Advanced Procedural Sedation

For an at risk patient requiring urgent intervention e.g. synchronised DC cardioversion, consider (as previously covered) a lighter level of sedation, or alternative or adjunctive techniques. Why not discuss such options with a senior colleague? And of course, the patient?

If you collectively elect to proceed with propofol, consider:

  • Doubling up – have a senior colleague perform the procedure who may then also act as airway support as necessary
  • Senior anaesthetic input
  • Apnoeic oxygenation – more on this in a minute
  • A potential role for non-invasive ventilation [14]

Smaller propofol doses in the elderly. In the large case series of propofol sedation in my own department [12], six of the eleven patients with a sentinel adverse event (two cases of hypoxia, four cases of hypotension) were elderly. All had an initial bolus exceeding the recommended 0.5 mg/kg.

Learning Bite

Use an initial bolus of 0.5mg/kg (or less) in the elderly.

Apnoeic oxygenation

Apnoeic oxygenation can extend the duration of safe apnoea when used after the administration of sedatives [14].

With diaphragm standstill, diffusion of gases still takes place; diffusion of oxygen into the bloodstream comfortably exceeding that of carbon dioxide into the alveoli. The net ‘subatmospheric’ pressure generated promotes passive flow of ‘gas’ (in this context oxygen enriched air) from the pharynx to the alveoli. Nasal cannulae are the best oxygen delivery apparatus to facilitate this.

So practically: deliver oxygen via nasal prongs at 2-4 l/min as part of your pre-oxygenation strategy – that’s right, under the reservoir mask! When you sense that the propofol has reached your patient’s brain (look at the capnography trace) rack it up to 15 l/min, while still maintaining the (high as possible – >15 l/min) oxygen flow rate of the non-rebreathe mask/facemask with reservoir bag. Your patients will find 15 l/min via nasal prongs prior to sedation uncomfortable.

Learning Bite

Consider apnoeic oxygenation in ‘at risk’ patients.

Obese patients

For obese patients, sit them up as much as the clinical situation allows. This reduces the pressure from the abdominal contents on the diaphragm, thereby increasing the functional residual capacity [15]. Achieving the ‘sniffing the morning air’ position may be easier if you site a pillow (or equivalent) behind the shoulders and a pillow or two behind the head. Is your patient’s head in front of their chest when viewed from the side? With sitting sedated patient be cautious not to allow over-flexion of neck leading to partial airway obstruction.

Learning Bite

Sit obese patients up as much as clinically possible and maximise efforts at achieving the ‘sniffing the morning air’ position.

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Dr. Ainsley Heyworth November 9, 2020 at 9:50 am

Great module and great summary of ApOx – would add that you need to maintain an open airway to allow ApOx to work

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