Monitoring anaesthesia Flashcards
Why do we monitor patients
To prevent patient response to surgical stimulation (nociception)
To detect abnormalities before they turn into major complications
Helps monitor for worsening of underlying or subclinical diseases
Enables early interventions to keep patient close to their physiological norm
To maintain tissue perfusion & oxygenation so we can improve patient outcome
What is the purpose of anaesthetic monitoring charts?
Serve as legal clinical record
Facilitate handover between clinicians
Help identify trends in patient parameters over time
Guide early interventions to prevent complications
Why is it important to record trends rather than single values in anaesthesia?
Trends provide clearer picture of patient’s condition over time
e.g. Gradual increases in HR, BP, & RR can indicate nociception, prompting intervention (e.g., IV ketamine)
What do the following abbreviations mean in anaesthesia monitoring?
BP
HR
RR
MAP
IPPV
BP: Blood Pressure
HR: Heart Rate
RR: Respiratory Rate
MAP: Mean Arterial Pressure
IPPV: Intermittent Positive Pressure Ventilation
What is tissue perfusion?
Adequate supply of oxygen & nutrients are delivered to tissues & CO2 & other waste products are removed
Requires fully functioning respiratory & cardiovascular system
How do anaesthetic drugs affect tissue perfusion?
Cause cardiac depression, reducing blood flow
Cause respiratory depression, limiting oxygen delivery
Decrease patient’s ability to maintain homeostasis (e.g., temperature control, electrolyte balance)
How does low blood pressure affect tissue perfusion?
Insufficient blood pressure reduces flow of oxygenated blood to tissues, impairing metabolism & waste removal.
What are causes of decreased blood flow that can decrease tissue perfusion?
Reduced heart rate (HR) or cardiac output
Haemorrhaging (blood loss)
Anaemia (low red blood cell count)
Conditions that impair blood flow (e.g., vascular obstructions)
What can cause decreased oxygen delivery to tissues?
Reduced respiratory rate (RR)
Oxygen delivery issues: Equipment failure or low oxygen flow
Pulmonary disease: Reduces oxygen exchange
Obesity in dorsal recumbency: Excess pressure on diaphragm decreases tidal volume, impairing inspiration
What are the 3 problems that are bound to occur to a certain extent during anaesthesia?
Hypotension
Hypothermia
Hypoventilation
How can we establish depth of anaesthesia?
Checking jaw tone
- Ideally nice & loose
Eye position check
Negative palpebral reflex
- Positive palpebral reflex = too light
Other indicators:
- capnography, HR, RR, BP
What are the stages of eye position during anaesthesia?
Picture A (Conscious): Central eye position
Picture B (Early induction): Slight eye rotation
Picture C (Deeper induction): Further rotation, eye points rostrally
Picture D (Ideal for surgery): Eye rotated ventrally, indicating surgical plane
Picture E (Central eye):
- Dilated pupils: Too deep (excess CNS depression)
- Normal or constricted pupils: Too light for surgery.
Why can eye position be unreliable with ketamine?
Ketamine increases muscle tone, preventing normal relaxation of eye muscles that causes eye rotation during anaesthesia
Eye position may not correlate with anaesthetic depth in patients receiving ketamine.
Why is it important to lubricate eyes regularly throughout anaesthesia?
They can’t blink when anasethetised which means eyes can dry out, this could lead to problems such as corneal drying &/or corneal ulceration
How can brachycephalic breeds and ketamine affect jaw tone?
Brachycephalic breeds: Often maintain some jaw tone throughout anaesthesia
Ketamine: Increases muscle tone, making jaw tone unreliable indicator of depth
(remember that not every animal will follow what textbook suggests)
Why is monitoring temperature during anaesthesia important?
Hypothermia is leading cause of slow recoveries & is painful
What are the 2 most common ways of monitoring temperature?
