Anaesthetics: Conduct of General Anaesthesia Flashcards
What roles are anaesthetists involved in?
- Pre-op Assessment & Care
- Critical Care / Intensive Care
- Pain Management
- Anaesthesia
- Post-operative care
What are the stages in the process of anaesthesia?
- Pre-operative Assessment
- Preparation
- Induction
- Maintenance
- Emergence
- Recovery
- Post-operative Care and Pain Management
What preparation is required for anaesthesia?
- Planning
- Right patient, right operation
- Right (or left) side…..
- Pre-medication
- Right equipment, right personnel
- Drugs drawn up
- IV access
- Monitoring
How is anaesthesia induced?
Gas or IV agent
What drugs are used in IV induction?
- Propofol
- Thiopentone
- others
What are the general features of IV induction?
- Rapid (One “arm-brain” circulation ~ 20s)
- No obvious planes
- Easy to overdose
- Generally rapid loss of airway reflexes
- Apnoea is very common
What agent is used in gas induction?
Sevoflurane (halothane)
Who is gas induction commonly used in?
Young children
What are the general features of gas induction?
- Slow
- Considerably more obvious ‘planes’ of anaesthesia
List the planes of anaesthesia.
- Analgesia / Sedation
- Excitation
- Anaesthesia: Light —> Deep
- Overdose
What are the 4 components of induction?
- Quietness
- Gas or IV Agent
- Careful monitoring of conscious level
- Airway maintenance
How is conscious level monitored?
- Loss of Verbal Contact
- Movement
- Respiratory Pattern
- Processed EEG
- “Stages” or “planes” of anaesthesia
What happens to the airway as someone loses consciousness
The epiglottis falls back and obstructs the airway
When is airway maintenance required in GA?
Always
What is the triple airway manoeuvre?
- Head tilt
- Chin lift
- Jaw thrust
What simple apparatus can be used in airway maintenance?
- Face mask
- Guedel
- NP airway
What are the features of the anaesthetic face mask?
- Identical to those used in Resuscitation
- Contoured to face to allow a gas-tight seal
- Sizes from neonatal - large adult
- Technique involves lifting the face into
- Standard connector
Who tolerates placement of a Guedel?
Only unconscious patients
What can insertion of a guedel into a ‘light’ patient cause/
Vomiting or laryngospasm
How should a guedel be inserted?
Adult
-Upside down and then rotated 180 once in the mouth
Children
-Can be inserted directly
What are the features of a LMA?
- Cuffed tube with ‘mask’ sitting over glottis
- Maintains, but DOES NOT PROTECT the airway
- Sizes for adults and children
How should a LMA be inserted?
- Direct insertion
- Inflation of cuff
What are the features of an I-gel?
- 2nd generation” LMA
- (Relatively) Easy insertion
- Does NOT protect from aspiration
- Can use suctioning when inserted
How should an I-gel be inserted?
- Direct insertion
- No cuff inflation required
What obstructive airway complications may occur?
- Ineffective Triple Airway Manoeuvre
- Airway Device malposition or kinking
- Laryngospasm = Laryngeal spasm
What is laryngospasm?
- 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
What aspiration airway complications may occur?
Loss of protective airway reflexes (gag, swallow, cough) can lead to foreign material entering the lower airway (gastric contents, blood, surgical debris)
What is a maintained airway?
One which is open and unobstructed
What is the only way to protect an airway from contamination?
Use of a cuffed ET tube
How is ET intubation carried out?
- 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 patients?
- Protect airway from gastric contents
- Need for muscle relation and therefore artificial ventilation
- Shared airway with risk of blood contamination (tonsillectomy)
- Need for tight control of blood gases
- Restricted access to airway
What are the risks to an unconscious patient?
- “Airway, Airway, Airway”
- Temperature
- Loss of other protective reflexes eg corneal, joint position
- Venous thromboembolism risk
- Consent & Identification
- Pressure areas
How can a patient be positioned when anaesthetised?
- Supine
- Lithotomy
- Prone
- Lying on side
- Sitting
How should a patient be cared for following anaesthesia?
- Care of the unconscious patient
- Muscle relaxation, analgesia
- Monitoring and physiological support
- Fluid management
- Documentation and recording
What happens after the administration of the induction agent?
- Induction agents wear
- Maintenance: IV / Inhalational or both
- Self- or Artificial Ventilation
- “Balanced” (multi-modal) technique
- Analgesia
- Gas supply from anaesthetic “machine”
What monitoring should be take place whilst a patient is anaesthetised?
- Minimum monitoring (SpO2, ECG, NIBP,FiO2, ETCO2)
- Respiratory parameters
- Agent monitoring
- Temperature, urine output, NMJ
- Invasive venous/arterial monitoring
- Processed EEG
- Watch for VENTILATOR DISCONNECT
What are the risk factors for awareness during anaesthesia?
- Paralysed and ventilated
- Previous episode of awareness
- Chronic CNS depressant use
- Cardiac surgery
- Major trauma
- GA c/section
What happens as someone awakens from anaesthetic?
- Muscle relaxation reversed
- Anaesthetic agents off
- Resumption of spontaneous respiration
- Return of airway reflexes / control
- Extubation
How are local (regional) anaesthetics administed?
- Same care as GA
- IV access required
- Monitoring
- Presence of anaesthetist
- Spinal, epidural, plexus block, nerve block
- Each technique has its own indications, benefits, hazards and complications
What is involved in the recovery area following anaesthetic?
- 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 may occur
- Set criteria for discharge back to ward
