[Biochemical stress monitoring during cataract surgery; phenylephrine 10% shows no changes in serum-catecholamines in...

There is a controversy about the concentration of topical phenylephrine recommended for diagnostic or therapeutic mydriasis. Phenylephrine 10% leads to a faster and more pronounced mydriasis but cardio-vascular side-effects like hypertension and arrhythmia have been reported. A maximal pupillary dilatation is a prerequisite for successful cataract surgery. The aim of this study was to evaluate the risk-benefit ratio of phenylephrine 10% in comparison to 5% in the daily practice of the cataract-surgery unit in our clinic by clinical assessment and monitoring of biochemical stress parameters.

30 informed and consenting patients were randomly allocated to 2 groups of equal size. After a single application of 2 drops of phenylephrine 5% in group 1 and 10% in group 2 respectively and 1 drops of cyclopentolate 1% with neutral pupil (time 0), an ECG was recorded and blood pressure, pulse, oxygen-saturation and pupil size were measured. Simultaneously a blood-sample was taken and the serum-catecholamines adrenaline and noradrenaline were determined by HPLC (High Pressure Liquid Chromatography). These measurements were repeated after 5, 10 and 30 minutes.

The mean pupil area after 30 minutes in group 1 was 31.97 (+/- 0.43) mm2 compared to 45.72 (+/- 0.39) mm2 in group 2. Our data showed no other significant variation between the groups: neither clinical monitoring nor catecholamine measurements showed concentration-dependent patterns in blood pressure development or serum levels. No systemic cardiovascular effects were observed.

These results demonstrate that a controlled application of phenylephrine 10%--under observation of contraindications--yields no increased risk for the occurrence of cardio-vascular side-effects in comparison with phenylephrine 5%. Therefore, we recommend the use of phenylephrine 10% in the described dosage as routine medication for cataract surgery.