Rectal thermometer: simple & widely available method
Oesophageal temperature probe: Requires multiparameter monitor & provides continuous temperature readings
How do you insert an oesophageal temperature probe?
- Measure probe length from incisors to caudal scapula to determine insertion depth
- Pull patient’s tongue forward
- Slide probe down side of ET tube
- Guide it into oesophagus to required depth
How can you monitor the cardiovascular system?
can assess:
- heart rate & rhythm
- mm colour & CRT
- bleeding
- BP
- heamoglobin oxygen saturation
- arrythmias
Equipment:
- BP monitors
- Pulse oximeters
- ECG
- Stethoscope
What factors influence a normal heart rate under anaesthesia?
Normal HR under anaesthesia is 60-120bpm
Species & size of the animal
Underlying conditions
Stress levels.
Drugs administered during premedication or induction.
Breed-specific phenomena (e.g., Dachshunds may have HR of 50–60 bpm under anaesthesia due to increased vagal tone).
Why is knowing pre-induction HR important?
Helps establish what is normal for individual patient
Guides decisions during anaesthesia monitoring to avoid unnecessary interventions
Why does the presence of a heart beat not always indicate adequate circulation?
beating heart doesn’t guarantee sufficient cardiac output or tissue perfusion
Monitoring should include pulse palpation & blood pressure measurement to assess circulation adequacy
What tools should be used to monitor heart rate and rhythm during anaesthesia?
Stethoscope: To confirm presence & rate of heartbeat
- can also use oesophageal stethoscope which is more reliable & useful if patient is draped
Pulse palpation: To assess peripheral circulation
Blood pressure measurement: To evaluate tissue perfusion
Why is it important to listen to heart while palpating a pulse?
To detect pulse deficits, which occur when peripheral pulse doesn’t match heart rate determined by stethoscope
Pulse deficits may indicate cardiac dysrhythmias, which require ECG evaluation.
What are the commonly used sites for pulse palpation?
Sublingual artery: Ventral aspect of tongue
Mandibular artery: Along mandible
Digital metacarpal artery: Palmar surface of forelimb
Digital metatarsal artery: Plantar surface of hindlimb
Dorsal pedal artery: Dorsum of metatarsal area
Femoral artery: Medial aspect of femur
Coccygeal artery: Ventral surface of tail
What are the common signs of pulse deficits during palpation?
Irregular rhythm
Pauses in the pulse
Pulse rate is less than heart rate determined by stethoscope
What is capillary refill time (CRT)
Assessment of peripheral perfusion and oxygenation
should be <2s
What does this mucous membrane assessment show?
Vasodilation (usually very pink or red with rapid CRT)
examples:
- Sepsis
- Anaesthetic drugs (e.g. anaphylaxis)
- Low MAP (mean arterial blood pressure); this depends on root cause
What does this mucous membrane assessment show?
Healthy = pink & moist
Dry/Tacky = dehydration, hypovolaemia
Wet = over infusion, nausea (risk of regurgitation/gastric reflux, aspiration)
What does this mucous membrane assessment show?
Vasoconstriction (usually very pale with slow CRT)
examples:
- Anaemia
- Inadequate blood flow
- Alpha 2 Agonists
What does this show?
Cyanosis is bluish/purplish discolouration of skin or mucous membranes due to tissues near skin surface having low O2 saturation
Indicates sebere hypoxaemia (very close to death)
(Chow Chows always have blue tongue)
Why is communication between the anaesthetic monitor and the surgeon important during intraoperative bleeding?
Surgeon can alert anaesthetic monitor to suspected bleeding, prompting monitoring for signs like:
- Prolonged CRT.
- Low blood pressure.
Monitor can inform surgeon of any detected issues to help them check surgical site & adjust their approach
How can you estimate the volume of blood lost during surgery?
Weigh blood-soaked surgical swabs
1 mL of blood = ~1 g of weight
What signs might indicate intraoperative bleeding from the monitoring perspective?
