We read with great interest the review and metanalysis by Yang et al. concerning the effects of propofol and inhalational anesthetics on the optic nerve sheath diameter (ONSD) in patients undergoing surgery in the steep Trendelenburg position (1).
We laud our colleagues for the brilliant paper, but we would like to offer them some observation.
In this article the colleagues have observed that the ONSD was lower during propofol anesthesia than during inhalational anesthesia after adopting the Trendelenburg position and CO2 pneumoperitoneum, suggesting that propofol anesthesia may help to minimize intracranial pressure (ICP) changes compared with inhalational anesthetics.
As the authors did not report the ventilation technique utilized in the studies that they analyzed, we were wondering if the difference of increase in ONSD could have a relation to the ventilation technique and not only to the type of anesthesia.
Karaca found the ONSD after anesthesia’s induction was significantly lower in the pressure-controlled ventilation (PCV) mode than in the volume-controlled ventilation (VCV) mode (2).
The explanation for such differences could be the choice to utilizing B scan technique to measure the ONSD.
We are conscious that evaluation of the ONSD by US B scan has been applied as a non-invasive technique to identify an increased ICP, but unfortunately a considerable number of artefacts could make that evaluation not strictly accurate (3,4). Unluckily, even considering the suggestion to image the central retinal artery with color Doppler (5) these complications cannot be surmounted.
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- 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]
- 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]
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- De Bernardo M, Vitiello L, Rosa N. Optic nerve ultrasonography for evaluating increased intracranial pressure in severe preeclampsia. Int J Obstet Anesth 2019;38:147. [Crossref] [PubMed]
- Rosa D, Graziano M, De Paola I. Evaluation of Intracranial Pressure During Neural Laser Discectomy. Pain Physician 2022;25:E414. [PubMed]