ANAESTHESIA - Monitoring Flashcards
Which four factors should you monitor to assess anaesthetic depth?
Movement
Eye position
Eye reflexes
Jaw tone
Which two eye reflexes should you monitory to assess anaesthetic depth?
Palpebral reflex
Corneal reflex
What should you assess instead of jaw tone in large animals?
Tension of the strap muscles of the neck
What are three indicators of good anaesthetic depth?
Ventro-medial eye rotation
Absent palpebral reflex
Relaxed jaw tone
What are three indicators of excessive anaesthetic depth?
Central eye rotation
Absent corneal reflex
Mydriasis (pupil dilates)
How can you manually monitor the respiratory system?
Monitor the respiratory rate
Which two methods can you use to manually monitor the respiratory rate?
Take respiratory rate by counting the chest movements or by counting the movements of the resevoir bag
How can you manually monitor the cardiovasular system?
Palpate pulses
Auscultate heart
Assess mucous membrane colour
CRT
Why is palpating pulses preferable to auscultating the chest when a patient in under anaesthesia?
Palpating pulses provides a pulse rate, rhythm and allows you to assess pulse quality/strength which gives some indication as to the levels of peripheral perfusion
Give three examples of arteries you can use to palpate pulses
Femoral artery
Dorsal pedal artery
Metacarpal artery
Why is it better to take pulses from the more peripheral arteries (i.e. dorsal pedal and metacarpal arteries)?
Palpating pulses using the more peripheral arteries gives a better idea of peripheral perfusion
Why should you always compare the pulse rate to the heart rate?
If the pulse rate and heart rate are not the same, this is abnormal (known as an anacrotic pulse)
Which pieces of equipment are used to monitor the respiratory system?
Pulse oximetry
Capnography
What is blood gas analysis?
Blood gas analysis is when you take an arterial blood sample and use this to measure the partial pressure of oxygen and carbon dioxide (PaO2 and PaCO2) in the arterial blood
Why is blood gas analysis less commonly used?
Blood gas analysis is an invasive procedure which requires skill and also doesn’t allow for continuous monitoring
What information do pulse oximeters typically provide?
SpO2
Pulse rate
Signal quality
Which five parts of the body would be appropriate for the placement of a pulse oximetry sensor?
Tongue
Nail bed
Ear tip
Vulva/prepuce
Lip fold
How does the pulse oximetry sensor detect the percentage of arterial haemaglobin saturated with oxygen (SpO2)?
The pulse oximetry sensor is placed onto an appropriate part of the body. The probe transmits, and detects, specific wavelengths of red and infra-red light that are differentially absorbed by oxygenated and de-oxygenated haemoglobin on passage through tissue. Analysis of this differential absorption allows calculation of SpO2
List six possible factors that can result in unreliable pulse oximetry readings
Poor contact between tissue and sensor
Pigmented skin
Movement
Peripheral vasoconstriction
Hypotension
Abnormal haemoglobins
How does peripheral vasoconstriction affect pulse oximetry readings?
Peripheral vasoconstriction reduces blood flow to the peripheral tissues and thus decreases the flow of oxygen to the periphery and the pulse
How does hypotension affect pulse oximetry readings?
Hypotension reduces blood flow to the periphery by lowering the overall pressure being excerted within the arteries, meaning there is less force pushing the blood to the periphery hence reducing the flow of oxygen
What is used to monitor the signal quality of a pulse oximeter?
Plethysmograph
Flashing lights (red/orange/green)
What is a plethysmograph?
A plethysmograph is a graphical display of the pulse oximetry signal over time, with well defined waveforms being indicative of good signal quality
What should the SpO2 be in animals breathing in room air?
SpO2 should be over 90% in animals breathing in room air
What should the SpO2 be in anaesthetised animals breathing in 100% oxygen?
SpO2 should be over 95% in anaesthetised animals breathing in 100% oxygen
What can cause a low SpO2?
Low inspired oxygen
Lung disease
Right to left cardiac shunting
Hypoventilation