Hemodialysis causes severe orthostatic reduction in cerebral blood flow velocity in diabetic patients

Orthostatic hypotension is a serious problem in patients with diabetes mell itus (DM) undergoing hemodialysis (HD). To evaluate cerebral circulation du ring orthostasis in patients with DM, we examined changes in mean blood flo w velocity in the middle cerebral artery (VMCA) during 60 degrees head-up t ilt for 5 minutes in patients with DM (six men, two women; age, 57 +/- 3 ye ars [mean -/+ SEM]; HD duration, 47 +/- 27 months) before and after bicarbo nate HD by using transcranial Doppler sonography. The findings were compare d with those in HD patients without diabetes (non-DM; 12 men, 5 women; age, 47 +/- 3 years; HD duration, 82 +/- 23 months), Mean blood pressure (MBP) in the supine position, hematocrit (Hct), plasma fibrinogen, and volume of fluid removed by HD were not significantly different between the two groups (MBP, 106 +/- 6 versus 103 +/- 4 mm Hg; Hct, 26% +/- 1% versus 28% +/- 1%; fibrinogen, 355 +/- 37 versus 357 +/- 27 mg/dL; fluid, 2.5 +/- 0.2 versus 2.3 +/- 0.2 L). Percentage of change in VMCA (%VMCA) during tilt was compar ed between the groups before and after HD. Before HD, MBP decreased signifi cantly to 93 +/- 5 mm Hg during tilt only in patients with DM, The degree o f MBP reduction was -13 +/- 2 mm Hg in DM and -2 +/- 2 mm Hg in non-DM pati ents (P < 0.01), %VMCA equally decreased during tilt; DM, -12% +/- 3%, and non DM, -12% +/- 2%, After HD; MBP decreased by 36 +/- 7 mm Hg in patients with DM, which was significantly greater than before HD. VMCA also decrease d In both groups after HD, and %VMCA in DM (-32% +/- 5%) was significantly greater than before HD (P < 0.01) and in non-DM patients (-13% +/- 2%; P < 0.01), %VMCA positively correlated with the percentage of change ratio of M BP during tilt in both groups after HD (DM, r = 0.87, P < 0.01; non-DM, r = 0.61, P < 0.01). Our results showed a significant decrease in cerebral blo od flow velocity during tilt of equal magnitude in both groups before HD de spite differences in the level of hypotension, whereas reduction in cerebra l blood flow velocity and decrease in MBP were more marked in DM after HD. Orthostasis could thus cause hemodynamically mediated brain damage after HD , especially in patients with DM. (C) 1999 by the National Kidney Foundatio n, Inc.