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Flashcards in Principles of anaesthesia Deck (17)
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1
Q

Local anaesthetics overview

A

△ membrane permeability
→ ✖ nerve impulse

Topical
Direct infiltration
Blocks including IV RA
Spinal 
Epidural 

Stored as acidic salts, activated when put into alkalinity of tissue
i.e. ineffective in infected wounds

1% = 10mg/ml

2
Q

LA & Doses

A

Lidocaine: 3mg/kg
+ Epi : 7mg/kg

Bupivacaine : 2mg/kg
Prilocaine : 6mg/kg
Epi doesn’t affect max dose in last 2.

Last 2 also cardiotoxic in spinals & Bier’s blocks respectively

Avoid LA near end-arteries

3
Q

LA & Toxicity

A

Local: Inflam & Nerve Dmg

Systemic:
Perioral tingling & parathesia
Anxiety, Tinnitus
Drowsy, ↓ GCS
Paralysis, apnoea
CVS collapse (-ve inotropic & a vasodilator)

Mx:
Stop LA → ABC (IVT +/- inotropes)

4
Q

Regional Anaesthesia using LA

A

Field block: affects entire surgical field
e.g. Hernia repair uses infiltration of LA + Injection of LA into Ilioinguinal nerve

Ring block: area usu. digit / penis
- do not use with Epi

Plexus block:

  • Brachial, Femoral, Sciatic
  • Bier’s , Intercostal

Brachial plexus (C5-T1)
Interscalene (trunk)
Supra/Infra-clav (divisions)
Axillary (cords)

Femoral (L2-L4)
- 1cm lateral to femoral artery as it exits the inguinal ligt

Sciatic (L4-S3)
- 2cm lateral to ischial tuberosity at level of GT

5
Q

Regional anaesthesia & IV LA

A

IV regional anaesthesia
Bier’s block
- exsanguinate, ↑ upper cuff then LA, ↑ lower & ↓ upper

Intercostal: chest drains etc

  • nerve under overhanding edge of rib
  • Posterior ⦞ of rib at Post. axillary line, needle below rib edge
6
Q

Regional Anaesthesia : Spinal

A

Contraindications;

  • anticoagulation
  • septic
  • previous back Sx
  • Aortic stenosis

Subarachnoid space @L1-2.

Complications: toxicity, ↓ BP,h-ache, urinary retention

7
Q

Regional Anaesthesia: Epidural

A

Extra-dural space
- △ in resistance as needle passes through ligament flavum signifying placement

Complications:
Dural tap, backache, infection, haematoma

↓ haematoma by leaving catheter until 12h post-heparin
↑ Inf if catheter left >72h

8
Q

Important dermatomes & RA

A

T5 : Nipples
T10: Umbilicus
T12: Inguinal ligt

Block @ C4 → Respiratory arrest

9
Q

Sedation Overview

A
Premedication anxiolytic
Amnesic
For invasive inv e.g. OGD
RA adjunct
ICCU e.g. tolerate tube

Caution in
Elderly
Obese
Cardio-resp disease

10
Q

GA Overview

A
Pre-op assessment & prep
Induction & muscle relax
Maintenance & monitoring
Recovery
Post-op monitoring & transfer
11
Q

ASA

A
1 healthy
2 mild systemic
3 sev systemic, limits ADLs
4 incapacitating dis, constant threat
5 Moribund
12
Q

Pre-op medications considerations

A
Anxiolytic (benzo)
Antiemetic 
Anticholinergic
Abx
Anticoagulation
Antirejection
Addison's (Steroid)
13
Q

GA induction agents

A

IV quicker, hydrophobic

  • Na Thiopentone (barbiturate)
    • Narrow TI → CVS/RS dep
  • Propofol (phenol)
    • better antiemetic
    • but -ve inotrope
  • Etomidate
    - better CVS profile

Complications

  • ↓ BP
  • RS Dep
  • Laryngospasm
  • Allergy

Avoid in allergy & porphyria

14
Q

GA muscle relaxants

A

Depolarising

  • Sux (2Ach):
    • hydrolysed by cholinesterase
    • rapid onset, 2-6 min duration
Complications: 
↑ K+ → ∴ avoid in burns
↓HR
↑/↓ BP
Myoglobinaemia
Malig hyperpyrexia

Non-depolarising

  • Atri, Cis-Atri,
    • non-enzymatic metabolism
    • slower than Sux
    • Reverse with neostigmine

↑ NM Blockade in

  • ↓ Temp
  • ↓ pH
  • ↑ K+
  • ↑ Age
  • Concurrent Sux use

MG : ↓ post-syn receptors 2° to auto- Ab

  • ↑ Sensitivity to Atric
  • ↑ resistance to Sux
15
Q

GA Maintenance agents

A

Isoflurane (halogenated ether)
- CVS & RS Depression

Sevoflurane (halogenated ether)
- rapid recovery ∴ need to plan post-op pain relief

NO2

  • allow dose ↓ of other agents.
  • can lead to bowel distention.. avoid in pneumothorax, recent diving or high p(Atm) exposure
  • Prolonged expo → myelosuppression & anaemia

Containdications

  • pyrexia after halothane admission
  • Hx of jaundice
16
Q

GA & Complications

A

Intubation

  • difficult intubation
  • post-op sore throat
  • trauma in OP

Anaesthetic Rx

  • Anaphylaxis
  • Malign Hyperpyrexia
  • PONV
  • Drowsy

CVS:

  • Myocardial ischaemia
  • ↓/↑ BP
  • Arrhythmia

RS:

  • Obstr
  • ↓ Ventilation, ↓ O2
  • Residual NM block
  • Aspiration
17
Q

Malignant Hyperpyrexia

A

Usu. inhalation agents & Sux

  • except NO2
  • AD inheritance

Rapid Ca2+ influx into muscle

  • M. Rigidity
  • ↑ Temp, HR & RR
  • DIC
  • ↑ CO2 prod & O2 demand → acidosis & ↑ K+

Mx:
Dantrolene 1mg/kg & rpt
Cooling
↑ Ventilation to ↓ CO2