Haemodynamic changes and skeletal muscle oxygen tension during complete blood exchange with ultrapurified polymerized bovine haemoglobin

Objective: The study investigates the effect of continuous blood exchange with ultrapurified, polymerized bovine haemoglobin (UPBH) in comparison to hetastarch on haemodynamics, oxygen transport and skeletal muscle oxygen tension in a canine model. Design: Sixteen anaesthetized beagle dogs underwent haemodilution with lactated Ringer's to a starting haematocrit of 20 % followed by progressive blood exchange with 6 % hetastarch 200,000/0.5 (HES, group 1) or UPBH (haemoglobin 13 ± 1 g· dl^-1, molecular weight (MW) 32-500,000, group 2) to haematocrit target levels of 15 %, 10 % and 5 % or less. Measurements and results: Besides haemodynamics, skeletal muscle tissue oxygen tension (tPO₂) was measured using a polarographic needle probe. In HES-treated animals, heart rate, cardiac output and blood flow were higher while systemic vascular resistance, systemic and regional arterio-venous oxygen difference (avDO₂) and oxygen extraction ratios were lower when compared to the UPBH group. In spite of a higher final haematocrit of 5 % in group 1, in comparison to group 2 with 2 %, final muscular oxygen uptake (4.7 ± 4 vs 10.1± 2 ml min^-1) and mean tPO, (11.8 ± 2.3 vs 51.1 ± 2.9 mm Hg) were lower in group 1 than in group 2. While tPO₂ histograms were continuously shifted to lower oxygen tensions during progressive haemodilution with HES, UPBH-exchanged animals showed tPO₂ histograms shifted to higher values than baseline. Conclusion: In spite of vasoconstriction, UPBH provided more haemodynamic stability and enhanced skeletal muscle tPO₂ during progressive blood exchange when compared to HES.