Maintenance Flashcards
What are the pros/ cons to Xenon?
- Quick to induce anaesthesia
- Inert gas
- Very expensive
What are vapours?
Liquids that are vapourised in a carrier- if it is below its critical temperature it can become a liquid when you compress it.
How does the carrier gas collect the vapour?
When you turn the dial you divert a proportion of the carrier gas into the vapouriser where it picks up vapour molecules which are then delivered to the patient
What are the kinetics of the vapour drug?
- At alveolar surface it passes into the blood
- Blood carries it to the brain
- Interacts with GABA or another channel causing unconsciousness
- Also interact with spinal cord
- Solubility of agent differs (more soluble the slower the onset of anaesthesia)
- Cardiac output: bigger it is the harder it is to anaesthetise
- Resp rate affects speed too
What is the blood: gas partition coefficient?
The LESS soluble agents are washed away less quickly therefore alveolar conc rises faster
i.e. the lower the coefficient the more rapid the induction/ recovery
Why do obese animals recover slower than thin ones?
Some of the anaesthetic gas moves into the fat so more remains in the body for longer
What is MAC?
Minimum Alveolar Concentration
-The alveolar concentration producing immobility in 50% of patients in response to a noxious stimulus
What affects MAC?
Age Hypotension Hypoxia Anaemia Opioids Pregnancy
What are the MAC values for Iso and Sevo?
Iso: dog 1.28, cat 1.63
Sevo: dog 2.2, cat 2.58
What are the negative effects of inhaled agents to the patient?
- CVS depression
- Poor kidney perfusion
- Carbon monoxide forming with soda lime
What are the negative effects of inhaled agents to the anaesthetist?
Little/ no evidence apart from nitrous oxide:
long term exposure causes bone marrow suppresion and teratogenesis
What measure help protect practice staff/ environment from the negative effects of inhalents?
- Active/ passive scavenging
- Flushing circuit before disconnecting
- Staff where badges that measure amounts they are exposed too- audited every year
What is often encountered during equine anaesthesia?
Hypoxia (ventilation/ perfusion mismatch)
caused by dorsal recumbancy/ lungs collapse, guts press of diaphragm/ giving CVS depressant drugs
What is permissive hypercapnia?
Tolerated levels of hypercapnia (60mmHg) in equine anaesthesia, helps keep the BP higher.
What are the goals of PIVA?
- Reduce MAC
- Reduce cardiopulmonary depression
- Provide some analgesia
- Improve plane of anaesthesia
