We read with great interest the recently published report by Eskandr et al. 1 of a randomised controlled trial investigating the role of dexmedetomidine in parturients with pre-eclampsia undergoing general anaesthesia for caesarean section. That welcome investigation evaluated the effect of preoperative dexmedetomidine on the suppression of cardiovascular and hormonal responses to tracheal intubation. The authors showed that administration of dexmedetomidine in doses of 0.4 and 0.6 μg kg−1 h−1 was associated with haemodynamic and hormonal stability, without causing significant adverse neonatal outcome. However, there are several aspects of this study that need to be clarified and discussed.
First, in this article, the author stated that patients in the dexmedetomidine groups received a dexmedetomidine loading dose of 1 μg kg−1 over 10 min, followed by a continuous infusion at a rate of 0.4 or 0.6 μg kg−1 h−1, or a similar volume of 0.9% saline in the control group. According to the authors’ description, the operator was aware of group assignments. In other words, the operator was not blinded, which may result in the possibility of observation bias. We suggest that the study drugs (dexmedetomidine 200 μg per 2 ml and 0.9% saline 2 ml) should be diluted with 0.9% saline to 50 ml in identical syringes, and infused at a loading rate of 0.25 ml kg−1 over 10 min, followed by either a continuous infusion at a rate of 0.1 ml kg−1 h−1 (0.4 μg kg−1 h−1) or 0.15 ml kg−1 h−1 (0.6 μg kg−1 h−1) according to the study by El-Tahan et al. 2 The operator may then be blinded to group allocation.
Second, in the methods section, the authors did not describe the first-attempt success rate of tracheal intubation, intubation time and the number of intubation attempts in both groups. These are likely to have an impact on the cardiovascular response to tracheal intubation. 3 Without providing this additional information, it is not convincing to believe that dexmedetomidine attenuates both the stress response and the haemodynamic response to tracheal intubation.
Finally, the induction-to-delivery times in both groups were not mentioned. Induction-to-delivery time may be related to Apgar score. It has been observed that a prolonged induction-to-delivery time is associated with a poor foetal outcome regardless of the type of anaesthesia. 4 Thus, we suggest the authors should provide the average induction-to-delivery time of each group in order to avoid potential bias. We believe that this article would be much stronger and more useful to readers by addressing the above issues.
Acknowledgements relating to this article
Assistance with the letter: none.
Financial support and sponsorship: none.
Conflicts of interest: none.
Comment from the Editor: Dr Eskandr and colleagues did not respond to our invitation to submit a reply to this letter.
1. Eskandr AM, Metwally AA, Ahmed AEA, et al. Dexmedetomidine as a part of general anaesthesia for caesarean delivery in patients with preeclampsia: a randomised double-blinded trial. Eur J Anaesthesiol
2. El-Tahan MR, Mowafi HA, Al Sheikh IH, et al. Efficacy of dexmedetomidine in suppressing cardiovascular and hormonal responses to general anaesthesia for caesarean delivery: a dose–response study. Int J Obstet Anaesth
3. Xue FS, Zhang GH, Li XY, et al. Comparison of hemodynamic responses to orotracheal intubation with the GlideScope videolaryngoscope and the Macintosh direct laryngoscope. J Clin Anesth
4. Agrawal NK, Palan A. Effect of induction delivery time on Apgar score in lower segment cesarean section under spinal anesthesia. PJSR