97th DOG Annual Meeting 1999
BIOCHEMICAL STRESS MONITORING IN CATARACT SURGERY:
PHENYLEPHRINE 10% SHOWS NO CHANGES IN
SERUM-CATECHOLAMINES IN COMPARISON WITH 5%
F. C. Schlichtenbrede1, M. C. Bartram1, K. U. Burkhard2, R. Wiedemann1
Background: A maximal pupillary dilatation is a prerequisite for successful cataract surgery. The combination of the sympathicomimetic drug phenylephrine 5% with the anticholinergic drug cyclopentolat 1% frequently shows insufficient mydriasis. Phenylephrine 10% leads to a faster and more pronounced my-driasis but cardio-vascular side-effects have been described. To objectively evaluate the risk-benefit ratio of phenylephrine 10% these side-effects were to be documented in our patients by monitoring biochemical stress parameters and obtaining a clinical assessment.
Patients and Methods: Informed and consenting patients were randomly allocated to 2 groups, comprising 15 patients each. All patients received midazolam p.o. (0.05 mg/kg bw) as premedication. After a single application of 2 drops of phenylephrine 5% in group 1 and 10% in group 2 respectively and also 2 drops of cyclopentolate with neutral pupil (time 0), an ECG was performed and blood pressure, pulse, oxygen-saturation and pupil size were measured. Simultaneously a blood-sample was taken and in the centrifugally separated serum the catecholamines adrenaline and noradrenaline were determined using the HPLC (High Performance Liquid Chromatography). These measurements were repeated after 5, 10 and 30 minutes.
Results: The mean pupil size after 30 minutes in group 1 was 7,5 mm compared with 9 mm in group 2. The maximal pupil size was reached in this group after 20 minutes. In all patients the planned surgical procedures were performed without complications. Our preliminary data show no significant variation between phenylephrine 5% and 10%: neither the clinical monitoring nor the catecholamine measurements showed concentration-dependent patterns in blood pressure development or serum levels. No systemic cardiovascular effects were observed.
Conclusion: These results demonstrate that a controlled application of phenylephrine 10% - under observation of contraindications - yields no increased risk of occurrence of cardiovascular side-effects in comparison with 5%. It appears that the advantages of an optimal pupillary dilatation justify the use of phenylephrin 10% as routine medication in cataract surgery.
We thank Mrs. B. Vetter for performing of the HPLC-measurements.
1Dept. Ophthalmology, 2Dept. Anesthesiology,Univ. Leipzig, Liebigstr 10-14, 04103 Leipzig