Anaesthesia for sicker patients

Question 1

Answer 1

You might also want to ask about exercise tolerance, any episodes of coughing, any syncopal or pre-syncopal episodes, any episodes of increased respiratory rate & effort

Question 2

Answer 2

Echocardiogram
- allows you to diagnose murmur, stage disease & take accurate measurements

Haematology & biochemistry
- cardiac disease can reduce perfusion to liver & kidneys so assessing organ function may be useful in assessing risk to patient

PCV & TS
- why?

POCUS
- useful for assessing patients for gross cardiac disease & presence/absence of pulmonary oedema

Question 3

Answer 3

B2

Question 4

What ASA classification will you assign Wookie

Answer 4

2/3

Question 5

Answer 5

Methadone
- opioid & full mu agonist so excellent analgesic
- good sedative with minimal cardiovascular effects & thus little effect on BP

Alfaxalone
- good for patients with cardiovascular disease as it has minimal cardiovascular effects & is reliable sedative when given IM
- not an analgesic

Question 6

Answer 6

Oxygen in Blood:
- 98% bound to haemoglobin (Hb)
- 2% dissolved in plasma

Pre-Oxygenation Benefits:
- Increases FiO₂ (fraction of inspired oxygen)
- Replaces alveolar nitrogen with oxygen
- Increases O2 reserves in lungs

Oxygen Dissociation:
- PaO₂ (arterial partial pressure of O₂) decreases with alveolar O₂ pressure
- SaO₂ (>90%) remains stable as long as Hb is re-oxygenated
- Drops rapidly once lung O₂ stores are depleted

Clinical Importance:
- Pre-oxygenation buys time during induction when respiration is depressed or absent

Question 7

Answer 7

Propofol IV

Alfaxalone IV

Alfaxalone & midazolam IV

Propofol & midazolam IV

Question 8

Answer 8

3-5ml/kg/hr

Question 9

Answer 9

This is likely to result form sympathetic stimulation/ nociception

Question 10

Can you think of any nerve blocks which might have reduced the likelihood of this happening in Wookie

Answer 10

Radial/ulnar/median/musculocutaneous (RUMM) nerve block which can easily be performed using blind technique

Ring block either around mass or around limb caudal to mass

Brachial plexus block which is more technically difficult to perform

Question 11

Answer 11

Sedation with detomidine and butorphanol

Question 12

Answer 12

Phenylbutazone
- Licensed NSAID in horse (IV or IO)

Flunixin
- Licensed NSAID in horse (IV or IO)

Question 13

Answer 13

Epidural coccygeal 1-2

Epidural sacrococcygeal

Question 14

Answer 14

Mepivacaine

Licocaine

Question 15

Answer 15

Increased risk of dyspnoea & airway obstruction following sedation

Potential for difficult intubation leading to hypoxaemia

Increased risk of regurgitation & thus oesophagitis/ stricture formation & aspiration pneumonia

Corneal abrasions of normal eye due to exopthalamus

Airway obstruction on extubation

Question 16

What ASA status are you going to give Duchess

Answer 16

2/3

Question 17

You’ve decided to premedicate Duchess with 3mcg/kg dexmedetomidine and 0.2mg/kg methadone IV. Dexmedetomidine is available as a 0.5mg/ml solution and methadone as a 10mg/ml solution. What volume of each are you going to draw up?

She weighs 4.8kg

Answer 17

0.03mls dexmedetomidine and 0.10ml methadone

Question 18

Answer 18

Methadone

Question 19

Answer 19

Peribulbar block
- LA injected into peribular space & diffuses into retrobulbar space blocking cranial nerves II (optic), III (oculomotor), VI (abducens) & branches of V1 (opthalamic)
- Desensitises structures of globe, conjunctiva & ocular muscles

Retrobulbar block
- LA injected into retrobulbar space blocking cranial nerves II (optic), III (oculomotor), VI (abducens) & branches of V1 (opthalamic)
- Desensitises structures of globe, conjunctiva & ocular muscles but doesn’t reliably desensitise eyelids

Question 20

You have a 0.5% bupivacaine solution and can use up to 2mg/kg to perform the block. What is the maximum volume you can inject?

Answer 20

1.9ml

Question 21

Answer 21

Vagal

Question 22

Answer 22

Just monitor
- MAP is still >60mmHg
- Once block is effective it will most likely resolve but be ready to treat if necessary

Inject LA more slowly
- may help reduce the pressure or traction on nerve

Question 23

Start IVFT

Give meloxicam

Give methadone

Give frurosemide

Give lidocaine based on ECG

Supplement oxygen

Give bicarbonate

Supplement potassium

Decompress the stomach

Answer 23

Start IVFT
- Patients with GDV become rapidly hypovolaemic
- Crystalloid fluid therapy should form basis of initial resuscitative efforts
- Patient is haemoconcentrated & acidotic
- Aim being to restore circulating volume, tissue perfusion & oxygen delivery
- Volume requirements should be based on patient response to fluid resuscitation

Give methadone
- Patient will be very painful so full mu agonist opioid is good choice with minimal cardiovascular effects

Give lidocaine based on ECG
- Ventricular arrhythmias are common & you can assess this by placing ECG lead
- Early use of lidocaine IV bolus followed by infusion is beneficial (reduced occurrence of cardiac arrhythmias, risk of acute kidney injury & hospitalisation time)

Supplement oxygen
- Good idea esp. in patients where there is evidence of poor perfusion & poor tissue oxygenation
- Can also pre-oxygenate prior to induction whilst stabilising patient

Supplement potassium
- Patient is hypokalaemic & this is likely to get worse as you correct fluid deficit
- Common in GDV as K is lost into gastric lumen
- Hypokalaemia can potentiate cardiac dysrhythmias
- K can be supplemented in intravenous fluids

Decompress stomach
- Reduces risk of cardiovascular collapse during induction of anaesthesia as distention of stomach leads to reduced venous return to heart by compression of vena cava & portal veins

Question 24

What would you like to premed Magnus with?

Answer 24

Methadone

Question 25

Answer 25

Ventricular premature complexes

Question 26

Answer 26

Ventricular tachycardia

Question 27

How are you going to treat this arrhythmia?

Answer 27

Give Lidocaine

Question 28

The drug you’ve chosen comes as a 2% solution. You want to give a 2mg/kg bolus. What volume are you going to draw up to give to Magnus?

He weighs 74kg

Answer 28

7.4ml

Question 29

You repeat the bolus and this seems to help so you decide to start a CRI. Calculate a CRI of 40mcg/kg/minute for Magnus. Calculate the rate in ml/hour.

2% solution

Answer 29

8.88ml/hr