Identifying at risk patients
In this section you will cover four questions. Which of my patients:
- might predictably be difficult to ventilate?
- might predictably desaturate?
- are more likely to regurgitate and potentially aspirate?
- might predictably drop their blood pressure?
Pre-procedural airway evaluation is vital in order to address the first question. Table 3 lists several factors that may be associated with difficulty in airway management. A single factor in isolation may not be significant, but two or more should prompt you to reconsider your strategy.
You may find the simple pneumonic BOOTS helpful:
- Beard
- Obese
- Older patient
- Toothless
- Snores?
Table 3: Airway assessment procedures for sedation and analgesia
| History | Previous problems with anaesthesia or sedation (look in the hospital and ED records if possible) Stridor, snoring or sleep apnoea Advanced rheumatoid arthritis Chromosomal abnormality (e.g. trisomy 21) |
| Physical Examination | Habitus Significant obesity (especially involving the neck and facial structure) Head and neck Short neck, limited neck extension, decreased hyoid-mental distance (<3cm in an adult), neck mass, cervical spine disease or trauma, tracheal deviation, dysmorphic facial features (e.g. Pierre-Robin syndrome), excessive facial hair Mouth Small opening (<3cm in an adult, edentulous, protruding incisors, high arched palate, macroglossia, tonsillar hypertrophy and nonvisibule uvula) Jaw Micrognathia, retrognathia, trismus and significant malocclusion |
Learning Bite
In your preparation for conscious sedation always ask yourself whether you are confident you could ventilate the patient using a bag and mask if required.
Fasting is not needed for minimal sedation, sedation with nitrous oxide/ oxygen mixtures alone, or moderate sedation where verbal contact is maintained. For procedures where deeper sedation is required, consider:
- The urgency of the proposed procedure. In many life or limb threatening situations (e.g. cardioversion of a cardiac arrhythmia causing significant cardiovascular compromise, or an orthopaedic procedure to correct distal limb ischaemia) the patient is unable to wait and the main question becomes the choice of sedation/anaesthetic technique rather than the possibility of deferment.
- The proposed depth and duration of sedation. Longer periods of sedation, greater sedation depth and airway interventions may stimulate airway reflexes (coughing, hiccoughs or laryngospasm) and gastro-intestinal motor responses (gagging or recurrent swallowing) leading to gastric distension, regurgitation or vomiting.
- Patient factors. Conditions such as raised intracranial pressure, hiatus hernia and gastrointestinal obstruction are known to delay gastric emptying, and these patients may be at greater risk. Gastric emptying may also be delayed in patients who have previously undergone upper gastrointestinal surgery, in those recently injured or receiving opioids, and in pregnancy. Morbidly obese patients may be at risk, because the intra-abdominal pressure is higher and the incidence of hiatus hernia is greater than in non-obese patients. The timing of food intake in relation to the injuries also important.
For those un-starved patients needing deeper levels of sedation (for prosthetic hip relocation for example), ensure pre-oxygenation is maximised and consider employing apnoeic oxygenation so as to minimise the need for bag-valve-mask ventilation (which when delivered may insufflate the stomach and increase the likelihood of regurgitation). However, it is worth noting that pre-procedural fasting for any duration has not been demonstrated to reduce in the risk of aspiration when administering procedural sedation and analgesia, and as per RCEM guidance: concerns about aspiration vastly exceed the actual risk.”3