Prolonged CRT
Low blood pressure (BP)
Other signs of poor perfusion or hypovolemia
What are the 2 main methods of measuring blood pressure?
Doppler: Portable; measures systolic BP in dogs & mean arterial pressure (MAP) in cats & animals <10 kg
Oscillometric: Usually part of multiparameter monitor; measures systolic, diastolic & MAP
How do you select correct cuff size for measuring blood pressure?
cuff width should be 40% of circumference of limb where it is placed
Too large cuff: Underestimates BP
Too small cuff: Overestimates BP
What are the normal BP ranges for healthy animals?
Systolic BP: 100–160 mmHg.
Diastolic BP: 80–120 mmHg.
Mean arterial pressure (MAP): 60–100 mmHg
What can an MAP <60mmHG for <30min lead to?
MAP of 60mmHg (systolic >90mmHg) needed to properly perfuse heart, brain & kidneys
Can lead to:
- Renal failure.
- Delayed recovery
- Neuromuscular complications
- Decreased hepatic metabolism of drugs
- CNS abnormalities such as blindness
What do these 3 values show?
Reading to left (127) is systolic Bp, one next to that (92) is diastolic & one in brackets (105) is mean arterial pressure.
How is a Doppler device used to measure BP?
- Place pressure cuff proximal to Doppler probe & connect it to sphygmomanometer
- Inflate cuff until Doppler sounds are no longer audible (artery is occluded)
- Slowly deflate cuff while observing sphygmomanometer
- Record pressure at which first audible arterial pulse is heard:
- Dogs: Closest to systolic BP.
- Cats: Closest to MAP.
Why should multiple measurements be taken in conscious patients using a Doppler?
Variability between readings is common
Take several readings & average the middle 3 measurements.
What is the ideal patient position for Doppler BP measurement?
Patient should lie in lateral recumbency
cuff should be positioned on limb at level of right atrium
How does the Doppler detect blood pressure?
Doppler probe detects blood flow in vessel, producing whooshing sound
Blood pressure is determined by return of pulse sound as cuff is deflated
What are the 2 types of pulse oximeters?
Portable pulse oximeters: Standalone devices
Integrated pulse oximeters: Built into multiparameter monitors
What does a pulse oximeter measure?
percentage of haemoglobin saturated with oxygen (SpO₂)
Displays pulse rate & waveform called plethysmograph (“pleth” for short)
Waveform indicates strength & consistency of pulse, helping assess peripheral perfusion.
What is the normal SpO₂ value for a healthy patient?
Over 95% indicates sufficient oxygenation
How does a pulse oximeter help detect hypoxemia?
low SpO₂ reading (<95%) indicates insufficient oxygenation, which is sign of hypoxemia
Where can pulse oximeter probe be placed on patients?
Tongue.
Ear pinna.
Lip.
Digit.
Prepuce or vulva.
What are the advantages of pulse oximetry?
Inexpensive.
Non invasive
Well tolerated
Continuous
Automatic
Portable
Audible
User friendly.
What do these arrows show?
Why is a SpO₂ reading over 95% not always indicative of normal oxygenation?
SpO₂ <95% means haemoglobin is saturated with oxygen, but patient may still be hypoxic due to poor circulation or low oxygen delivery to tissues.
Why should pulse oximetry be used alongside other monitoring methods?
Pulse oximeters can’t detect circulatory issues or other forms of hypoxia
Using additional tools helps identify problems that pulse oximeter may miss.
What are some limitations of pulse oximeters?
Can’t differentiate between hypoxemia & hypoxia
May be inaccurate with poor peripheral perfusion (e.g., vasoconstriction, shock)
Affected by movement, pigmentation, or improper probe placement.
Why is a low SpO₂ on 100% oxygen during anaesthesia concerning?
If patient can’t maintain normal saturation on 100% oxygen, it indicates serious problem with oxygenation or ventilation.
