Managing hypertension using home blood pressure monitoring among haemodialysis patients--a call to action

Abstract

Over the last hundred years, the diagnosis of hypertension has rested upon the indirect measurement of blood pressure (BP) through the auscultation of Korotkoff sounds. Among patients on haemodialysis, BP measurement is particularly important because disparate outcomes are obtained depending on the timing, location, frequency and technique of measurement of BP [1]. This disparity of outcomes has profound implications for the management of hypertension especially among haemodialysis patients. Why home BP monitoring should become the standard of care among patients on haemodialysis is the subject of this review. To compare tests, such as one that tests home BP to pre-dialysis BP, a diagnostic test study must be performed. A diagnostic test study can have one of the following four paradigms (Figure 1): Test A (e.g. home BP) is compared to test B (e.g. pre-dialysis BP) using a ‘gold-standard’ or reference test. If test A performs better than test B, then test A is preferred. Whether test A should be favoured over test B depends on a variety of considerations such as its cost, practicality, invasiveness and acceptability. The two tests may be compared not to a reference standard but to some intermediate end point. A valid intermediate end point among hypertensive patients is the presence of target organ damage such as left ventricular hypertrophy. In other words, home BP can be compared to pre- or post-dialysis BP and the results compared in their ability to predict echocardiographic left ventricular hypertrophy. If home BP measurement is more strongly related to target organ damage then, compared to paradigm 1, it provides a higher level of evidence that it is superior to pre-dialysis or post-dialysis BP. The two tests can be compared with respect to prognosis, for example, all-cause mortality. For example, with respect to outcomes such as all-cause mortality, dialysis unit BP measurements can be compared to home BP measurements. If home BP measurement is more strongly related to all-cause mortality then, compared to paradigm 2, it provides even a higher level of evidence that it is superior to pre-dialysis or post-dialysis BP. Finally, a randomized controlled trial can be performed to assess the value of a diagnostic test. For example, management of the patient based on home BP monitoring vs dialysis unit BP measurements can be compared in a randomized trial. If the outcomes are better with home BP monitoring, then home BP monitoring would be said to be superior. The outcomes can be one of three outcomes: the reference test, in this case ambulatory BP, regression of left ventricular hypertrophy or improvement in all-cause mortality. This paradigm would provide the highest level of evidence of the superiority of home BP recordings over dialysis unit BP recordings. Fig. 1 Relative strength of evidence of superiority of test A vs test B. This review will focus on the data which support the use of out-of-office BP monitoring among patients on haemodialysis. The use of out-of-office BP monitoring among patients with chronic kidney disease who are not on haemodialysis is discussed elsewhere [2].