Anaesthetics Flashcards
What is general anaesthesia?
Centrally acting drugs causing loss of sensation to the whole body
What is regional anaesthesia?
Local anaesthesia applied to nerves supplying area
What drugs are used in anaesthetics?
Inhalation/IV anaesthetics
Muscle relaxants
Local
Analgesics
What techniques/equipments are used in anaesthetics?
Tracheal intubation Ventilation Fluid therapy Regional anaesthesia Monitoring
What is the Triad of anaesthesia?
Hypnosis
Analgesia
Relaxation
What are the common problems of anaesthesia?
Polypharmacy
Muscle relaxation -> ventilation
Separation of relaxation & hypnosis
General anaesthetics act on which part of the triad?
Relaxation
Hypnosis
How do general anaesthetics act?
Interfere with neuronal ion channels
Hyperpolarise Cl- channels
Bind GABA receptors (IV)
How is cerebral function affected by general anaesthesia?
Affected from top down
Complex first - hearing later
Reflexes spared
What are the benefits of intravenous anaesthesia?
Rapid onset, recovery
How is IV anaesthesia metabolised?
Hepatic metabolism
Renal excretion
In what order do IV anaesthetics enter different compartments of the body?
Blood
Viscera
Muscle
Fat
Where are inhaled anaesthetics excreted?
Lungs
Arterial concentration of inhaled anaesthetics equates to what?
Alveolar partial pressure
What is MAC?
Minimum alveolar concentration
Measure of potency (low number = high potency)
How are patients awakened from inhaled anaesthetics?
Stop administration
Washout of conc. gradient
What are the common forms of IV anaesthetic?
Propofol
Opiate
What are the central effects of General Anaesthetic?
Depress CVS
Reduce sympathetic outflow
Negative inotrope
Reduced vasoconstrictor tone (vasodilation)
What are the direct effects of General Anaesthetic?
Negative inotrope
Vasodilation
Venodilation
What are the effects of venodilation?
Decreased venous return, decreased cardiac output
What are the effects of vasodilation?
Decreased peripheral resistance
What are the respiratory effects of GA?
Respiratory depressants
Paralyse cilia
Decrease FRC
When are muscle relaxants indicated?
Ventilation and intubation
When immobility is essential
In which surgeries is immobilisation essential?
Laparotomy
Neurosurgery
Body cavity surgery
What problems are associated with muscle relaxants?
Awareness
Incomplete reversal may require ventilation
Apnoea
Opiates affect which of the anaesthetic triad?
Hypnosis
Analgesia?
Local anaesthetics affect which of the anaesthetic triad?
Analgesia
Relaxation
Why is intraoperative analgesia used?
Prevention of arousal
Opiates contribute to hypnotic effect
Suppress reflex responses to painful stimuli
What are the benefits of local anaesthesia?
Retain awareness
Lack of global effects
Spare respiratory function
What are the negatives of local anaesthesia?
Derangement of CVS physiology
Toxicity
Toxicity of local anaesthesia is associated with what?
Absorption > metabolism Dose used Rate of absorption Patient weight Drug used
What are the signs of local anaesthesia toxicity?
Circumoral/lingual numbness Light headedness Tinnitus Visual disturbances Muscular twitching Drowsiness Cardiovascular depression Convulsions Coma Cardiorespiratory arrest
Which fibres are affected by local anaesthesia?
Thick fibres spared (motor)
Pain blocked
What are the effects of neuraxial block?
Inspiration spared
Expiratory function impaired (loss of abdominal muscle function)
Decreased FRC
Increased V/Q mismatch
What are the main types of local anaesthesia?
Local anaesthesia Field blocks Plexus blocks Limb blocks Neuraxial blocks
