CRS ECC Cases

Question 1

An 8-year old, 25 kg dog is having surgery to remove an abdominal tumour.

Premed = Methadone

Induction = Propofol + Diazepam

Maintenance = Isoflurane

1 hour into surgery this is what you see

1. Is there a problem?

• No, everything is ok
• The heart rate is too high
• The respiratory rate is too high
• The blood pressure is too low

Answer 1

The heart rate is too high

Question 2

An 8-year old, 25 kg dog is having surgery to remove an abdominal tumour.

Premed = Methadone

Induction = Propofol + Diazepam

Maintenance = Isoflurane

1 hour into surgery this is what you see - the heart rate is too high

1. What might have caused the tachycardia?
   * Pain
   * Light anaesthesia
   * Hypovolaemia
   * Hypotension
   * Hypoxaemia
   * Hypercapnia
   * Hyperthermia

Answer 2

• Pain
• Light anaesthesia
• Hypovolaemia
• Hypotension
• Hypoxaemia
• Hypercapnia
• Hyperthermia

All of the above potentially can

In this dog, BP is okay

End CO2 is okay,

Most likely is one of the first 2 – pain or too light

Question 3

An 8-year old, 25 kg dog is having surgery to remove an abdominal tumour.

Premed = Methadone

Induction = Propofol + Diazepam

Maintenance = Isoflurane

1 hour into surgery this is what you see - the heart rate is too high. Lots of things could have caused this, most likely pain or light anaesthesia.

1. What do you do to work out what is going on?

Answer 3

• ANALGESIA
• Check dog isn’t awake, check reflexes
• Palpate pulses
• Take a blood pressure
• Look at mucous membrane colou
• Evaluate blood loss
• Evaluate anaesthetic depth
  
  • Jaw tone, eye position, reflexes etc.
• Check pulse oximeter, capnograph, blood gas (evaluate O2 and CO2)

Question 4

An 8-year old, 25 kg dog is having surgery to remove an abdominal tumour.

Premed = Methadone

Induction = Propofol + Diazepam

Maintenance = Isoflurane

1 hour into surgery this is what you see - the heart rate is too high. Lots of things could have caused this, most likely pain or light anaesthesia. You have given analgesia, checked the anaesthetic depth etc. You note the following

1. What do you do next?
   * Calculate blood loss
   * Administer a bolus of crystalloid fluid
   * Administer a bolus of colloid
   * Give a blood transfusion referral practice, autologous transfusion if not due to tumour
   * Decrease anaesthetic depth
   * Switch anaesthesia to a less cardio-depressant drug
   * Start a dopamine infusion to increase blood pressure – probably try something else first

Answer 4

• Calculate blood loss Would be good to calculate blood loss by weighing swabs and tank. At around 15% of blood loss you would start to see clinical signs, therefore if clinical signs can jump to 15% at least.
  
  • Get someone else to do it ideally whilst you try and sort the dog out! But still good to do!
• Administer a bolus of crystalloid fluid – might haemodilute blood so care
• Administer a bolus of colloid
• Give a blood transfusion referral practice, autologous transfusion if not due to tumour
• Decrease anaesthetic depth
• Switch anaesthesia to a less cardio-depressant drug - would if you had one but all dugs essentially depress. Perhaps give more analgesia so that can turn iso down.
• Start a dopamine infusion to increase blood pressure – probably try something else first

Question 5

An 8-year old, 25 kg dog is having surgery to remove an abdominal tumour.

Premed = Methadone

Induction = Propofol + Diazepam

Maintenance = Isoflurane

1 hour into surgery this is what you see - the heart rate is too high. Lots of things could have caused this, most likely pain or light anaesthesia. You have given analgesia, checked the anaesthetic depth etc. You note a large amount of blood loss and you deal with it.

You manage to stabilise the patient and surgery continues. It is now 4 hours since the dog received his methadone. You note the following changes

1. What is happening?

• The patient is bleeding
• The depth of anaesthesia is too light - plane is not where it needs to be!!
• The patient is having a reaction to the anaesthetic
• The CO2 is causing a tachycardia this time

Answer 5

The depth of anaesthesia is too light - plane is not where it needs to be!!

Question 6

An 8-year old, 25 kg dog is having surgery to remove an abdominal tumour.

