Apr. 22, 1997 Caffeine, stress, sleep loss, anxiety and physical exertion all can induce unnoticeable hand tremors. Now, experiments with a drug commonly used to treat rapid heart beats appears to significantly improve hand steadiness of surgeons during simulated eye operations.
Results of the study with 17 volunteer eye surgeons showed that propranolol, used to slow the heart rate, decreases tremors, pulse rate and blood pressure without noticeable side effects.
The study appeared in the March issue of Archives of Ophthalmology.
"Eye surgeons know that the very delicate work we do can be affected by tremors," says Dante J. Pieramici, M.D., chief resident at Wilmer Eye Institute and a retinal surgeon. "While hand steadiness is only one of a number of factors that may influence a surgeon's performance, we're obligated to study ways to improve our work. But we are not advocating in any way drug use by surgeons to reduce tremors."
The researchers measured hand tremor in each subject immediately before and one hour after randomly giving them one of three treatments: a placebo, 10 milligrams of propranolol or 200 milligrams of caffeine added to a juice drink--about as much as in two cups of coffee. The tests were repeated on three separate days until each surgeon had received all three treatments.
As part of a performance improvement initiative, the Hopkins team measured hand tremors using a device they created and named MADSAM--Microsurgery Advanced Design Laboratory Stability, Activation, and Maneuverability tester. MADSAM tests a subject's ability to hold hands steady under conditions similar to eye surgery. MADSAM records the position of a small magnet on the end of a microsurgical instrument used to illuminate the inside of the eye during an operation. Sitting on an operating room stool, the surgeons held the illuminator in a model eye containing a sensor that recorded how far the magnet moved in any direction. The sensor and eye were in a life-size mannequin head positioned beneath an operating room microscope.
Before receiving a treatment, the average pretest tremor of surgeons was 3.8 microns (1 micron = a millionth of a meter). Following treatment with caffeine, tremors increased by an average of 31 percent, compared to a 15 percent increase following placebo. Only propranolol caused a statistically significant decrease in hand tremor--an average of 22 percent.
When compared to the increase in tremors caused by placebo, propranolol decreased the average hand tremor of the surgeons by 37 percent, while decreasing pulse rate by 11 percent and systolic blood pressure by 5 percent. Systolic blood pressure is the pressure in the blood vessels measured just after the heart contracts and pumps blood into the arteries.
Other authors of the study include Michael U. Humayun, R. Scott Rader, Eugene de Juan, Jr., and Carl C. Awh (Retina-Vitreous Associates, Nashville, Tenn.).
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