Modes of mechanical ventilation and ultrasound scan technique for evaluating the optic nerve sheath diameter in patients undergoing surgery in the steep Trendelenburg position

We appreciate the thoughtful comments shared by Mario Graziano et al. on our manuscript entitled “Effects of propofol and inhalational anesthetics on the optic nerve sheath diameter in patients undergoing surgery in the steep Trendelenburg position: a systematic review and meta-analysis”, which was published in Annals of Palliative Medicine (1).

In their letter, Graziano et al. (2) mentioned that optic nerve sheath diameter (ONSD) after anesthesia’s induction was significantly lower in the pressure-controlled ventilation (PCV) mode than in the volume-controlled ventilation (VCV) mode referred to Karaca et al.’s study (3). However, this study was conducted during the surgery in the reverse-Trendelenburg position. While applying the reverse Trendelenburg position can prevent an increase in the ONSD undergoing laparoscopic cholecystectomy (4), the conclusion of ventilation mode’s effect on ONSD was not efficient.

Until now, there was insufficient evidence to prove that different ventilation patterns cause differences in ONSD in the steep Trendelenburg position, thus data of ventilation mode was not extracted and analyzed through our study according to a standardized Population Intervention Comparison Outcome (PICO) scheme .

We agree that the B-scan sonographic technique used in ONSD measurement has several limitations. Nevertheless, it is currently the most widely used and valid method for evaluating the optic nerve (5). Although the Standardized A-scan technique has been already demonstrated by Ossoinig (6) in the 1970s and despite being reliable and effective, there are rarely study in relevant databases, which utilize this technique for optic nerve assessment (7).Therefore, we believe that high-quality studies with larger sample sizes are still needed in the future to further confirm the result.

Acknowledgments

Funding: None.

Footnote

Provenance and Peer Review: This article was commissioned by the editorial office, Annals of Palliative Medicine. The article did not undergo external peer review.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://apm.amegroups.com/article/view/10.21037/apm-2022-04/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

References

1. Yang J, Yang X, Li X, et al. Effects of propofol and inhalational anesthetics on the optic nerve sheath diameter in patients undergoing surgery in the steep Trendelenburg position: a systematic review and meta-analysis. Ann Palliat Med 2021;10:10475-85. [Crossref] [PubMed]
2. Graziano M, Di Paola I, Marotta G. Ultrasound evaluation of optic nerve sheath diameter in relation to propofol and inhalational anesthetics in patients having surgery in the Trendelenburg position. Ann Palliat Med 2023; [Crossref] [PubMed]
3. Karaca U, Onur T, Okmen K, et al. Effect of Various Modes of Mechanical Ventilation in Laparoscopic Cholecystectomies on Optic Nerve Sheath Diameter and Cognitive Functions. J Laparoendosc Adv Surg Tech A 2021;31:808-13. [Crossref] [PubMed]
4. Demirgan S, Özcan FG, Gemici EK, et al. Reverse Trendelenburg position applied prior to pneumoperitoneum prevents excessive increase in optic nerve sheath diameter in laparoscopic cholecystectomy: randomized controlled trial. J Clin Monit Comput 2021;35:89-99. [Crossref] [PubMed]
5. Shevlin C. Optic nerve sheath ultrasound for the bedside diagnosisof intracranial hypertension: pitfalls and potential. Crit Care Horizons 2015;1:22-30.
6. Ossoinig KC. Standardized echography of the optic nerve. In: Till P, editor. Ophthalmic Echography 13; Documenta Ophthalmologica Proceedings Series. Springer: Dordrecht, The Netherlands, 1990;55:3-99.
7. De Bernardo M, Vitiello L, De Luca M, et al. Optic Nerve Changes Detected with Ocular Ultrasonography during Different Surgical Procedures: A Narrative Review. J Clin Med 2022;11:5467. [Crossref] [PubMed]