In what situations is pulse oximetry particularly useful during recovery?
esp. helpful in monitoring brachycephalic breeds, which are prone to airway obstructions & oxygenation issues during recovery.
What are the 2 options for attaching ECG leads to patient?
Crocodile clips: Pinch skin but are effective & reusable
ECG pads: Stick to patient & clip leads onto them; more expensive but gentler
Where are ECG leads placed?
Red: Cranial right
Yellow: Cranial left.
Green: Caudal left.
Why should surgical spirit be used on ECG leads, and what precautions should be taken?
Purpose: Acts as conduction agent to improve ECG readings
Precaution: Avoid excessive use, especially on small patients, as it can cool body
What is the main purpose of ECG monitoring during anaesthesia?
To assess heart rate & rhythm
Detect tachycardia, bradycardia, & arrhythmias
What are tachycardia & bradycardia & how can you identify them on ECG?
Tachycardia: Fast heart rate, QRS complexes are close together on the trace
Bradycardia: Slow heart rate, QRS complexes are spaced further apart.
What parameters can be monitored in the respiratory system?
can monitor:
- resp rate, rhythm & effort
- assess adequacy of respiration (EtCO2)
- check or estimate blood gases (O2 & CO2)
Why is it important to monitor respiratory rhythm and effort in addition to respiratory rate?
Animal could have same resp. rate (e.g. 12 breaths/min) but differ in breath depth
Deep, sufficient breaths ensure proper ventilation, while shallow, insufficient breaths may result in inadequate CO2 expulsion
Patient weight or positioning can also affect respiratory effort & ventilation quality
What tools can be used to monitor lung sounds?
stethoscope can be used to identify breath sounds, compare sides of chest & assess changes between ventral & dorsal areas
What is capnography used for during anaesthesia?
It monitors ventilation in spontaneously breathing or mechanically ventilated patients, confirms endotracheal tube placement & provides EtCO2 levels
What are the 3 levels of informations provided by capnography?
Level 1: Confirms if patient is breathing & provides resp rate
Level 2: Measures expired & inspired CO2 levels to ensure CO2 is expelled sufficiently & not being rebreathed
Level 3: Provides waveform data, which can indicate obstructions, allergic reactions, rebreathing, hypercapnia, hypocapnia, or issues with ET tube inflation
What does a change in EtCO2 suggest?
What are normal EtCO2 ranges for dogs & cats?
Dogs: 35-45 mmHg
Cats: 28-45 mmHg
What can cause hypocapnia in anaesthetized animals?
Hyperventilation, as CO2 is exhaled faster than its produced
What can cause hypercapnia in anaesthetized animals?
Hypoventilation, as CO2 is exhaled slower than its produced
What is this?
What do these lines show?
What is the most commonly used capnography system in veterinary practice?
Side-stream systems, where capnograph line is attached to connector between breathing system & endotracheal tube
What can blood gas analysis measure?
PaCO2
PaO2
Blood pH
Electrolytes
Lactate
Others…
What is the difference between arterial and venous blood gas tests?
Arterial blood gas: Measures arterial O2 & CO2, mainly for assessing lung function
Venous blood gas: Measures O2 & CO2 in veins, mainly for assessing metabolic function
What is Adenosine triphosphate (ATP)?
ATP is “energy currency” of cell, providing readily releasable energy in bond between 2nd & 3rd phosphate groups
What cellular processes rely on breakdown of ATP?
ATP is used for signaling, DNA/RNA synthesis, ion transport, muscle contraction, nerve impulse propagation, substrate phosphorylation & chemical synthesis.
What should you assess first when identifying bradycardia?
Determine animal’s normal heart rate & check if it compromises perfusion & oxygen delivery using SpO2% & ABP
What are common causes of bradycardia during anaesthesia?
