One BP Target Won't Fit All Dialysis Patients

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One BP Target Won't Fit All Dialysis Patients
   
By Crystal Phend, Senior Staff Writer, MedPage Today
October 15, 2010
 
Note that this large observational study indicates that the association between mortality and blood pressure in dialysis patients is modified by age, race, and the presence or absence of comorbid diabetes.

Point out that the study cannot determine causality, and randomized trials will be necessary to determine optimum blood pressure targets in the various subpopulations of dialysis patients.
 
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One size doesn't fit all for blood pressure management in dialysis patients, researchers found in a large cohort study.

Age and diabetes status impacted the link with mortality -- higher at low blood pressures in some groups but high pressures in others, Philip G. Zager, MD, of the University of New Mexico Health Sciences Center and Dialysis Clinic, both in Albuquerque, N.M., and colleagues reported.

Blood pressure targets should take these factors into account, they recommended online in the Journal of the American Society of Nephrology.

"Future Kidney Disease Outcome Quality Initiative (K/DOQI) guidelines may need to consider different blood pressure targets for subgroups of hemodialysis patients," they wrote in the paper.

Those guidelines call less than 140/90 mm Hg a reasonable goal for predialysis blood pressure, but with weak supporting evidence.

Targets have largely been extrapolated from general population studies, since end-stage renal disease patients have largely been excluded from blood pressure trials. The existing epidemiologic data in the appropriate population has been somewhat conflicting.

Zager's observational study is one of the best, but more guidance is needed, according to an accompanying editorial by Deidra C. Crews, MD, ScM, of Johns Hopkins University, and Neil R. Powe, MD, MPH, MBA, of San Francisco General Hospital and the University of California San Francisco.

"Perhaps we should be less aggressive with blood pressure in older patients or those with diabetes and more aggressive with younger patients, but how should we treat a patient with comorbid illnesses, systolic dysfunction, high intradialytic weight gain, intradialytic hypotension, and medication nonadherence (none of which were analyzed in this study)?" they wrote in the editorial.

Zager's group studied patients initiating hemodialysis at facilities operated by Dialysis Clinic over a six-year period.

These 16,283 patients were new to hemodialysis, had survived at least 150 days from their first outpatient dialysis, and had recorded predialysis blood pressure.

Over a median 1.5 years of follow-up, 6,250 patients died.

Systolic blood pressure predicted mortality much more strongly than did diastolic blood pressure.

Low systolic pressure correlated with elevated mortality overall. This association was more pronounced among older patients (P<0.001) and those with diabetes, though.

Among patients over age 50, systolic pressure under 140 mm Hg was associated with higher mortality, while levels over 160 mm Hg were not.

Among patients who hadn't reached their 50s, systolic pressure under 140 mm Hg didn't predict increased mortality, whereas values over 160 mm Hg did. This relationship held true regardless of race or diabetes status in younger patients.

Thus, dialysis patients matched the general population only at the youngest ages (30-year-olds), the researchers noted. After that age, each additional decade boosted the risk of mortality associated with low blood pressure and reduced the risk associated with hypertension.

The reason may be that patients with low to normal blood pressure may not get enough sufficient blood flow to their organs during dialysis, the researchers suggested.

"Elderly patients and patients with diabetes, with stiff, noncompliant vessels and occlusive arterial disease, may experience significant reductions in organ perfusion during dialysis," they wrote in the paper.

Comorbidities may also be playing a role in the impact of diabetes on the mortality-blood pressure relationship, Zager's group noted.

Diabetes boosted mortality risk among these end-stage renal disease patients, but the effect was largely restricted to those with a low blood pressure -- under 140 mm Hg (P<0.001). The increased mortality of a low blood pressure in the presence of diabetes again was seen primarily older patients (P<0.001).

Black patients had an overall survival advantage (hazard ratio 0.70 compared with whites at 150 mm Hg), primarily accounted for by older patients.

The reason for this racial difference isn't clear but could involve underlying atherosclerotic cardiovascular disease, the investigators suggested.

The researchers cautioned that the study could not draw causal relationships because of its observational design. Also, the study may have been limited by unidentified confounding, lack of data on baseline cardiovascular disease and heart failure, and use of in-office blood pressure monitoring rather than home or ambulatory monitoring.

The study was funded in part by Dialysis Clinic, a not-for-profit corporation.

Zager and a co-author reported receiving salary support via their institutions from Dialysis Clinic.

The editorialists reported having no conflicts of interest to disclose.

Primary source: Journal of the American Society of Nephrology
Source reference:
Myers OB, et al "Age, race, diabetes, blood pressure, and mortality among hemodialysis patients" J Am Soc Nephrol 2010; DOI: 10.1681/ASN.2010010125.

Additional source: Journal of the American Society of Nephrology
Source reference:
Crews DC, Powe NR "Blood pressure and mortality among ESRD patients: All patients are not created equal" J Am Soc Nephrol 2010; 21: 1818–1819.
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