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*Medicine: Anaesthesia and ITU > Anaesthesia Preparation > Flashcards

Anaesthesia Preparation Flashcards

1
Q

What are the stages of general anaesthesia?

A
  • Stage 1 → analgesia, induction to LoC
  • Stage 2 → excitatory phase, from LoC to onset of automatic breathing
  • Stage 3 → surgical anaesthesia, from onset of automatic breathing to resp paralysis
  • Stage 4 → overdose, from stoppage of respiration to death where medullar pralysis occurs

Can compare to ‘alcohol intoxication’: dizzy and delightful → drunk and disorderly → dead drunk → dangerously deep

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2
Q

Where do anaesthetists work, in a hospital?

A
  • Theatres
  • Labour ward
  • Other procedural areas
  • Interventional radiology
  • Intensive Care Unitu (ICU)
  • Post-anaesthesia care unit (PACU)
  • Pain management: acute and chronic

Also: cardiac arrest team, research, sim, admin, education, management

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3
Q

What are the 3 main types of anaesthesia?

A
  • General
  • Regional
  • Local
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4
Q

What are advantages of general anaesthesia?

A
  • Applicable to all sites/types of surgery eg. cataracts, toe, nailbed, etc
  • ‘Never fails to work’
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5
Q

What are disadvantages of general anaesthesia?

A
  • Polypharmacy
  • Derangement of CVS and resp system → be aware of these problems and be ready to tackle
  • Recovery
  • Post-op N+V (PONV) → can delay discharge, and cause unsatisfaction, wound dihessence, electrolyte imbalance
  • Awareness → shouldn’t happen!
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6
Q

What is the mechanism of general anaesthesia?

A
  • Not clear (!)
  • Involves ascending reticular activating system, cerebral and olfactory cortex, hippocampus and limbic system
  • Modification of pre-synaptic release of NTs +/- postsynaptic binding
  • Reduced excitatory (glutamate) and increased inhibitory NTs (GABA)
  • Effect site: at cell membrane (lipid solubility) as well as microtubules and other cytoplasmic structures
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7
Q

What is the triad of general anaesthesia (Rees and Gray 1950)?

A
  • Hypnosis (midazolam)
  • Analgesia (WHO ladder, opiates, fentanyl, morphine)
  • Muscle relaxation (suxamethonium, atracurium)
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8
Q

What are types of regional anaesthesia?

A
  • Central neuro-axial block
    • spinal, epidrual or combined spinal epidural
  • Peripheral nerve blocks → block ulnar/axillary nerve
  • Plexus block → femoral nerve / supraclavicular blocks
  • Local infiltration → ring blocks (finger)
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9
Q

What are the relative drug strengths of opioids compared to each other?

A
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10
Q

What constitutes the process of anaesthesia?

A
  • Preoperative assessment
  • Anaesthetic technique
    • induction
    • maintenance
    • emergence
  • Postoperative care
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11
Q

What is the ASA classification?

A
  • Class I → healthy pt
  • Class II → mild systemic disease
  • Class III → severe systemic disease, not incapacitating
  • Class IV → severe systemic disease, threat to life
  • Class V → moribund patient not expected to survive +/- operation
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12
Q

What is the WHO safety checklist?

A
  1. Sign in
  2. Time out
  3. Sign out
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13
Q

What are the cannula sizes and colours?

A
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14
Q

What is important in pre-assessment?

A
  • Surgical/Anaesthetic Hx
  • Co-morbidities
  • Exercising tolerance
  • Smoking/ETOH
  • Medications → allergies, reg meds
  • Fasting time
  • Ix → bloods, radiological
  • Examination → general, airway
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15
Q

What are general medical enquiries that should be made in pre-op assessment?

A
  • CVS → IHD, angina, arrhythmias, HTN, functional ability
  • Resp → asthma, COPD, recent cough/cold, smoker
  • GI → reflux
  • Renal → impaired fxn
  • Liver → impaired fxn
  • Metabolic → diabetes, recent steroids
  • Paeds → immunisations, birth history

If the answer is yes to any of the above then find out more!

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16
Q

What’s important about medications in pre-assessment?

A
  • Tells you a lot about the patient
  • Meds to continue (cardio, resp, anti-convulsants)
  • Medications to stop
  • Drug interactions
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17
Q

What drugs need to be stopped before surgery?

