Monitoring Anaesthesia Flashcards
What are the aims of monitoring anaesthesia?
- Providing appropriate depth of anaesthesia for the procedure (Keep them asleep)
- Maintain normal physiological function of the patient (Keep them alive)
What 6 things do we monitor to assess cardiovascular function?
- HR and rhythm
- Pulse quality and BP
- CRT
- MM colour
- Hb Saturation
- Perfusion
What are the normal values for HR in dogs and cats
- Dog: 70-140bpm
- Cat: 100-200bpm
What must we consider when assessing HR in patients under GA?
That some drugs may affect HR e.g. alpha 2s can cause bradycardia
What does a stethoscope measure?
Monitors heart rhythm and rate, valve function and contractility
What a sinus arrhythmia?
Normal variation in HR that occurs during respiration- the pulse is ‘regularly irregular’
During inspiration, the HR increases
During expiration, the HR decreases
What 2 ways can we measure pulse quality (BP)
Indirect
Direct
What are the 3 indirect ways to measure BP
- Palpation of an artery
- Oscillo-tonometry - pneumatic cuff around limb
- Ultrasonic - doppler
How can BP be measured directly?
Transducer inserted via intra-arterial catheter
What is normal CRT
<2 seconds
What can cause a delayed CRT?
Hypotension
Vasoconstriction
Haemorrhage or unable to maintain CO
What does very bright pink MM mean?
Hypercapnia (excess CO2)
What does blue MM mean?
Cyanosis- inadequate Hb saturation
What does white MM mean?
Hypotension, blood loss, anaemia
What is petechiation?
Clotting problems
If an animal has septicaemia, what colour will the MM be?
Brown/ red
How can Hb saturation be measured?
Using a pulse oximeter.
It uses a red infrared light beams to detect the presence of oxygenated arterial blood.
What is perfusion?
The passage of blood through the capillary bed of the tissues
How can perfusion be measured?
- pulse oximeter
- CRT
- Visible signs of blood at surgical site
- Core: Peripheral Temperature difference
- Urine output of >1mls/kg/hr
How can the CNS function be monitored during GA?
- Cranial Nerve Reflexes
- Rate and Pattern of respiration (controlled by the pons and the medulla oblongata)
- Autonomic responses ( action of smooth muscle and cardiac muscle)
- Skeletal muscle tone and response to toe pinching
Describe some Cranial Nerve Reflexes
- Palpebral reflex - should be absent once surgical plane reached
- Jaw Tone - should be loose
- Eye position - reliable unless had a muscle relaxant or ketamine. Central at induction, rolls ventromedial as anaesthesia deepens, then back to central
- Pupil diameter - constrict light; dilate deep
- Salivation - profuse in inadequate anaesthesia
What is the normal respiratory rate of dogs and cats?
Dog: 10-30bpm
Cat: 20-30bpm
What is the normal respiratory rate of dogs and cats under anaesthesia?
Dog: 8-30bpm
Cat: 20-30bpm
What is the lowest RR that is safe in dogs ?
8 breaths per minute
What are the autonomic responses?
HR, BP, Pupil diameter, CRT
Apart from your eyes, what ways can we monitor respiratory function?
Wright’s respirometer - placed in the circuit and records minute volume
Pulse oximeter - measure oxygenation
Ap alert
Capnograph - small tube placed between ET tube and circuit
What does a Capnograph measure?
Measures exhaled CO2 (measures the partial pressure of CO2 levels in the patients arterioles which correlates well with the level of Co2 in the blood )
Useful to detect hypoventilation and circuit problems
