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Anaesthesia Flashcards

1
Q

ASA grading

A

Class I: completely healthy
Class II: mild systemic illness, no functional limitation
III: severe illness with end-organ damage (but still can work)
IV: incapacitating, constant threat to life
V: moribund patient not expected to live within 24h

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2
Q

Specific qns to ask in anaes hx

A

Past hx of anaesthesia

PMHx: Recent URTI, asthma, OSA, CVS diseases, severe GERD, severe motion sickness

Effort tolerance

Current medications

Last meal

Smoking hx

Fam hx of malignant hyperthermia

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3
Q

How long symptom free for URTI to qualify for GA?

A

6 weeks on paper, 2 weeks in practice

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4
Q

Why is smoking a problem in anaes?

A
  • nicotine causes vasoconstriction, SVR increases; BP will plunge if given drugs causing vasodilation
  • risk of laryngospasm, bronchospasm
  • ideally quit smoking 4-6 weeks before op, at least 48-72h before op
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5
Q

How long to fast before op?

A

2 hr - clear fluids
light meal: 6 hours
heavy meal: 8 hours

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6
Q

What to do in pts with history of OSA?

A

pt to be discharged to HDU and not general ward. OSA worse at night due to effects of anaesthesia, need monitoring

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7
Q

Mnemonic for pre-op PE

A

LEMON-D

Look: craniofacial deformities, short/thick neck/beard, recessed chin

Evaluate: 3 finger inter-incisor, 3 finger thyromental distance , 2 finger mentum to hyoid bone

Mallampati score

Obesity

Neck ROM

Dentures/loose teeth

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8
Q

Mallampati scoring

A

Class I: complete visualisation of soft palate with tonsillar pillars

Class II: complete visualisation of uvula

Class III: visualise only base of uvula

Class IV: soft palate not visible at all

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9
Q

___ classification of laryngoscopic view grades

A

Cormack and Lehane

Grade 1: full view of glottis
Grade 2: partial view
Grade 3: only epiglottis seen
Grade 4: neither glottis nor epiglottis seen

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10
Q

Pre-op ix for patients according to ASA

A

ASA I >50yo: FBC, UECr, ECG

All others ix as needed: HbA1c, ABG, PT/PTT, LFT, trops

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11
Q

Most common peripheral nerve injury

A

Ulnar nerve

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12
Q

What 3 axis to align using what position?

A

oral axis
pharyngeal axis
laryngeal axis

sniffing morning air position - flexion at lower c spine, extension at upper c spine

*obese patients - stack pillows such that mouth is at level of sternum

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13
Q

How to size oropharyngeal and nasopharyngeal airway?

A

oral: corner of mouth to tragus of ear

nasal: anterior nares to tragus of ear to angle of mandible

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14
Q

Laryngeal mask airway sizing

How much air to cuff?

A

70-100kg: #5
Asian males: #4
Asian females: #3

30ml of air to cuff

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15
Q

5 point auscultation spots

A

Epigastrium
bilateral upper anterior chest
bilateral bottom mid-axillary

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16
Q

CO2 detector changes from __ to ___ when CO2 is detected

A

purple to yellow

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17
Q

Sizing of ETT

How much air to cuff?

A

Asian male: 8-8.5
Asian females: 7-7.5
Children: age/4 + 4

cuff with 4ml of air

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18
Q

5 ways to check correct ETT placement

A

1) direct visualisation of tube passing through vocal folds
2) equal, bilateral chest rise
3) auscultation bilateral lungs
4) misting of ETT tube
5) CO2 indicator purple to yellow

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19
Q

When is ETT preferred over LMA?

A

Higher risk of aspiration
- obesity, pregnancy, severe GERD
- surgery with pneumoperitoneum (eg. laparoscopic)
- intraabdominal surgeries

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20
Q

Nasal cannula FiO2 formula

(max O2 flow = 1/2L/min)

A

21% + (4 x oxygen flow rate)

eg. 1L/min, FiO2 = 25%

Every 1L increase, increases FiO2 by 4%

**Max FiO2 on nasal cannula is 40%

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21
Q

Hudson mask FiO2

(max O2 flow = 5-10L/min)

A

FiO2: 40-60% (max usually <50%)

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22
Q

Non-rebreather mask FiO2

(max O2 flow = 8-10L/min)

A

FiO2 usually max 80%

Highest FiO2 in variable performance masks
But can cause basal atelectesis

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23
Q

What is venturi mask?

