Flashcards in Anaesthetic monitoring Deck (52)
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.
Don't become so focused on completing this form that you are neglecting your monitoring.
What should be monitored?
1. Anaesthetic depth
3. Respiratory system
What cranial nerve reflexes can be checked to aid in anaesthetic monitoring?
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
-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.
-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
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
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
-Between the toes
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
Define diastolic blood pressure
This is the minimum pressure within the arteries that occurs towards the beginning of the cardiac cycle. This is when the ventricles are filled with blood and is predominately determined by the peripheral vascular resistance.
The normal range for dogs, cats and horses is 55-90mmHg
Define mean blood pressure
This is the average blood pressure during the cardiac cycle. It provides information about tissue perfusion. The normal range for dogs, cats and horses is 60-85mmHg.
It is important to maintain a mean blood pressure > 60 mmHg to ensure adequate organ perfusion
Why would you use blood pressure monitoring?
Gives more direct information about the peripheral circulation than palpating a pulse
Useful measure of cardiovascular function specifically in patients with significant cardiovascular disease or those undergoing major surgery
It provides information of the heart’s ability to pump blood around the body and the fluid balance of the patient
Fluid therapy supports blood pressure, would be useful to know we are using an adequate flow rate
What might high blood pressure indicate?
A low blood pressure may indicate that vital organs are not being sufficiently perfused and/or the patient is under deep anaesthesia
What might low blood pressure indicate?
High blood pressure may indicate that an animal is only lightly anaesthetised or that there is sympathetic stimulation
Describe doppler ultrasonography
This method provides intermittent readings of blood pressure.
A cuff tourniquet is applied proximal to the artery (cuff width = 40% circumference of the limb)
The area where the Doppler is to be applied; normally over the carpal pulse is clipped and contact gel applied
The Doppler is then used to detect the pulse
Once detected the cuff is inflated using the sphygmomanometer until the sound disappears, then slowly deflated until the first sound is heard
The pressure at which the flow recommences is taken as the systolic blood pressure.
Describe oscillometric blood pressure
Measures the magnitude of arterial pulsations produced within an air filled cuff. It detects movement of the artery wall vibrating against the cuff
Inaccurate results can be given when there is patient movement (Shivering), dysrhythmia, hypotension and bradycardia
These monitors can be set up to take repeated measurements
Systolic, diastolic and mean blood pressure is recorded
Describe a capnograph
Provides information of both respiratory and cardiovascular function
Measures adequacy of ventilation (hyper or hypoventilation)
Provides measurement of carbon dioxide in each breath of the respiratory cycle
Gas breathed out a mixture of anatomical dead space gas followed by increasing levels of CO2 rich gas
When the animal breathes in the level of CO2 will return to zero (if breathing system working correctly)