Prasad N, MacFadyen R J, Ogston S A, MacDonald T M
Department of Clinical Pharmacology, Ninewells Hospital and Medical School, University of Dundee, UK.
J Hypertens. 1995 Mar;13(3):291-5.
Ambulatory blood pressure monitoring is being used increasingly in clinical practice and hypertension research. We have noted elevated blood pressure during the initial hours of monitoring. The objective of the present study was to examine the consistency, magnitude and duration of this elevation, and to determine whether this effect causes significant differences in the mean ambulatory blood pressure monitoring values comparing the first (day 1) and second (day 2) consecutive 24-h periods of monitoring.
Fifty patients who were hypertensive based on repeated clinic readings were studied prospectively. Each underwent continuous 48-h ambulatory blood pressure monitoring with a SpaceLabs 90207 monitor. The device recorded blood pressure at 15-min intervals during the daytime (0600-2159 h) and at 30-min intervals at night-time (2200-0559 h). From these readings hourly means were calculated. Repeated-measures analysis of variance was performed to compare the hourly means of days 1 and 2.
Repeated-measures analysis of variance indicated that a significant difference existed for both systolic and diastolic blood pressure between day 1 and day 2. Paired Student's t-test revealed that this difference occurred during the first 2 h of monitoring. The daytime blood pressure was higher on day 1 as a result of the initial elevation of blood pressure at the onset of monitoring. The initial elevation of blood pressure was present both in white-coat hypertensives and in essential hypertensives.
The first 2 h of ambulatory blood pressure monitoring are associated with elevated blood pressure both in white-coat hypertensives and in essential hypertensives. This has a minor effect on mean daytime and 24-h ambulatory blood pressures. We propose that improved ambulatory blood pressure monitoring recordings would be obtained in clinical practice, and more particularly in research applications, if 26-h ambulatory blood pressure monitoring was carried out, excluding the first 2 h from the summary analyses.
动态血压监测在临床实践和高血压研究中的应用日益广泛。我们注意到在监测的最初几个小时血压会升高。本研究的目的是检验这种升高的一致性、幅度和持续时间，并确定这种效应是否会导致在比较连续的第一个（第1天）和第二个（第2天）24小时监测期的动态血压监测平均值时产生显著差异。
对50名根据多次诊室血压读数诊断为高血压的患者进行前瞻性研究。每位患者使用太空实验室90207监测仪进行连续48小时的动态血压监测。该设备在白天（06:00 - 21:59）每隔15分钟记录一次血压，在夜间（22:00 - 05:59）每隔30分钟记录一次血压。根据这些读数计算每小时的平均值。采用重复测量方差分析来比较第1天和第2天的每小时平均值。
重复测量方差分析表明，第1天和第2天的收缩压和舒张压均存在显著差异。配对t检验显示，这种差异出现在监测的前2小时。由于监测开始时血压的初始升高，第1天的白天血压较高。血压的初始升高在白大衣高血压患者和原发性高血压患者中均存在。
动态血压监测的前2小时，白大衣高血压患者和原发性高血压患者的血压均会升高。这对白天平均血压和24小时动态血压的影响较小。我们建议，如果进行26小时的动态血压监测，并在汇总分析中排除前2小时，那么在临床实践中，尤其是在研究应用中，将能获得更好的动态血压监测记录。
