Topical 2.5% and 5% phenylephrine: comparison of effects on heart rate and blood pressure.

We compared the effects of 2.5% and 5% concentrations of topical ocular phenylephrine hydrochloride on blood pressure and heart rate in 200 adult patients undergoing extracapsular cataract surgery under either general or neuroleptic anesthesia. Although there was little initial change in mean systolic or diastolic blood pressure in either group, once anesthesia was induced there was a rise of 1 to 5 mm Hg in the lower-dose group, compared with 17 to 26 mm Hg in the higher-dose group. A slight decrease in mean heart rate of 5 to 6 beats/min was noted immediately after the instillation of either the 2.5% or 5% solution. The results suggest that lower doses of topical phenylephrine are safer than higher doses when used preoperatively. This may be particularly significant in hypertensive patients, who have higher baseline blood pressure.