General Anaesthesia Flashcards
Types of Anaesthesia (2).
- General Anaesthesia.
- Regional Anaesthesia.
What is General Anaesthesia?
Putting a patient in a state of controlled unconsciousness, so that a major surgical operation can be performed.
Fasting and General Anaesthesia :-
- Reason.
- Typical Time.
Reason : Empty stomach to reduce risk of gastric reflux into oropharynx and consequent aspiration into airway (pneumonitis).
Typical Time : 6 Hours of No Food/Feeds Before Operation and 2 Hours of No Clear Fluids.
When is the risk of Aspiration highest in General Anaesthesia?
When is the airway blocked and protected from Aspiration?
- Before and during intubation and then when they are extubated.
- Once endotracheal tube is correctly fitted.
What is Preoxygenation? (3)
- Before being put under GA, the patient will breathe 100% Oxygen for several minutes.
- This gives them a reserve of Oxygen for the period when they lose consciousness and are successfully intubated and ventilated (just in case there is difficulty establishing airway).
- Can be skipped in emergency GA.
What is Premedication?
Medications given before GA to relax, reduce anxiety, reduce pain and ease intubation :
1. Benzodiazepines (relax muscles and reduce anxiety) - can cause amnesia).
2. Opiates (reduce pain and hypertensive response to laryngoscope).
3. a-2 Adrenergic Agonists (sedation and pain).
What is RSI?
- Rapid Sequence Induction/Intubation : gain control over airway as quickly and safely where intubating in emergency.
- Risk of Aspiration (No Fasting) so position patient upright and cricoid pressure.
- Aim : Ensure successful intubation with ET tube as soon as possible after induction to protect airway.
Triad of General Anaesthesia (3).
HAM :-
1. Hypnosis.
2. Analgesia.
3. Muscle Relaxants.
IV Hypnotic Options (4).
- Propofol (Commonest).
- Ketamine.
- Thiopental Sodium.
- Etomidate (Rarest).
Inhaled Hypnotic Options (4).
- Sevoflurane (Commonest).
- Nitrous Oxide (with other Anaesthetic Medications - useful in gas induction for kids).
- Desflurane (bad for environment).
- Isoflurane (Rarest).
*Fluranes are volatile Anaesthetic Agents - vaporised and mixed with air.
IV vs Inhaled Hypnotic Medications (2).
- IV - Induction Agent; Inhaled - Maintenance Agent.
- TIVA - IV Medication for Induction and Maintenance of GA (usually Propofol) : Better Recovery.
Muscle Relaxants (3).
- Types : Depolarising (Suxamethonium); Non-Depolarising (Rocuronium and Atracurium).
- Method : Block NMJ from working so relaxes and paralyses muscles - make intubation and surgery easier.
- Reversal : AChE Inhibitors e.g. Neostigmine; Sugammadex (Reverse Non-Depolarising Only).
Common Analgesic Options in Anaesthetics (4).
- Fentanyl.
- Alfentanyl.
- Remifentanil.
- Morphine.
Common Antiemetic Options in Anaesthetics (3).
- Ondansetron (5-HT3 Antagonist) : Avoid QT Prolongation.
- Dexamethasone : Avoid in Diabetes and Immunosuppression.
- Cyclizine (H1 Antagonist) : Avoid in HF and Elderly.
Emergence Considerations (4).
- Muscle Relaxant needs to have worn off to avoid Awareness Under Anaesthesia - use Nerve Stimulator (to test muscle responses e.g. Ulnar Nerve or Facial Nerve using Train-of-Four).
- Train of Four - stimulate nerve 4x to see if muscle responses remain strong or whether they get weaker.
- Once muscle relaxant wears off, stop inhaled anaesthetic and patient regains consciousness.
- Extubate now.
