Controversies in Blood Pressure: Management in Hemodialysis
A majority of patients on HD have hypertension, and CVD is the leading cause of death.
Editor's note: The author will discuss this topic during a presentation at the National Kidney Foundation's 2014 Spring Clinical Meetings, which will be held April 22-26 at the MGM Grand in Las Vegas.
Hypertension is a major modifiable risk factor for myocardial infarction, stroke, heart failure, and other cardiovascular diseases. A majority of patients on hemodialysis (HD) have hypertension, and cardiovascular disease is the leading cause of death in these patients.1
However, there are many controversies regarding blood pressure (BP) management in HD. First, although accurate BP measurements are the cornerstone of hypertension management, the best method of measuring BP in HD patients remains uncertain.
Clinicians generally use in-center BP measurements taken pre- and post-dialysis to guide treatment decisions, yet studies have shown that these measurements correlate poorly with interdialytic ambulatory BP monitoring (considered to be the gold standard of BP measurement).2-4 Because incorporating ambulatory BP monitoring into routine clinical practice is impractical, some studies have examined standardized in-center BP measurements or home-based BP measurements.
They found that these methods better predict left ventricular hypertrophy and cardiovascular and all-cause mortality.5-7 However, persuading busy dialysis units to use standardized BP measurements or over-burdened patients to measure blood pressure at home may prove challenging.
Optimal BP targets
Optimal BP targets in HD patients are another controversial issue. While patients with preserved kidney function have a direct linear association between BP and adverse cardiovascular outcomes,8 in patients on HD, lower BP is associated with higher risks of death or cardiovascular events, and higher BP has shown weak or even no association with adverse outcomes.
For example, in a study of 69,590 North American HD patients, pre-dialysis systolic BP less than 120 mm Hg was associated with a 5.5-fold higher risk of death at one year, whereas patients with pre-dialysis systolic BP greater than 200 mm Hg had only a 1.5-fold higher risk compared with the reference group (systolic BP 160-180 mm Hg)9. Similar findings have been shown in patients on hemodialysis from around the world.10
The National Kidney Foundation Kidney Disease Outcomes Quality Initiative (NKF KDOQI) guidelines recommend targeting a pre-dialysis BP of less than 140/90 mm Hg and post-dialysis blood pressure below 130/80 mm Hg, but acknowledge that the evidence to support these guidelines is weak.11
A 2009 expert committee convened by the NKF's Kidney Disease: Improving Global Outcomes (KDIGO) program reviewed the evidence and concluded that, aside from aggressively treating BP over 200 mm Hg, no specific recommendations on BP targets could be made.12 Moreover, there is potential harm associated with trying to achieve lower BP in HD patients.
An audit of dialysis units in the U.K. showed that intradialytic hypotension was more common in units that had more patients achieving post-dialysis BP targets.13 Intradialytic hypotension is associated with myocardial stunning,14 vascular access thrombosis,15 and death.16-18 The Blood Pressure in Dialysis Patients (BID) trial, a pilot study that will randomize patients on HD to low (110-140 mm Hg) or standard (155-165 mm Hg) systolic BP targets, is currently underway (NCT01421771).
If this trial is expanded into a full-scale randomized clinical trial, the results will help to clarify optimal BP targets in HD patients.