Anaesthetics Flashcards
What are the 3 components of anaesthesia?
- Hypnosis
- Analgesia
- Muscle relaxation
What are the 3 levels of hypnosis?
- Awake
- Sedated
- Asleep
What are the 3 broad types of anaesthetic?
- Local
- Sedation
- General
Types of local anaesthetic techniques
- Small surgery - laceration or wound repair
- Target specific nerves - e.g. brachial plexus, sciatic
- Usually for post-op pain relief
- Spinal & epidural
Info: Spinals and epidurals
Spinal (subarachnoid block) → needle into CSF
* THROUGH ligaments + dura
* Local anaesthetic is injected as a bolus, which lasts around 2 hours
Epidural
* Needle goes BETWEEN ligaments + dura
* Catheter is passed
* Local anaesthetic can be given through the catheter as an infusion
Differences between spinals and epidurals
Spinal:
* Single bolus
* Anaesthetic
* Injected at lumbar region (below the level where the spinal cord ends)
* Same target as a lumbar puncture
Epidural:
* Continuous infusion
* Anaesthesia or analgesia (including labour)
* Thoracic or lumbar
What is a main limitation to spinals and lumbar epidurals?
Only allow you to operate below the highest nerve root affected by the block
Which normally means below the T10 dermatome
(below the umbilicus)
What are the 2 main types of anaesthesia?
- General anaesthesia
- Regional anaesthesia
Do patients have to be intubated under GA?
Under GA - the patient is in a state of controlled consciousness. Patients will have to be:
* Intubated
* OR have a supraglottic airway device
Their breathing will be supported + controlled by a ventilator
* Pt will be continuously monitored at all times immediately before, during and after general anaesthesia
Why do you have to fast before planned general anaesthetic?
Reduce the risk of the stomach contents refluxing into the oropharynx (throat) → then aspirated into the trachea
Gastric contents in the lungs = creates an aggressive inflammatory response → causing aspiration pneumonitis (inflammation of the lung tissue)
Aspiration pneumonitis = major cause of morbidity + mortality in anaesthetics (rare in planned procedures)
When is the risk of aspiration pneumonitis the highest?
The risk of aspiration = highest:
* before + during intubation
* When they are extubated.
Once the endotracheal tube = correctly fitted, the airway is blocked and protected from aspiration.
How long do you have to fast for?
- 6 hours of no food or feeds before the operation
- 2 hours of no clear fluids (fully “nil by mouth”)
In emergency situations the patient might not be fasted (rapid sequence induction)
What is preoxygenation?
Before being put under a general anaesthetic, the patient will have a period of several minutes where they breathe 100% oxygen → **gives them a reserve of oxygen **for the period between when they lose consciousness and are successfully intubated and ventilated (in case the anaesthetist has difficulty establishing the airway).
This step may need to be skipped when an emergency general anaesthetic is required.
Why is premedication given?
Premedication = given before the patient is put under a general anaesthetic:
* Reduce anxiety
* Reduce pain
* Make intubation easier
Give examples of premedication
- Benzodiazepines (e.g. midazolam) → relax muscle + reduce anxiety (+ amnesia)
- Opiates (e.g. fentanyl or alfentanyl) → reduce pain + reduce the hypertensive response to the laryngoscope
- Alpha-2-adrenergic agonists (e.g. clonidine) → sedation + pain
What is rapid sequence induction/intubation (RSI)?
RSI = used to gain control over the airway as quickly and safely as possible where a patient is intubated in an emergency scenario and detailed pre-planning is not possible.
- More risky (as pt has not been fasted) → ASPIRATION
Also used in non-emergency situations where the airway needs to be secured quickly to avoid aspiration, e.g. in patients with gastro-oesophageal reflux or pregnancy.
the anaesthetist has not had the chance to plan for individual factors and potential problems (e.g., a difficult airway)
What is the biggest concern with rapid sequence induction/intubation?
ASPIRATION
* Endotrachial tube used ASAP after induction → to protect airway
* Aspiration of the stomach contents into the lungs
The bed can be positioned so the patient is more upright to reduce the reflux of contents up the oesophagus.
Cricoid pressure (pressing down on the cricoid cartilage in the neck) may be used to compress the oesophagus and prevent the stomach contents from refluxing into the pharynx (this is somewhat controversial and should only be done by someone trained and experienced).
