6. Essentials of Monitoring Flashcards
• Triad of anaesthesia
Unconscousness
Muscle relaxation
Analgesia
Why do we monitor during perioperative period?
• 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
What do we record on a anaesthetic form?
– Time – When surgery occurred – Info about anaesthetic – what vapour, how much O2 – Recording variables • Mm, pulse quality • BP, HR
AIM when monitoring anaesthesia
- Maintain physiology
- Maintain adequate anaesthetic depth (not too light or deep)
- Prevent suffering and pain – unconscious
- Safety to personnel e.g. 800kg horse, aggressive dog
- Legal implications
What changes are we looking for?
changes in autonomic tone: sweating/ CV changes - bradycardia, sweating in horse
- Muscle tone
- Movement
- REsponse to surgical stimilation
More about msuckel tone - what muscle
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
What responses to surgical stimulation are we going to see
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
CV system
What do we monitor?
– Cardiac output
– Arterial pressure
– Peripheral perfusion
– Oxygenation
CNS monitoring
What do we monitor?
- Reflexes: Palpebral, Corneal
- Anal tone
- Eye position
- LAcrimaition
Talk about reflexes
Palpebral
Cornela
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
When do we check anal tone?
o If no access to head
o Relaxed = adequate or deep plane
o Normal towards lighter side
How do eyes rotate in SA and horses
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
LAcrimation
o Tears running off eyelid – lighter plane
o Decreases as anaesthetic depth increases
o Deeper = less lacrimation
Horses alcrimate mroe than SA
Horse dog cat normal HR and anaesthetised
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
Mucous membranes give indication of what
oxygenation and perfusion
a. pale, CO not great
b. congested = RED
List Monitoring AIDS
- ECG
- Blood pressure
- Pulse Oximetry (sPO2)
- Capnography
What is an oesophageal stethescope?
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
How do we monitor temp?
What are we trying to avoid
a. Thermometer
b. Oesophageal, rectal, oral temp probes
c. Avoid hypo or hyperthermia
What does ECG do?
a. Monitors electrical activity of the heart
b. Says nothing about mechanical activity of heart (no info on cardiac output)
Arterial blood pressure
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
Invasive arterial blood pressure
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
Non invasive arterial blood pressure
i. Quick and easy to apply cuff
ii. Intermittent readings
iii. No risk of infection
iv. Need correct cuffs
Pulse Oximetry
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
Limtiations to pulse oximetry
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
When do we use doppler
a. Useful in exotics
b. Probe placed over heart – can hear heart rate and blood flow
Capnography
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
What is blood gas analysis
- Gold standard
- Measures PO2 and PCO2 directly golf standars
- Can also measure pH, HCO3 - , lactate, electrolytes…….
- Arterial or venous?
- Does it matter?
- More expensive
