Ch 21 - Anaesthesia Principles and Monitoring Flashcards
Describe the 5 ASA grades
What is the rate of anaesthetic-related death in animals?
1 : 500 - 1000
Humans 1:10,000
What medications are contraindicated in animals with cardiac disease?
- alpha-2 agonists
- Acepromazine should only be used if they can tolderate vasodilation
- Caution wth ketamine in HCM (increases sympathetic activity)
- Propofol/alfax should be used cautiously due to vasodilation. Etomidate is ideal.
- Some animals wont be able to tolerate gas vasodilation
What medications are contradicted in the face of thyroid disease?
- Ketamine due to potential cardiomyopathy and possibility of thyroid storm
- Avoid NSAIDs and maintain normal/slightly elevated BP due to potential for underlying renal disease
- May have cardiomyopathy
What is the hypoxic pulmonary vasoconstriction?
A compensatory mechanism that results in vasoconstriction of the blood flow to the alveoli that do not have an adequate oxygen supply. Helps to balance a V/Q mismatch in awake patients
Inhalant anaesthetic agents impair or eliminate this compensatory mechanism causing V/Q mismatch to worsen in the anaesthetised patient
What are some potential benefits of ketamine when used on patients with airway disease?
- Causing bronchodilation (good for allergic airway disease)
- Maintains the respiratory center sinsitivty to PaCO2
- Maintains respiration making is a useful induction agent
What considerations should be made when making a plan for a patient with liver disease?
- Often require lower doses of drugs if hypoalbuminaemic as many anaesthetic drugs are highly protein bound to albumin
- Propofol has extrahepatic metabolism and so is a good choice, as is remifentanyl (plasma esterase)
- Inhalants undergo very little hepatic metabolism and are also a goof choice
List some drugs which are renally excreted and therefore effects may be prolonged in patients with renal disease
- Ketamine
- benzodiazepines
- opioids
- acepromazine
What anaesthetics should be avoided in renal disease?
- Ketamine
- Sevofluorane (Compound A)
- Epidural contraindicated due to potential coagulopathies in severe uraemia
What are the main risks after relieveing a urinary obstruction?
- Post-obstructive diuresis
- Dialysis disequilibrium - seen if BUN drops rapidly causing a decrease in serum osmolality and associated fluid shifts resulting in cerebral oedema
What is the maximal allowable pressure during laparoscopy?
At what pressure is there an association with anuria and acute renal failure?
-14cmH20 maximum allowable
- 25cmH2O anuria, AKI
What patient positioning is used for laparoscopic surgeries?
Trendelenburg positioning (head-down)
What is the only anaesthetic drug which has been shown to adversely effect neonate survival in C-sections?
xylazine
For lumbosacral epidurals, what volume is appropriate for the HLs? For abdominal/thoracic?
- 0.2ml/kg for HLs
- 0.3ml/kg for abdomen/thorax
What considerations need to be made when anaesthetising for an ophtho procedure?
- Maintaining central eye position (low dose neuromuscular blockade)
- Avoiding spikes in IOP such as can be caused by propofol and ketamine
