Increased Cerebral Blood Flow in Anemic Patients on Long-Term Hemodialytic Treatment

Abstract

Summary: CBP was measured in 15 patients on chronic hemodialytic treatment. CBP was measured with xenon-133 inhalation using single photon emission tomography. In addition, computerized tomography (CT) and a neuro logical examination were done prior to hemodialysis. Mean CBP was 66.2 ± 17.3 (SD) ml 100 g-I min-I, which was significantly higher (t-test, p < 0.05) than for an age-matched control group (54.7 ± 10.2 ml 100 g-I min -I). However, the hematocrit for the patients was considerably lower, 0.30 ± 0.07, as compared to 0.43 ± 0.03 in the controls. A significant negative correlation was observed between CBP and the hematocrit (y = -1.79x + 120.7, r = -0.71, p < 0.01). Calculating CBP from this equation in the dialyzed patients using a hematAs focal or diffuse brain tissue damage is invari ably followed by a reduction in CBF, there are rea sons to expect a CBF decrease in patients on long term hemodialytic treatment. First, the renal dis ease itself may cause uremic encephalopathy (Olsen, 1961;Tyler, 1968), although today most pa tients will receive hemodialysis early in the course of their disease to prevent long-standing severe ure mia. Second, a severe progressive neurological syn drome called dialysis dementia evolves in a number of patients regularly treated with hemodialysis. The etiology of this syndrome was originally found to relate to a high aluminum content in the dialysate (Alfrey et aI., 1976;Alfrey, 1987). Lately, it has Received November 22, 1991; final revision received March 18, 1992; accepted March 18, 1992. Address correspondence and reprint requests to Dr. Sissel Vorstrup, Department of Neurology, Rigshospitalet, 9, Blegdamsvej, 2100 Copenhagen, Denmark.Abbreviations used: CT, computed tomography; CM, can thomeatal (plane); Hct, hematocrit; PET, positron emission to mography. 745ocrit of 0.43 yielded a mean CBP value of 43.7 mlloo g-I min -I, i.e., 20% below the expected. Two patients showed a focal CBP decrease. CT showed central or cor tical atrophy in five patients, and two had small hypo dense lesions. The neurological examination revealed slight to moderate dementia in seven cases. Although mean CBP was found to be increased by 21% as com pared to the control group, an even higher CBP level would have been expected to outweigh the decreased ox ygen carrying capacity of the blood. The findings suggest a lowered metabolic demand of the brain tissue, probably due to subtle brain damage. Key Words: Anemia-CBP Hemodialysis.been suggested that even the moderately increased aluminum levels in the blood, often seen in these patients because of a high daily intake of aluminum containing phosphate-binding gels, may cause de mentia (Altmann et aI., 1989). Third, hypotensive episodes, arterial hypoxemia, and fluctuations in electrolytes and cerebral water content may occur during hemodialysis and cause subtle subclinical brain tissue damage (Savazzi et aI., 1985). Finally, the underlying process for the renal disease could cause brain damage and thereby decrease CBF. We therefore studied the in...

Doppler Sonographic Evaluation of Cerebral Blood Flow in Anemia Resulting From Chronic Renal Failure

“…[7][8][9][10][11][12][13] As well as causing a global increase in cardiac output, chronic anemia also increases the CBF. 6,18,19 Volstrup et al, 6 in their observation with single-photon emission tomography for the CBF in long-term hemodialytic patients with CRF, found a significant negative correlation between CBF and hematocrit level. This result is an expected consequence of hemodynamic changes occurring in chronic anemia that was also detected in our study.…”

“…[20][21][22][23] Although it was not measured in our study, cardiac output increase is a recognized issue in chronic anemia. 6,18,19 Eicke et al, 20 who established extracranial Doppler sonography for the measurements, found no association between common carotid artery blood flows and cardiac output. Because they did not include VAs in their measurements, it does not seem possible to make any comment on CBF in their study.…”

“…[1][2][3][4] Brain tissue hypoxia that results from a decreased cerebral oxygen supply raises the CBF. 5,6 Doppler sonography is a well-established method for assessing cerebrovascular circulation. It has been used for the evaluation of effects of various diseases and conditions.…”

“…[7][8][9][10][11][12][13] Cerebral blood flow studies using positron emission tomography in anemia secondary to CRF have been reported previously in the literature. 6,14 However, to the best of our knowledge, Doppler assessment of CBF in anemia secondary to CRF has not been reported before. This study describes Doppler sonographic evaluation of CBF in anemia secondary to CRF and compares the results with data gathered from healthy control subjects.…”

“…[1][2][3][4] The decrease in cerebral oxygen supply due to anemia results in brain tissue hypoxia, which thus increases cerebral blood flow (CBF). 5,6 The principal objective of cerebrovascular Doppler sonography is the analysis and characterization of cerebral hemodynamics under physiologic and pathologic circumstances. Although invasive electromagnetic studies are the standard for the measurement of blood flow, Doppler sonography enables noninvasive assessment of flow dynamics.…”