Randomized prospective double-blind placebo-controlled trial of effect of intravenous ondansetron on intraocular pressure during ophthalmic surgery

N. M. Robin1 and S. M. Mostafa*

Department of Anaesthesia, Royal Liverpool University Hospital, Prescot Street, Liverpool L7 8XP, UK 1Present address: Department of Anaesthesia, Dandenong Hospital, Southern Health Care Network, Dandenong, Victoria 3175, Australia*Corresponding author

Accepted for publication: April 10, 2001


    Abstract
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 Abstract
 Introduction
 Methods and results
 Comments
 References
 
The effect of i.v. ondansetron, before induction of anaesthesia, on intraocular pressure (IOP) in patients undergoing cataract surgery was investigated. Forty patients (two groups of 20) received either ondansetron 4 mg (treatment group) or 0.9% saline (placebo group) in a double-blind controlled manner. There were no significant differences in IOP between the groups. Ondansetron had no significant effect on IOP during the study period.

Br J Anaesth 2001; 87: 629–31

Keywords: eye, intra-ocular pressure; vomiting, antiemetics, ondansetron


    Introduction
 Top
 Abstract
 Introduction
 Methods and results
 Comments
 References
 
Over the last decade the use of local anaesthetic techniques for intraocular operations has increased. However, there remains a need for general anaesthesia in a number of patients undergoing intraocular surgery. Control of intraocular pressure (IOP) is necessary in these cases. Nausea and vomiting following anaesthesia are recognized postoperative complications in eye surgery. Both can increase IOP. Any increase in IOP especially in perforating eye injuries or glaucoma, may be deleterious to patient’s vision. Therefore, many anaesthetists routinely give antiemetic agents before or during anaesthesia for ophthalmic surgery.

Ondansetron is a commonly used antiemetic drug with few side-effects.1 It has a proven efficacy to prevent and treat postoperative nausea and vomiting in non-ophthalmic and ophthalmic surgery.2 3 However, its effects on IOP are unknown. Consequently, this study was undertaken to ascertain the effects of i.v. ondansetron on IOP.


    Methods and results
 Top
 Abstract
 Introduction
 Methods and results
 Comments
 References
 
This was a randomized, placebo-controlled, double-blind study. Approval from the Research Ethics Committee was given. Forty patients, ASA class I–III, undergoing elective cataract surgery under general anaesthesia, were recruited after a written informed consent was obtained. They were premedicated with temazepam 0.15 mg kg–1 90 min before surgery. Patients were randomly allocated to one of two groups of 20. Twenty patients per group represents a sample size sufficient to detect a difference in IOP of 4.2 mm Hg with 90% power, based upon a SD of 4 mm Hg.4

Patients under 18 yr of age, ASA class IV or V, who vomited or received antiemetics before surgery were excluded. Those with a history of substance abuse, glaucoma, those who were pregnant or breast-feeding or had a contraindication to the use of ondansetron were also excluded.

IOP was measured using a calibrated Keeler pulsair 2000 non-contact applanation tonometer (Keeler Plc, UK). It is a simple instrument to use with an accuracy of ±1 mm Hg.5 IOP measurements were obtained from the eye not undergoing surgery. Baseline IOP, arterial pressure (AP) and heart rate (HR) were measured. Ondansetron 4 mg or 0.9% saline as 2 ml solution was administered intravenously. Five minutes later, IOP, AP, and HR were measured. Anaesthesia and muscle relaxation were achieved with thiopentone 2–5 mg kg–1 and atracurium 0.5 mg kg–1. Patients’ lungs were ventilated to normocapnia with 35% oxygen in nitrous oxide and 1% isoflurane. Further IOP, AP, and HR were measured immediately before, immediately following and 5 min after intubation.

After the study period, droperidol 0.02 mg kg–1 was given and a rescue antiemetic was prescribed postoperatively. After surgery, muscle relaxation was reversed with glycopyrrolate and neostigmine.

Homogeneity of variance was established using Levene’s test and the data were compared using Student’s t and chi-squared tests according to variables. Within group analysis was performed with ANOVA with Bonferroni’s correction. P-value <0.05 was considered significant.

There were no significant differences between the ondansetron and the saline groups in terms of age, gender, mean baseline IOP, and systolic AP (SAP) (Table 1). Baseline HR and diastolic AP (DAP) were significantly lower in the ondansetron group than the saline group (P<0.05).