A

Uses valves to mix O2 with ambient air - precise concentration

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24
Q

Components of general anaesthesia

A

1) *analgesia
2) *amnesia
3) *anesthesia - pt unconscious, asleep

4) reflex suppression
5) paralysis

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25
__ classification on stages of anaesthesia
Guedel Stage 1: amnesia (respi pattern regular), can still follow commands Stage 2: uninhibited excitation, laryngospasm if airway manipulated, respiration irregular Stage 3: surgical anaesthesia (respi pattern regular) - target depth Stage 4: overdose, at risk for hypotension and cardiovascular collapse
26
pre-operative abx
Most: cefazolin GI surgeries: ceftriaxone + metronidazole
27
purpose of pre-oxygenation
To replace nitrogen in functional residual capacity in lungs (that is usually in room air) with oxygen allows 8 min of apnoea in 70kg adult without arterial o2 desaturation **functional residual capacity = 2L oxygen consumption = 250ml/min usually, at 21% oxygen FRC = 420mL apneic time = 1.68min at 100% oxygen FRC time = 2000mL apneic time = 8min**
28
Benzodiazepines work on the __ receptor Used for ___, ___, ___ (but no ___)
GABA receptors enhances GABA transmission (inhibitory neurotransmitter) anxiolysis, amnesia, sedation no analgesia
29
Reverse benzo overdose with ___
flumazenil *not used in chronic benzo users, can cause seizures
30
Opioids act on ___ receptors Used for ___ and ___, but no ___
mu, kappa, delta receptors sedation, analgesia no amnesia
31
Reverse opioid overdose with ___
naloxone
32
Types of induction agents
Inhalational: sevoflurane, isoflurane, desflurane - used as main induction agent in children (problems with IV) - can prolong stage 2 anesthesia, airway irritation, environmental pollution Intravenous: ketamine, etomidate, propofol - rapid, shortened stage 2 *adults usually TIVA or mixed inhaled/IV induction
33
Advantages of total intravenous anaesthesia (TIVA)
- avoid side effect of inhalational agents (hx of PONV, severe motion sickness) - Environmentally friendlier
34
facts about propofol
- most common induction agent - potent CVS and respi depressant - decreases BP: decreases cardiac contractility & causes peripheral vasodilation - works on GABA Made from soybean?? Contains egg lecithin - contra in egg allergy
35
facts about etomidate
- minimal cardiac and respi depression - works on GABA good to use in pts with compromised haemodynamics
36
facts about ketamine
- cardiovascular STIMULANT - minimal respi depression - works on NMDA receptors (antagonist) - potent analgesic and BRONCHODILATOR (good for asthmatics) Side effects: hallucination, emergence delirium, increased salivation, increase ICP
37
Two types of ventilation in maintenance of general anaesthesia
1) spontaneous respiration - no muscle paralysis - patient determines RR and tidal volume 2) Intermittent positive pressure ventilation - non-depolarising muscle relaxant used - anaesthetist determines RR and tidal volume
38
Depolarising neuromuscular blocker example
Succinylcholine - initially causes muscle fasciculations: depolarisation - prolonged binding prevents repolarisation - quick onset, shortest DOA
39
Non-depolarising neuromuscular blocker examples
rocuronium, pancuronium - competes with acetylcholine at nicotinic receptors - longer onset, longer duration of action DOA: rocuronium < pancuronium
40
When reversing nondepolarising NMB, use ___. Must use ___ together to prevent ____.
neostigmine - acetylcholinesterase inhibitor to increase Ach - overwhelm blockade glycopyrrolate (anticholinergic) prevents overstimulation of muscarinic receptors by increased Ach (can cause bradycardia, bronchospasm)
41
What is minimum alveolar concentration?
concentration of inhaled anaesthetic agent at 1 atmospheric pressure which prevents reflex movement in response to surgical stimuli in 50% of subjects Usually kept at 0.7-1.0
42
Examples of sympathomimetics and when to use what
Ephedrine - act on both alpha and beta receptor - vasoconstriction + increase HR - good for low BP and low HR Phenylephrine - act on alpha receptor only - vasoconstriction + reflex bradycardia - good for low BP and high HR
43
How to check for reversal of neuromuscular block?
Train of four stimulation (muscle twitch 4 times similar strength with stimulation) Using peripheral nerve stimulator
44
How do local anaesthetic drugs work?
Inhibits sodium channels on cell membrane of nerve axon - prevents conduction - membrane cannot depolarise, prevents generation of action potential
45
Examples of local anaesthetics
Amides: lidocaine, bupivacaine esters: procaine, cocaine
46
LA blocks ___ nerve fibers more readily than ___ nerve fibers
myelinated > unmyelinated
47
LA works faster in ___ pH __ is added to help LA work faster
higher pH (less acidic) Sodium bicarbonate is added to increase pH to speed up onset of action
48
___ is added to LA to prolong LA action by causing ___
Adrenaline causes local vasoconstriction, slows down absorption of LA from site of deposition -> prolong action
49
Toxicity effects of LA
CNS - lightheadedness, perioral/tongue numbness, tinnitus, slurred speech, visual disturbances, anxiety - CNS depression CVS - arrhythmia, cardiac arrest, hypotension
50