Premed = Methadone

Induction = Propofol + Diazepam

Maintenance = Isoflurane

1 hour into surgery this is what you see - the heart rate is too high. Lots of things could have caused this, most likely pain or light anaesthesia. You have given analgesia, checked the anaesthetic depth etc. You note a large amount of blood loss and you deal with it.

You manage to stabilise the patient and surgery continues. It is now 4 hours since the dog received his methadone. You note the following changes

1. What would you do immediately?

• Increase vaporiser setting
• Nothing- the patient is still anaesthetised
• Ventilate the patient – will not increase the amount of iso the patient is getting
• Give more blood

Answer 6

Increase vaporiser setting

Question 7

An 8-year old, 25 kg dog is having surgery to remove an abdominal tumour.

Premed = Methadone

Induction = Propofol + Diazepam

Maintenance = Isoflurane

1 hour into surgery this is what you see - the heart rate is too high. Lots of things could have caused this, most likely pain or light anaesthesia. You have given analgesia, checked the anaesthetic depth etc. You note a large amount of blood loss and you deal with it.

You manage to stabilise the patient and surgery continues. It is now 4 hours since the dog received his methadone. Vaporiser settings have been increased as the dog was too light.

1. What would you do now?
   * Increase vaporiser setting some more
   * Nothing- the patient is still anaesthetised
   * Administer more analgesia

Answer 7

Administer more analgesia – full mu agonist as going through major surgery. Can give methodone IV (lasts 4 hours, this is 4 hours later). Pethidine can be given but IM and not licensed

Question 8

An 8-year old, 25 kg dog is having surgery to remove an abdominal tumour.

Premed = Methadone

Induction = Propofol + Diazepam

Maintenance = Isoflurane

1 hour into surgery this is what you see - the heart rate is too high. Lots of things could have caused this, most likely pain or light anaesthesia. You have given analgesia, checked the anaesthetic depth etc. You note a large amount of blood loss and you deal with it.

You manage to stabilise the patient and surgery continues. It is now 4 hours since the dog received his methadone. Vaporiser settings have been increased as the dog was too light. The dogs heart rate was stil high, so he was given some more analgesia.

You administer a second dose of methadone (0.2 mg/kg i/v) and after a few minutes you note the following:

• HR = 100/ minute
• Mean arterial blood pressure = 80 mmHg
• Eye: rotated ventrally, weak palpebral reflex
• RR = 2/minute
• End-tidal CO2 = 60mmHg

1. What has happened?
   * The patient is having an unexpected adverse reaction to the methadone
   * The patient is bleeding again
   * The patient is too deep
   * The methadone has caused respiratory depression

Answer 8

• The methadone has caused respiratory depression -

common after bolus with methadone, fentanyl, pethidine etc. might stop breathing, will start again.

Would make sure to turn down the iso – treat the pain and bring down the iso

Especially if given as a bolus IV, respiratory depression - HR and BP is okay. Hypoventilation. Common to see

Question 9

An 8-year old, 25 kg dog is having surgery to remove an abdominal tumour.

Premed = Methadone

Induction = Propofol + Diazepam

Maintenance = Isoflurane

1 hour into surgery this is what you see - the heart rate is too high. Lots of things could have caused this, most likely pain or light anaesthesia. You have given analgesia, checked the anaesthetic depth etc. You note a large amount of blood loss and you deal with it.

You manage to stabilise the patient and surgery continues. It is now 4 hours since the dog received his methadone. Vaporiser settings have been increased as the dog was too light. The dogs heart rate was stil high, so he was given some more analgesia.

You administer a second dose of methadone (0.2 mg/kg i/v) and this methadone has caused respiratory depression. This is common. You give the patient a few breaths from the breathing system and the ET CO2 decreases to 40mmHg. You nip off, come back and see this:

1. What is happening?
2. What should you do?

• Squeeze the bag to ventilate the patient
• Administer atropine- that heart rate is too slow
• Open the pop-off valve to relieve the pressure
• Check depth of anaesthesia

Answer 9

• People close the valve, squeeze the bag and forget to reopen the valve! Always remember to open the valve - don’t even need to close the valve, squeezing bag will still give a good enough breath
• Open the pop-off valve to relieve the pressure – if you’re going to ventilate a patient do not take your hand off the valve! Must open it again – can even give the bag a big squeeze without closing the valve.

