Introduction to anaesthesia Flashcards
What 3 A’s make up the normal state of consciousness?
Alertness
Awareness
Attention
What is the most common scale used to measure consciousness clinically?
Glasgow Coma Scale (GCS)
What is the difference between anaesthesia and sedation?
Anaesthesia = drug-induced, predictably reversible form of coma characterised by a lack of feeling
Sedation = state that allows patients to tolerate unpleasant diagnostic or surgical procedures an to relieve anxiety and discomfort, during which verbal contact can be maintained
What is the difference between anaesthesia and sedation?
Anaesthesia = drug-induced, predictably reversible form of coma characterised by a lack of feeling
Sedation = state that allows patients to tolerate unpleasant diagnostic or surgical procedures an to relieve anxiety and discomfort, during which verbal contact can be maintained
What are the 3 main scales used to assess levels of sedation?
Ramsey scale
Richmond Agitation Sedation Scale (RASS)
Riker Sedation Agitation Scale (SAS)
What are the most commonly used drugs for sedation?
Benzodiazepines Opiates Entonox (NO/ O2) Anaesthetics Dexmedetomidine (alpha2 antagonist)
Name the common benzodiazepines used for sedation
Lorazepam
Midazolam
Diazepam
Temazapam
Name 3 common anaesthetics
Ketamine
Propofol
Sevoflurane
What is the mechanism of action of Benzodiazepines?
Benzodiazepines are allosteric positive modulators
Work near GABA receptor sites to increase chloride entry into the cell - leads to hypopolarisation thus decreasing neuronal firing
What conditions are Benzodiazepines commonly used for?
Anxiety
Insomnia
Epilepsy
Why should Benzodiazepines only be used short term?
Long term use can lead to tolerance and dependence
What opioids are commonly used for sedation
Alfentanil
Fentanyl
Remifentanil
What is the principal opioid receptor that short acting opioids (such as fentanyl) bind to?
Mu-opioid receptors
What are the 3 cardinal signs of opioid overdose?
Hypoventilation
Coma
Miosis (pinpoint pupils)
What are the main receptors upregulated by opioid receptor activation?
Upregulation of voltage sensitive K+ channel increases movement of K+ out of cell (causing hyperpolarisation of cell thus making it harder for the cell to fire afterwards)
What are the main receptors downregulated by opioid receptor activation?
Downregulation of Ca2+ channels reduces vesicular release from the presynaptic terminal and plasticity on the post-synaptic terminal
What is Entonox?
50:50 mixture of Nitrous Oxide and Oxygen
Inhaled
Used for light sedation and as an analgesic
What is Dexmedetomidine?
Selective alpha2-adrenoceptor agonist
Where is Dexmedetomidine most commonly used?
Intensive Care
Used when patient needs to maintain verbal responsiveness
Where are alpha2-adrenoceptor mainly located?
Pre-synaptic terminals of neurons in the brain and ANS.
Also found on pancreatic islets, platelets and fat cells.
What is the mechanism of action of Dexmedatomidine?
Binds to presynaptic alpha2-adrenoceptors in the brain
Inhibits release of noradrenaline
Terminates propagation of pain signals
What are the 3 key elements making up the triangle of balanced anaesthesia?
Analgesia
Anaesthesia (hypnosis)
Muscle relaxation
What are the common local anaesthetics?
Bupivacaine
Levobupivacaine
Lidocaine
[All amino amides]
What are the common general anaesthetics?
Ketamine
Propofol
Nitrous Oxide
Isofluorane
What are the two main routes of administration for general anaesthetics?
IV
Inhalation
What properties of nerves can affect speed/effectiveness of block from local anaesthetic?
Myelination (work more easily on un- or light-myelinated axons)
Length of axon (work more easily on shorter neurons)
What is the mechanism of action of local anaesthetics?
- Enter cell in an unionised form
- Become ionised in intracellular space
- Blocks Na+ channel from inside
Why do local anaesthetics not work as well on inflammed tissue?
pH-dependent and inflammatory soup in damaged soup is generally acidic.
Local anaesthetics ionise in acidic pH which reduces ability to cross the neuronal membrane to attach to the Na+ channel.
What are the 2 groups of local anaesthetics?
Amino esters (metabolised in the plasma) Amino amides (metabolised in the liver)
What is the ideal score for each sedation scale?
Richmond = 0 Ramsey = 2 Riker = 4
