Intraocular pressure measurement in children under general anaesthesia with sevoflurane

Anaesthetic protocol for paediatric glaucoma examinations: the prospective EyeBIS Study protocol

INTRODUCTION

Neonates and young infants with diagnosed or highly suspected glaucoma require an examination under anaesthesia to achieve accurate intraocular pressure (IOP) measurements, since crying or squinting of the eyes may increase IOP and lead to falsely high values. IOP considerably depends on perioperative variables such as haemodynamic factors, anaesthetics, depth of anaesthesia and airway management. The aim of this paper is to report the design and baseline characteristics of EyeBIS, which is a study to develop a standardised anaesthetic protocol for the measurement of IOP under anaesthesia in childhood glaucoma, by investigating the link between the magnitude of IOP and depth of anaesthesia.

METHODS AND ANALYSIS

This is a single-centre, prospective cohort study in 100 children with diagnosed or highly suspected glaucoma all undergoing ophthalmological examination under general anaesthesia. 20 children, who undergo general anaesthesia for other reasons, are included as controls. The primary outcome measure is the establishment of a standardised anaesthetic protocol for IOP measurement in childhood glaucoma by assessing the relationship between IOP and depth of anaesthesia (calculated as an electroencephalography variable, the bispectral index), with special emphasis on airway management and haemodynamic parameters. The dependence of IOP under anaesthesia on airway management and haemodynamic parameters will be described, using a mixed linear model. Restricting the model to patients with healthy eyes will allow to determine a 95% reference region, in which 95% of the measurement values of patients with healthy eyes can be expected.

ETHICS AND DISSEMINATION

The study has been approved by the local ethics committee of the Medical Association of Rhineland-Palatine (Ethik-Kommisssion der Landesaerztekammer Rheinland-Pfalz), Germany (approval number: 2019-14207). This work will be disseminated by publication of peer-reviewed manuscripts, presentation in abstract form at national and international scientific meetings and data sharing with other investigators.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov Registry (NCT03972852).

Effect of airway device and depth of anesthesia on intra-ocular pressure measurement during general anesthesia in children: A randomized controlled trial

Background and Aims:

Accurate measurement of intraocular pressure (IOP) under anaesthesia is essential for diagnosis and further management of pediatric glaucoma patients. However, depth of anaesthesia and use of airway device like laryngeal mask airway (LMA) or endotracheal tube can influence IOP values measured. We planned this study to compare change of IOP with facemask or LMA. Change of IOP at varying depth of anaesthesia was also assessed.

Material and Methods:

After Institutional ethical clearance and informed parental consent, 89 children of glaucoma aged 0-12 years were included in this prospective randomized controlled trial. The children were randomized to facemask (Group M) and LMA (Group L). Sevoflurane was the sole general anaesthetic used in both the groups and IOP were recorded after induction, at BIS 40-60, after LMA insertion (Group L), at BIS 60-80 and BIS more than 80.

Results:

The IOP values did not differ significantly between the groups at BIS 40-60 and at BIS 60-80. Moreover, pre and post LMA insertion IOP values were also comparable in Gr L (p = 0.11). However, significant increase in IOP values were observed with increasing BIS values within each group. The mean IOP in Group M at BIS 40-60 was 13.41 ± 4.04 as compared to 14.18 ± 3.64 at BIS 60-80 (p = 0.003). There was a similar pattern observed in Group L, where mean IOP at BIS 40-60 & BIS 60-80 was 14.13 ± 4.90 and 15.52 ± 4.57 respectively (p < 0.001).

Conclusion:

Either facemask or classic LMA can be safely used as per anaesthesiologist's preference without any significant effect on IOP. BIS monitoring may be used during IOP measurement in paediatric glaucoma suspects for accurate assessment of IOP.

How does sevoflurane induction, followed by a ketamine maintenance infusion, affect intraocular pressure? Establishment of an anaesthetic protocol for paediatric glaucoma examinations under anaesthesia

Accurate measurement of intraocular pressure (IOP) is essential in paediatric glaucoma management. Children require serial measurements and examination under anaesthesia (EUA). Most anaesthetic agents reduce IOP, and the ideal time to measure IOP under anaesthesia is questionable.

STUDY PURPOSE

To determine the effect of sevoflurane induction, followed by intravenous ketamine infusion on IOP, in children undergoing EUA for glaucoma or suspected glaucoma, and to establish the earliest time point at which reliable, repeatable IOP measurements can be obtained under anaesthesia.

METHOD

A prospective, descriptive study of IOP changes occurring in children requiring EUAs. A standardised anaesthetic protocol: sevoflurane induction, intravenous cannulation, 2 mg/kg intravenous ketamine bolus and 4 mg/kg/hour maintenance for 15 min. IOP measurements (taken supine with a Perkins applanation tonometer) and physiological variables were recorded.

RESULTS

IOPs were measured in 25 children (50 eyes). Twenty-six eyes (52%) were glaucomatous. Mean patient age was 29 months (2-88 months). Physiological variables returned to baseline at 8 min, correlating with recorded sevoflurane elimination. Mean IOP after sevoflurane induction was 3.68 mm Hg lower than with ketamine maintenance at 15 min (95% CI 1.35 to 6.02 mm Hg) (p=0.002). Contrastingly, the difference in IOP between ketamine anaesthesia at 15 min and near wakefulness was 0.28 mm Hg (95% CI -2.23 to 2.79 mm Hg) (p=0.826).

CONCLUSION

Sevoflurane's IOP-lowering effect is reversed 15 min after the discontinuation of the inhalational gas, if anaesthesia is maintained with an intravenous ketamine infusion. IOP measurements appear to stabilise at this time point until the point of near wakefulness and may reflect awake values.