How to prevent LA toxicity? How to manage toxicity?
- use lowest dose - ultrasound guidance - communicate with patient intraop and ask about symptoms Mx: infuse lipid emulsion solution to remove from plasma give BZD/propofol for seizures
51
Spinal cord end at __ in adults and __ in children
Adults - L1 Children - L3
52
Layers of dura and what is in between? Where does CSF flow?
Pia mater - adheres to spinal cord Arachnoid mater - adheres to dura mater CSF is between arachnoid and pia mater (subarachnoid space)
53
Anatomical landmark of spinal cord
Iliac crest/intercristal line indicates L4-L5 interspace when pt is in lateral flexed position
54
Layers of tissue LA needle goes through at spine
Skin -> subcutaneous tissue -> supraspinous ligament -> interspinous ligament -> ligamentum flavum -> epidural space -> subdural space -> arachnoid mater -> subarachnoid space
55
Spinal block given at ___ space. Catheter only placed in ___ space due to risk of infection.
subarachnoid space epidural space
56
How to control flow of LA in the subarachnoid space?
Using baracity of solution - Hyperbaric: LA + glucose/dextrose. Heavier than CSF, flows in direction of gravity and settles in dependent areas - Hypobaric: LA + sterile water, rises in relation to gravity
57
___ dose is ___ higher than ___ as there are more layers of mater to traverse before acting on nerve roots
Epidural 10x spinal
58
If LA blocks sympathetic nerves at ___ level, can cause bradycardia
T1-T4
59
What is post dural puncture headache?
CSF leaks through hole faster than it is being produced when dura mater is damaged Downward displacement of brain structures Pain worsened with sitting/standing. Relieved on lying down RF: young, female, pregnant, big needle
60
Risk of doing spinals in pts with coagulopathy. How to manage?
Epidural/spinal haematoma. Need urgent MRI and surgical decompression of spine
61
Types of blocks for surgeries - shoulder - below elbow - femoral fracture
Shoulder: interscalene block anything below elbow: infraclavicular/axillary block femoral fracture: femoral nerve
62
Minimum monitoring standards in anaesthesia
Non-invasive BP ECG Capnography Inspired oxygen analyser Pulse oximetry (BECOP)
63
At what PaO2/SpO2 does hypoxemia occur?
60mmHg PaO2 91% SpO2
64
How does pulse oximetry work? When is it limited?
measures transmission of light across vascular tissue bed comparing spectra of oxygenated Hb over deoxygenated Hb Limitations - low SpO2 <70% - Loss of pulsatile component: irregular blood flow, hypothermia, hypoperfusion, vasoconstriction - nail polish - dyes in circulation: methylene blue
65
How does automatic BP work?
Oscillometry - senses oscillations when cuff pressure falls below systolic pressure peak amplitude of oscillations is read as mean BP
66
Intraarterial waveforms and what do they mean
Upstroke: ventricular contraction Dicrotic notch: closure of AV valves
67
ECG monitoring in anesthesia usually ___, displays lead __. ___ leads required to display leads __ and __. Used for patients ____
3 leads: lead II 5 leads: lead II, V5. For pts with cardiac ischemia, cardiothoracic op
68
Phases of capnography
AB: exhale dead space B: start expiration BC: exhale dead space and alveolar air CD: plateau, exhaled CO2 from alveoli D: end of plateau phase. END TIDAL CO2 that corresponds to PaCO2 (~40mmHg) E: start of inspiration
69
Different patterns on capnography and what they mean
Upward slope, slower rise = bronchospasm Low ETCO2 = hyperventilation, airway obstruction, hypotension High ETCO2 = hypoventilation, high production Curare clefts - patient starting to wake up, tries to take a breath in
70
target number on bispectral index for adequate anaesthesia
40-60
71
Key components of PACU handover
- pt biodata: age, ASA, comorbids, PMHx, allergies, regular meds - surgery, type of anaesthesia, intraoperative issues - blood loss, urine output, transfusions - problems expected post op - pt current status - post op instructions
72
respi cx at PACU
1) airway obstruction - tongue falling back** - laryngospasm, oedema - secretions - neck haematoma 2) hypoventilation - residual effect of anaesthesia** 3) hypoxemia
73
haemodynamic issues at PACU
1) hypotension - bleeding - vasodilation - cardiac dysfunction 2) hypertension - pain - ARU causing discomfort - intracranial HTN: HTN + bradycardia
74
Shivering in the PACU - causes - effects - how to stop?
cause - hypothermia (<35deg) - use of volatile agents effect - increased O2 consumption: can lead to cardiac ischemia - coagulopathy (impairs plt function) - delayed awakening IV Pethidine can stop muscle contractions to stop shivering, but doesn't mean pt not cold
75
Risk factors for post op nausea and vomiting (PONV)
pt factors - young women, children - obesity - NON-smoker - hx of motion sickness, hx of PONV anaesthetic factors - inhalational agents - opioids surgical factors
76
Mx of PONV
- Use less inhalational agents, use TIVA - give more antiemetics (ondansetron, dexamethasone, droperidol, metoclopramide)
77
What medications to stop pre-op?
SGLT2 inhibitors (empagliflozin etc): stop 72hrs prior to surgery to prevent euglycemic DKA all other meds: stop day of surgery - OHGA - insulin (do not stop basal insulin) - ACEI/ARBs

Acute Medicine (1 decks)

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