Module 3 IV induction Flashcards
What is considered a true IV induction agent
This is an agent that can cause LOC in one arm brain circulation time
What are the 4 Rapidly acting induction agents
Thiopentone
Etomidate
Propofol
Ketamine
What are the 3 slower acting induction agents
Benzo: Midazolam
Neurolept anaestetics e.g. Haloperidol
Large dose opiods
What are the advantages of IV induction 4
- Rapid onset
- More pleasant and acceptible
- Pollution free
- Low incidence of side effects
What are the 4 disadvantages to IV induction
- Require IV access
- Can give too much
- Removal takes longer
- Sudden loss of protective reflexes
What is the main 2 mechanisms of action of IV agents
- Increase GABAa channel activity causing the neurons to hyperpolarise
- They inhibit the release of Glutamate
What is the pharmokinetics
This describes the kinetic movements of the drug in the body
Absorbtion
Distrabution
Metabolism
Elimination
What is the pharmacodynamics of a drug
This describes how the drug affects the body
What are the factors that affect the drugs onset of action
- Speed of injection
- Lipid soluability of the drug
- Protein binding of the drug
- Blood flow to the brain
What affects the speed of recovery from an IV induction agent
- The redistrabution of the drug in the body
- Speed of metabolism and excretion of the drug
What are the 5 properties of an ideal induction agent
- Smooth and rapid onset of action
- Cheap
- Rapid recovery
- Minimal side effects
- No pain on injection
What can be done to reduce pain on injection for propofol
You can give 10-20mg of lignocaine IV
What is the colour code for IV induction agents and sedatives
Induction agents: Yellow
Sedatives: Orange
Is propofol water soluable and what is the problem with it
No it is placed in an emulsification of fats, the problem with this is that within 6hours of openning a bottle it must be thrown away because the fats create a medium of growth
What is the dose of 1% propofol
1% is 1mg/10ml
What makes propofol a versitile agent
- Induction agent
- Maintance e.g. TIVA
- Sedation at low doses
What do doses in children and elderly look like
In children the dose per kg is always higher and in the elderly it is always lower
What is the main CVS drawback to propofol
It decreased the systemic resistance
What is the benefit of propofol in resp. function
- Inhibits the laryngeal reflex
- Does not cause histamine release
What is propofols effect on PONV
It decreases it
What is the main risk in propofol use
Propofol infusion syndrome
What does Thiopentone look like
Yellow powder that is mixed with saline or water
What is the main drawback when it comes to thiopentone and pain
It lowers the pain threshold
What is the best patients to give thiopentione in
In patients that are status epilepticus as it is an anticonvulsive and has neuroprotective effects
What is thiopentones effects on the CVS
Causes 10-20% decreases in cardiac output by causing vasodilation and so causes a compensatory increase in the HR
What is the main disadvantage of thiopentone in resp
It causes release of histamines and so can cause an asthma attach
What is a serious side effect of thiopentone
It the patient has sepsis the thiopentone with intravenously precipitate into crystals
What are the 4 contraindications to the use of thiopentone
- Pophoria
- Allergy
- Asthma
- Cardiovascularly unstable patients
Why cant etomidate be used as a continous infusion
It can cause adrenocortical suppression
What is the main reason for using etomidate
It is the most cardio stable
What are some of the drawbacks of etomidate 3
- Causes severe PONV
- Causes inhibition of steroid synthesis
- Myoclonus and involuntary movement
What is the MOA of ketamine
It antagonises the NMDA reseptors
What is the benifit of ketamine
It is a potent analgesic
What are the 2 main CNS side effects of ketamine
- It can have psychiatric reactions
- Increases ICP
What is the CVS effects of ketamine
It causes sympathetic stimulation but causes myocardial depression
What is the benefit of ketamine in patients with asthma
It is a bronchodialator because it stimulates the sympathetic NS
What are 2 side effects of ketamine that are undesirable
- Causes PONV
- Can cause uterine contraction in the 1st trimester
What is a benifit of ketamine in patients that are at high risk of aspiration
Ketamine maintains the pharyngeal and gag reflex and so patient are less likely to aspirate
Where do benzos act
They act on the GABA reseptors
What are the effects of benzos on the CNS
- Anxiolytics
- Sedation
- Anterograde amnesia
What is a drawback of using benzos in pregnancy
They can cause floppy baby by crossing the placenta
What does Flumazenil do
It acts as a benzo antagonist
Which 2 drugs can be used for TIVA
- Ketamine
- Propofol
What are the 4 main indications for TIVA
- Risk of MH
- Severe PONV
- Day case
- Cheap
What are the requirements of a TIVA
Infusion pump
Why is the does the anaesthetic wear off if the drug is not metabolised
This is because the brain is well perfused and so initially large amounts of the agent are deposited in the brain but over time the agents redistribute to less well perfused areas
Where are the drugs metabolised
Most of the lipid soluable drugs are metabolised in the liver and then excreted by the kidney
What is meant by TCI
This is target controlled infusions in which a microprocessor controls the rate of infusion to target levels in the plasma or target organ
In which scenario would the speed of volatile induction be decreased?
Increase Cardiac output
A true induction agent will cause loss of consciousness in what time frame?
One arm-brain circulation time
What is a common side-effect following propofol administration?
Apnoea and hypotension
Which IV agents can cause nausea and vomiting
Etomidate and ketamine
Which IV agent can trigger porphyria?
Thiopentone
Which IV agent usually maintains respiration?
Ketamine
