Regional blood flow in normovolaemic and hypovolaemic haemodilution. An experimental study

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.