Review article: The present state of hemodilutional therapies: Potentials and limits of the most potent tool of “clinical hemorheology”

Abstract

Strictly normovolemic. individualized exchange hemodilution is rapidly developing into the most potent therapeutic remedy of clinical hemorheology. Firm evidence from critically ill patients show that resolute reduction of the hematocrit level down to around 0.33 l/l is both safe and efficient in the treatment of various localized and global low flow states (or “hypokinetic” circulatory situations), provided that anaemia is accompanied by careful (and if possible monitored) maintenance of the cardiovascular filling pressure. Under these conditions the oxygenation and the performance of the myocardium (14) is maintained, as is the peripheral vascular bed in patients with decompensated POAD (30). The significance of the latency between critical vascular incidents (shown in central retinal artery occlusion (27)) has come to the forefront. Urgency of treatment and the recruitment of expert intensive care competence has now led to the administration of “custom taylored hemodilution” in the treatment of cerebrovascular stroke. As shown by the success of the AMSTERDAM STROKE STUDY (Goslinga et al. 1992), when carefully separating exsiccated from non-exsiccated patients, mortality in both groups can be dramatically reduced by either aggressive rehydration or custom-taylored exchange hemodilution (Hct 0.32 l/l, pulmonary capillary wedge pressure 12 mmHg). Reduction of mortality from the conventional value of 30% down to 16 or 9%, accompanied by an elevation of full rehabilitation from 34 to 59 (and 48%) by far exceeds the success of any competing form of therapy. As an explanation for the obvious success of induced anaemia, the new paradigm of “optimum circulatory stability” for hypokinetic states by means of normovolaemic dilution has been formulated from theoretical, experimental and clinical studies. It focusses on the preponderance of benefits from iatrogenic dilution over normal hematocrit in bed ridden patients, and is set in opposition to the paradigm of “maximum oxygen transport efficacy”, which is largely irrelevant in low flow states.