Optimal hematocrit for the maximum oxygen delivery to the brain with recombinant human erythropoietin in hemodialysis patients

Aim: Although hematocrit (Ht) around 33 to 36% has been recommended, Wt of 30% is usually achieved as a target level during recombinant human erythrop oletin (rHuEPO) therapy in the majority of hemodialysis (HD) patients. The present study aimed at estimating an optimal hematocrit (Wt) for the maximu m oxygen delivery to the brain with rHuEPO. Patients and methods: Oxygen de livery was defined as a product of cerebral blood flow and arterial oxygen content (CaO2). The regional cerebral blood flow (rCBF) in each region of i nterest was measured by positron emission tomography and CaO2 was calculate d from hemoglobin concentration, arterial oxygen saturation, and arterial o xygen tension before and after rHuEPO therapy (1500 units, 3 times a week) in 5 HD patients (the mean age of 52 +/- 2 (SEM) years old and the mean HD duration of 98 +/- 21 months). Results: Ht rose significantly from 21 +/- 1 to 31 +/- 1% (p < 0.001) after the 3 -month rHuEPO treatment in associatio n with a significant increase in CaO2 from 7.7 +/- 0.4 to 11.6 +/- 0.3 mi O -2/100 mi (p < 0.01). Hemispheric rCBF decreased significantly from 40 +/- 3 to 32 +/- 1 ml/100 g/min (p < 0.02). In all data both before and after rH uEPO treatment, Wt inversely correlated with the hemispheric rCBF (y =55.7 - 0.76 x, where y is rCBF and x is Wt, r = -0.80, p < 0.01), and positively with CaO2 (y = 0.85 + 0.34 x, where y is CaO2 and x is Ht, r = 0.95, p < 0 .01). By using these correlations, the hemispheric oxygen delivery was expr essed as a function of Wt, being y = 47.3 + 18,3 x - 0.3 x(2), where y is c erebral oxygen delivery and x is I-It. From this curve, Wt at the highest c erebral oxygen delivery in the hemisphere, i.e. an optimal Wt was found to be 35.2%. Above this level of Wt, the hemispheric cerebral oxygen delivery would rather decline. Conclusion: The present study indicated that Wt of ab out 35% is required for a better oxygen delivery to the brain metabolism du ring anemia correction with rHuEPO.