QUANTITATIVE MEASUREMENT OF THE EFFECTS OF CAFFEINE AND PROPRANOLOL ON SURGEON HAND TREMOR

Objective: To quantitatively measure the effects of caffeine and propr anolol, a nonselective beta-blocking agent, on surgeon hand tremor dur ing simulated vitreoretinal microsurgery. Methods: Seventeen ophthalmi c surgeons were tested on 3 separate days. On each day, subjects inges ted 200 mg of caffeine, 10 mg of,propranolol hydrochloride, or gelatin placebo. The drugs were administered as part of a double-masked, plac ebo-controlled trial. Hand tremor was measured using the Microsurgery Advanced Design Laboratory Stability, Activation, and Maneuverability tester (MADSAM), a high-resolution, noncontact position tracking syste m. Results: The average percent magnitude changes from baseline tremor measurements were +15%, +31%, and -22% for placebo, caffeine, and pro pranolol groups, respectively. Analysis of variance techniques account ing for effects of individuals, drugs, and day order demonstrated that only drug effects on percent magnitude change of tremor were statisti cally significant (P=.01, F test). Detailed comparisons of the 2 drug groups with the placebo group revealed that, after adjusting for indiv idual and order effects, only the mean decrease in tremor due to inges tion of propranolol was a statistically significant trend (P=.03, F te st). Although caffeine caused a larger mean increase in percent magnit ude change in tremor than placebo, this trend was not statistically si gnificant (P=.34, F test). The evaluation of systemic physiologic meas urements showed that there were statistically significant drug effects on percent change in systolic (P<.001, F test) and diastolic (P=.002, F test) blood pressure and pulse rate (P=.002, F test). Individual an d day order effects were not significant. No adverse side effects were observed or reported in our test subjects. Conclusion: Physiologic su rgeon hand tremor can be decreased by the oral intake of a low dose of propranolol.