“Hold your breath, make it last long.” – Korn
A randomised controlled trial comparing transnasal humidified rapid insufflation ventilatory exchange (THRIVE) pre-oxygenation with facemask pre-oxygenation in patients undergoing rapid sequence induction of anaesthesia. Mir et al.
Pre-oxygenation is an essential part of rapid sequence induction (RSI) of general anaesthesia for emergency surgery. Options for re oxygenation and ventilation are limited in these patients due to potential for aspiration with bag mask ventilation. The transnasal humidified rapid insufflation ventilator exchange (THRIVE) technique has been demonstrated to extend apnoea time maintaining oxygenation and achieving carbon dioxide clearance when used in cases with difficult airways.
This was a single center randomised controlled trial comparing transnasal humidified rapid insufflation ventilatory exchange (THRIVE) pre-oxygenation and facemask pre-oxygenation in patients undergoing emergency surgery. Twenty patients were allocated to each group. Arterial blood gases were sampled from an arterial catheter immediately after intubation. The primary outcome was PaO2 after intubation.
There was no difference in the PaO2 between the two groups. The mean (SD) PaO2 was 43.7 (15.2) kPa in the THRIVE group vs. 41.9 (16.2) kPa in the facemask group (p = 0.722); PaCO2 was 5.8 (1.1) kPa in the THRIVE group vs. 5.6 (1.0) kPa in the facemask group (p = 0.631); arterial pH was 7.36 (0.05) in the THRIVE group vs. 7.34 (0.06) in the facemask group (p = 0.447). No airway rescue maneuvers were needed.
The authors defined apnoea time as the time from completion of injection of the induction agent until when the trachea was successfully intubated. Patients in the THRIVE group had a significantly longer apnoea time of 248 (71) s compared with 123 (55) s in the facemask group (p < 0.001).
There was no difference between the two groups in terms of PaO2, PaCO2 or arterial pH. The mean apnoea time was 125 s longer in the THRIVE group. This was not due to apparent differences in procedural difficulty. The authors speculated that, if the time taken to intubate had been the same in both groups, then the arterial blood gases and pH would have been more favourable in the THRIVE group, but this speculation is not borne out by their data. The results do not indicate the superiority of either method, but have shown that THRIVE is practicable and likely to be safe.
Appraisal of the paper
The research question was focused and well addressed. Simple randomisation was conducted with an equal allocation ratio (1:1) which is an adequate method of sequence generation. No withdrawals were described and the sample size was calculated before the trial to yield a power of 80%. The mean difference calculated for PaO2 was 1.8 kPa which was not clinically or statistically significant.
As for apnoea time, between the two groups there was a 15% increase in effect which would be considered significant. A graphical trend showing patient specific analysis of PaO2 taken at the start and immediately after intubation with apnoea time between the groups would have been useful as well looking at patient satisfaction postoperatively.
Concern has also been raised on the findings of extended apnoea time and whether that may lead to increased risk of aspiration in this cohort of patients who are presenting for emergency surgery.
Summary by Dr Kavitha Aravinth.