The effect of different doses of ketamine on intraocular pressure in anesthetized children.

BACKGROUND

When used for induction of anesthesia, ketamine usually increases intraocular pressure (IOP). However, the effect of low doses of ketamine, which are used for parental separation in children, is unknown. We studied the effect of two different doses of ketamine on IOP in anesthetized children.

METHODS

Forty children age 1 to 6 years who met American Society of Anesthesiologists physical status I criteria scheduled to undergo surgery were randomly selected to receive either an induction dose (6 mg/kg) or a low dose (3 mg/kg) of ketamine intramuscularly. Anesthesia was induced and maintained with halothane, and ketamine was injected 10 minutes after induction. Intraocular pressure was measured using a Perkins applanation tonometer before ketamine administration and every 5 minutes thereafter for 20 minutes by an observer who was unaware of the ketamine dose used. 10.8 +/- 2.2 mm Hg to 12.6 +/- 2.8 mm Hg at 5 minutes and 11.9 +/- 2.5 mm Hg at 10 minutes after administration of ketamine in the induction-dose group. There was no significant change in IOP after administration of ketamine in the low-dose group. Intraocular pressure was significantly higher in the induction-dose group compared to the low-dose group at 5 minutes after administration of ketamine. More patients in the induction-dose group had postoperative airway obstruction and sedation than in the low-dose group.

CONCLUSIONS

In children anesthetized with halothane, ketamine had a dose-dependent effect on IOP, with 6 mg/kg of the drug causing a small increase in IOP at 5 to 10 minutes and 3 mg/kg not altering the IOP. The higher dose of ketamine also was associated with an increased incidence of postoperative complications.