Anaesthetic drugs Flashcards
(25 cards)
What is anaesthesia?
A reversible drug induced absence of sensation and awareness
Any lipid soluble agent that causes depression of the brain in a predictable order
State the order in which anaesthetics cause depression to the brain
Cortex
Midbrain
Spinal cord
Medulla
What are the effects of ethanol?
Tranquillization Excitation Dysarthria Ataxia Sedation/hypnosis Anaesthesia Coma Medullary depression Death
How do anaesthetics work?
Stimulation of inhibitory receptors - GABAA, Glycine
Inhibition of excitatory receptors - Nicotinic, Serotonin, Glutamate/NMDA
How doe GABAA anaesthetics work?
Pentameric
Single amino acids
Chloride ions
Hyperpolarisation
How do we give anaesthetics?
Inhale
Inject
Name some inhalation agents
Oxygen Nitrous oxide Ideal properties Isoflurane Other volatile agents
State some side effects of oxygen
O2 free radicals CNS convulsions Pulmonary oxygen toxicity Retrolental fibroplasia CO2 narcosis
When is oxygen a gas?
Above -119 degrees
Describe nitrous oxide
Weak anaesthetic Good analgesic Quick onset/offset Cardiorespiratory depressant Neuropathy/BM depression
List some physical properties of inhalational agents
Cost Chemical stability Non-flammable/explosive Vaporizable Environmentally stable
List some chemical properties of inhalational agents
Non irritant Low blood:gas solubility High potency - lower MAC Minimal side effects (pharmacodynamics) Biotransformation (pharmacokinetics) Non-toxic
List some older inhalational agents
Ether - side effect is nausea and vomiting
Chloroform
Cyclopropane
Methoxyflurane
Halothane - causes kidney problems
Enflurane - lowered threshold for epilepsy and seizures
Describe isoflurane
Inhalational agent Halogenated ether 1965 Relatively cheap Stable and non flammable Vaporizable BP 49C Irritable to airway Relatively potent MAC 1.1% B:G co 1.4 - works quickly and wears off relatively quickly Side effects CVS/RS 0.2% metabolised
Describe sevoflurane
Inhalational agent Non irritable Quick onset/offset MAC 2% 5% metabolised CVS stability Emergence phenomena Expensive
Describe Desflurane
Inhalational agent Very quick onset/offset 0.02% metabolised Moderately expensive Irritant Special vaporizer MAC 6.35%
How are inhalational agents delivered to the patient?
Machine/vapourizer
Describe intravenous agents
Shorter history Induction agents/iv opiate Rapid and pleasant Lipid soluble Redistribution - into fat or muscles short acting Metabolised CVS/RS depression
Describe thiopentone
Thiobarbituate 1933 Powder Smell of garlic Antiepileptic CVS/RS depression Anaphylaxis/ arterial Half life 10 hours
Describe 2,6-diisopropylphenol (propofol)
Solvent Redistribution half life 4 minutes Elimination half life 4 hours Minimal accumulation TIVA Anti emetic Anti epileptic Painful to inject Abnormal movements CVS/RS effects Also used to keep ICU patients asleep
Name some other intravenous agents
Ketamine
Etomidate
Midazolam
What are muscle relaxants?
Dangerous drugs Muscle paralysis Facilitate intubation Maintain paralysis for surgery/ventilation Depolarising Non depolarising Anaesthetists only
What are depolarising agents?
Suxamethonium Post-synaptic membrane Mimics acetylcholine Rapid onset offset Short half life ~ 2min Plasma cholinesterase Multiple side effects
What are non depolarising blockers?
Competitive with Ach Ach moiety blocks Na channel with size Duration is variable Slower onset Slower offset Steroid group rocuronium Benzylisoquinoliniums atracurium
