Anaesthesia and Critical Care Flashcards
Name 2 types of oxygen delivery devices that are considered “variable performance” (i.e they deliver a variable inspired oxygen concentration, depending on the patient’s peak inspiratory flow rate)
Nasal cannulas
Simple facemasks/Hudson masks
Name 2 types of oxygen delivery devices considered “fixed performance” devices (i.e. they deliver a fixed inspired oxygen concentration to the patient, independent of the patient’s peak inspiratory flow rate)
Venturi masks
Non-rebreather face masks
- What is the typical flow rate of a nasal cannula?
- Is nasal cannulae considered a variable or fixed performance delivery device?
- What side effect can occur when high flow oxygen is delivered through a nasal cannula?
- 1-4 litres per minute
- Variable performance
- Drying of the nasal mucosa
What range of FiO2 is delivered through a nasal cannula?
24-36% (1-4L/minute flow rate)
What acts as the oxygen reservoir when using a nasal cannula?
Nasal pharynx
- What flow rate of oxygen can be delivered through a Hudson mask?
- What acts as the oxygen reservoir with a Hudson mask?
- Is the Hudson mask a variable or fixed performance device?
- 2-10 litres/minute
- The mask itself
- Variable
What is the approximate maximum FiO2 with a non-rebreather (trauma) mask?
What is the maximum flow rate of oxygen with a non-rebreather (trauma) mask?
What acts as the oxygen reservoir?
85%
15 Litres/minute
The reservoir bag
Is a Venturi mask a fixed or variable performance delivery device?
In what situation may a Venturi mask be useful?
Fixed performance
When FiO2 accuracy is important I.e for patients with COPD
Venturi masks are colour coded depending on what FiO2 they produce. What colours correspond to what FiO2?
Blue - 24% White - 28% Yellow - 35% Red - 40% Green - 60%
Is High Flow Nasal Oxygen (HFNO) considered a variable or a fixed performance device?
What is the maximum FiO2 achievable with HFNO?
What is the maximum flow rate?
Fixed
97%
60 Litres/minute
Name two types of Non-Invasive Ventilation.
Continuous Positive Airway Pressure
Bi-Level/BIPAP
What is the main use of Continuous Positive Airway Pressure (CPAP) in:
(a) the community
(b) hospital
(a) Obstructive sleep apnoea - keeps the upper airway open
(b) Pulmonary Oedema - pushes pulmonary oedema out of the alveoli
What is the main use of BIPAP?
In COPD exacerbations
What type of oxygen delivery devices are usually used postoperatively in the recovery room?
Why do patients need oxygen post-operatively?
Hudson mask (4-6 Litres / minute) or Venturi mask (35-50%)
Nitrous oxide during anaesthetic can cause diffusion hypoxia + anaesthetics and opioid analgesia can reduce respiratory drive
What are some of the clinical signs and history features that could indicate hypovolaemia?
High HR, low BP, high RR
Cool peripheries and reduced CRT
Reduced urine output
Postural hypotension
History of poor fluid intake or fluid loss
What features would indicate that a patient is euvolaemic?
Normal HR and BP
Warm peripheries
CRT<2 seconds
What clinical signs would indicate hypervolaemia?
Peripheral oedema
Inspiratory crackles
Raised JVP
What are the daily maintenance fluid requirements according to the NICE guidelines?
Daily sodium chloride requirements?
Daily potassium requirements?
Daily glucose requirements? (to prevent starvation ketosis)
25-30 ml/kg/day of water
1-2 mmol/litre sodium chloride
1 mmol/litre potassium
50-100g glucose
Give a rough description of how you would carry out fluid resuscitation in a hypovolaemic patient.
Administer a 500ml bolus of crystalloid fluid (i.e. either 0.9% saline or Hartmann’s) over less than 15 minutes
Reassess patient using the ABCDE approach looking for evidence of ongoing hypovolaemia
If the patient still has continuing evidence of hypovolaemia give a further 250-500ml bolus
Continue this process up to 2000ml of fluid. If persistently hypovolaemic seek senior help.
Name a few indications for IV fluid resuscitation.
What must you remember to do in a patient who has had a large bleed?
Severe dehydration, sepsis, blood loss with hypovolaemia and hypotension
Activate the major haemmorhage protocol
How long would patients usually need to be fasting for for them to get maintenance fluids?
What is the absolute maximum rate at which maintenance fluid can be prescribed?
8 hours
100 ml/hour
What are the 4 key aims of anaesthesia?
- establish lack of awareness
- analgesia
- optimise surgical conditions
- protect patient safety
What is the triad of anaesthesia?
Unconsciousness
Analgesia
Muscle relaxation
Name 4 of the main IV agents used for induction of anaesthesia.
Propofol
Thiopentone
Ketamine
Etomidate
What is the basic mechanism of action of ketamine as an anaesthetic induction agent?
Inhibits NMDA receptors, causing the patient to fall asleep
What is the thought to be the basic mechanism of action of propofol?
Acts on ligand gated potassium channels which increases the inhibitory effects, resulting in sleep
Name 2 of the main inhalational agents used in the maintenance and induction of anaesthesia.
Sevoflurane
Desflurane
Why is desflurane being phased out as an inhalational agent?
Because it contributes to global warming
Name 1 depolarising and 3 non-depolarising neuro-muscular blocking agents.
Depolarising - suxamethonium
Non-depolarising - rocuronium, atracurium, vecuronium
What is the basic mechanism of action of suxamethonium? (depolarising neuromuscular blocking agent)
Suxamethonium is similar chemically to acetylcholine. It binds to the acetylcholine receptor, causing depolarisation (patient has initial fasciculations) but last longer at the receptor than ACh because it is not broken down by acetylcholineesterases. Therefore the muscle cannot repolarise and the patient is paralysed.
What is the mechanism of action of non-depolarising neuromuscular blocking agents?
They inhibit neuron transmission to muscle by blocking the nicotinic acetylcholine receptor.
Name 2 neuro-muscular blocker reversal agents.
Neostigmine
Sugamadex