Anaesthesiology Flashcards
Local anaesthetic
Consciousness maintained (lidocaine)
General anaesthetic
Consciousness reversibly lost (isoflurane)
Depress excitable tissues - CNS, cardiac muscle, smooth muscle (some less sensitive)
Stages of anaesthesia
Stage 1- analgesia
Stage 2 - excitement
Stage 3 - surgical anaesthesia
Stage 4 - Medullary depression (death)
Mechanisms of anaesthetics
Act on ligand gated ion channels
Agonists at GABAa
Inhibit glutamate receptors
Anaesthetic potency
Related to lipid solubility
Minimun Alveolar Concentration (MAC)
1 MAC = concentration to prevent response 50% of pop
Low MAC = higher potency = more lipid soluble
Stages of general anaesthesia
Premedication, induction, maintenance
Premedication
Anxiolytics - diazepam
Muscarinic antagonist - hyoscine (prevent arrhythmias/bronchial secretions)
Analgesics - fentanyl
Anti-emetics - ondansetron
Induction
May be used alone for short procedures, very lipid soluble
Barbiturates - thiopental
Non-barbiturates - propofol
Ketamine (can cause hallucinations, paediatric anaesthesia)
Maintenence
Nitrous oxide - not potent enough alone, carrier gas
Halothane, enflurane, isoflurane, desflurane, sevoflurane
Halothane
High potency, myocardial depression, hypotension, arrhythmias, cardiac arrest
Metabolised by the liver = hepatotoxicity
Enflurane
Less metabolism than halothane
Seizure activity, muscle twitching
Isoflurane
Less cardiac depressive than halothane
Hypotension (decrease resistance), low hepatotoxicity risk
Desflurane
Less potent isoflurane
High concentrations inhaled - respiratory tract irritation
Rapid recovery
Sevoflurane
More potent deflurane
Rapid recovery
Malignant hyperthermia
Triggered by potent inhales agents
Treat with dantrolene (Ca2+ channel blocker)
