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Flashcards in Anaesthetic monitoring Deck (52)
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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.

Legal document

Don't become so focused on completing this form that you are neglecting your monitoring.


What should be monitored?

1. Anaesthetic depth

2. Circulation

3. Respiratory system

4. 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



-Between the toes

-Ear pinna



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


Describe capnography

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)


What can affect capnography?

Problems with either the circulation or respiratory system will affect amount of CO2 breathed out

Skill needed to interpret the trace