Effects of Hematocrit Variations on Cerebral Blood Flow and Oxygen Transport in Ischemic Cerebrovascular Disease

Kusunoki, Masahito; Kimura, Kazufumi; Nakamura, Masaichi; Isaka, Yoshinari; Yoneda, Shotaro; Abe, Hiroshi

doi:10.1038/jcbfm.1981.45

Cited by 93 publications

(41 citation statements)

References 13 publications

(12 reference statements)

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“…It should be noted, however, that this may vary under different circumstances because of the blood's non-Newtonian behavior (13). Factors affecting this variation include the species, the organs involved, and whether the organism is in resting or exercising conditions (11,12,(14)(15)(16). Thus, the above mentioned observations do not always reflect the general situation in exercising mammals and humans.…”

mentioning

confidence: 90%

Optimal hematocrit for maximal exercise performance in acute and chronic erythropoietin-treated mice

Schuler

Arras

Keller

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

100

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Erythropoietin (Epo) treatment increases hematocrit (Htc) and, consequently, arterial O 2 content. This in turn improves exercise performance. However, because elevated blood viscosity associated with increasing Htc levels may limit cardiac performance, it was suggested that the highest attainable Htc may not necessarily be associated with the highest attainable exercise capacity. To test the proposed hypothesis that an optimal Htc in acute and chronic Epotreated mice exists-i.e., the Htc that facilitates the greatest O 2 flux during maximal exercise-Htc levels of wild-type mice were acutely elevated by administering novel erythropoiesis-stimulating protein (NESP; wtNESP). Furthermore, in the transgenic mouse line tg6 that reaches Htc levels of up to 0.9 because of constitutive overexpression of human Epo, the Htc was gradually reduced by application of the hemolysis-inducing compound phenylhydrazine (PHZ; tg6PHZ). Maximal cardiovascular performance was measured by using telemetry in all exercising mice. Highest maximal O 2 uptake ( _ VO 2max ) and maximal time to exhaustion at submaximal exercise intensities were reached at Htc values of 0.58 and 0.57 for wtNESP, and 0.68 and 0.66 for tg6PHZ, respectively. Rate pressure product, and thus also maximal working capacity of the heart, increased with elevated Htc values. Blood viscosity correlated with _ VO 2max . Apart from the confirmation of the Htc hypothesis, we conclude that tg6PHZ adapted better to varying Htc values than wtNESP because of the higher optimal Htc of tg6PHZ compared to wtNESP. Of note, blood viscosity plays a critical role in limiting exercise capacity.blood viscosity | doping | excessive erythrocytosis | exercise performance | hemolysis

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mentioning

confidence: 90%

Optimal hematocrit for maximal exercise performance in acute and chronic erythropoietin-treated mice

Schuler

Arras

Keller

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

100

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“…5 -11 In fact, the effect of hematocrit reduction on tissue oxygenation is still uncertain, even in the normal brain. 4 - 13 Clinically, unintended hemodilution can easily occur in many of our postoperative neurosurgery patients because we usually do not transfuse erythrocytes when a patient's hematocrit is >30%.…”

Section: B Lood Flow Increases As Hematocrit Decreases Andmentioning

confidence: 99%

Effect of hemodilution on cerebral hemodynamics and oxygen metabolism.

Hino

Ueda

Mizukawa

et al. 1992

Stroke

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Background and Purpose:To evaluate the effects of hemodilution on cerebral hemodynamics and oxygen metabolism in the normal human brain, we measured regional cerebral blood flow, oxygen extraction fraction, oxygen metabolic rate, and regional cerebral blood volume in eight normal volunteers before and after hemodilution using positron emission tomography and oxygen-15-labeled gas inhalation technique.Summary of Report: Hemodilution was accomplished by phlebotomy of 400 ml and drip infusion of 500 ml low molecular weight dextran, which reduced hematocrit from 42.5% to 37.2% and arterial oxygen content from 19.1 to 16.9 ml/dl (both p< 0.005). It also increased mean cerebral blood flow from 45.2 to 47.7 ml/100 ml/min (p<0.025), but decreased tissue oxygen delivery from 8.7 to 8.0 ml/100 ml/min (p<0.05) and cerebral blood volume from 4.9% to 4.6% (p<0.025) in the overall cortical gray matter.Conclusions: Our results indicate that hemodilution in the tested range does not improve oxygen transport or tissue oxygenation in the normal human brain, although it increases cerebral blood flow. (Stroke 1992;23:423-426) KEY WORDS • cerebral blood flow • hemodilution • tomography, emission computed

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“…Instead, the oxygen delivery seems to be constant over the entire normal hematocrit range. 8 " 10 However, the interrelations between hematocrit and oxygen supply in acute cerebrovascular disease with compromised nutritive flow and impaired autoregulation can only be a matter of speculation: It appears likely that hemorheological factors are more important determinants of cerebral blood flow as normal regulatory mechanisms do not operate. Our present data and the observation that the hematocrit level on admission to hospital for acute stroke is a prognostic factor for the clinical outcome 52 lend support to this contention.…”

Section: Adverse Reactions To the Hemodilution Therapymentioning

confidence: 99%

A randomized controlled trial of hemodilution therapy in acute ischemic stroke.

Strand¹,

Asplund²,

Eriksson³

et al. 1984

Stroke

159

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SUMMARY Rapid hemodilution in the early phase of ischemic stroke by the combination of venesection (250-650 ml during the first 2 days) and administration of low-molecular weight dextran was evaluated in a prospective controlled trial. Fifty-two patients were randomized to hemodilution therapy and 50 to a control group; the two groups were comparable in important prognostic variables. Mean hemoglobin was reduced from 147 to 127 g/1, hematocrit from 43 to 37% and, in a subsample of patients, whole-blood viscosity at a shear rate of 23 sec' 1 from 7.0 to 4.3 cps over the first 2 days. Hemodilution was then maintained by repeated dextran infusions.Of the hemodiluted patients, 85% improved in neurological scoring over the first 10 days as compared to 64% of the control patients (p < 0.025). The case fatality rate during the first 3 months was little affected by hemodilution. Among the survivors, 8% of the hemodiluted and 31% of the non-hemodiluted patients were unable to walk at 3 months. The proportion of surviving patients still hospitalized at the 3-month follow-up was 13% in the hemodilution group and 39% in the control group (p < 0.01).The combination of venesection and dextran 40 administration is thus an unsophisticated but effective way to achieve rapid hemodilution in patients with acute cerebral infarction, and it improves the overall clinical outcome over the first 3 months.Stroke Vol 15, No 6, 1984

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Effects of Hematocrit Variations on Cerebral Blood Flow and Oxygen Transport in Ischemic Cerebrovascular Disease

Cited by 93 publications

References 13 publications

Optimal hematocrit for maximal exercise performance in acute and chronic erythropoietin-treated mice

Optimal hematocrit for maximal exercise performance in acute and chronic erythropoietin-treated mice

Effect of hemodilution on cerebral hemodynamics and oxygen metabolism.

A randomized controlled trial of hemodilution therapy in acute ischemic stroke.

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