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? And what is the normal HR under anaeasthesua?
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? What else should monitoring include?
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.