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Table 1 Mean (SD) values of IOP, HR=heart rate and arterial pressure (SAP=systolic, DAP=diastolic). Significant change from: *, baseline; {dagger}, pre-intubation within group; or {ddagger}, difference between groups (P<0.05). 1=Before administration of test solution; 2=after administration; 3=after induction/before intubation; 4=immediately after intubation; 5=5 min after intubation
 
No significant differences in mean IOP values were noted between the ondansetron and the saline groups throughout the study period (Table 1). In the ondansetron group, mean IOP decreased below baseline value following induction (P>0.05). Although IOP increased immediately following intubation, the increase was not significant and was absent at 5 min after intubation. Similar observations were seen in the saline group, but the changes in mean IOP were significant (P<0.05). With the exception of the baseline differences and mean HR at 5 min post-administration of ondansetron, cardiovascular variables were similar in the two groups.


    Comments
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 Abstract
 Introduction
 Methods and results
 Comments
 References
 
Although baseline mean HR and DAP were significantly different between groups, the difference was small and clinically unimportant. Furthermore, there was no significant difference in either baseline mean IOP or SAP in the two groups. A possible explanation could be that five patients in the ondansetron group were receiving calcium-channel blockers vs none in the saline group. This does not appear to have influenced the results as the usual cardiovascular changes that follow tracheal intubation were observed in both groups (Table 1).

The purpose of this study was to ascertain the effects of ondansetron on IOP, not to assess its efficacy as an antiemetic, which has been reported previously.1 2 Ondansetron was associated with cardiovascular stability6 and no effect on intra-cranial or cerebral perfusion pressures7 and, therefore, unlikely to affect IOP. This study confirms that ondansetron does not increase IOP before, or during, induction of anaesthesia for ophthalmic surgery. These findings contrast with other antiemetics used in ophthalmic anaesthesia, which are associated with side effects. Metoclopramide may increase IOP8 and droperidol causes hypotension, postoperative drowsiness and confusion in elderly patients.9 The former agent should not be given before induction of anaesthesia in patients with perforating eye injuries, as it may lead to loss of intraocular contents. The latter should be used cautiously in aged patients.

In conclusion, IOP appears to be stable following i.v. administration of ondansetron before induction of anaesthesia. We suggest that ondansetron can be safely given before induction for the prevention or the treatment of nausea and vomiting in patients in whom it is essential to minimize changes in IOP such as those with perforating eye injuries or glaucoma.


    Acknowledgements
 
We thank Glaxo Wellcome for supplying ondansetron ampoules for the study and Dr A. N. Chonchubhair for her help in writing the protocol.


    References
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 Abstract
 Introduction
 Methods and results
 Comments
 References
 
1 Fortney JT, Gan TJ, Graczyk S, et al. A comparison of the efficacy, safety, and patient satisfaction of ondansetron versus droperidol as antiemetics for elective outpatient surgical procedures. S3A-409 and S3A-410 Study Groups. Anesth Analg 1998; 86: 731–38[Abstract]

2 Figueredo ED, Canosa LG. Ondansetron in the prophylaxis of postoperative vomiting: a meta-analysis. J Clin Anesth 1998; 10: 211–21[ISI][Medline]

3 Doe EA, Jones P, O’Hara MA. A comparison of prophylactic ondansetron hydrochloride and droperidol for strabismus repair in adults. J Ped Ophth Strab 1998; 35: 264–9

4 Mostafa SM, Lockhart A, Kumar D, et al. Comparison of effects of fentanyl and alfentanil on intra-ocular pressure. A double-blind controlled trial. Anaesthesia 1986; 41: 493–8.[ISI][Medline]

5 Bricker SR, McGalliard JN, Mostafa SM. The Keeler Pulsair air impulse tonometer. Comparison with the Perkins hand-held applanation tonometer for peri-operative measurement of intra-ocular pressure. Anaesthesia 1990; 45: 36–9[ISI][Medline]

6 Heyman JS, Young ML, Bagshaw RJ, et al. Cardiovascular stability with rapid intravenous infusion of ondansetron. Can J Anaesth 1993; 40: 448–52[ISI][Medline]

7 Jacot A, Bissonnette B, Favre JB, Ravussin P. The effect of ondansetron on intracranial pressure and cerebral perfusion pressure in neurosurgical patients. Ann Franc Anesth Reanim 1998; 17: 220–6

8 Parris WCV, Kambam JR, Flanagan JFK, Elloitt J. The effects of metochlopramide on intraocular pressure. Anesth Analg 1987; 66: S135

9 Grond S, Lynch J, Diefenbach C, Altrock K, Lehmann KA. Comparison of ondansetron and droperidol in the prevention of nausea and vomiting after inpatient minor gynecologic surgery. Anesth Analg 1995; 81: 603–7[Abstract]





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