Automated 24-hour ambulatory blood pressure monitoring in preeclampsia

A prospective controlled study was designed to compare automated 24-hour ambulatory blood pressure monitoring with intermittent blood pressure recordings obtained using a sphymomanometer. Blood pressure was measured in 20 hospitalized preeclamptic women in the third trimester. Data obtained using the Spacelabs automated blood pressure monitor was recorded over a period of 24 hours, and thereafter stored and processed in a computer. During the same 24 hour period, blood pressure and heart rate were measured by experienced staff at 07.00, 10.00, 13.00, 15.00, 18.00 and 21.00 hours, with the patient in a semi-recumbent position using a conventional mercury sphygmomanometer with a cuff of appropriate size. Korotkoff phase 5 was used as the indicator of diastolic blood pressure in all recordings by the staff. The main outcome measures were systolic and diastolic blood pressure, mean arterial blood pressure and maternal heart rate. Automated ambulatory monitoring was well tolerated and gave 91.6% successful readings. The mean differences between the blood pressure readings recorded by the monitor and of intermittent mercury sphygmomanometry during daytime were 0.7 (95% confidence interval -2.6 to 4.0) mmHg for the mean arterial blood pressure, -1.7 (95% confidence interval -6.8 to 3.5) mmHg for the systolic blood pressure, and 1.9 (95% confidence interval -2.2 to 6.0) mmHg for the diastolic blood pressure. The mean differences between day-time and night-time monitored blood pressures were 4.3 (95% confidence interval 0.8 to 7.8) mmHg, 4.6 (95% confidence interval 2.0 to 7.2) mmHg, and 4.4 (95% confidence interval 1.5 to 7.2) mmHg, respectively. The number of patients diagnosed as being hypertensive was similar whether automated blood pressure monitor or mercury sphymomanometry was used. Mean maternal heart rate recorded by the monitor or by the staff did not differ. Automated ambulatory blood pressure monitoring is reliable and might improve our understanding of the dynamic changes in blood pressure in pre-eclamptic women and may be a more suitable method to assess the blood pressure control achieved by different drugs.