Conduct of anaesthesia

Question 1

What are the Stages and Phases of anaesthesia?

Answer 1

• Pre-operative assessment and planning
• Preparation - right people, skills, place and time
• Anaesthetic itself
  
  • Induction
  • Maintenance
  • Emergence
  • Recovery
• Post-operative Care

Question 2

What are the 5 minimum standards of monitoring in theatre? i.e these 5 things need to be working and in place before anaesthetic is commenced

Answer 2

• ECG - arrythmias are possible under anaesthesia
• O2 saturations
• Non-invasive blood pressure - patient’s often drop their BP during an anaesthetic - agents are potent vasodilators
• End tidal CO2
• Airway Pressure Monitoring

Question 3

What is End Tidal CO2 monitoring?

Answer 3

• Measures the amount of CO2 that is released at the end of an exhaled breath
• Gives an idea of how much CO2 is in patient’s blood but also can assess patency of patient’s airways
• Shows the adequacy with which CO2 is carried in the blood back to the lungs and exhaled.

Question 4

Why are patients given O2 (pre-oxygenation) before being given anaesthesia?

Answer 4

• Under anaesthetic - muscles relax and total lung volume decreases.
• The Functional Residual Capacity therefore reduces
• With reduced FRC – there is less O2 available overall – less time before patient starts to desaturate (O2 levels drop)
• By giving 100% O2 beforehand, it means that in the gas that is left over, there is more O2 than N2 and this extends the time to desaturation

Question 5

What is the Functional Residual Capacity?

Answer 5

The volume of air present in the lungs at the end of passive expiration

Question 6

Induction: phase 1 of anaesthetic

Answer 6

• Can be IV or inhalational/gaseous
• It is unusal to perform a gaseous induction in an adult - usually reserved for small children who won’t tolerate a canula

Question 7

IV induction: what is the usual combination given?

Answer 7

• Analgesic
  
  • Normally a short acting opiate e.g Fentanyl or Alfentanil
• Hypnotic
  
  • Most commonly Propofol
  • Can also be Thipentone or Ketamine
• +/- a muscle relaxant
  
  • Only used if necessary!

Question 8

What are the ‘Planes of Anaesthesia’?

Answer 8

Distinct stages between consciousness and unconsciousness. They are easier to identify with gaseous induction as it is slower.

• 1. Analgesia and amnesia
• 2. Delirium to unconsciousness
• 3. Surgical anaesthesia - patient will not move in response to surgical stimulus
• 4. Apnoea to death - want to avoid

Question 9

Once the patient has undergone their induction and is anaesthetised they need their airways managed. Why is this the case?

Answer 9

Process of anaesthesia causes:

• Loss of airway reflexes - don’t cough or swallow - can’t protect their own airway from secretions or blood etc
• Relaxation of tissues - collapse down and causes a degree of obstruction

Question 10

Reasons to intubate

Answer 10

• Protection from aspiration - patients who are unfasted i.e emergency intervention
• Need for muscle relaxation for their operation - to facilitate ventilation
• Shared airway - anaesthetist and surgeon are working in same place i.e mouth or face
• Need for tight C02 control
• Minimal access to patient

Question 11

What are the 3 options for how a patient can breathe under anaesthesia?

Answer 11

• Spontaneous ventilation - by themselves
• Controlled ventilation - take control of their breathing
• Supported ventilation - mixture

Question 12

What are some risks at induction of anaesthesia?

Answer 12

• Anaphylaxis - due to the agents used
• Regurgitation and aspiration
• Airway obstruction and hypoxia
• Laryngospasm - constriction of vocal chords restricting gas from getting into lungs - usually due to inadequate anaesthesia
• CV instability
• Rarely, cardiac arrest

Question 13

What are some risks associated with anaesthesia that occur throughout surgery (after induction)?

Answer 13

• Awareness
• Eye injury
• Hypothermia
• Pressure sores/injury
• VTE - depends on the patient and surgery
• Nerve injury

Question 14

Eye injury during surgery

Answer 14

Under anaesthesia patients don’t close their eyes:

• Corneas can dry out
• Something can brush against them and damage them as they can’t protect them with corneal reflex etc

Tend to tape the eye shut or use lubricant to prevent this

Question 15

Why is hypothermia a major concern in theatre?

Answer 15

A low body temperature in theatre increases your risk of:

• surgical site infection
• post-operative pain
• bleeding and acquiring a transfusion

Question 16

How is hypothermia caused in theatre?

Answer 16

• Anaesthetic agents cause vasodilation which results in a drop in body temperature
• Patients are exposed for an extended period of time in theatre too

Question 17

How are VTE’s from surgery prevented?

Answer 17

• Keeping the patient active in the run up to surgery
• TED stockings
• Flowtron - garment around the lower leg - inflate and deflate to pump blood out of the venous system of the legs
• Chemical prophylaxis

Question 18

What are the 2 options for the maintenance phase of an anaesthetic?

Answer 18

• Vapour / inhalational
• IV anaesthesia - continous infusion

Need to constantly alter the amount of anaesthetic being given to the patient to keep them in the correct plane of anaesthesia

Question 19

What are the steps of Emergence?

Answer 19

• Theatre ‘sign-out’ - check that the right procedure has been done and everyone is happy with what has been done
• If a NM blockade (muscle relaxant) has been used it needs to be reversed
• Anaesthetic agent is stopped - they work their way out of the patient in time
• Return of spontaneous breathing
• Return of airway reflexes - swallowing/coughing
• Suctioning and removal of airway device
• Transfer to recovery room