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(Circulation. 1999;100:222-225.)
© 1999 American Heart Association, Inc.

Brief Rapid Communications

Muscle and Skin Sympathetic Nerve Traffic During the "White-Coat" Effect

Guido Grassi, MD; Carlo Turri, MD; Sabrina Vailati, MD; Raffaella Dell'Oro, MD; Giuseppe Mancia, MD

From the Cattedra di Medicina Interna, Università di Milano, Ospedale S. Gerardo, Monza (G.G., R.D., G.M.), and Centro di Fisiologia Clinica e Ipertensione, IRCCS (G.G., C.T., S.V., R.D., G.M.), Milano, Italy.

Correspondence to Prof Giuseppe Mancia, Cattedra di Medicina Interna I, Ospedale S. Gerardo dei Tintori, Via Donizetti 103, Monza, Milano, Italy.

Background—Sphygmomanometric blood pressure measurements induce an alerting reaction and thus an increase in the patient's blood pressure and heart rate. Whether and to what extent this "white-coat" effect is accompanied by detectable changes in sympathetic nerve traffic has never been investigated.

Methods and Results—In 10 mild untreated essential hypertensives (age 37.9±3.8 years, mean±SEM), we measured arterial blood pressure (by Finapres), heart rate (by ECG), and postganglionic muscle and skin sympathetic nerve activity via microneurography. Measurements were performed with the subject supine during (1) a 15-minute control period, (2) a 10-minute visit by a doctor unfamiliar to the patient who was in charge of measuring his or her blood pressure by sphygmomanometry, and (3) a 15-minute recovery period after the doctor's departure. The entire procedure was performed twice at a 45-minute interval to obtain, in separate periods, muscle or skin sympathetic nerve traffic recordings, whose sequence was randomized. The doctor's visit induced a sudden, marked, and prolonged pressor and tachycardic response, accompanied by a significant increase in skin sympathetic nerve traffic (+38.6±6.7%, P<0.01). In contrast, muscle sympathetic nerve traffic was significantly inhibited (-25.5±4.1%, P<0.01). All changes persisted throughout the doctor's visit and, with the exception of skin sympathetic nerve traffic, showed a slow rate of disappearance after the doctor's departure.

Conclusions—Thus, the pressor and tachycardic responses to the alerting reaction that accompanies sphygmomanometric blood pressure measurement is characterized by a behavior of the adrenergic nervous system that causes muscle sympathoinhibition and skin sympathoexcitation.

Key Words: blood pressure • nervous system • reflex • hypertension

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