Effects of short daily hemodialysis and extended standard hemodialysis on blood pressure and cardiac hypertrophy: a comparative study.

BACKGROUND: Causes of hypertension and cardiac hypertrophy in hemodialysis (HD) patients are multiple, but the role of fluid overload appears to be crucial. Short daily HD (sDHD = 2 hr x 6/week) seems to allow reductions in left ventricular mass (LVM) through the reduction of extracellular water (ECW). Better cardiovascular stability during HD can be obtained with short, but more frequent HD sessions, but also by increasing the session length accompanied with a reduction in ultrafiltration (UF)/hr. Regardless of the method, the adequate reduction in extracellular volume should permit better control of hypertension and left ventricular hypertrophy (LVH). This study aimed to compare sDHD with an extended form of standard HD (eSHD = 4.5-5 hr x 3/week) on the reduction of fluid overload, blood pressure (BP) and LVM index (LVMi).

PATIENTS AND METHODS: Twenty-four HD patients with hypertension and LVH were enrolled in a prospective non-randomized study. After a 3-month run-in period they were divided in two comparable groups: 12 patients treated with sDHD, and 12 patients treated with eSHD for 6 months. LVMi, 24 hr BP monitoring, ECW, determined with electrical bio-impedance, biochemical correlates and spKT/V were studied at the beginning of the study and 6 months later.

RESULTS: The weekly session length was increased in eSHD from 722.9 +/- 7.5 to 877.3 +/- 35.5 min. ECW% was reduced similarly in the two groups (Delta ECW: eSHD = 4.6 +/- 2.4 L; sDHD = 4.1 +/- 2.3 L); 24 hr BP decreased significantly from 157/81 to 137/75 mmHg in eSHD, and from 149/79 to 128/72 mmHg in sDHD. The reduction in systolic BP was similar in the two groups (eSHD = 20.1 +/- 15.3 mmHg, sDHD = 21.2 +/- 16.7 mmHg). Finally, LVMi was similarly reduced (eSHD = 55 +/- 30.3 g/m(2), sDHD = 54.4 +/- 21.3 g/m(2). The number of antihypertensive drugs decreased significantly after ECW% reduction: only 2/10 patients on eSHD and 4/12 patients on sDHD were maintained on therapy (p = ns). Intra-dialysis hypotension episodes did not differentiate between SHD and DHD. The reduction in LVMi was significantly correlated to fluid volume changes when these were measured as phase angle (PA) with bio-impedance (r = -0.43, p < 0.05).

CONCLUSIONS: In hypertensive HD patients with LVH, fluid overload is invariably present and its reduction allows the decrease of BP and LVM. These results can be obtained by forcing UF with eSHD and sDHD, but patients maintained on x 3/week schedules need longer dialysis sessions to avoid intra-dialysis symptoms.