L23: Pharmacology Of CNS And Breathing Flashcards
Where can drugs act to affect breathing
Lungs
CNS
Where in the brain are drugs likely to act on to affect breathing
Brainstem
What are in the brainstem
A collection of automatic neurone nuclei such as DRG, VRG, PRG and botzinger complex
What are the functions of respiratory stimulants
Increase ventilation
What are the examples of respiratory stimulants
Doxapram
Aminophyllines
What is the mechanism of action of doxapram
Stimulates carbon dioxide and oxygen chemoreceptors by non specific action to increase the electrical activity of the neurones
What are the adverse effects of respiratory stimulants
They can work on any other neurones to cause
Cardiac arrhythmia
When is doxapram used
In emergencies such as:
Acute ventilator failure with COPD
Post operative respiratory depression
What are respiratory depressants
Any agent which has a generalised CNS depressant that depresses ventilation via action at the nuclei in the brainstem
What are the examples of respiratory depressants drugs
General anaesthetic Alcohol Barbiturates Opioids Benzodiazepines
Do respiratory depressants completely shut down the breathing system
No they decrease the activity
What are the 2 sorts of general anaesthetic
Volatile (inhaled)
Injected
What happens to the physiological response when patients inhale general Anaesthetics
Reduced response in central chemoreceptors
What happens as a consequence of reducing the response of central chemoreceptors
Paco2 increases
What is the mechanism of action for general anaesthetics
Not really sure but has an effect on the neurotransmitter of GABA
What type of neurotransmitter is GABA
Inhibitory neurotransmitter
When are benzodiazepines used
Pre-anaesthetic
Management of anxiety disorders
What is the physiological response of benzodiazepines at low dose
Decreases response in peripheral chemoreceptors
What does a decrease in peripheral chemoreceptors result in
Hypoxia
What is the physiological action of benzodiazepines in higher doses
Reduces response in central chemoreceptors
What is the mechanism of action of benzodiazepines
1) GABA bound to GABAa receptors causes voltage gated chloride ion channels to cause chloride influx and give hyper polarisation occurring
2) benzodiazepines bind to a different site next to GABA and increase the effect of GABA to increase the chloride influx and result in hyperpolarisation
Can benzodiazepines work on their own or do they require GABA
Require GABA to work
What is the physiological action of barbiturates
Reduce the response to central chemoreceptors
What is barbiturates rarely used
The anaesthetic dose is really close to its fatal respiratory depression dose
