Monitoring Anaesthesia Flashcards
What are the main reasons for monitoring anaesthesia?
To ensure adequate DEPTH of anaesthesia to ensure adequate PERFUSION and OXYGENATION of tissues.
How do we monitor adequate depth in an anesthetized animal?
Mainly by monitoring neurological function. e.g. Cranial nerve reflexes + other reflexes.
What reflexes are used to monitor anaesthetic depth? Which drug may affect these reflexes under anaesthesia?
Palpebral reflex, jaw tone, pupil position and dilation. Also, lacrimation, salivation, and the corneal reflex. Drug = KETAMINE.
Why do we monitor CVS function? What types of CVS parameters are measured during anaesthesia?
To assess delivery of blood to tissues. Heart rate, pulse, mucous membrane colour, CRT, arterial BP, central venous pressure
Why is arterial BP measured in anaesthesia?
It is in indirect indicator of cardiac output.
What is a normal systolic, diastolic and mean arterial BP? What must mean ABP be kept above in anaesthesia?
Systolic = 100-160mmHG
Diastolic = 60-100mmHG
Mean = 80-120mmHG
Mean ABP MUST be kept above 60-70mmHG
Why do we monitor respiratory function? What types of respiratory parameters are measured during anaesthesia?
To assess adequacy of ventilation and uptake of oxygen. RR, rhythm and depth, arterial blood gases, arterial haemoglobin saturation, end tidal CO2
In what three ways can arterial BP be measured?
Doppler flow detection (non-invasive), Oscillometric method (non-invasive), arterial catheter in artery (invasive)
How does Doppler flow detection work to measure arterial BP? Which measurement does it give you? What are some advantages and disadvantages?
Put a pressure cuff on an extremity, ultrasound is distal to cuff. It gives you a systolic ABP. It is good in concious patients esp SA, however it can underestimate in cats.
How does Oscillometric method work to measure arterial BP? Which measurement does it give you? What are some advantages and disadvantages?
Automatically inflating cuff which sensed oscillation as it deflates. It gives you mean, systolic and diastolic ABP and HR. It is good for dogs, less reliable in cats and hypotensive patients.
Which measurements does arterial catheter in an artery (to measure ABP) give you? What are some advantages and disadvantages?
Systolic, mean and diastolic. It is good because it allows continuous monitoring and can take blood gas analysis samples, however it is invasive.
What is a normal central venous pressure? What is this a measure of? When would you use central venous pressure as a monitor?
0-10mmH20 / 0-7 mmHG
It measures the pressure in the vena cava. You would use it when you have HF, PSS ligation, or when you expect large BV changes.
What does pulse oximetry measure?
Arterial haemoglobin saturation, pulse rate, and thus adequacy of oxygenation.
How does pulse oximetry work?
A sensor detects pulsatile signals of arterial blood, and the differential LED absorption of oxygenated haemoglobin and reduced haemoglobin.
What is a normal arterial haemoglobin saturation (SpO2) in %?
Normal = 95-100%
If arterial haemoglobin saturation (SpO2) is <95%, what does this mean for the partial pressure of oxygen (PaO2)? Why?
If SpO2 <60mmHg (which is classed as hypoxaemia). This is because of the shape of the oxygen dissociation curve.
What partial pressure of oxygenation (PaO2) in arterial blood is considered as hypoxaemia?
<60mmHg
When should you measure arterial haemoglobin saturation during anaesthesia? Why?
During and AFTER. Why? Because it is impossible for an animal on 100% oxygen to reduce SpO2 levels to hypoxic levels, therefore you should keep the probe in until you know it is breathing properly on normal air.
Where can you measure using a pulse oximeter?
You can monitor using the tongue, toe, prepuce, ear and mammary gland.
What are some limitations of pulse oximetry?
Need to remember to monitor after when not breathing 100% oxygen, it does not tell you anything about ventilation. It can read some other kinds of haemoglobin as saturated, it underestimates saturation in anaemia.
Can you name a few circumstances in which you may get a low partial pressure of oxygen in arterial blood?
Hypoventilation, V/Q mismatch, CVS depression, increased oxygen demand.
What does a capnograph measure? What is a normal measurement? When may you want to intervene with IPPV?
It measure end tidal CO2 (ETCO2) (which indicates gas exchange, metabolic production and CVS function)
What is a normal measurement on a capnograph? When may you want to intervene with IPPV?
Normal = 35-45mmHg End tidal CO2
Values >60mmHg may warrant IPPV.
What types of situations may cause hypercapnia?
Hypoventilation, hyperthermia, bicarbonate administration, rebreathing
What types of situations may cause hypocapnia?
Hyperventilation, decreased cardiac output (e.g. shock), hypothermia
What are some limitations of capnography?
Samples errors (falsely low ETCO2)
What measurements can arterial blood gas analysis give you?
Arterial oxygen tension, arterial CO2 tension, and pH.
What is a normal arterial O2 tension? What does this measurement tell you?
Normal = >80mmHG, Hypoxaemia = <60mmHG
It tells you how well the lungs oxygenate blood
What is a normal arterial CO2 tension? What measurement indicates hypoventilation and hyperventilation?
Normal = 35-45mmHg Hypoventilation = >45mmHg Hyperventilatiob = <35mmHg
What does an arterial CO2 tension measurement tell you?
It measures alveolar ventilation (which is similar to ETCO2) in a healthy animal.
