Effect of hemodilution on maximal oxygen consumption, blood lactate response to exercise and cerebral blood flow in subjects with a high-affinity hemoglobin

Abstract: 10 subjects with Hb Linkdping (β 36 Pro>Thr), a high-affinity hemoglobin variant, with a P₅₀ of 2.2 kPa (16.5 mm Hg) were investigated before and 3–4 days after normovolemic hemodilution. Blood hemoglobin concentration decreased from 176 ± 13 (SD) to 146 ± 15 g 1^-1and the red cell volume from 2.77 ± 0.83 to 2.23 ± 0.67 1. Maximal oxygen consumption decreased slightly by 2.7 ± 3.8 ml min^-1kg^-1and maximal exercise power by 11 ± 23 W; these changes were, however, not statistically significant. Maximal heart rate was unchanged (— 1.1 ± 6.4 beats min^-1) while submaximal heart rate was consistently increased on comparable loads after hemodilution compared to before. The exercise ECG was normal both before and after hemodilution. Capillary lactate levels at exercise were always higher after hemodilution than before. Cerebral blood flow was normal both before and after hemodilution in all subjects but one who had a high flow. The grey matter blood flow increased slightly but significantly by 8.6 ± 10.3 ml min^-1100 g^-1from before to after hemodilution. The results indicate that subjects with Hb Linkoping have only limited benefit from their increased blood hemoglobin concentration.