Intraocular pressure changes in a Nigerian population--effects of tracheal tube and laryngeal mask airway insertion and removal

Abstract

Objectives: Laryngoscopy and tracheal intubation lead to acute elevation in intraocular pressure (IOP); the ocular hypertensive response. The Laryngeal mask airway prevents sudden surges in IOP. We compared IOP changes to the insertion and removal of the Laryngeal mask airway (LMA) and the endotracheal tube (ETT).

Patients and methods: Seventy ASA I and II patients aged 18 to 60 years at the Lagos University Teaching Hospital between January and December 2003 were randomly allocated to receive either an LMA or ETT for airway management. Anaesthesia was induced with propofol and atracurium. Intraocular pressure was measured by applanation tonometry post induction (baseline) and prior to removal (pre-extubation), after insertion or removal (0 minute), at 1,2,3,5 and 10 minutes after insertion or removal.

Results: Insertion of the airway device caused an immediate rise in IOP of 4.6% in the LMA group (from 13.1 +/- 2.4 to 13.7 +/- 2.4 mmHg) and 49.2 in the ETT group (from 12.0 +/- 2.5 to 17.9 +/- 4.0 mmHg) (p<0.001). Removal of the airway device caused an immediate rise in IOP of 14.6 in the LMA group (from 11.26 +/- 2.4 to 12.9 +/-2.4 mmHg) and 50.3 in the ETT group (from 11.37 +/- 2.0 to 17.1 +/- 3.3 mmHg) (p<0.001). IOP thereafter declined towards baseline in both groups. Cardiovascular responses accompanied IOP changes. The mean insertion time was 39.8 +/- 9.1 seconds (ETT) vs 31.5 +/- 4.4 seconds (LMA). (p<0.001) Cough (17.1) and mild laryngeal spasm (2.9) occurred in the ETT group only following removal.

Conclusion: The LMA produced better IOP stability following its insertion and removal compared to the tracheal tube.