Intravenous Anaesthetic Agents Flashcards
What are the two main groups of IV Anaesthetics?
1- Rapid LOC +-30sec
2- slower onset
Name a few Rapid Acting Agents
Propofol
Thiopentone
Entomidate
Ketamine
Slower -Acting Agents
Benzodiazepines (Diazepam, Midazolam)
Neurolept Anaesthetics (droperidol or haloperidol + opiod)
Large Dose Opiods (Fentanyl, Sufentanil, morphine)
Advantages of IV Induction
- Rapid Onset
- Smooth induction with rapid transfer through stage of excitement
- more pleasant for pt
- pollution free
Disadvantages of IV Induction
- Venepuncture needed
- overdose easy
- No removal of drug via lugs “if its in, its in”
- Sudden loss of normal protective mechanisms (apnoea)
Describe the mechanism of action of IV Agents
-modulates GABA neuronal transmission and thus interferes with transmembrane electrical activity. GABA is common inhibitory neurotransmitter.
Ketamine is an opioid receptor agonist and antagonises NMDA receptor
Briefly Describe The Pharmacokinetics
Termination of action is due to redistribution of the drug from the brain to less well perfused sites. The reason a person wakes up after a few minutes is due to redistribution from the brain.
- Rapid awakening is not due to metabolism or excretion of drug
- Subanaesthetic concentrations may remain in the brain and result in impaired higher fucntioning (why pt shouldnt drive). This also raises senstivity to alcohol and sedatives and analgesia.
- Caution pt about this behaviour and making legally binding decisions for atleast 24hrs
Briefly describe metabolism and excretion
Drugs are lipid soluble—> LIVER—>Inactive water soluble metabolites—->excreted in urine
What is TIVA
Total IV Anaesthesia - no inhalational agents are used during induction or maintenance of general anaesthesia
-the pt will still require air (o2 +NO) via breathing circuit
What drug is commonly used for TIVA?
Propofol. Ketamine used on occasion.
Why is a syringe pump commonly used?
Administer IV drug at a steady , set rate, and to avoid over dosage or awareness under anaesthesia.
