6. Essentials of Monitoring

Question 1

• Triad of anaesthesia

Answer 1

Unconscousness
Muscle relaxation
Analgesia

Question 2

Why do we monitor during perioperative period?

Answer 2

• Anaesthesia induces significant changes to:
– Cardiovascular system
– Respiratory system
– Central nervous system
– Metabolism
– Anaesthesia carries an inherent risk
• Legal aspects
• Anaesthetic related mortality happens☹
• Approx. 1 in 100 horses die under anaesthesia☹
Humane pre, intra, post operative conditions
Maximise change of survival

Question 3

What do we record on a anaesthetic form?

Answer 3

–	Time
–	When surgery occurred
–	Info about anaesthetic – what vapour, how much O2
–	Recording variables
•	Mm, pulse quality
•	BP, HR

Question 4

AIM when monitoring anaesthesia

Answer 4

1. Maintain physiology
2. Maintain adequate anaesthetic depth (not too light or deep)
3. Prevent suffering and pain – unconscious
4. Safety to personnel e.g. 800kg horse, aggressive dog
5. Legal implications

Question 5

What changes are we looking for?

Answer 5

changes in autonomic tone: sweating/ CV changes - bradycardia, sweating in horse

2. Muscle tone
3. Movement
4. REsponse to surgical stimilation

Question 6

More about msuckel tone - what muscle

Answer 6

sternocephalicus muscle)
o Jaw tone is easily accessible masseter muscle
o Check regularly to notice any changes
o Large animals Jaw tone very hard due to size so use sternocephalicus

Question 7

What responses to surgical stimulation are we going to see

Answer 7

o If animal responds to this = light
o Changes BP and HR when painful = provide more analgesia
o Toe pinch
o Large animals harder to

Question 8

CV system

What do we monitor?

Answer 8

– Cardiac output
– Arterial pressure
– Peripheral perfusion
– Oxygenation

Question 9

CNS monitoring

What do we monitor?

Answer 9

1. Reflexes: Palpebral, Corneal
2. Anal tone
3. Eye position
4. LAcrimaition

Question 10

Talk about reflexes
Palpebral
Cornela

Answer 10

o Palpebral (stroke eye lid) (dogs, cats, farm) touch medial and lateral canthus and assess blinking
 Slow blink (esp medial) acceptable
 Quick blink is too light plane
 Horse just stroke upper and lower eyelid (no tapping)
• Slow blink acceptable plane
o Corneal
 Touch cornea
 Don’t tend to do as repeated poking can cause corneal damage and ulceration
 Drip sterile saline onto cornea which will make animal blink – corneal reflex without damage
 Only really do to check if dead

Question 11

When do we check anal tone?

Answer 11

o If no access to head
o Relaxed = adequate or deep plane
o Normal towards lighter side

Question 12

How do eyes rotate in SA and horses

Answer 12

o Normal pupillary light response
o Light plane – eye rotates ventromedially
o Look at eyes to assess plane of anaesthesia before do many things including intubation
o Central = light plane or Deep
Alwsy asess eyes before intubate
Ruminants same
HORSES:
• Horse eye moves around so hard to use eyes

Question 13

LAcrimation

Answer 13

o Tears running off eyelid – lighter plane
o Decreases as anaesthetic depth increases
o Deeper = less lacrimation
Horses alcrimate mroe than SA

Question 14

Horse dog cat normal HR and anaesthetised

Answer 14

a. Horse  20-40 bpm
b. Dog  50-100 bpm
c. Cat  80-160 bpm

Debatable
–	>60/min large dogs
–	>80/min cats
–	>25/min horses
–	>50/min cattle

Question 15

Mucous membranes give indication of what

Answer 15

oxygenation and perfusion

a. pale, CO not great
b. congested = RED

Question 16

List Monitoring AIDS

Answer 16

1. ECG
2. Blood pressure
3. Pulse Oximetry (sPO2)
4. Capnography

Question 17

What is an oesophageal stethescope?

Answer 17

a. Normal earpiece, bell removes and in tube, tube sits in oesophagus of animal. AVOID stomach as could case regurgitation
b. Thin, flexible tube attached to regular stethoscope
c. Allows auscultation of heart and lung sounds, even if animal is covered by drapes
d. Only really small animals, maybe small sheep but not adult

Question 18

How do we monitor temp?

What are we trying to avoid

Answer 18

a. Thermometer
b. Oesophageal, rectal, oral temp probes
c. Avoid hypo or hyperthermia

Question 19

What does ECG do?

Answer 19

a. Monitors electrical activity of the heart

b. Says nothing about mechanical activity of heart (no info on cardiac output)

Question 20

Arterial blood pressure

Answer 20

Can use non invasive and invasive methods

a. To give indication of cardiac output and perfusion
b. BP tells us the animal has cardiac output
c. 3 Values:
i. Systolic pressure  80-140 mmHg
ii. Diastolic pressure  50-90 mmHg
iii. Mean pressure  60-90 mmHg

Question 21

Invasive arterial blood pressure

Answer 21

i. Placement catheter into peripheral artery
ii. Gold standard
iii. Continuous readings – see beat to beat changes in BP
iv. Takes time to place indwelling arterial cannula
v. Skill depending on what species – cat harder to get into artery than vein
vi. Expensive equipment

Question 22

Non invasive arterial blood pressure

Answer 22

i. Quick and easy to apply cuff
ii. Intermittent readings
iii. No risk of infection
iv. Need correct cuffs

Question 23

Pulse Oximetry

Answer 23

a. Also known as SpO2 (oxygen saturation)
i. Tells you if patient getting enough O2
b. Measures % saturation of haemoglobin with oxygen
c. Normal is 98%, if <95% WORRY
d. Related to PO2 by sigmoid curve
e. Measures pulse too!
f. An abnormal reading can be indictive of equipment problems but DO NOT ASSUME
g. Plesthysmograph (indication of perfusion) place on thin area
i. Tongue
ii. Lip
iii. Vulva, prepuce
iv. To do with infra red light absorption, light needs to pass through tissues and be detected

Question 24

Limtiations to pulse oximetry

Answer 24

i. Hypoperfusion/ vasoconstriction
1. If use alpha 2 agonist = vasoconstriction = will interfere with results
ii. Bright lights can affect results
iii. Movement can affect results
iv. Anaemia – limits usefulness of output
v. Probe can blanch capillary bed – move around
vi. It doesn’t tell us much about the adequacy of ventilation as patient on pure oxygen. So Capnography is preferred as more sensitive
vii. Fairly late indicator of problems so capnography better

Question 25

When do we use doppler

Answer 25

a. Useful in exotics

b. Probe placed over heart – can hear heart rate and blood flow

Question 26

Capnography

Answer 26

Extremely important. If only one piece of equipment we would want this:

a. Attached to breathing system animal is attached to
b. Measures end tidal CO2 (conc/ partial pressure of CO2 in expired air)
c. Normal – 35-45 mmHg
d. Inspired CO2 should eb zero
e. Tells about perfusion and ventilaiton
f. Capnography tell animal has adequate ventilation and if it has cardiac output or not as all CO2 produced in body is able to get through blood stream, into lungs and out
g. Tells you if ET tube in correct place – if in Oesophagus won’t have CO2!!!
h. Issues with breathing system will tell if we have kinks or leaks
i. Can get blocked with respwater
j. Few seconds lag

Question 27

What is blood gas analysis

Answer 27

• Gold standard
• Measures PO2 and PCO2 directly golf standars
• Can also measure pH, HCO3 - , lactate, electrolytes…….
• Arterial or venous?
• Does it matter?
• More expensive