Abstract
In the obese, the evidence for the choice of the optimal emergency front-of-neck access technique is very limited and conflicting. We compared cannula and scalpel-bougie emergency front-of-neck access techniques in an anaesthetised porcine model with thick pretracheal tissue. Cannula and scalpel-bougie cricothyroidotomy techniques were performed in 11 and 12 anaesthetised pigs, respectively. Following successful tracheal access, oxygenation was commenced and continued for 5 min using Rapid-O2 device for cannula and circle breathing system for scalpel-bougie study groups. The primary outcome was a successful rescue oxygenation determined by maintenance of arterial oxygen saturation >90% 5 min after the beginning of oxygenation. Secondary outcomes included success rate of airway device placement, time to successful airway device placement, and trauma to the neck and airway. The success rate of rescue oxygenation was 18% after cannula, and 83% after scalpel-bougie technique (P = 0.003). The success rate of airway device placement was 73% with cannula and 92% with scalpel-bougie technique (P = 0.317). Median (inter-quartile-range) times to successful airway device placement were 108 (30–256) and 90 (63–188) seconds (P = 0.762) for cannula and scalpel-bougie emergency front-of-neck access, respectively. Proportion of animals with iatrogenic trauma additional to the procedure itself was 27% for cannula and 75% for scalpel-bougie technique (P = 0.039). Thus, in the porcine model of obesity, the scalpel-bougie technique was more successful in establishing and maintaining rescue oxygenation than cannula-based technique; however, it was associated with a higher risk of severe trauma.
Highlights
The current Difficult Airway Society (DAS) guidelines recommend the scalpel-bougie cricothyroidotomy as a default technique for emergency front-of-neck access procedure
Since the thickness of pre-tracheal tissue in the pig model coincides with the measurements in the morbidly obese patients, the findings of this study can be extrapolated to the obese patient population [24]
In accordance with NAP4 data, our study reconfirms the low success rate of the cannula technique in the obese, primarily attributed to relative shortness of the cannula with respect to pre-tracheal tissue which increased the risk of cannula displacement and kinking despite using the 14 gauge InsyteTM catheter with a good memory of initial shape [25]
Summary
The current Difficult Airway Society (DAS) guidelines recommend the scalpel-bougie cricothyroidotomy as a default technique for emergency front-of-neck access (eFONA) procedure. Failed cannula insertion may make subsequent landmark recognition and scalpel technique more difficult if associated with subcutaneous emphysema [8]. This uncertainty of the optimal eFONA technique has led to a number of national difficult airway guidelines recommending differing eFONA techniques [9,10,11,12]. Given the potential impact of the thickness of the pretracheal tissue on the success of the particular eFONA technique, we set up the study using an anesthetized porcine model to compare the cannula and the scalpel-bougie techniques using the success rate of rescue oxygenation as the primary outcome measure
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