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Observational Study
Effects of tracheal intubation and tracheal tube position on regional lung ventilation: an observational study.
Positive pressure ventilation with an endotracheal tube shifts regional lung ventilation ventrally.
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In this review, Karmali & Rose challenge the dogma surrounding endotracheal tube sizing for adult anaesthesia, traditionally sizing based on sex.
What did they cover?
They explored both the functional consequences (good and bad) of ETT size, as well as airway trauma.
Noting that an ETT ≥ 6.0mm ID will accomodate most intraluminal devices, and in fact at these smaller sizes fibreoptic intubation or passage through an LMA is easier, however smaller tubes are more readily obstructed and deformed.
Ventilation through smaller ETTs
While smaller tubes may require slightly higher inspiratory pressures, these are generally not clinically significant with modern ventilators, and importantly do not translate to higher intra-tracheal or alveolar pressures experienced by the patient.
Similarly, expiratory gas flow is not significantly effected by a small ETT (6.0 mm) for most patients even at high minute ventilations (although use cautiously in patients with chronic airway limitation). Significant gas trapping at normal MV will start to occur with ETT < 5.0 mm.
Size and airway trauma?
While the internal diameter (ID) is important for anaesthesia conduct, it is the external diameter that matters for airway trauma (a standard 8.0 mm ID ETT has a 10.5 mm ED!).
They note while there is wide individual variation in tracheal dimensions, the trachea is narrowest at the subglottis – and thus adequate visualisation of the glottis at time of intubation is an incomplete indicator of the tube size suitability for the subglottis.
Not only do some adult women have an airway size at the lower-limit of acceptability for traditional 7.0-8.0 mm ETTs, but there is also correlation between ETT size and airway trauma, hoarseness and sore throat. A large ETT can result in mucosal ischaemia and ulceration after as little as 2 hours.
They conclude...
"Instead of opting for ‘the largest tube that the larynx will comfortably accommodate’, we perhaps should consider using the smallest tube which permits the safe conduct of anaesthesia."
For routine anaesthesia of ASA 1 & 2 patients, an ETT sized 6.0-7.0 mm is probably the best balance between ventilation needs and airway trauma.
Be smart
But remember, many of the concerns for tracheal tube trauma are based upon critical care experience, not anaesthesia. While a smaller tube is very likely beneficial for most elective adult patients, most benefit will simply be reduction in post-operative sore throat and hoarseness.
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Anesthesia and analgesia · Jul 2020
Safety and Efficacy of the Combination of Propofol and Ketamine for Procedural Sedation/Anesthesia in the Pediatric Population: A Systematic Review and Meta-analysis.
Propofol and ketamine are acceptable either alone or in combination for pediatric procedural sedation.
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Curr Opin Anaesthesiol · Jun 2020
ReviewPreeclampsia and the anaesthesiologist: current management.
Preeclampsia diagnostic technologies continue to advance. Peripartum care is improved with multidisciplinary teams, specialist anaesthesia care and the availability of critical care support.
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Randomized Controlled Trial Multicenter Study Comparative Study
Crystalloid versus Colloid for Intraoperative Goal-directed Fluid Therapy Using a Closed-loop System: A Randomized, Double-blinded, Controlled Trial in Major Abdominal Surgery.
Closed-loop goal-directed fluid therapy with colloids is associated with lower volume infused and fewer postoperative complications than with crystalloids.
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