Drugs (e.g., alpha-2 agonists, opioids)
toxaemia
vagal stimulation
hypoxia
hypothermia
underlying heart problems
2 yr old Frenchie ASA 1, HR 110 bpm prior to surgery for cherry eye
Premed: acepromazine & methadone
Induction: alfaxalone to effect
Maintenance: isoflurane in oxygen, during surgery HR suddenly drops from 98bpm to 55 bpm
What do you think? What do you do?
Cause of bradycardia:
- Could be due to vagal stimulation during surgery, anaesthetic depth, hypothermia, or drug effects (e.g., methadone or acepromazine)
Response:
- Check depth of anaesthesia & reduce if too deep
- Investigate potential vagal stimulation (e.g., surgical manipulation)
- Administer anticholinergic (e.g., atropine or glycopyrrolate) if bradycardia compromises perfusion
- Ensure there is no hypoxia or toxaemia contributing to bradycardia
Cockerpoo, castrate, ASA 1, HR 108 bpm prior to surgery
Premed: dexmedetomidine & methadone
Induction: alfaxalone to effect
Maintenance: isoflurane in oxygen, 5 mins after induction you see this
What do you think? What do you do?
Bradycardia (HR: 60 bpm):
- Likely due to dexmedetomidine (alpha-2 agonist), which reduces sympathetic tone
Perfusion & oxygenation:
- Normal MAP (91 mmHg) & SpO2 (100%) indicate no immediate compromise in perfusion or oxygen delivery
Response:
- Monitor closely: Since perfusion (MAP) & oxygenation (SpO2) are adequate, immediate intervention may not be required
- Reverse alpha-2 effects if needed: If bradycardia worsens or perfusion is compromised, administer atipamezole to reverse dexmedetomidine
- Check anaesthetic depth: Ensure anaesthesia is not excessively deep
- Administer anticholinergics if needed: Consider atropine or glycopyrrolate if perfusion deteriorates
GSD X, TPLO, ASA 2, HR 96bpm prior to surgery
Premed: acepromazine & buprenorphine
Induction: propofol to effect
Maintenance: isoflurane in oxygen, during anaesthesia gradual decline in HR & ABP
What do you think? What do you do?
Bradycardia:
- Likely due to acepromazine (vasodilation) & buprenorphine (opioid effects), combined with propofol & isoflurane, which depress cardiovascular system
Hypotension (MAP 57 mmHg):
- Suggests compromised tissue perfusion & requires intervention to prevent further complications
Response:
- Address bradycardia:
- If perfusion is compromised, consider atropine or glycopyrrolate to increase HR - Manage hypotension:
- Reduce isoflurane vaporiser settings if anaesthetic depth is excessive
- Administer IV fluids to improve circulating volume.
- If needed, use inotropes like dobutamine or vasopressors like norepinephrine to support blood pressure - Monitor closely:
- Continuously assess ABP, HR, & SpO2 to ensure interventions are effective
TBx, ASA 1, HR 40 bpm prior to surgery, bilat hock arthroscopy
Premed: acepromazine, morphine
Induction: romifidine, ketamine, midazolam
Maintenance: sevoflurane in oxygen 3.1% (ET), 30 minutes later during prepping of leg, this is the situation
What do you think? What do you do?
What’s happening:
- Severe bradycardia likely caused by romifidine (alpha-2 agonist) & morphine effects.
- Hypercapnia (EtCO2 67 mmHg) due to hypoventilation caused by respiratory depression from sevoflurane & sedatives.
- MAP (76 mmHg) acceptable, indicating perfusion is not yet critically compromised
Response:
- Reverse romifidine with atipamezole if needed or use atropine/glycopyrrolate for bradycardia if perfusion worsens
- Ventilate manually or mechanically to address hypercapnia.
- Reduce sevoflurane vaporiser setting to decrease respiratory depression
- Monitor HR, EtCO2 & MAP to ensure stability
Male 6y DSH, HR 90bpm prior to sedation, v large bladder
Premed: methadone
Induction: ketamine, midazolam
Maintenance: isoflurane in oxygen, 0.8% (ET)
What do you think? What do you do?
