Anaesthetic agents Flashcards
Anaesthesia definition
A defect of sensation
A reversible drug induced absence of sensation and awareness
Stages of ethanol
Tranquillization
Excitation
Dystharia
Ataxia
Sedation/ hyponosis
Anaesthesia
Coma
Medullary depression
Death
How do anaesthetics work?
Diverse range
Lipid solubility
Cell membrane
Stereo-selectivity
Interaction with membrane proteins
Modulation of ligand gated ion channels
Global depression in neuronal activity
How?
Stimulation of inhibitory receptors
- GABAa
- glycine
Inhibition of excitatory receptors
- nicotinic
- serotonin
- glutamate/ NMDA
How it works on a molecular level
Changes structure of protein
Cl- pass into cell
Stops actions of cell
How are anaesthetics given?
Inhale
Inject
Inhalation agents
Oxygen
Nitrous oxide
Isoflurane
Other volatile agents
Oxygen
Gas above -119C
Supports combustion- not flammable
Black cylinders with white shoulders at 137 bar
Piped oxygen out of walls from VIE
Side effects of oxygen
O2 free radicals
CNS convulsions
Pulmonary oxygen toxicity
Retrolental fibroplasia
CO2 narcosis
Nitrous oxide
Odourless gas in blue cylinder
Liq/vapour at 44 bar
Poor anaesthetic MAC 105%
Good analgesic
Quick onset/ offset
Cardio respiratory depressant
Neuropathy/ BM depression
35x more soluble than N2
Physical properties of inhalational agents
Cost
Chemical stability
Non-flammable/ explosive
Vaporisable
Environmentally stable
Chemical properties of inhalational agents
Non irritant
Low blood: gas solubility
High potency MAC
Minimal side effects
Biotransformation
Non-toxic
Older agents
Ether
Chloroform
Cyclopropane
Methoxyflurane
Halothane
Enflurane
Isoflurane
Halogenated ether
Relatively cheap
Stable and non flammable
Vaporisable BP 49C
Irritable to airway
Relatively potent MAC 1.1%
Side effects CVS/RS
0.2% metabolised
Sevoflurane
Non irritable
Quick onset/ offset
MAC 2%
5% metabolised
CVS stability
Emergence phenomena
Expensive
