CHAPTER 2

I. Blood Pressure Measurement—Timing and Targets Recommendations Use predialysis blood pressure to guide therapy. (Grade C) Target predialysis blood pressure to be <140/90 (Grade C); optimal blood pressure is unknown. Ambulatory recording devices or home self-measurement should be applied to patients where difficulty occurs in reaching target blood pressure levels. (Grade D, opinion) Background Blood pressure (BP) varies significantly in hemodialysis patients depending upon the time taken: predialysis, postdialysis, or interdialytic. It is currently unknown which time period correlates best with long-term patient outcome, given the lack of treatment trials (1–3). It is difficult to relate usual clinical BP measurements in hemodialysis patients to published research studies because usual systolic and diastolic pressures both pre- and postdialysis are significantly higher by about 14/5 mmHg than if measured according to standardized American Heart Association criteria (4). There is convincing evidence in the general population that hypertension is associated with increased cardiovascular mortality and morbidity, and that its control can reduce these adverse consequences (5). Observational studies in the hemodialysis population have demonstrated that hypertension is also associated with adverse consequences in these patients, especially with longer-term follow-up (6–9). Although there are no controlled trials demonstrating that control of BP by dialytic or pharmacologic means in hemodialysis patients reduces these mortality and morbidity rates, it would seem reasonable to generalize from the extensive evidence available for the general population with hypertension (2,3). Long-term observational studies suggest that even mean arterial BP of >98 mmHg is associated with an increased risk of death compared with lower pressures (8). Other observational studies, performed in populations with older patients having a higher prevalence of cardiovascular comorbidity than the study cited above, suggest that low pre- and/or postdialysis BP may be associated with a higher risk of death than BP in excess of 140 to 150 mmHg systolic (10,11). The discrepancy between the above observations may well be an artifact of the confounding of reduced BP by severe cardiac disease (12). Given the absence of enough data to define an optimal BP in the dialysis population, the committee selected a target predialysis BP of <140/90 mmHg. The lower target of <130/80 mmHg recommended by the Canadian Hypertension Education Program (13) for patients with diabetes or chronic kidney disease was not selected, because there are two randomized clinical trials documenting no benefit for a lower target in nondialysis patients (14,15) and associative studies (above) suggesting possible risks for the lower target in dialysis patients. II. Management of Hypertension Recommendations Limit patients to a dietary sodium intake of 80 to 100 mEq/d. (Grade C) Reduce patient weight gradually by ultrafiltration, targeting for the “dry” weight, as antihypertensive medications are withdrawn. (Grade C) “Paradoxical” rises in BP during individual dialysis/ultrafiltration sessions should be corrected by further gradual volume removal. (Grade D) Background In nondialysis hypertensive patients, dietary sodium restriction may lower BP by 4.2/2.0 mmHg to 5.2/3.7 mmHg (16). It is also possible to control hypertension in many hemodialysis patients by restriction of dietary sodium to <100 mEq/d and aggressive and recurrent efforts to reduce body weight by ultrafiltration during dialysis to the “dry” weight. “Dry” weight may be defined as the lowest attainable weight at which patients are normotensive without antihypertensive medications and do not have symptoms of postural hypotension or intra/postdialytic hypotension. During this process of probing for “dry” weight, antihypertensive medications are gradually withdrawn (8,17). In turn, improved survival is associated with better BP control (8,18). Paradoxical elevation of BP during ultrafiltration is associated with volume overload and can be corrected by further aggressive reduction in target body weight (19). The lag phenomenon has been described in hemodialysis patients whereby BP reduction lags behind reduction in volume status for weeks to months (20). Thus, efforts to control BP by reduction of dry weight must be gradual but persistent. There is preliminary, nonrandomized evidence that extended forms of hemodialysis such as nocturnal dialysis and short daily dialysis are effective in improving BP control (21). In contrast, there is no convincing evidence at this time that intradialytic volume monitoring is effective in reducing symptoms or improving BP control. In fact, a recent randomized trial suggests that intradialytic volume monitoring may be harmful (22). Avoid positive sodium balance induced by hypertonic dialysate and/or sodium profiling during volume status adjustment. (Grade C) Reduce dialysate temperature when intradialytic hypotension limits ultrafiltration. (Grade C) If antihypertensive agents are required, select agents with pharmacokinetics suitable for dialysis patients and appropriate for existing comorbid conditions. (Grade D) Background Hypertonic dialysate and sodium profiling may induce net positive sodium balance in some patients, worsening hypertension and interdialytic thirst (23–25). Lowering dialysate temperature is often effective in moderating intradialytic hypotension during attempts to achieve dry weight, particularly for hypothermic patients. A minimum dialysate temperature of 35°C has been used if feedback-controlled isothermic dialysis is not available (26,27). There are no published controlled trials of specific antihypertensive agents in dialysis patients, and retrospective studies have provided conflicting evidence for the possible survival benefits of various classes of antihypertensive drugs (28–30). Long-acting (renally-excreted) agents such as atenolol, perindopril, or lisinopril can control hypertension occurring in dialysis patients. Administered thrice weekly after dialysis, these agents can assist in BP control without inducing significant hypotension (31,32). Recommendations for Research Treatment trials are required in which specific BP targets in hemodialysis patients are compared with regard to mortality and morbidity outcomes. Randomized trials are needed to determine the optimal use of specific classes of antihypertensive agents in hemodialysis patients.

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