Anaesthetics - Conduct of anaesthesia Flashcards
What are some of the roles in preparation in anaesthesia?
- Planning
- Pre-medication: right medication, right personnel
- Drugs drawn up
- IV access
- Monitoring
What is involved in induction?
- Quietness
- In a lot of theatres induction is carried out in the theatre itself, not in a separate room
- Gas or IV agent
- Careful monitoring of conscious level
- Airway maintenance
What drugs are used in IV induction?
- Propofol (less associated with hangover)
- Thiopentone
- others
What are the benefits/risks of IV induction?
- Rapid induction - 20secs
- relatively quickly from awake to asleep
- It is however easy to overdos
- These are dangerous drugs: cause a rapid loss of airway reflexes
- Apnoea is very common
What gases are used in gas induction?
- Sevoflurane
In whom is gas induction normally used? And what are the characteristics?
- Children
- Slow
- Considerably more obvious planes of anaesthesia
What are planes of anaesthesia?
- Analgesia/sedation (eyes sometimes close here - mistaking this for excitation is bad) [sleepy]
- The excitation: disinhibition
- Anaesthesia: light to deep (depending on a patients responsiveness to stimulus)
- Too deep and start to get serious CVS and resp depression = overdose
How do we monitor conscious level? [this is carried out after giving gas or IV agent]
- Loss of Verbal Contact
- Movement
- Respiratory Pattern
- Processed EEG
- “Stages” or “planes” of anaesthesia
After monitoring conscious level we maintain the airway [this tongue loses tone and obstructs the airway]. How do we do this?
- Simple manoevres: head tilt, chin lift, jaw thrust is the primary way to clear the airway, often accompanied by holding a face mask with anaesthetic gas
- Jaw thrust is best because tongue is attached to the mandible
What is the oropharyngeal airway (adjunct) used?
- Guedel airway
- Rigid plastic
- Will only be tolerated by an unconscious patient
- Look at image of technique of inserting
What is a laryngeal mask airway?
- Cuffed tube with ‘mask’ sitting over glottis
- Maintains, but does not protect the airway
- Sizes for adults and children
What is the most popular airway to use?
- i-gel®
- “2nd generation” LMA
- (Relatively) Easy insertion
- Does NOT protect
- from aspiration
What are some airway complications?
Airway obstruction
- Ineffective Triple Airway Manoeuvre
- Airway Device malposition or kinking
- Laryngospasm = Laryngeal spasm [tends to occur at an excitable stage of anaesthesia]
- Forced reflex adduction of the vocal cords
- May result in complete airway obstruction
- Caused by airway (or other) stimulation in light planes of anaesthesia
- Often unrelieved by simple manoeuvres
Please elaborate on aspiration as an airway complication.
- Anaesthesia means loss of protective airway reflexes
- Gag, swallow, cough etc
- Foreign material in the lower airway
- Gastric contents, blood, surgical debris
What is airway maintenance?
If airway is open or unobstructed
What is airway protection?
How can we protect the airway?
- Protecting the airway from contamination
- Only a cuffed tube in trachea can protect
What is endotracheal intubation?
- Placement of a cuffed tube in the trachea
- Oral route most commonly used
- Laryngeal reflexes must be abolished
- Classic method uses laryngoscope, muscle relaxant, “sniffing the morning air” position
- Also possible in the awake patient using local anaesthesia and fibre-optic scope
Why do we intubate?
- Protect the airway from gastric contents (risk of aspiration)
- Need for muscle relaxation therefore artificial ventilation
- eg laparotomy
- Shared airway with risk of blood contamination
- Need for tight control of blood gases
- Restricted access to airway
What are the risks to the unconscious patient?
- “Airway, Airway, Airway”
- Temperature
- Loss of other protective reflexes
- eg corneal, joint position
- Venous thromboembolism risk
- Consent & Identification
- Pressure areas
What are the risks of patient position?
All these positions carry particular risks of pressure area damage, cardiovascular compromise or respiratory impairment:
- Supine - horizontal on back
- Lithotomy - horizontal on back, with legs separated and raised
- Prone - horiontal on front
- Lying on side
- Sitting
What is the role of the anaesthetist once the patient has been induced?
- Care of unconscious patient
- Monitoring and physiological support
- Fluid management
- Documentation and recording
What is the anaesthetist monitoring during surgery?
- Basic “minimum” monitoring
- SpO2, ECG, NIBP, FiO2, ETCO2
- Respiratory parameters
- Agent monitoring
- Temperature, Urine Output, NMJ
- Invasive Venous / Arterial Monitoring
- Processed EEG
- VENTILATOR DISCONNECT
- The anaesthetist is the best monitor…
What are the risks of dreaming/awareness? What are the risk factors for awareness?
- Dreaming: 6/100
- Awareness (all): 1/14,000
- Awareness (low risk): 1/42,000
RF
- Paralysed & ventilated
- Previous episode of awareness
- Chronic CNS depressant use
- Cardiac Surgery 1 in 100
- Major Trauma 1 in 20
- GA C/Section 1 in 250
What needs to be done during emergence/awakening?
- Muscle relaxation reversed
- Anaesthetic agents off
- Resumption of spontaneous respiration
- Return of airway reflexes / control
- Extubation
- Can be very quick or very, very slow
What is expected of the conduct of local anaesthesia?
- Same level of care
- IV access
- Monitoring
- Presence of the anaesthetist
- Spinal, epidural, plexus block, nerve block
- Each technique has its own indications, benefits, hazards and complications
What is the role of ‘recovery’?
- A dedicated area with trained staff
- Many patients have not yet regained consciousness or AIRWAY CONTROL
- Continuing responsibility of anaesthetist
- Problems with A, B, C
- Pain control
- Post-operative Nausea & Vomiting
- Set criteria for discharge back to ward
