Monitoring and Responding Flashcards
What are possible causes of bradycardia?
Drugs (e.g., alpha 2 agonist, induction agent, opioid)
Toxaemia (endogenous/exogenous)
Vagal stimulation
Heart problem (e.g. sick sinus)
Hypoxia
Hypothermia
What should you check when assessing bradycardia or tachycardia?
Determine animal’s normal heart rate & check if it compromises perfusion & oxygen delivery using SpO2% & ABP
2 yr old Frenchie ASA 1, HR 110 bpm prior to surgery for cherry eye
Premed: acepromazine and methadone
Induction: alfaxalone to effect
Maintenance: isoflurane in oxygen, during surgery the 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 and 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 and buprenorphine
Induction: propofol to effect
Maintenance: isoflurane in oxygen, during anaesthesia a 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 the 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
What drug should be used to treat alpha 2 induced bradycardia?
atipamezole (alpha 2 antagonist)
What anticholinergics can be used to treat bradycardia?
atropine or glycopyrrolate
What are possible causes of tachycardia?
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 and 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 and what is your response?
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 in approaching the treatment of tachycardia?
Assess if output is being compromised (ABP and SPO2%)
Identify the cause (check anaesthesia depth, CO2 levels etc)
Administer IV opioid, lidocaine or propanolol/esmolol (beta-blockers)
Adjust vaporiser setting to deepen anaesthesia if needed
what are ventricular ectopic beats?
extra or early heartbeats that occur when the heart’s electrical signals start in the wrong place
No, they are typically benign finding & don’t indicate clinical issue
