ENT, gynae, and GI procedures
* Anaesthetic factors - Peri-operative opioid use, Gastric insufflation during intubation, Volatile anaesthetics, NO2 use, Duration of anaesthesia
Phase 3b
flashcards
Decks in class (5)
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