Sedation and general anaesthesia Flashcards
Explain the role of sedation in dentistry
- Make is possible to treat anxious/ phobia patients
- Ensure unpleasant procedures don’t cause distress to the patient
- To avoid general anaesthesia for patients with special needs
- Avoid onset of medical conditions that are triggered/ aggravated by stress
- For medical conditions affecting the patient’s ability to cooperate
Remember the names of drugs used to sedate patients for PAINLESS dental procedures
First line drugs (wide margin of safety)
Benzodiapzines
• Children: Midazolam
• Adult: diazepam, triazolam, lorazepam
Second-line drugs (narrow margin of safety, specialist technique)
• Propofol
• Sevoflurane
Remember the names of drugs used to sedate patients for PAINFUL dental procedures
• Consider local anaesthetic in all cases
Minimal to moderate sedation:
• Nitrous oxide (inhalation)
• Benzodiazepines
Moderate sedation:
• Ketamine (IV or IM)
General anaesthesia:
• Propofol + fentanyl (IV, specialist technique)
Define minimum alveolar concentration (MAC)
- The alveolar concentration of an inhaled anaesthetic at which 50% of patients will respond well i.e, no motor response to an incision
- 99% will not respond to 1.3 MAC
List the disadvantages of oral sedation
- Takes long for drug to take effect
- Unreliable drug absorption
- Inability to achieve desired drug effect (lack of titration)
- Prolonged duration of action: 3 to 4 hours
Define “never events”
- Death or severe harm as a result of overdose of midazolam injection
- Death or severe harm as a result of the administration of the wrong gas, or failure to administer any gas, through a line designated for medical gas pipeline systems (MGPS) or through a line connected directly to a portable gas cylinder.
- Death or severe harm as a result of failure to monitor or respond to oxygen saturation levels in a patient undergoing general or regional anaesthesia
Describe the mode of action of glutamate
- Glutamate is a powerful excitatory neurotransmitter
- It is released by nerve cells in the brain
- Glutamate is released by the pre-synaptic neuron
- It binds to ligand-gated ion channels in the post synaptic neuron
- This allows Na+ ions to come in and cause depolarisation
- When the electrical potential goes from -65mV to -40mV, voltage gated sodium channels will open. This allows even more Na+ to enter and cause -40mV to go to 40mV
- Action potential occurs
Describe the mode of action of GABA
- GABA is an inhibitory neurotransmitter
- GABA molecules bind to their receptors called GABAA
- This allows Cl- ions to enter the neuron. Since Cl- is negatively charged, it drops the electrical potential of the membrane further
- It also means that a huge amount of glutamate molecules will be required to raise the electrical potential and generate an action potential
- Thus, high levels of GABAergic transmission decrease action potentials
List the mode of administration and describe the mechanism of action of benzodiazepines: Drug names; most end with lam or pam
Mode of administration
• IV sedation
• Minimum to moderate anaesthesia
Mechanism of action
• Benzodiazepines act as a sedative; slowing down the body’s functions
• They work by increasing the effect of GABA
• Bind to “benzodiazepine receptors”located between alpha and gamma subunits of GABAA receptor
• After binding, it increases the frequency of the chloride ion channel opening, thereby increasing the inhibitory effect of GABA on neuronal excitability
• GABA needs to be present for benzodiazepine effects to be detectable
• Works in the limbic system, thalamus & hypothalamus
List the mode of administration and describe the mechanism of action of propofol
Mode of administration
• IV sedation
• General anaesthesia
Mechanism of action
• Propofol increases GABAergic transmission.
• Binds to beta sites on GABAA receptor
• This increases the affinity of GABAA receptor to GABA
• Also, it decreases the rate of dissociation of the GABA from the receptor = longer GABAergic effect
• In addition, it will block the pores of voltage gated sodium channels to stop Na+ from coming in = no action potential
Describe the mechanism of action of magnesium in blocking transmission
- A NMDA receptor (glutamate receptor) opens, when 2 molecules of glutamate bind to it
- When the channel is open it allows cations to come in, especially Na+ ions = depolarisation
- Mg+ can block NMDA pores = no action potential
- If the voltage changes, Mg+ will no longer block the pore and an action potential can be generated
List the mode of administration and describe the mechanism of action of ketamine
Mode of administration
• IV sedation
• Moderate anaesthesia to general anaesthesia
Mechanism of action
• Binds to inside pore of NDMA receptor and blocks it
• Na+ ions cannot pass through = no depolarisation = no action potential
• Neuronal activity decreases = sedation
List the mode of administration and describe the mechanism of nitrous oxide
Mode of administration
• Inhalation
• Minimum to moderate anaesthesia
Mechanism of action
• Binds to inside pore of NDMA receptor and blocks it
• Na+ ions cannot pass through = no depolarisation = no action potential
• Neuronal activity decreases = sedation
• K2P receptors normally allow K+ to leave the cell, allows the neuron to polarise again
• N20 bids to K2P receptors to keep it open for longer so that K+ can continue leaking and cause the electrical potential to remain negative for longer
