Intravenous drugs Flashcards
Define onset of action
How long it takes from the moment of induction to the patient sleeping
Is GABA A inhibitory or stimulatory?
They are the main inhibitory receptors of the CNS
What are NMDA receptors?
The main stimulatory receptors of the CNS
How do the intravenous drugs affect GABA A?
They stimulate it
- Thiopentone
- etomidate
- propofol
How do the intravenous drugs affect NMDA?
They inhibit it
-ketamine
Which drug is in powder form?
Thiopentone and you mix it with 20ml of water
- Which drug is a barbitone?
2. Which drugs are non-barbitones?
- Thiopentone
2. Propofol,ketamine, etomidate
What is the dose of thiopentone?
What is the maximum concentration we can give?
- 3-5 mg/kg
2. The maximum concentration is 2,5%(25mg/ml)
What is the taste of thiopentone?
Garlic
What is the ph of thiopentone?
Why can’t we inject it intramuscularly?
- 10-11
2. It is painful and it can cause gangrene and spasm and arterial anderitis if injected in the wrong place
What drug helps as an excellent anti-convulsant?
Thiopentone
What is the effect of thiopentone on the respiratory system?
It can cause laryngospasm in someone with asthma already and has a high risk of apnoea
What is the effect of thiopentone on the CVS?
Decreased CO about 10-20% caused by vasodilators , SVR and it increases the HR to compensate(baroreceptors)
What is the absolute contra-indication for thiopentone?
Porphyria
What drug is referred to as the milk of amnesia?
Propofol
What can we give to lessen the effects of burning on injection of propofol?
lignocaine
What is the dose of propofol?
2-2,5 mg/kg
What is the benefit of propofol on the respiration?
Allows for the use of an LMA
What is the effect of propofol on the CVS?
- causes hypotension because of decreased Cardiac output and SVR
- The HR does not compensate and it can lead to bradycardia
- make sure not to use in patients with sepsis or septic shock
Why is propofol too good to be true?
- anti-emetic
- anti-pruritic
- anxiolytic
- amnesia
- no hangover/ accummulation
- it is good with porphyria
Why must we use propofol within 6 hours of opening a vial?
To prevent bacterial cultures
If we mix the propofol with lignocaine or saline how fast do we need to use it by?
30 minutes because it can cause an emulsion deterioration and can cause thrombosis
What is the drug dose for Etomidate?
0,3 mg/kg
What is the function of etomidate on GABA?
Etomidate stimulates the GABA-A receptor
What is the function of etomidate on the CVS?
It is very stable and only has a risk of bradycardia when mixed with a high dose of opioids and suxamethonium
What is the function of etomidate in the Resp system?
It has decreased chance of allergic reaction, respiratory depression, coughing and hiccups and so suitable for asthmatics
What are the 5 B’s of Etomidate?
- Braak- PONV
- Beweeg- myoclonic movements especially when sleeping due to the increased hyperactivity of the brainstem
- Brand-It burns
- Bynier- it causes adrenal insufficiency
- baie duur- used to be very expensive
Why can we not use Etomidate in TIVA? (total intravenous anaesthetic)
It causes adrenal insufficiency which leads to Addison’s disease
What does an intravenous induction agent do?
-It will induce unconsciousness when it is being injected at the start of general anaesthetic. You can give it to maintain maintenance
What is TIVA?
- Stands for total intravenous anaesthesia
- This means that the patient will not be receiving any other inhalational anaesthesia
- The patient still receives oxygen or N20 or oxygen
- Propofol is usually used and sometimes ketamine
What is the 10-8-6 rule?
It is the rule that is applied for propofol infusion
-we give the patient 1mg.kg as an initial dose and then 10mg.kg for 10 minutes and then 8mg.kg after the next 10 minutes then 6mg.kg thereafter
What are the concentrations of propofol for induction in elderly people and young children/infants?
Infants- 2,5-3mg.kg
Elderly-1-1,5mg.kg
What is the effects of propofol on CNS?
- can be used for epilepsy
- has rapid loss of unconsciousness
- causes sedation and drowsiness at low doses
What are the effects of propofol on respiratory system?
- it has a high risk for apnea
- reduces alveolar minute ventilation
- decreased functional residual capacity
What is the effects of propofol on GIT?
-good anti-emetic properties
What is propofol infusion syndrome and what is the danger?
- Long term infusion for more than 48 hours particularly of 5mg.kg in children
- it causes lipaemia, metabolic acidosis, cardiomyopathy
In which patients should we not use propofol in?
-patients with hypovolaemia, heart failure and fixed cardiac output
What is the effect of thiopentone on CNS?
-it decreases CRM02(cerebral metabolic rate of oxygen consumption), intracranial pressure
What is dangerous about injecting thiopentone in the tissue?
-sloughing and necrosis
What is dangerous about injecting thiopentone into an artery?
Intense arterial spasm and pain down the arm
-white arm with cyanosis fingers and skin discoloration
What are the absolute and relative contra-indications for thiopentone?
Absolute: porphyria, known allergy
Relative: heart conditions, asthma
What is the effect of etomidate on the CNS?
-It causes epilogenic(myoclonus and involuntary movements) in patients that are known with epilepsy
Why is etomidate called vomidate in the anaesthetic community?
-because it leads to post-operative nausea and vomiting
How do we treat the hallucinations caused by ketamine?
Benzodiazepines or opioids
What is the effect of ketamine on the CNS?
- It causes myoclonus, nystagmus vocalisation especially in uncontrolled epilepsy
- increases intra-cranial and intra-ocular pressure
- Very effective analgesia that can work alone particularly in general anaesthesia
What is the effect of ketamine on the CVS?
- Causes sympathetic nervous system stimulation which causes increase in heart rate, cardiac output, increase blood pressure, peripheral resistance
- the possible myocardial depression is overridden by the sympathetic nervous system
What is the effect of ketamine on the resp system?
- causes increased secretions(saliva, bronchial secretions) which will need to be treated pre-operatively by anticholinergics eg. atropine
- maintains good functional residual capacity
What are the indications for using ketamine?
-bronchodilatory reasons
-paediatric patients
-analgesia
-
What are some of the contra-indications for ketamine?
- epileptic pts
- psychiatric patients
- not suitable for eye surgeries, cerebral surgeries
- CVS disorder- hypertension, ischaemia Herat disease
What is the induction dose for ketamine?
IV: 1-2 mg.kg
IM: 5-10 mg.kg
Maintenance: 0,5 mg.kg incremental boluses
What is the analgesic dose for ketamine?
IV: 0,2-0,4 mg.kg
IM: 2-4mg.kg
Give two examples of benzodiazepines?
- Midazolam
2. Diazepam
Which benzodiazepines are soluble and insoluble in water?
Soluble-midazolam
Insoluble- diazepam
What is the dosage for IV in midazolam?
0,1-0,3 mg.kg
What is most likely cause for post induction hypotension?
-propofol and thiopentone
Which IV induction agent works on the same receptor as nitrous oxide?
Ketamine which works on the NMDA receptor
Which induction agent causes an increase in cardiac output
Ketamine
Which agent is they least metabolized by the liver?
Sevoflurane
