Principles and Pharmacology of Anaesthesia Flashcards
What is general anaesthesia
Produces insensibility in the whole body, usually causing unconsciousness
What is regional anaethesia
Producing insensibility in an area or region of the body. Applied to nerves supplying relevant areas.
What is local anaesthesia
Producing in sensibility in only the relevant part of the body. Local anaesthetics applied directly to the tissue
List the drugs used in anaesthetics
Inhalational anaesthetics Intravenous anaesthetics Muscle relaxants Local anaesthetics Analgesics
List the techniques of administrating anaesthetic drugs
Tracheal intubation Ventilation Fluid therapy Regional anaesthesia Monitoring
Describe the current use of anaesthesia
Triad of anaesthesia, analgesia, hypnosis and relaxation
State the purpose of relaxation
refers to muscle relaxation necessary to provide immobility for certain procedures, allow access to body cavities and to permit artificial ventilation amongst other things.
State the advantages of balanced anaesthesia
Titrate doses seperately and therefore more accurately to requirements.
Avoid overdosage.
Enormous flexibility.
State the disadvantages to balanced anaesthesia
Polypharmacy results in an increased risk of drug reactions and allergies
Muscle relaxation makes way for the requirement of artificial ventilation.
Seperation of relaxation and hypnosis - awareness
State the function of general anaesthetic agents
Provide unconcsciousness and small degree of muscle relaxation, they may also provide a small degree of analgesia
How do general anaesthetic agents work
They interfere with neuronal ion channels causing them to hyperpolarise (thus making them less likely to fire).
Inhaled agents dissolve in the membranes
IV agents - allosteric binding on GABA receptors thus open chloride channels
State the current IV anaesthetic agents
Thiopentone or propofol
Describe the bodies reaction to IV anaesthetics
Rapid onset of unconciousness and rapid recovery due to the disappearance of drug from circulation
What type of chemical are inhaled anaesthetics
Halogenated hydrocarbons
MAC
Minimum alveolar concentration, a measure of potency
Describe the induction period in inhaled anaesthesia
Slow
How is a patient awakened when on inhalation anaesthetics
Stop the inhalation admin and washout by breathing a gas mixture containing no anaesthesia
State the most common sequence of general anaesthesia
IV induction followed by inhalation maintenance
How does general anaesthetic act on CVS centrally
It depresses cardiovascular centre reducing the sympathetic outflow, creating a negative inotropic/chronotropic effect on the heart. Also results in reduced vasoconstrictor tone - vasodilation
How does general anaesthesia act on the CVS directly
Negative inotropic effect resulting in vasodilation and venodilation (decreased venous return and decreased cardiac output)
How does general anaesthetic act on the respiratory system
Depressants. Reduce hypoxic and hypercarbic drive and decreased tidal volume and increased respiratory rate.
Paralyses cilia
Decreased FRC
State the indications for muscle relaxants
Ventilation and intubation, when immobility is essential and body cavity surgery
How do Non-depolarising NMBs work in muscle relaxation
They competetively block nicotinic acetylecholine receptors at the neuromuscular junction (preventing opening of sodium ion channels)
How can the effects of
non-depolarising NMBs be reversed
Anticholinesterases stop the removal of Ach from the synapse
