Effects of normovolemic and hypervolemic hematocrit variations on muscle tissue oxygen pressure in patients with chronic ischemia of the calf muscle

Abstract

It was the aim of the study to characterize the effects of normovolemic and hypervolemic hemodilution on the muscle pO₂ in the tibialis anterior muscle of patients suffering from chronic arterial occlusive disease (stage IIb according to the Fontaine classification) with a pain-free walking distance below 100 m. To compare various Hct levels (ranging from 30% to 50%), normovolemic and hypervolemic hemodilution was performed either by subsequent withdrawal of whole blood and substitution with hydroxyethylstarch solution (200/0,5) or only by infusion of the same plasmaexpander. At rest, muscle pO₂ readings obtained by a polarographic method (micro-pt-needle electrodes) indicated clearly an impaired oxygen supply as compared to age-matched elderly volunteers. At the extreme ends of hematocrit in this study (Hct 33.75% and Hct 50.60%) muscle pO₂ was significantly decreased as compared to Hct ranging from 38,57% to 45,38%. After a standardized pedal-ergometric exercise test a significant increase of muscle pO₂ (2α<0,005) was found at Hct 40%–42%. Comparing normovolemic and hypervolemic hemodilution, hypervolemia at Hct 40%–42% did not improve muscle pO₂ values after the pedalergometric exercise test. The data indicate, that normovolemic hemodilution towards the lower normal range (Hct 40% - 42%) can indeed improve muscle pO₂ after pedalergometric exercise test in patients with severe intermittent claudication and concomitant increased Hct (Hct > 45%), whereas hypervolemic hemodilution showed no increase of muscle pO₂. Thus, normovolemic hemodilution should be the preferred hemodilution regimen in patients suffering from intermittent claudication.