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
Name 4 vasopressor drugs and the receptors they work on.
Adrenaline - alpha 1, alpha 2, beta 1, beta 2
Noradrenaline - alpha 1, alpha 2
Metaraminol - alpha 1
Ephedrine - alpha 1, beta 1
What do vasopressors drugs do?
Increase the blood pressure
What do vagolytic drugs do?
Increase the heart rate
Name 2 vagolytic drugs.
Roughly how do these drugs work?
Atropine
Glycopyrrolate
Inhibit the action of the vagus nerve.
Name 7 patient risk factors for aspiration during surgery.
GORD hiatus hernia Lack of fasting Pregnancy Obesity Previous gastric surgery Delayed gastric emptying I.e diabetes, recent trauma, opioids
How long do patients need to fast from food and clear liquids before surgery?
Food - 6 hours
Clear liquids - 2 hours
List the different patient features assessed for a pre-operative airway assessment.
Mouth opening Teeth Neck extension Jaw protrusion Thyromental distance Obesity and neck shape Facial hair Mallampati score
Describe classes 1-6 of the ASA grading score to measure pre-operative health status.
- A normal healthy patient
- Mild systemic disease
- Severe systemic disease
- Severe systemic disease that is a constant threat to life
- Moribund patient who is not expected to survive without operation
- Declared brain-dead patient whose organs are being removed for transplantation
List the normal physiological mechanisms which reduce the risk of aspiration.
Gastro-oesophageal junction
Upper oesophageal sphincter
Laryngeal reflexes I.e cough, gag reflex, laryngospasm
Describe the mechanism of aspiration under anaesthesia. (i.e. how do anaesthetic drugs affect the normal anatomical and physiological barriers to aspiration)
Lower oesophageal barrier pressure is reduced by IV and inhalational anaesthetic agents, opioids and anticholinergics.
Upper oesophageal sphincter tone and laryngeal reflexes are reduced by IV and inhalational anaesthetic agents and neuromuscular blockers.
Name some anaesthetic and surgical risk factors for aspiration under anaesthesia.
Anaesthetic factors
- light anaesthesia
- supra-glottic airways
- length of surgery > 2 hrs
- positive pressure ventilation
- difficult airway
Surgical factors
- upper GI surgery
- lithotomy or head down position
- laparoscopy
List five strategies used to reduce the risk of aspiration in an unfasted patient (i.e. emergency or obstetric surgery) and an example of how this would be done.
Reduce gastric volume - i.e. nasogastric aspiration pre-induction
Avoid general anaesthesia - opt for regional
Increase pH of gastric contents - I.e. antacids or PPIs
Airway protection - tracheal intubation
Prevent regurgitation - head up positioning
Give 2 reasons why we fast patients to prevent aspiration.
- prevent hypoxia - aspiration of solid matter can cause hypoxia through physical obstruction
- prevent aspiration pneumonitis
Name 4 modifiable lifestyle risk factors for surgery.
ASDA
Alcohol
Smoking
Diet
Exercise
Name 3 surgical risk calculators that can be used as part of a peri-operative risk assessment.
POSSUM
NSQIP
SORT
Name 7 different ways to assess functional capacity in peri-operative risk assessment.
CPET (formal test where patient is put on a bike and inspired and expired CO2 and O2 is measured) METS (metabolic equivalents) Shuttle walk test Timed up and go test Frailty scoring Cognitive assessment Plasma bio markers (hsCRP, NP-BNP)
Describe some ways that you might pre-optimise chronic health conditions in patients undergoing surgery.
Pulmonary rehabilitation for COPD
Anaemia treatment (iron therapy)
Optimise diabetic control
Optimise renal function (discontinue nephrotoxic drugs)
Prehabilitation (exercise to improve fitness)
At what 3 points during an operation should the WHO checklist be completed?
- Before induction of anaesthesia
- Before skin incision
- Before patient leaves operating room
What are the 5 steps in the WHO checklist that need to be completed before induction of anaesthesia? (sign in)
- confirmation of patient identity, site, procedure and consent
- marking of the operating site
- anaesthesia machine and medication check
- ensure pulse oximeter is on patient and functioning
- note any patient allergies, difficult airway or aspiration risk, blood loss risk
What 5 points of the WHO checklist need to be completed before skin incision? (surgical pause)
- team members introduce them self by name and role
- confirm patient name procedure and incision site
- note whether antibiotic prophylaxis has been given
- surgeon, anaesthetist and nurse discuss anticipated critical events
- make sure essential imaging has been displayed
What 4 points of the WHO checklist need to be completed before the patient leaves the operating room? (sign out)
nurse verbally confirms
- name of procedure
- completion of instrument, sponge and needle counts
- specimen labelling
- any equipment problems needing addressed
Discuss key concerns for recovery and management of this patient.
How long after an operative procedure could you diagnose surgical site infection?
