How does sevuflurane induction, followed by a ketamine maintenance infusion affect intraocular pressure? : establishment of a protocol for paediatric glaucoma examinations under anaesthesia

Master Thesis


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University of Cape Town

Purpose: 1.To determine the effect of sevoflurane induction, followed by intravenous (IV) ketamine infusion on intraocular pressure (IOP) in the paediatric glaucoma population. 2. To establish the earliest time point at which IOP measurement most closely resembles awake values. Methods: A prospective, descriptive study of the IOP changes occurring in 25 children requiring IOP measurements at our institution. A standardised anaesthetic technique was employed; sevoflurane induction, intravenous cannulation, ketamine bolus (2mg/kg) and maintenance (4mg/kg/hr) for 15 minutes. IOP measurements and physiological variables were recorded after sevoflurane induction, then every 2 minutes for a period of 10 minutes, one at 15 minutes as well as 5 minutes after ketamine discontinuation. Results: IOP was measured in 25 patients (50 eyes). Twenty-six eyes (52%) had glaucoma. The mean patient age was 29 months (range 2-88 months). The mean IOP after sevoflurane induction was 3,68mmHg lower than that with ketamine maintenance (sevoflurane eliminated) (95% CI 1,35 to 6,02mmHg) (p=0,002)). Physiological variables return to baseline at 8 minutes, which correlates with the time taken for sevoflurane to be eliminated from exhaled gas. The difference in IOP between ketamine anaesthesia (time 15 minutes) and near wakefulness was only 0,28 mmHg (95% CI -2,23 to 2,79mmHg) (p=0,826). Mixed effects models showed similar trends but a higher baseline (7,85mmHg (6,19 to 9,51mmHg) (p<0,001)) in those with glaucoma when compared to those without. Conclusion: Sevoflurane lowers IOP significantly when compared to ketamine anaesthesia. While eyes with glaucoma had a higher baseline than those which did not have glaucoma, both groups follow similar trends in response to the anaesthetic agents. This standardised anaesthetic protocol allows reliable IOP measurement 15 minutes after termination of sevoflurane and commencement of ketamine infusion, with no reported adverse events.

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