Quantitative measurement of the effects of caffeine and propranolol on surgeon hand tremor

M. U. Humayun, R. S. Rader, D. J. Pieramici, C. C. Awh and E. de Juan Jr
Microsurgey Advanced Design Laboratory, Wilmer Ophthalmological Institute, Johns Hopkins Hospital, Baltimore, Md, USA.

OBJECTIVE: To quantitatively measure the effects of caffeine and propranolol, a nonselective beta-blocking agent, on surgeon hand tremor during simulated vitreoretinal microsurgery. METHODS: Seventeen ophthalmic surgeons were tested on 3 separate days. On each day, subjects ingested 200 mg of caffeine, 10 mg of propranolol hydrochloride, or gelatin placebo. The drugs were administered as part of a double-masked, placebo-controlled trial. Hand tremor was measured using the Microsurgery Advanced Design Laboratory Stability, Activation, and Maneuverability tester (MADSAM), a high-resolution, noncontact position tracking system. RESULTS: The average percent magnitude changes from baseline tremor measurements were +15%, +31%, and -22% for placebo, caffeine, and propranolol groups, respectively. Analysis of variance techniques accounting for effects of individuals, drugs, and day order demonstrated that only drug effects on percent magnitude change of tremor were statistically significant (P = .01, F test). Detailed comparisons of the 2 drug groups with the placebo group revealed that, after adjusting for individual and order effects, only the mean decrease in tremor due to ingestion of propranolol was a statistically significant trend (P = .03, F test). Although caffeine caused a larger mean increase in percent magnitude change in tremor than placebo, this trend was not statistically significant (P = .34, F test). The evaluation of systemic physiologic measurements 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 and day order effects were not significant. No adverse side effects were observed or reported in our test subjects. CONCLUSION: Physiologic surgeon hand tremor can be decreased by the oral intake of a low dose of propranolol.