Anesthetics Principles and Pharmacology Flashcards
What is general anaesthesia
Anaesthesia which produces insensibility in the whole body, usually causing unconsciousness
What type of drugs are used for general anaesthesia
Centrally acting drugs such as:
Hypnotics
Analgesics
What is regional anaesthesia
Anaesthesia producing insensibility in an area or region of the body.
The anaesthetic agent is applied to the nerve and anaesthesia produced in a distal site, remote from the injection.
Includes nerve and plexus blocks
How is regional anaesthesia administered
Local anaesthetics applied to nerves supplying relevant area
What is local anaesthesia
Anaesthesia producing insensibility in only the relevant part of the body
How is local anaesthesia administered
Local anaesthetics applied directly to the tissues
What are the disadvantages of using large amounts of chloroform or ether
Toxic side effects such as:
Cardiac depression
Respiratory depression
What are the 5 TYPES of anaestheic drugs available
Inhalational anaesthetics Intravenous anaesthetics Muscle relaxants Local anaesthetics Analgesics
What are the three functions of anaesthesia
Analgesia
Hypnosis
Relaxation
(Anaesthesia does not have to contain all three aspects)
What are the problems with anaesthesia
Polypharmacy
Muscle Relaxation
Separation of relaxation and hypnosis
Why could polypharmacy be a problem with anaesthesia
There is an increased chance of drug reactions/allergies
Why could muscle relaxation be a problem with anaesthesia
The patient will require artificial ventilation as they could lose airway control
Why could the separation of relaxation and hypnosis be a problem with anaesthesia
A patient could be paralysed with muscle relaxant yet insufficiently anaesthetised therefore being aware of their surroundings
What is the mechanism of action of general anaesthetic agents
They interfere with neuronal channels to hyperpolarise neurones (less likely to fire)
How are inhalational general anaesthetic agents absorbed
They dissolve in membranes therefore having a direct physical effect
How are intravenous general anaesthetic agents absorbed
They use allosteric binding so the GABA receptors open chloride channels
How does general anaesthesia affect cerebral function
Most of the complex processes are interrupted first with consciousness being lost early and hearing later.
More primitive functions are lost later.
Does IV anaesthesia have a slow or rapid onset of unconsciousness and recovery
Rapid as they are fat soluble so can cross membranes quickly
The recovery is rapid due to the disappearance of drug from circulation
What is a target controlled infusion pump system
It allows very accurate infusion to achieve specific blood or brain concentrations of agents using complex pharmacokinetic algorithms
What is a disadvantage of total intravenous anaesthesia
You cannot measure drug concentration in real time
This has to be done using a computer which produces an estimate
What type of compound/element are inhalational anaesthetics
Halogenated hydrocarbons
How are inhalational anaesthetics taken into the body
The uptake and excretion is via the lungs
As the concentration gradient increases in the lungs, it will increase in the blood and eventually in the brain
At induction the patient is given a relatively high concentration of the agent to breath. The gas then moves down the concentration gradient in to the patients blood and finally brain to achieve a high enough partial pressure there to produce unconsciousness.
Can inhalational anaesthetics cross aveoli easy
Yes
What does the arterial concentration when using inhalational anaesthetics equate to
Alveolar partial pressure
