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Effect of Boyle-Davis mouth gag placement on intracranial pressure in children undergoing tonsillectomy: A

Kayacan Kaya1, Başak Akca1, Aysun Ankay Yilbas1

  • 1Department of Anesthesiology and Reanimation, Hacettepe University Faculty of Medicine, Ankara, Turkey.

Medicine
|February 24, 2026
PubMed

Insights

Pediatric adenotonsillectomy using a Boyle-Davis mouth gag may slightly increase intracranial pressure (ICP), indicated by optic nerve sheath diameter (ONSD). This transient ONSD rise is mainly due to positioning, not hypercapnia, suggesting careful patient positioning is crucial.

Area of Science:

  • Pediatric Anesthesiology
  • Neurocritical Care
  • Ophthalmology

Background:

  • Pediatric adenotonsillectomy commonly uses the Boyle-Davis mouth gag.
  • Mouth gag placement may transiently elevate intracranial pressure (ICP).
  • Optic nerve sheath diameter (ONSD) ultrasonography is a noninvasive ICP marker.

Purpose of the Study:

  • To assess the impact of endotracheal intubation and Boyle-Davis mouth gag on ONSD in children.
  • To evaluate changes in eyeball transverse diameter (ETD) and the ONSD/ETD ratio during the procedure.

Main Methods:

  • Prospective observational study of 120 pediatric patients (2-18 years).
  • Bilateral ONSD and ETD measurements at four time points: post-induction, post-intubation, post-gag placement, and post-gag removal.
  • Statistical analysis included repeated-measures ANOVA and linear mixed-effects models, adjusting for end-tidal carbon dioxide (EtCO2) and mean arterial pressure (MAP).

Main Results:

  • A statistically significant overall time effect was observed for ONSD and ONSD/ETD (P < .01).
  • Mouth gag placement (T2) showed a significant increase in ONSD (+0.108 mm) and ONSD/ETD (+0.0033) compared to post-induction (T0), persisting after adjustment for EtCO2 and MAP.
  • EtCO2 demonstrated a modest positive association with ONSD, while MAP was not significant. Heart rate and MAP varied significantly over time.

Conclusions:

  • Boyle-Davis mouth gag suspension causes a small, transient increase in ONSD and ONSD/ETD, peaking during gag placement.
  • The observed changes are primarily attributed to positioning and suspension forces, rather than hypercapnia.
  • Findings underscore the importance of careful patient positioning and monitoring in pediatric patients undergoing adenotonsillectomy with mouth gag use.

Keywords:
ONSD/ETDadenotonsillectomyintracranial pressuremouth gagoptic nerve sheath diameterpediatric anesthesia

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