Optimal hematocrit in patients with peripheral occlusive arterial disease (POAD): Exercise induced muscle tissue pO2 after isovolemic hemodilution

Abstract

Isovolumetric hemodilution (IHD) is an established therapeutic procedure to improve chronic ischemia in patients suffering from intermittend claudication of the lower limbs. It is, however, still subject of discussion at which hematocrit the relation between blood flow properties and oxygen carrying capacity of blood is at its optimum in this defmed ischemic disease. The aim of the present study was to characterize the influence of hematocrit variations on the muscle tissue oxygen supply as the defmed muscle tissue pO2 in these patients at rest and afte exercise. Design, Material, and Methods: IHD was performed twice within 14 days in 23 patients (age: 41–72yrs) with a painfree walking distance less than 100 by withdrawl of whole blood and subsequent infusion of the same amount of a 10% hydroxyethyl starch solution 200/0.5 (HAES steril 10%, Fesenius, Oberusrsel Germany). Measurements of muscle tissue pO2 in the anterior tibial muscle (micro-needle-electrode method according to Ehrly and Schroeder) were performed regularly three days before and after pedalergometric exercise in parallel to several other hemodynamic and hemorheological tests. Results: At rest muscle tissue pO2 reading revealed an impaired oxygen supply at high (51 and low (34%) hematocrit values whereas an increase was found with hematocirt levels in ther normal range (approx. 40%). Mter excercise, significant increase of the muscle tissue pO2 was found exclusively at hematocrit levels of 40%–42%. This increase was accompanied by a “normalisation” of the execise induced pattern of “reactive hypoxia” as defmed by micro-needle-electrodes. Conclusion: In patients suffering from intermittent claudication IHD towards a hematocrit of 40%–42% resulted in improvement of muscle tissue oxygen supply and execise conditions. Further reduction of hematocritto hematocrit levels below 38% impairs muscle tissue oxygenation. Thus, for conservative treatment strategies, isovolemic hemodilution should be applied regularly and “optimal hematocrit” is the lower boderline of the normal range (40%–42%).