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The hemodynamic effects of acute hemodilution with dextran 70 as dilutional agent were evaluated in a group of elderly patients (mean age 68, range 60-79 years) anesthetized with neurolept analgesia. The isovolemic exchange of 1.1 liter of blood (mean) with a 6% solution of dextran 70 decreased the hematocrit value from 41 to 28%. As cardiac index did not exchange, the oxygen transport capacity was significantly reduced. The main compensating mechanism for this was an increased extraction of oxygen in the tissues and, to a minor extent, a raised arterial oxygen tension. The results of this study suggest that intentional hemodilution should be used with caution in aged patients.

The effects on the circulation of limited normovolaemic haemodilution with dextran 70 and subsequent haemorrhage to a mean arterial pressure of 60 mm Hg were studied with isotope-labelled microspheres in the dog. Following haemodilution, cardiac output, stroke volume and systemic oxygen transport increased. The distribution of oxygen to the heart, liver (hepatic artery), spleen and carcass (mainly muscle, skeleton and skin) was increased, while a decrease in oxygen supply to the brain was found. Following haemodilution and haemorrhage, cardiac output, systemic oxygen transport and mixed venous oxygen tension decreased. Blood flow was redistributed to maintain the cerebral, renal, hepatic arterial and coronary circulations, mainly at the expense of blood flow to the carcass and through systemic arterio-venous shunts. Thus, limited normovolaemic haemodilution does not affect the normal circulatory response to moderate haemorrhagic hypotension.