Now you know the basics, it’s time to dig into the special cases. These are common sub-specialties within anaesthesia that you might see.
Rapid Sequence Intubation ⏱
Rapid sequence intubation (RSI) is a technique designed to minimise the time between loss of consciousness and tracheal intubation. RSI is most useful in patients at high risk of aspiration (e.g. pregnant and unfasted patients).
An RSI is different to a conventional induction because…
- Premedication is often omitted
- There is no bag-mask ventilation (it inflates the stomach)
- An assistant applies cricoid pressure to hold the oesophagus closed1
- 10 N while awake (the weight of one kilogram)
- 30 N once asleep (the weight of three kilograms)
- Suxamethonium is given immediately after induction
- A modified RSI uses high-dose rocuronium instead
- Your first shot at intubation should be your best shot
- Most senior airway operator
- Gadgets and gizmos aplenty
Awake Fibreoptic 🎥
The awake fibreoptic intubation is ideally suited to the high-risk patient who is still awake and protecting their own airway.2 It is very unpleasant, so you need a cooperative patient to succeed.
Process
A lubricated endotracheal tube is loaded onto a fibreoptic bronchoscope that is guided through the nose (or mouth), the pharynx, and the vocal cords.
Before inserting the scope, we topicalise the entire airway with a mixture of lignocaine and phenylephrine (co-phenylcaine). The lignocaine suppresses coughing and the phenylephrine reduces mucosal bleeding.
Once the tube is passed through the vocal cords, the patient is put to sleep.
Obesity ⚖️
Obesity is associated with virtually every complication of anaesthesia and surgery, including death. The major implications for anaesthesia are…
- Airway
- High incidence of difficult intubation
- Difficult bag-mask ventilation
- Obscured front of neck access
- GORD and gastroparesis increase aspiration risk
- Respiratory
- Reduced chest wall compliance
- Reduced functional residual capacity (FRC)
- More post-operative respiratory problems
- Cardiovascular
- Difficult IV access
- Co-morbid heart disease
- Propensity for venous thromboembolism
- Mechanical aorto-caval compression
- Drugs
- Increased glomerular filtration rate
- Unpredictable distribution of anaesthetic drugs
- Insulin dependence and resistance
- Practical
- Long surgery time due to operative complexity
- Poor ultrasound views for regional anaesthesia
Pregnancy 🫄
Surgery and anaesthesia are generally safe for the mother and baby at any stage of the pregnancy, but should be avoided unless it’s an emergency.
At first blush, the physiological changes are similar to the those in obesity. The important difference is that these changes are quickly reversed after delivery and are generally occurring in young, healthy individuals.
In the parturient at full term, you can expect to see…
- Airway
- Oedema and engorgement of the upper airway
- Higher overall incidence of unexpected difficult intubation
- Breathing
- Reduced chest wall compliance
- Reduced functional residual capacity (FRC)
- Cardiovascular
- Aorto-caval compression by the uterus (solved with a left-lateral tilt)
- 50% increase in cardiac output
- 40% increase in blood volume
- Slight reduction in haematocrit
- Torrential and unpredictable hemorrhage (two big cannulae)
- Practical
- Lots of neuraxial anaesthesia
- 30% decrease in MAC
- The anaesthetist needs to ooze confidence
Paediatrics 👶
Children that aren’t neonates are physiologically like miniature adults.
Gas Induction
The hardest part of routine paediatric anaesthesia is induction because children don’t like needles. Gas inductions are one (imperfect) solution to this problem.
They’re not as safe as an IV induction, but they’re virtually unavoidable in small children. The process goes…
- Spend time explaining the process to the parent
- Get the child as relaxed and entertained as possible
- Apply a pulse oximeter
- Use a tight-fitting face mask
- Some kids will hold it on by themselves
- For the rest, you’ll need to hold it yourself
- Have them breathe high-concentration (8%) sevoflurane
- They will generally fall asleep within ten breaths
- Quickly secure IV access and an airway once the child is sleep
Other Differences
- Propofol is not licensed for use in children (but everyone uses it)
- IV access is typically difficult, even after they’re asleep
- Laryngospasm is far more common and deadly
- Safe apnoeic time is shorter because of their high V’O2 low FRC