What is happening:
- Bradycardia (HR 75 bpm): Not critical but may be influenced by methadone (opioid) & midazolam, with no immediate compromise to perfusion or oxygen delivery
- Hypocapnia (EtCO2 30 mmHg): Likely caused by hyperventilation (RR 24) & shallow ventilation
- MAP (77 mmHg): Within acceptable range for perfusion.
- SpO2 (92%): Indicates borderline hypoxaemia; possible ventilation-perfusion mismatch
Response:
- Address hypocapnia: Reduce RR if manually ventilating & evaluate anaesthetic depth.
- Improve oxygenation: Adjust fresh gas flow & ensure proper ETT placement.
- Monitor closely: Observe for any further changes in HR, MAP, SpO2 & EtCO2 to maintain stability
- Support perfusion: Administer fluids if indicated to sustain MAP & oxygen delivery
How do you treat bradycardia caused by alpha-2 agonists?
Administer atipamezole (alpha-2 antagonist
What are 2 anticholinergics used to treat bradycardia?
Atropine and glycopyrrolate
What could be causing tachycardia during anaesthesia?
Sympathetic stimulation, too ’light’
PaCO2, PaO2, pH abnormalities
CNS disturbances
Low ABP, or cardiac disease
Drugs e.g. anticholinergics
2 yr old Bassett ASA 1, HR 96 bpm prior to surgery for lumpectomy
Premed: dexmedetomidine, methadone
Induction: propofol, local block
Maintenance: isoflurane
2 mins after incision, HR increased
What do you think? What do you do?
What’s happening:
- Tachycardia: due to pain or insufficient anaesthetic depth
- Hypotension: Compromised perfusion from vasodilation or sympathetic overdrive.
- SpO2 92%: Borderline hypoxaemia
Response:
- Increase anaesthetic depth or provide additional analgesia (e.g., fentanyl).
- Administer IV fluids & consider vasopressors (e.g. norepinephrine) if hypotension persists
- Verify oxygen delivery & adjust fresh gas flow or ETT placement
- Monitor HR, MAP & SpO2 to ensure stabilisation
14yr old DSH cat chronic renal insufficiency, ASA 3, dental
Premed: midazolam & methadone
Induction: alfaxalone to effect
Maintenance: isoflurane in oxygen
What do you think? What do you do?
What’s happening:
- Tachycardia (HR 231 bpm): due to pain, stress, or hypoxia, exacerbated by renal insufficiency
- Hypotension (MAP 56 mmHg): Compromised perfusion from vasodilation or poor cardiac output
- Hypocapnia (EtCO2 24 mmHg): Indicates hyperventilation or poor perfusion
- SpO2 90%: Borderline hypoxaemia, needs addressing.
Response:
- Administer analgesia (e.g., fentanyl) & reassess depth of anaesthesia
- Provide IV fluids & consider vasopressors (e.g. norepinephrine) to improve BP.
- Ensure proper oxygen delivery by adjusting ETT placement or increasing oxygen flow.
- Monitor HR, MAP, SpO2 & EtCO2 for stabilization.
1 year old 2.2kg Dutch rabbit for castration
Premed: buprenorphine SC
Induction: Medetomidine, ketamine SC
What do you think? What do you do?
What’s happening:
- Tachycardia (HR 209 bpm): stress or pain response from insufficient analgesia or light anaesthesia.
- Hypocapnia (EtCO2 24 mmHg): due to hyperventilation or poor cardiac output.
- MAP 94 mmHg & SpO2 97%: Perfusion & oxygenation adequate
Response:
- Administer additional analgesia (e.g., fentanyl) to manage pain
- Assess & adjust anaesthetic depth to address potential stress or sympathetic stimulation
- Monitor ventilation to ensure hyperventilation resolves & EtCO2 normalises.