A

CHOW

  • Clopidogrel → stopped 7d prior, bleeding risk, aspirin + other antiplatelets can often be continued
  • Hypoglycaemics
  • Oral contraceptive pill (OCP) or HRT → stopped 4wks prior due to DVT risk, advise pts to use alternative contraception
  • Warfarin → stopped 5d prior to surgery due to bleeding risk + commenced on therapeutic dose of LMWH ; INR needs to be <1.5 for surgery
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18
Q

Before surgery, which drugs need to be altered?

A
  • Subcut insulin → switched to IV variable rate insulin infusion
  • Long-term steroids → must be continued, due to risk of Addisonian crisis if stopped, if pt cannot take orally, switch to IV
    • simple conversion rate is 5mg PO prednisolone = 20mg IV hydrocortisone
19
Q

What drugs should be started before surgery?

A
  • LMWH
  • TED stockings
  • Antibiotic prophylaxis (ortho, vasc, GI surg)
20
Q

What specific anaesthetic Qs need to be asked?

A
  • Previous GA/LAs
  • Airway issues
  • FHx → malignant hyperthermia, suxamethonium apnoea
  • Fasting duration
21
Q

What are the durations for preoperative fasting periods?

A
  • Food & Dairy (incl tea/coffee) - 6hrs
  • Clear fluids - 2hrs
  • Breast milk - 4hrs

Pulmonary aspiration of gastric contents, even 30-40mL, is associated with significant morbidity and mortality. Fasting aims to reduce volume of gastric contents, and hence risk of aspiration.

22
Q

Which pre-operative investigations need to be completed?

A
  • Bloods → FBC, U+Es, LFTs, clotting, G+S/X match
  • Radio → ECG, CXR
  • Other → pregnancy, sickle cell, urine, MRSA swabs
23
Q

What is the difference between G&S vs cross-match?

A
  • G&S → determines pt’s blood group (ABO and RhD) and screens the blood for atypical antibodies; process takes 40 mins + no blood is issued, recommended if blood loss not anticipated, but blood may be required should there be greater loss than expected
  • Cross-match → involves physically mixing pt’s blood with donor’s blood, in order to see if any immune rxn takes place; if it doesn’t, the donor blood issued and can be transfused in to the patient, otherwise alternative blood is trialled; also takes 40 mins (in addition to 40mins required to G&S blood, which must be done first) and should be done if blood loss is anticipated
24
Q

How do you do an airway assessment?

A
  • General:
    • level of consciousness + co-operation
    • BMI
    • prev grade of intubation
  • Mouth
    • mallampati score
    • mouth opening - inter-incisor distance (>3cm good)
    • jaw protrusion
  • Face
    • beard
    • craniofacial deformity
  • Teeth
    • edentulous
    • teeth prominence and condition
    • dentures/caps/crowns/loose teeth
  • Neck
    • neck length
    • range of motion
    • thryo-mental distance (>6cm good)
    • soft tissue
25
Q

Airway assessment: What is “LEMON”?

A
  • L - look
  • E - evaluate 3-3-2 rule
    • inter - incisor distance 3 fingers
    • hyoid - mental distance 3 fingers
    • thyroid - mouth distance 2 fingers
  • M - mallampti
  • O - obstruction
    • epiglottis/trauma
  • N - neck mobility
26
Q

What is the perioperative care of patients with T1DM?

A
  • Should be first on morning list and may need admitting night before
  • On night before, reduce subcut basal insulin dose by 1/3rd
  • Omit morning insulin + commence IV variable rate insulin infusion pump (sliding scale) - syringe driver 49.5mL NaCl 0.9% + 50U Actrapid
  • Whilst NBM, prescribe 5% dextrose - given 125mL/hr, ask nurse to check BM every 2hrs
  • Continue until pt is able to eat + drink
  • Once able to eat/drink → overlap IV variable rate insulin infusion stopping and their normal SC insulin regimens starting. To do this, give their SC rapid acting insulin 20mins before a meal and stop their IV infusion 30-60 mins after they’ve eaten
27
Q

What is the perioperative care of patients with T2DM?

