Does mouth gag application during Tonsillectomy or Adentonsillectomy alter optic nerve sheath diameter?

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Our aim is to evaluate changes in the optic nerve sheath diameter (ONSD) in patients undergoing tonsillectomy adenoidectomy/tonsillectomy surgery while mouth gag is opened at the mouth.After obtaining approval from the Mugla Sitki Kocman Scientific Clinical Researches Ethics Committee 40 patients, 3 to 18 years old with an American Society of Anesthesiologists physical status of I and II scheduled for tonsillectomy, adenoidectomy, tonsiladenoidectomy will be enrolled into the study. Patients with the following conditions will be excluded: hypertension, preexisting acute or chronic eye disease, history of eye surgery, use of drugs known to influence IOP, expected duration of mouth gag opening <30 min. ONSD will be measured in all patients by an anesthesiologist trained in this procedure. With the patient supine horizontally, a two-dimensional axial cross-sectional view of the ONSD will be obtained by positioning a 12-MHz transducer transversely on a single closed eyelid. On the ultrasound monitor, the ONSD will be measured 3 mm posterior to the orbital globe. Each measurement will be performed on the same orbit. ONS diameter measurements will be compared at four time frames (after anesthesia induction, after tracheal intubation, after mouth gag application, 30 minutes after application. The baseline ONSD and the measurements at the time frames will be compared. In addition end tidal CO2 and mean arterial pressure will be assessed and recorded for every time point.