- close monitoring of HR, EtCO2, & MAP for stability.
What’s happening:
- Initial tachycardia progressing to bradycardia: due to prolonged anaesthesia, inadequate ventilation, or cardiac strain
- Hypotension (MAP 56 mmHg): decreased perfusion from vasodilation or inadequate cardiac output
- Hypercapnia (EtCO2 54 mmHg): Due to hypoventilation or insufficient respiratory support
Response:
- Address hypotension: Increase IV fluids, consider inotropes (e.g., dobutamine) to support cardiac output.
- Improve ventilation: Increase intermittent positive pressure ventilation (IPPV) to reduce EtCO2 & support oxygenation.
- Adjust anaesthetic depth: Reduce isoflurane concentration to minimize cardiovascular depression.
- Monitor HR, MAP & EtCO2 continuously to ensure stabilisation
What are the key steps to treat tachycardia during anaesthesia?
- Assess if cardiac output is compromised (check ABP & SpO2%)
- Identify cause: Check anaesthetic depth, CO2 levels & other factors
- Administer IV opioid (e.g., fentanyl), lidocaine, or beta-blockers (propranolol/esmolol)
- Adjust vaporiser setting to deepen anaesthesia if needed
What are common causes of ventricular ectopic beats?
Circulating catecholamines (stress)
hypoxia
hypercapnia
hypovolaemia
anaesthetic drugs
myocardial irritation
major organ disease
How do you manage ventricular ectopic beats?
- Assess if perfusion is compromised (check ABP & SpO2%)
- Identify cause (depth of anaesthesia, CO2 levels, etc.)
- Administer lidocaine or beta-blockers (propranolol/esmolol) if needed
- Monitor for progression to ventricular fibrillation.
What are common causes of hypotension during anaesthesia?
Anaesthetic drugs, hypovolaemia, haemorrhage, or cardiac insufficiency
How do you treat hypotension?
- Reduce inhalant agent (TIVA or PIVA may be used).
- Increase IV fluids to restore circulating volume.
- Administer inotropes (e.g. dobutamine) or vasopressors (e.g. norepinephrine) if required
- Monitor urine output to ensure perfusion
What are common causes of hypercapnia during anaesthesia?
Hypoventilation, rebreathing, low fresh gas flow, exhausted soda lime, or increased metabolic rate
How do you treat hypercapnia?
- Increase ventilation (manual or mechanical)
- Check breathing system for rebreathing or soda lime exhaustion
- Adjust anaesthetic depth to prevent respiratory depression.
Why do cats on non-rebreathing systems often have lower ETCO2 readings?
high fresh gas flow (FGF) rate dilutes sampled exhaled CO2, leading to artificially lower ETCO2 readings
What are common reasons for falling ET CO2 values during anaesthesia?
Obstruction: Partial airway blockage
Hyperventilation: Exhaling CO2 too quickly
Circulatory failure: Reduced blood flow to lungs
Hypotension: Poor perfusion affecting gas exchange
Cardiac arrest: Cessation of circulation
How do you treat hypocapnia?
- Decrease ventilatory rate if hyperventilation is occurring
- Check for & resolve airway obstructions or mis-intubation
3.Support perfusion if circulatory failure is identified.
No, they are typically benign finding & don’t indicate clinical issue
How do you identify hypoxaemia?
What causes hypoxaemia during anaesthesia?
Disconnection, hypoventilation, anaesthetic depth, or ventilation-perfusion mismatch
How do you treat hypoxaemia?
- Reconnect breathing system or re-intubate if necessary
- Increase oxygen flow & ventilation
- Improve perfusion using IV fluids or inotropes (e.g., dobutamine)
- Verify oxygenation with arterial blood gases in equine patients.
What are common recovery issues after anaesthesia?
Dysphoria, prolonged recovery (often from hypothermia), or delayed recovery caused by drug effects or hypoglycaemia.