A
  • Management depends if controlled
  • If diet controlled, no action required peri-operatively
  • Ih pts controlled by oral hypoglycaemics, metformin to be stopped on morning of surgery, whilst others should be stopped 24hrs before operation
  • These pts will be put on IV variable rate insulin infusion along with 5% dextrose as described for T1DM
28
Q

What are the induction agents?

A
  • Propofol
  • Thiopentone
  • Ketamine
  • Etomidate
29
Q

Which opiates are used?

A
  • Morphine
  • Fentanyl
  • Alfentanil
  • Remifentanil
30
Q

Which muscle relaxants are used?

A
  • Suxamethonium (polarising agent)
  • Rocuronium (non-depolarising)
  • Atracurium (non-depolarising)
31
Q

Which anti-emetics are used?

A
  • Ondansetron
  • Cyclizine
  • Dexamethasone
32
Q

Which hypnotic is used?

A

Midazolam

33
Q

Emergency drug: What does Ephidrene do?

A
  • Beta 1 agonist
  • Increases BP
  • Increases HR
34
Q

Emergency drugs: What does Atropine / Glycopyyrolate (green) do?

A

Increases HR

35
Q

Regional anaesthesia is ideal for many operations, in particular those on the limbs and lower abdomen. For those who do not wish to be fully awake for surgery, sedation can also be used. For many other operations, regional analgesia can complement GA and provide lasting and effective post-operative pain relief.

What are ‘Desert island blocks’?

A

No single anaesthetist can be proficient in all blocks. ‘Desert island blocks’ are those that ideally all anaesthetists should know how to perform, do not require high-tech equipment, and cover as much of the body as possible, including:

  • interscalene brachial plexus block → shoulder + elbow
  • axillary brachial plexus block → every other part of arm
  • labat sciatic nerve block → almost all leg
  • femoral nerve block → rest of leg
  • spinal anaesthesia → for abdomen
36
Q

Which (regional) blocks are used for which part of the body?

A
37
Q

What are commonly used local anaesthetics?

A
38
Q

What are commonly used adjuncts to regional anaesthesia?

A
39
Q

Local anaesthetics: What are features of lidocaine?

A
  • An amide
  • Local anaesthetic + less commonly used antiarrhythmic
  • Hepatic metabolism, protein bound, renally excreted
  • Toxicity → due to IV or XS administration, inc risk of liver dysfunction or low protein states, can be treated w/ IV 20% lipid emulsion
  • Drug interactions → beta-blockers, ciprofloxacin, phenytoin
  • Features of toxicity → initial CNS over-activity, then depression as lidocaine initially blocks inhibitory pathways then blocks both inhibitory and activating pathways, also cardiac arrhythmias
  • Increased doses may be used when combined w/ adrenaline to limit systemic absorption
40
Q

Local anaesthetics: What are features of cocaine?

A
  • Clinical use concentrations 4 and 10%
  • Applied topically to nasal mucosa
  • Rapid onset + additional advantage of marked vasoconstriction
  • Lipophillic + readily crosses BBB
  • Systemic effects → cardiac arrhythmias, tachycardia
  • Some use in ENT surgery, but otherwise rare in mainstream surgery
41
Q

Local anaesthetics: What are features of Bupivacaine?

A
  • Binds to intracellular portion of sodium channels + blocks sodium influx into nerve cells, prevents depolarisation
  • Much longer duration of action than lignocaine
  • Used for topical wound infiltration at the conclusion of surgical procedures with long duration analgesic effect
  • It’s cardiotoxic + contraindicated in regional blockage in case tourniquet fails
  • Levobupivicaine is less cardiotoxic and causes less vasodilatation
42
Q

All local anaesthetic agents dissociate in tissues + this contributes to their therapeutic effect. The dissociation constant shifts in tissues that are acidic eg. where an abscess is present and this reduces the efficacy.

What are doses of local anaesthetics?

A
43
Q

Summary of basic anaesthetic drugs

A
44
Q

What are some commonly used intravenous anesthetics?

A
  • Propofol standard drug for induction of anaesthesia
  • Etomidate used in cases of haemodynamic instability
  • Ketamine for emergency medicine - strong dissociative, sympathomimetic and analgesic effects
  • Barbituates useful in pts w/ high ICP and/or head trauma

*Medicine: Anaesthesia and ITU (8 decks)

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