Anaesthetics Flashcards
What is general anaesthetic?
Produces insensibility in the whole body, usually causing unconsciousness.
Centrally acting drugs - hypnotics/analgesics.
What is regional anaesthetic?
Producing insensibility in an area or region of body. Applied to nerves supplying relevant area.
What is local anaesthetic?
Producing insensibility in an only the relevant part of the body. Applied directly to the tissues.
What types of anaesthetics are there?
Inhalational Intravenous Muscle relaxants Local anaesthetics Analgesics
What techniques are used?
Tracheal intubation Ventilation Fluid therapy Regional anaesthesia Monitoring
What does the triad of Anaesthesia consist of?
Analgesia, Hypnosis, Relaxation.
What are the problems with polypharmacy?
Increased chance of drug reactions / allergies.
Problems with muscle relaxation?
Requirement for artificial ventilation.
Means of airway control.
Problems with separation of relaxation and hypnosis?
Need to have a greater awareness. Patients can be awake but paralysed.
How do general anaesthetic agents work?
Inhalational:
IV:
Interfere with neuronal ion channels.
I: Dissolve in membranes - direct physical effect.
IV: Allosteric binding - GABA receptors - open chloride channels.
What do general anaesthetic agents do?
Provide unconsciousness as well as a small degree of muscle relaxation. Also provide some analgesia to different extents. Except ketamine all are negligible.
What functions are lost in General?
Cerebral function “lost from top down”.
Most complex processes interrupted first.
LOC early - hearing later.
More primitive functions lost later.
Why are reflexes relatively spared?
Primitive and small number of synapses.
What are the main things to note when using general?
ABC - long drawn out resuscitation.
Mandates airway management.
Impairment of Resp function and control of breathing.
CVS impact.
Care for unconscious patient.
Why is there a rapid recovery and onset with IV? (propofol)
1 arm - brain circulation time.
Rapid recovery - due to disappearance of drug from circulation. Redistribution V’s metabolism.
Why are inhalational slower?
Halogenated hydrocarbons.
Uptake and excretion via the lungs.
Conc G – lungs - blood - brain.
MAC - low number = high potency.
Slow induction - breathe in a washout to reverse conc gradient.
What is most common sequence of General?
IV induction followed by inhlational maintanence.
What are the physiological effects on the CVS system using general?
Central - depresses CV centre - reduces symp outflow.
Direct - negatively inotropic, vasodilation, venodilation (decreased venous return)
MAP = CO x SVR
Physiological effects on Resp system?
Resp depressants - reduce hypoxic and hypercarbic drive. Decreased TV and Increased rate.
Paralyse cilia.
Decrease FRC - lower lung volumes, VQ mismatch. Can be prolongued.
What are the indications for Muscle relaxants?
Ventilation and intubation.
Immobility is essential.
Body cavity surgery.
What are the problems with using muscle relaxants?
Awareness
Incomplete reversal - airway obstruction, vent insufficiency in immediate postop.
Apnoea = depends on airway and vent support.
POSSIBLE TO PARALYSE SOMEONE BUT GIVE AN INSUFFICIENT DOSE OF ANAESTHITIC - AWAKE DURING PROCEDURE.
Why use local and regional analgesia?
Retain awareness / consciousness
Lack of global effects of GA.
Derangement of CVS physiology.
Relative sparing of resp function.
What is a limiting factor when using local?
Toxicity - high plasma levels.
Signs and symptoms – Tinnitus, visual disturbance, drowsiness, coma.
How can LA block be used?
Due to differential penetration into different nerve types.
What do anaesthetist do?
Pre -op Assessment and care Critical care / intensive care Pain management Anaesthesia Post-op care
What is usually used in IV induction?
Propofol.
Quietness - gas or IV - careful monitoring of conscious level.
When would gas induction usually be used?
Young children. (Sevoflurane)
Adults with special needs.
What are the planes of anaesthesia?
Analgesia / sedation Excitation Anaesthesia: Light --> deep. Overdose Or Sleepy / Excited // Anaesthetised.