ACC: Anaesthetics Flashcards
What are the key functions of general anaesthetic
- Amnesia - loss of response and memory to noxious stimuli (i.e. unconscious)
- Akinesia - loss of muscle contraction (i.e immobilisation)
- Analgesia
Name the two forms of amnesia?
- Induction agents - induce loss of consciousness by one-arm brain circulation time (IV) effective from 10-20 seconds, lasts 4-10 mins
- Inhalation/vapours - maintenance of amnesia
Name the 4 key induction agents, which is most commonly used?
- Profolol (95%)
- Thiopentone
- Etomidate
- Ketamine
Tell me the type of drug, appearance, dose, beneficial effects, unwanted effects and cautions of propofol?
- White emulsion (milk like) - lipid based
- 1-5-2.5mg/kg - must inject at 2-4mg/sec (rapid injection causes CV suppression)
- lowest incidence of PONV; excellent for airway reflex suppression
- Increases HR + BP; unwanted movements; pain on injection; resp suppression when combined with narcotics
- Must not use with extremes of age or egg/soy allergy
Tell me the type of drug, dose, beneficial effects and unwanted effects of Thiopentone?
- Barbiturate
- 4 - 5mg/kg
- Rapid sequence induction (quick onset/offest) for full stomachs and high risk vomiting e.g. emergency procedures; Antiepileptic properties which also protect brain
- decreased BP but increased HR; CI for acute porphyria; thrombosis and gangrene (due to intra-arterial injection) ; bronchoconstriction and rash (due to histamine release); Extravasation (treat with hyaluronidase)
Tell me the type of drug, dose, beneficial effects and unwanted effects of Etopomide?
- Steroid based
- 0.3mg/kg
- Used for patients with significant cardiovascular co-morbidities; lowest incidence of hypersensitivity reactions; complete haemodynamic stability
- Adrenal suppression - inability to maintain BP; pain on injection; highest incidence of PONV; thrombophlebitis at local injection site
Tell me the dose, beneficial effects, unwanted effects and CI of Ketamine?
- 1-1.5mg/kg
- Slow onset
- Useful for Burns dressing changes due to dissociative amnesia causing anterograde amnesia and profound analgesia; Increases HR + BP, bronchodilataion (due to sympathetic stem)
- Emergence phenomenon (vivid dreams, hallucinations, crying), N+V
- CI: HTN, Stroke, raised ICP, psychiatric patients
Which induction agent would you use for burns? And how long does it take to work?
Ketamine - slow acting 90 seconds
Which induction agents can you use for a patient with acute porphyria
Propofol
Etopomide
Ketamine
Which induction agent is best used for a patient with significant coronary artery disease and IHD?
Etopomide
Which induction agent has side effects of bronchospasm, rash, thrombi and gangrene? How does this drug affect BP and HR?
Thiopentone
- releases histamines to cause bronchospasm and rash
- intra-arterial injection causes thrombi and gangrene
- increases HR, decreases BP
Which induction agent increase HR and BP?
Ketamine
Which drug causes dissociative amnesia and emergence phenomenon?
Ketamine
What is the dose of all 4 induction agents?
Profolol (lipid) 1.5-2.5mg
Thiopentone (barbiturate) 4-5mg (fast acting RSI)
Etopomide (steroid) 0.3mg/kg
Ketamine 1-1.5mg/kg
What are the uses, CV effects, unwanted effects and MAC concentrations of the inhaled/vapourised agents?
- Sevflurane (2% MAC) - sweet smelling, good for difficult cannulation, decreases BP (vasodilatation)
- Isoflurane (1.15%) - least organ effect on organ blood flow. irritant - causes cough i.e. good for organ transplant. Decreases BP but increases HR
- Desflurane (6%) - lipid based rapid onset/offset (i.e. rapid abrosption to brain, excretion of body). Decreases BP but increases HR
- Enflurane (1.6%)
What are the most commonly used short acting analgesia and when are they used?
High potency, fast acting opioids - Fentanyl (1st line) –> Remifentanil (rapid onset/offset good for long ops) –> alfentanil
intra operative analgesia, laryngoscopy, surgical pain
What are the most commonly used long acting analgesia and when are they useD?
Intra and post-operative
1. Morphine (1st line), Oxycodone
What are the three common forms of long term analgesia other than strong opioids?
- Paracetamol 1g QDS
- NSAIDS: Diclofenac 50mg TDS, Ibuprofen 400mg TDS
- Weak opioids: Tramadol 50-100mg QDS and dihydrocodeine 30mg QDS
What are the two types of muscle relaxants? and how do they work?
- Depolarising - Nicotinic receptor agonist that works similarly to Ach but broken down slower with Ach-e –> full muscular contraction –> once Ca2+ depletes causes muscle relaxation
- N-depolarising - blocks nicotinic receptors –> Ach cannot bind –> muscle relaxation