Anaesthesia For The Critical Patient: Is It Different? Flashcards
Why is anaeasthesia different in the emergency case?
•Emergency patients have minimal ‘physiological reserves’ to tolerate the stress of anaesthesia
What doo we need to do differently for an emergency anaesthesia? What do you do the same?
•Vital that we fine tune the anaesthetic to minimise effects of the condition
–Tailor the anaesthetic and change what you do for each case
•But basic principles still apply
–In fact they become more important
Why are emergency pateints challenging? (6)
Unstable cardiorespiratory system
–Can be TC or BC which is worse
–Have to stabilise prior to give
• Altered circulating fluid volume
–Normally a loss – hypovolaemic patients –can drop dead at induction
–Dehydration isn’t so bad
- Metabolic derangements
- Time pressures and patient status
- May limit comprehensive preanaesthetic examination
- Need to weigh up stabilising the patient and getting to the point of “enough is enough”
- Potentially unknown/limited history
- Off the street or brought in by a neighbour – what does the animal have underlying?
- Emotional and financial pressures from the owners
- Have to be aware of the emotional side and TRY to stay away
What do you need to do prior to anaesthetising?
•Thorough pre-operative clinical examination with blood sampling as necessary and subsequent anaesthetic plan is vital
–CE – where we pick up where the patient will detoriate
–Write a plan; discuss what could go wrong
Where does success lie with anaesthestic? (2)
- Preparation and anticipation of problemos
CASE:
‘Max’
10 year old Labrador
Large meal, went for a walk, collapsed with swollen abdomen
What is this?
GDV
What are the Anaesthetic Challenges With GDV Cases? (6)
•Electrolyte imbalances (potassium and calcium) with cardiac arrhythmias
–Correct haemodynamically significant arrhythmias before induction if possible
–THESE ARE WHAT KILLL GDV PATIENTS esp K+ as very common. Likely to see changes in potassium: Hypokalaemia
–Any chronic or acute GI disease – patient is likely to leak potassium into lumen of the gut.
–A lot of patients die on induction with low K+ - tachycardia and loss of T waves Flip into ventricular fibrillation
–IF YOU DON’T HAVE T YOU DON’T PEE
- Hypovolaemia
- Respiratory compromise
–Pressure on diaphragm and cannot ventilate
•Possible regurgitation and aspiration
–Reason they die 3 days later
–Aspiration pneumonia, nothing can go down, still produce saliva and then it sits in oesophagus and then we anaesthetise (everything relaxes)and within one breath it is in the lungs
- Pain and distress
- Metabolic acidosis and increased lactate
How can we preopare critical patients for pre op stabilisation? (3)
–Intravascular access via a patent cannula
- Rapid administration of anaesthetic, analgesic and emergency drugs
- Pre- and intraoperative fluids
- Possibly 2 FL cannulae in GDV cases (both cephalics, or both in one vein)
–Fluid by one and drugs in another
–DO NOT USE HL; Return from caudal abdo to heart reduces – cant give fluids and drugs well
–Fluid stabilisation +/- additives
–Appropriate drug therapy
What can you give to an animal with GDV and low potassium?
•’Shock rates’ of CSL – a bolus of 30ml/kg over 20 minutes plus potassium infusion (separate line)
–If you give potassium at this rate youd kill. Will stop the heart. This is why we need 2 cannulas
What can be seen here?
Premature ventricular beats
Not too worried about these singular ones
Lung gap post VPC and back to normal. This is a good sign as means the heart is listening and putting it back
Cranial abdo disease dysrhythmia – pancratitis, splenic tumours, gastric tumour – tend to see
Need to question whether haemodynamically normal – use a Pulse Ox and still normal when a VPC
Put an ECG o prior to and during induction
What do we do about pre med in critical patients?
•Potentially unnecessary if the patient is obtunded
–Always need analgesia for surgery!!
•Drugs such as the alpha-2 agonists which have major cardiovascular effects should generally be avoided
–Vasoconstrict
–Hypertension followed by reflex Hypotension (can also at times have normotension)
–Reflex bradycardia
•Although the emphasis is usually on correcting the underlying condition quickly it is always necessary to ensure good analgesia in any surgical patient
What analegsia in pre med is okay?
•Pethidine administered intramuscularly is often a good choice
–Short acting, excellent analgesia with some sedation, minimal effects on the cardiovascular system
- Methadone or morphine suitable but may cause a degree of bradycardia and emesis. (usually so painful you do not see this)
- Following premedication monitor the patient for adverse effects
What do we need to do prior to anaesthesia induction?
•Prepare well
–Critical patients you do not want to need to leave the room
–ECG to examine the electrical rhythm of the heart with treatment as necessary
–Oxygen for a minimum of five minutes – only if they tolerate the mask.
What do we need to have prepared when anaeasthetisisng?
•Have emergency drugs (doses calculated) to hand plus syringes/needles
–Dose charts can be very useful
How do we induce the patient?
•Any induction agent can be used
–No right or wrong
–Give slowly to effect
- Emphasis on minimal effective doses to allow endotrachea intubation
- For example
–Calculate the full dose of an agent such as propofol, but only administer half of the dose over 10-15 seconds
–In most patients this will be sufficient to allow intubation
A GDV developed this intra op
- Worsening hypotension on gastric de-rotation
- Required dopamine infusion
- 10ml/kg colloid bolus over 15 minutes
- Common scenario to come across
- When you rotate the stomach all the rubbish builds back up in the body and circulation
- Mean pressure should be above 65. Low pressure
- Turn down iso, give a fluid bolus
What can you do about this?
- Required lidocaine bolus 2mg/kg
- Check BP and pulse ox at same time – little output. Worried will develop into ventricular fibrillation.
- Magnesium also given as good anti-dysrrhtymia