30 days of the procedure
90 days of the procedure if a prosthesis is used
Name 3 reasons why surgical site infection is important.
- increases hospital length of stay
- increases morbidity
- increases mortality
List 6 patient risk factors for surgical site infection.
Any from: Immunosuppression Age ASA status Comorbid state Colonisation with staph. aureus Diabetes mellitus Malnutrition Hypoxaemia Obesity
Name 5 surgical risk factors for surgical site infection.
Haematoma formation Anastomotic leak Poor surgical technique Choice of skin antiseptic Prolonged on technically difficult procedure
What kind of organisms may be important in surgical site infection with:
(a) a clean procedure
(b) a clean-contaminated procedure
(c) procedures involving a viscus
(a) skin flora I.e. streptococcal species, staphylococcus aureus, coagulase negative staph
(b) gram negative rods, enterococci
(c) endogenous flora of the viscus or mucosal surface
What’s the point of peri-operative antibiotic prophylaxis?
Reduces the risk of post-operative infection
According to the NICE guidelines (2019), in what 3 situations should patients be given antibiotic prophylaxis?
- before clean surgery involving placement of a prosthesis or implant
- before clean-contaminated surgery
- before contaminated surgery
List 5 things to take into account for choosing an antibiotic for peri-operative antibiotic prophylaxis.
Any 5 from: Cost Safety Pharmacokinetic profile Antimicrobial activity Local sensitivity Epidemiology Resistance patterns Surveillance data
When is the optimum time to give antibiotic prophylaxis?
How do you know if a further dose of the antibiotic is required?
30 minutes before surgical incision
If the procedure lasts longer than the half life of the antibiotic or if there has been significant blood loss (I.e. more than 1.5L)
What are the 3 main risks of antibiotic prophylaxis?
Adverse effects I.e. perioperative anaphylaxis
Drug resistance
C.diff infection
Name 2 procedures which are high risk for surgical site infection.
Hip arthroplasty
Caesarean section
Name 5 patient related risk factors for PONV.
Female gender History of PONV motion sickness Non-smoking status Age<50 years
Name 5 anaesthesia related risk factors for PONV.
Prolonged duration of anaesthesia Intraoperative or post op opioid analgesics Volatile agents Nitrous oxide Increases doses of neostigmine
Name 2 surgery related risk factors for PONV.
Prolonged surgery
Type of surgery I.e neurosurgery or intra abdominal surgery
Name 3 strategies to decrease the baseline risk of PONV.
Use locoregional anaesthetics rather than general
Limit volatile agents and nitrous oxide
Limit opioid use
Name 4 first line prophylactic drugs for PONV.
Ondansetron
Dexamethasone
Droperidol
Metoclopramide
How do we avoid preoperative blood transfusion in elective patients?
Test Hb in everyone undergoing major surgery and if patients are anaemia, delay surgery to allow investigation and management. This could involve iron therapy (IV or oral). Stopping anticoagulants and antiplatelet medications. Plan alternative surgery/blood sparing strategies.
Which patients should receive preoperative blood transfusion?
Only those with significant anaemia requiring urgent surgery with high risk of bleeding.
What risks are associated with allogeneic blood transfusion?
Transfusion reactions - either due to giving the wrong blood or unanticipated immunological reactions to correctly cross matched blood.
Transfusion transmitted infections
Poorer outcomes in surgical patients who are transfused
Name 3 types of elective surgery which would require patients to be crossmatched in case the need for intraoperative transfusion arises.
Major orthopaedic, vascular and cardiac surgery
At what haemoglobin concentration on hemacue would you consider given someone a blood transfusion intraoperatively?
<80 g/L (but only if the patient in normovolaemic cos if not the haemoglobin concentration won’t be accurate)
Name 8 complications of massive blood transfusion.
Impaired oxygen delivery to tissues
Metabolic acidosis
Hypocalcaemia
Coagulopathies
Hypothermia
Hyperkalaemia
Fluid overload
Transfusion related acute lung injury (TRALI)
How would you treat hypovolaemic shock (I.e due to haemorrhage, dehydration, diarrhoea)?
IV fluids or blood transfusion
Conditions such as sepsis, anaphylaxis or neurogenic shock can cause systemic vasodilation. What drugs could be used to treat this?
Vasoconstrictors I.e. alpha agonists like noradrenaline
Myocardial infarction or acute cardiomyopathy can cause cardiogenic shock. What can be used to treat this?
Inotropes i.e. beta 1 agonists (dobutamine) or mechanical support
What are 5 risks of mechanical ventilation?
Ventilator associated lung injury Intubation associated pneumonia Respiratory muscle deconditioning Cardiovascular effects Effects of sedation (sedation is required for patients to tolerated intubation
What is the name of the scoring system used in hospital to quickly identify patients who are at risk of organ dysfunction?
National Early Warning Score (NEWS)
