Anaesthetic monitoring Flashcards
What are the goals of anaesthetic monitoring?
Provide an appropriate depth of anaesthesia for the procedure required;
Whilst maintaining normal physiological function
How often is anaesthetic monitoring carried out?
Patients monitored continuously, parameters recorded every 5 min
Allows for action
Chances of surviving slim if not checked at least every 5 minutes
Describe monitoring charts
Must be completed for all cases.
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Don’t become so focused on completing this form that you are neglecting your monitoring.
What should be monitored?
- Anaesthetic depth
- Circulation
- Respiratory system
- Temperature
What cranial nerve reflexes can be checked to aid in anaesthetic monitoring?
Palpebral Reflex
Corneal reflex
Pedal reflex
(Jaw tone)
Avoid doing too often or can become refractory (palpebral)
Describe eye position and pupil diameter
Observe both eyes
Surgical plane of anaesthesia eye ventromedial position with some sclera visible
Depth increases
-the eye becomes central again
The use of ketamine will affect this pattern
As the depth of anaesthetic increases the pupil becomes more dilated
What might salivation indicate?
Excessive with an inadequate anaesthetic depth/pain
Note breed variation
Describe indications from mucous membranes and capillary refill times
Mucous membrane colour should be pink
Capillary refill time (CRT) is measured by pressing on a non-pigmented area of gingiva. This will cause it to blanch
The time for the colour to return is the CRT
Should be ~2seconds
How can the response to surgical stimulation aid in monitoring?
Lost during surgical planes
If present increase in heart rate, respiratory rate and muscle tone
Describe the heart rate and pulse quality
Check every 5 minutes.
Rapid when
-the patient is light
Slows in surgical planes
Will slow further
-as anaesthetic depth increases
Describe the respiratory rate and pattern
Check every 5 minutes
Rapid and irregular
-patient is too lightly anaesthetised
Slower and regular at surgical planes
Shallower and slower when
-too deep until irregular jerky breathing movements are seen, eventual apnoea.
How might temperature aid in anaesthetic monitoring?
Hypothermia is common
Temperature should be monitored regularly
-Every 5-30mins
Frequency of measurement depends on the case details
What is the purpose of monitoring aids?
To provide additional information about the physiological status of the patient. They should never replace the basic hands on monitoring detailed previously
Describe the advantages/disadvantages regarding mechanical aids
Allows a more precise picture of the patients health status
May detect early changes in patients’ health status allowing early intervention
Allow closer control over anaesthetised patients
Must be monitored to ensure information provided is correct
Should never take the place of routine, basic monitoring procedures i.e. observations, listening and touching the patient
Describe the oesophageal stethoscope
Often overlooked
Simple and effective
Allows VN to hear heart beat reliably
Describe the pulse oximeter
Non-invasive method of measuring arterial oxygen saturation
Gives information about gas exchange and arterial oxygenation
Provision of an audible indicator of heart rate is reassuring
but the remaining information is limited- when breathing oxygen, the saturation will not fall unless your patient is in serious trouble
The oxygen saturation of a patient receiving 100% oxygen should always be above 95%.
How do pulse oximeters work?
Two sources of light originate from the probe at different wavelengths (red and infra-red)
Absorbed by the red blood cells differently depending on how well the RBCs are saturated with oxygen
The device recognises the pulsatile flow of the arteries and can display both the oxygen saturation and the pulse rate.
Where is the probe of the pulse oximeter usually placed?
Usually the probe is placed on the tongue
Can be placed on other non-pigmented areas of skin
- Prepuce
- Vulva
- Between the toes
- Ear pinna
- Lip
When might a pulse oximeter fail?
f there is peripheral vasoconstriction, or low blood pressure
In smaller patients the heart rate may be too high for a standard machine to register
Diathermy and bright operating lights can both disrupt the signal
Can be misleading in the anaemic patient
Define systolic blood pressure
This is the peak pressure within the arteries that occurs towards the end of the cardiac cycle, when the ventricles are contracting. It is determined by a combination of peripheral vascular resistance, stoke volume and intravascular volume.
The normal range in dogs, cats and horse is 90-120mmHg