Question 10

What does increased alveolar pressure cause?

Answer 10

• Increased alveolar pressure causes:
  
  • Compression (collapse) of pulmonary capillaries (reduced preload)
  • Compression of heart chambers (decreased filling)
  • Compression of aorta (increased afterload)
• => Dramatic reduction in cardiac output
  
  • **Circulatory arrest**
• Alveolar damage / rupture

Question 11

You anaesthetise a 3 year-old DSH cat for a dental.

Premed = Medetomidine + Buprenorphine

Induction agent = Propofol

Maintenance = Isoflurane in 100% oxygen

One hour into the procedure you see this

1. What is happening?

• The heart rate is 86
• The blood pressure is 86mm Hg
• The oxygen saturation is 86%
• The CO2 is 86mm Hg

Answer 11

The heart rate is 86 which is too low – medetomidine (alpha 2) causes HR to decrease

The blood pressure is 86mm Hg which is ok

The oxygen saturation is 86% which is too low

The CO2 is 86mm Hg which is too high

Question 12

You anaesthetise a 3 year-old DSH cat for a dental.

Premed = Medetomidine + Buprenorphine

Induction agent = Propofol

Maintenance = Isoflurane in 100% oxygen

One hour into the procedure you see this: the oxygen saturation is 86% , which is too low

1. Why might this occur?
   
   • The respiratory rate is too low
   • It is due to medetomidine causing vasoconstriction
   • There is an obstruction of the ET tube
   • The cat is anaemic
   • You have intubated one bronchus only (tube too long)

Answer 12

• The respiratory rate is too low - potentially, but it cannot be medetomidine as the effects of this should have worn off by now - resp rate isn’t too low to be honest
• It is due to medetomidine causing vasoconstriction – yes possibly
• There is an obstruction of the ET tube – possibly, capnograph will show typical shape
• The cat is anaemic – unlikely and this won’t alter the pulse oximeter reading!
• You have intubated one bronchus only (tube too long) – can happen, pre-measure from nose to thoracic inlet. But number 3 is mostly likely

Question 13

You anaesthetise a 3 year-old DSH cat for a dental.

Premed = Medetomidine + Buprenorphine

Induction agent = Propofol

Maintenance = Isoflurane in 100% oxygen

One hour into the procedure you see this: the oxygen saturation is 86% , which is too low.

Despite exaggerated chest movements, the reservoir bag is barely moving. You are worried about airway obstruction

1. What could be the cause of this?

Answer 13

• Kinking the endotracheal tube
• Material within the endotracheal tube
• Over-inflation of the tube cuff – happens a lot, don’t be over generous
• Be sure to disconnect the patient before you flip them!

Question 14

You anaesthetise a 3 year-old DSH cat for a dental.

Premed = Medetomidine + Buprenorphine

Induction agent = Propofol

Maintenance = Isoflurane in 100% oxygen

One hour into the procedure you see this: the oxygen saturation is 86% , which is too low.

Despite exaggerated chest movements, the reservoir bag is barely moving. You are worried about airway obstruction

1. What would you do?

• Squeeze the bag to ventilate the cat –
• Remove the ET tube
• Administer doxapram to stimulate respiration
• Xray the chest

Answer 14

Remove the ET tube

Get rid of the problem, can always reintubate!

Question 15

What are some problems you can get with ET tubes?

Answer 15

Endobronchial intubation – other lung collapses, progressive problems

Red tubes are bad – cause many problems with necrosis etc.

Care with over inflation, can occlude tubes and cause a significant narrowing!! Significant in small ET tubes, espeically cats - gets worse as they warm up and tube becomes more pliable, so bend gets more and can be a real problem

Question 16

You anaesthetise a 3 year-old DSH cat for a dental.

Premed = Medetomidine + Buprenorphine

Induction agent = Propofol

Maintenance = Isoflurane in 100% oxygen

One hour into the procedure you see this: the oxygen saturation is 86% , which is too low.

Despite exaggerated chest movements, the reservoir bag is barely moving. You are worried about airway obstruction.

