Anaesthesia for sicker patients Flashcards
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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
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
B2
What ASA classification will you assign Wookie
2/3
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
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
Propofol IV
Alfaxalone IV
Alfaxalone & midazolam IV
Propofol & midazolam IV
3-5ml/kg/hr
This is likely to result form sympathetic stimulation/ nociception
Can you think of any nerve blocks which might have reduced the likelihood of this happening in Wookie
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
Sedation with detomidine and butorphanol
Phenylbutazone
- Licensed NSAID in horse (IV or IO)
Flunixin
- Licensed NSAID in horse (IV or IO)
Epidural coccygeal 1-2
Epidural sacrococcygeal
Mepivacaine
Licocaine
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
What ASA status are you going to give Duchess
2/3
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
0.03mls dexmedetomidine and 0.10ml methadone
Methadone
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
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?
1.9ml
Vagal
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
Start IVFT
Give meloxicam
Give methadone
Give frurosemide
Give lidocaine based on ECG
Supplement oxygen
Give bicarbonate
Supplement potassium
Decompress the stomach
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
What would you like to premed Magnus with?
Methadone
Ventricular premature complexes
Ventricular tachycardia
How are you going to treat this arrhythmia?
Give Lidocaine
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
7.4ml
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
8.88ml/hr
