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

Kaya K., AKÇA B., Yilbas A. A., Celebioglu G., KILIÇASLAN B.

Medicine, vol.105, no.8, 2026 (SCI-Expanded, Scopus) identifier identifier

  • Publication Type: Article / Article
  • Volume: 105 Issue: 8
  • Publication Date: 2026
  • Doi Number: 10.1097/md.0000000000047697
  • Journal Name: Medicine
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus, BIOSIS, CINAHL, EMBASE, Directory of Open Access Journals
  • Keywords: adenotonsillectomy, intracranial pressure, mouth gag, ONSD/ETD, optic nerve sheath diameter, pediatric anesthesia
  • Hacettepe University Affiliated: Yes

Abstract

Pediatric adenotonsillectomy frequently requires Boyle-Davis mouth gag placement, which may transiently increase intracranial pressure (ICP). Ultrasonographic optic nerve sheath diameter (ONSD) is a validated noninvasive marker of ICP. This study aims to investigate the impact of endotracheal intubation and Boyle-Davis mouth gag placement on ONSD, eyeball transverse diameter (ETD), and ratio of optic nerve sheath diameter to eyeball transverse diameter (ONSD/ETD) ratio in children. In this prospective observational study of 120 children (American Society of Anesthesiologists I-II, 2-18 years), bilateral ONSD and ETD were measured at post‑induction (T0), post‑intubation (T1), post‑gag placement (T2), and post‑gag removal (T3). Unadjusted profiles used repeated-measures ANOVA. Adjusted analyses used linear mixed-effects models with time and random intercept for subject; end-tidal carbon dioxide (EtCO2) and mean arterial pressure (MAP) were entered as time-varying covariates. Means (±standard deviation) for ONSD were 5.74 ± 0.46 (T0), 5.79 ± 0.46 (T1), 5.86 ± 0.44 (T2), 5.77 ± 0.48 (T3); for ONSD/ETD: 0.251 ± 0.021, 0.252 ± 0.020, 0.255 ± 0.020, 0.249 ± 0.021. The overall time effect was significant for both outcomes (P < .01). In adjusted models, T2 versus T0 remained higher for ONSD (+0.108 mm; 95% confidence interval (CI): 0.046-0.170; P < .001) and ONSD/ETD (+0.0033; 95% CI: 0.0003-0.0063; P = .03), whereas MAP was not significant and EtCO2 showed a modest positive association with both outcomes (ONSD: +0.007 mm/mm Hg; 95% CI: 0.002-0.012; P < .01). Heart rate and MAP varied over time (both P < .001), EtCO2 rose early and declined by T3 (P < .001). No neurologic events occurred. Mouth-gag suspension produces a small, transient rise in ONSD and ONSD/ETD that peaks at T2 and recedes after removal. Effects persisted after adjustment for EtCO2 and MAP, primarily suggesting contributions from positioning and suspension rather than hypercapnia. Findings support prudent positioning and monitoring in at‑risk children.