You remove and replace the tube and the oxygen saturation improves. At the end of the procedure you switch off the anaesthetic agent. One hour later the cat shows no sign of anaesthetic recovery.

Eventually the cat recovers. Later that day the nurse calls you to wards as the cat is having difficulty breathing

On examination, the cat is dyspnoeic with subcutaneous emphysema

1. What is the most likely explanation?
   * The cat is in heart failure due to excessive i/v fluids
   * Anaphylactic reaction to anaesthesia with bronchospasm
   * The cat has a ruptured trachea –
   * The cat has developed a respiratory infection

Answer 16

• The cat is in heart failure due to excessive i/v fluids
• Anaphylactic reaction to anaesthesia with bronchospasm -would have been a possibility 2 hours ago, drugs should be metabolised by now
  
  • Would have seen this by now!!
• The cat has a ruptured trachea – as removed and replaced tube, most likely. Can check with small endoscope. Will get worse over time. Each time it breaths in it is dragging air subcutaneously.
  
  • Phone VDS! Referral surgery at this stage!! Something that can just happen. Give oxygen and call
• The cat has developed a respiratory infection – too soon

Question 17

What are some causes of prolognued anaesthetic recovery?

Answer 17

• Hypothermia
• Hypoglycaemia – these cases have been starved for 24 hours or so
• Anaesthetic overdose
• Hepatic or renal failure
• Very thin/ very fat animal
• Hypovolaemia
• Hypotension
• Cardiovascular collapse
• DIFFERENTIATE WITH A CLINICAL EXAM

Question 18

You anaesthetise a 20kg, 4-year old Springer Spaniel for repair of a radius-ulna fracture.

Premed = Morphine + Medetomidine

Induction = Propofol

Maintenance = Isoflurane in oxygen

You administer a brachial plexus block for analgesia

You observe the following over the next 2 minutes

1. What has happened?

• The dog had an abnormal reaction to the premed
• You have disconnected your monitoring leads
• The dog has had a cardiopulmonary arrest

Answer 18

• The dog has had a cardiopulmonary arrest
  
  • Just after block - might need to call VDS again!

Question 19

You anaesthetise a 20kg, 4-year old Springer Spaniel for repair of a radius-ulna fracture.

Premed = Morphine + Medetomidine

Induction = Propofol

Maintenance = Isoflurane in oxygen

You administer a brachial plexus block for analgesia. Ropivacaine 1.5mg/kg and lidocaine 1.5mh/kg - total volume 8ml diluted with saline.

You observe the following over the next 2 minutes and the dog has gone into cardiopulmonary arrest.

1. Why has this happened?
   * Isoflurane overdose
   * Pre-existing cardiac disease which was missed pre-op
   * Delayed histamine release from morphine premed
   * Intra-vascular injection of local anaesthetic
   * Always pull back when doing blocks!!!!!

Answer 19

• Intra-vascular injection of local anaesthetic – Ropivaciane is very cardiotoxic
  
  • Always pull back when doing blocks!!!!!

Question 20

You anaesthetise a 20kg, 4-year old Springer Spaniel for repair of a radius-ulna fracture.

Premed = Morphine + Medetomidine

Induction = Propofol

Maintenance = Isoflurane in oxygen

You administer a brachial plexus block for analgesia. Ropivacaine 1.5mg/kg and lidocaine 1.5mh/kg - total volume 8ml diluted with saline.

You observe the following over the next 2 minutes and the dog has gone into cardiopulmonary arrest. This is due to IV injection of LA - ropivacaine is very cardiotoxic.

1. What do you do to treat this?!

Answer 20

• Don’t panic!
• Start CPR - keep the brain alive while the dog gets through it. Once the drug is out of the system, the dog will come back. If seeing signs of arrest, no excuse not to start CPR!
• Specific treatment for local anaesthetic overdose?
  
  • Lipid infusion: Intralipid 20% absorbs the LA – very expensive, won’t stock it. Propofol and diazepam are very oily suspension so boluses of these drugs during CRP may work. Can also try IV nutrition containing lipid. Propofol is a lipid,
  • Bolus 1 ml/kg over 1 min Q 3-5mins
  • Total dose 3-4 ml/kg
  • CRI: 0.25 ml/kg/min “until haemodynamic recovery”