Hydroxyethyl starch (HES) 130/0.4 during acute normovolemic hemodilution increases tissue oxygen tension larger and faster than HES 70/0.5 or HES 200/0.5.

Standl et al. (1) contribute new values for muscle oxygen tension (ptO2; mm Hg), which challenge their published scope of baseline ranges, i.e., 21–50 mm Hg (1–12). Inevitably, hyperoxia either increased (from 25 to 99 mm Hg (3,12) or decreased ptO2 (from 43 to 26 mm Hg (11). Hemodilution by administration of crystalloids (hematocrit 25 %) either did not influence ptO2 (10,11) or caused an increase from 32 to 38 mm Hg (8,9). Using HES resulted in ptO2 increases [6% HES 40, hematocrit 32%: from 16 to 23 mm Hg (4); HES 200/0.5, hematocrit 20%: from 35 to 45 mm Hg (5)]. A ptO2 decrease (hematocrit 10%) was related to the diluent [HES 200/0.5: from 29/34 to 14/18 mm Hg (6); crystalloid or crystalloid/HES 70/0.5: from 32 to 18 mm Hg (8,9)]. Presently (1), hemodilution (6% HES 130/0.4, 70/0.5, and 200/0.5) caused increases in the 50th percentile of ptO2 (from 44/49 to 56/60 mm Hg). Notably, the relative changes in the 10th percentile of ptO2 (6 % HES 130/0.4) are advocated for a “larger and faster ptO2 increase” (1), although clearly caused by the varying ptO2 baseline values [18 mm Hg with HES 130/0.4 vs 21.5 or 27 mm Hg (1)]. In addition, ptO2 proved clinically irrelevant due to the lack of normal values.