Lecture Notes in Anaesthesia - Chapter 2 Flashcards
How to choose the correct size of Guedel?
Which sizes for adults?
The size required is estimated by comparing the airway length with the vertical distance between the patient’s incisor teeth and the angle of the jaw.
Size 2-4 for small to large adults respectively.
How to choose correct size of nasopharyngeal airway?
Commonest sizes for adults?
They are sized according to their internal diameter in millimetres,
and their length increases with the diameter. The correct size is estimated by made by comparing the airway diameter with that of the external nares.
Sizes 6–8mm in diameter are suitable for
small to large adults, respectively.
Most common sizes of LMA in adults?
The most commonly used in female and male adults are sizes 3, 4 and 5.
Difference between Macintosh, McCoy and Magill laryngoscopes?
Macintosh - curved blade
McCoy - lever on handle elevated epiglottis improving view
Magill - straight blade
How are expired gases safely recycled by the anaesthetic machine?
What is the most commonly used indicator to show that an absorber is saturated?
Expired gases are passed through a container of soda lime (the absorber), a mixture of calcium, sodium and potassium hydroxide that removes carbon dioxide chemically.
After the carbon dioxide has been removed the expired gas has supplementary oxygen and anaesthetic vapour added to maintain the
desired concentrations, and the mixture is rebreathed by the patient.
Soda lime changes from pink to white.
Difference between a cannula and a catheter?
In general, the term ‘cannula’ is used for those less than 7cm in length and ‘catheter’ for those more than 7cm long.
Uses of capnometry?
- Degree of alveolar ventilation
- Disconnection indicator
- ETT tube correctly site
- Degree of rebreathing
- Indicator of cardiac ouput
- 1st clue as to development of malignant hyperpyrexia
What is a peripheral nerve stimulator used for?
How does it work?
What are TOF and tetanic stimuli?
What is fade?
How do depolarising and non-depolarising blockades differ in their response?
Used to assess neuromuscular blockade after giving neuromuscular blocking drugs
A peripheral nerve supplying a discrete muscle group is stimulated transcutaneously with a current of 50mA (commonly ulnar nerve/adductor pollicis).
Train of four - 4 stimuli of 0.2ms. Tetanic - 1 stimulus of 5s.
Non-depolarising - progressive decremental response to sequence (fade). Can use twitch 4 : twitch 1 in TOF.
Dopolarising - response is reduced but consistent (no fade)
What is a thermistor?
Locations of patient temperature monitoring (3)
What would a sudden unexpected rise suggest?
A thermistor is a semiconductor that varies in resistance according to its temperature.
- Oesophagus (cardiac temperature)
- Nasopharynx (brain temperature).
- The rectum can be used but, apart from being unpleasant, faeces may insulate thermistor.
Unexpected rise could be first warning of the development of malignant hyperpyrexia.
How is CVP measured?
How can CVP be used to assess fluid responsiveness?
Raised CVP low BP may indicate?
Measured by inserting a catheter via a central vein (CVC), usually the internal jugular or subclavian, so that its tip lies at the junction of
the superior vena cava and right atrium.
Fluid challenge -In the hypovolaemic patient the CVP increases briefly and then falls back to around the previous value, whereas in the euvolaemic patient the CVP will show a greater and more sustained rise. Overtransfusion will be seen as a high, sustained CVP.
Raised CVP low BP may indicate heart failure
How does oesophageal doppler cardiac output monitoring work?
US sensor placed in oesophagus behind descending aorta. Flow through aorta is proportional to cross-sectional area and velocity of fluid (measured by Doppler).
What does BIS stand for? What is it used for?
How does it work and what is the possible range of values?
What is an appropriate value for a GA?
When is it used(3)?
Bispectral index.
EEG monitoring processed by proprietary algorithm to produce a number between 0 (no cortical activity) and 100 (fully awake).
40-60 suitable for GA.
Useful when can’t monitor inspired/expired anaesthetics (bypass/TIVA) or avoidance of deep anaesthesia desirable (haemodynamically unstable).
