Anaesthesia in ASA 2-4 Categories Flashcards
What are categories 2-4?
Category 2 - Mild Systemic Disease, well compensated
Category 3 - Severe systemic disease and animal is not compensating fully
Category 4 - Poorly compensated disease
What is the focus in these patients?
Stabilising animal
Reducing risk anaesthesia poses to patient
Making them the best anaesthetic candidate
Be aware of potential complications and be prepared to treat them
How can we determine Cardiovascular disease in patients?
○ Echocardiogram
○ FAST scan
Left atrial enlargement
□ Greater risk of CHF
Pleural/ abdominal oedema/effusion
□ CHF already present
○ Conscious radiograph
Cardiomegaly
○ ECG
Arrythmias
○ NT-proBNP
Blood test for myocardial disease
○ Check for anaemia/albumin levels
What are the effects of poor Cardiac Output and perfusion?
Reduced GFR in kidneys
Pre-renal or renal azotaemia
How can you stabilise a patient with cardiovascular disease?
Heart medication
Diuretics
Drain effusions
How will anaesthetic drugs affects a patient with cardiovascular disease?
Longer onset time for drugs give IV or IM
Due to poor peripheral perfusion
Quicker increase in plasma concentration of inhalation anaesthetic agents
Due to reduced cardiac output
Effect of drugs may be less predictable compared to healthy patient
E.g. volume of distribution is altered in a patient with effusion
Water soluble drugs are more likely to leave blood plasma more quickly into effusion filled spaces
Reduced albumin means more unbound and active drug
○ Need to use lower doses
Reduced blood flow to liver
○ Takes longer for drug to be metabolised
○ Longer duration of action
What drugs should you use in category 2 Cardiovascular disease?
Alpha-2 agonist or ACP
(alpha-2 can depress cardiac function so be careful)
Inhalational anaesthesia also depresses cardiac function
What drugs should you use in category 3/4 Cardiovascular disease?
Midazolam and an opioid
Alfaxalone and an opioid
○ In sicker patients consider co-induction
Propofol/midazolam
What other considerations are there in patients with cardiovascular disease?
Reduce stress
○ Prevent catecholamine release (worsens hypercapnia)
Reduce nociception
○ Increase analgesia
Ensure adequate oxygen saturation to prevent hypoxia
○ Prepare to provide IPPV if necessary
○ Intermittent Positive Pressure Ventilation
What is the surgeon doing?
○ Avoid increasing vagal tone - careful with eyes and head
Leads to bradycardia
Be careful with IVFT
○ Don’t want to create more work for the heart
Always have emergency drugs to hand
How can we determine renal disease in patients?
Pre-op bloods - determines degree of azotaemia
Urinalysis - determines re-renal or renal
In post renal cases potassium can be elevated and result in potentially fatal arrythmias so you may want an ECG
Considerations in patients with Renal disease
Patients with CKD have reduced erythropoietin production
If anaemic need to determine if it is compensating well or not
Cats with CKD may be hypokalaemic
CKD can cause hypertension - might not tolerate same degree of BP reduction as a ‘normal’ patient
Patient with post-renal obstruction
Palpate enlarged bladder
How can you stabilise a patient with renal disease?
Provide IVFT - Hartmann’s
Patients usually have metabolic acidosis due to H+ ions excreted through kidneys
Anti-emetics to prevent regurgitation
If patient is severely anaemic may need to consider blood transfusion
Will effect oxygen deliver to tissues
Blocked patients with cardiac arrhythmias due to hyperkalaemia
Treat with insulin/glucose or calcium gluconate first
Also cystocentesis to relieve blockage
In chronic disease low potassium might cause weakness so may need to supplement
What are the goals in anaesthesia of a patient with renal disease?
Normotension
Normovolaemia
Maintain cardiac output
How can you stabilise a patient with gastrointestinal disease?
Anti-emetics
Treat dehydration (IVFT)
Does the patient have azotaemia that needs treating?
Raise head when intubating and use cuffed ET tube
Avoid emetic drugs
Morphine
Alpha-2 agonists
Potentially treat with prokinetic
Metoclopramide
Protein pump inhibitor to prevent oesophagitis if they reflux (omeprazole)
May need supplementing (glucose, insulin, calcium etc)
Analgesia - can be very painful
NSAIDs contraindicated with vomiting/diarrhoea
Alternatives:
□ Opioids
□ Paracetamol
What to consider if a patient has liver disease
Think about how drug is metabolised - reduce metabolism?
Use short acting/reversible drugs?
Increase dosing interval
Low albumin - more free drug
Reduce doses
May be hypoglycaemic (gluconeogenesis and glycogenolysis occurs in liver)
May be hypotensive
Bile acids affect endothelium of blood vessels
Monitor blood pressure carefully
Increased risk of infection due to immunological role of liver
