Search

The hemoglobin solution covalently linked to dextran benzene tetracarboxylate (dex-BTC) described in Part I, offered the following characteristics: [Hb] =70 g/l, non modified Hb < 15%, metHb < 5%, P50 close to blood value, viscosity and oncotic pressure near to physiological values (37°C). It was biocompatible, stable in plasma, non hypotensive in rat model, non pyrogenic and did not present abnormal toxicity (on mice, according to the french Pharmacopea).Nevertheless, on account of the presence of dextran in the conjugate and due to the literature, we observed an anaphylactoïd reaction in rats consecutive to the injections: absence of hypotension but presence of a massive oedema resulting from an important increase in the capillary permeability with harmful consequences to the vascular retention and survival time.As guinea pigs are insensitive to dextran, we are beginning to assess this conjugate solution in this animal. The first results are very promising: a lack of mortality after large injection, an almost complete vascular retention, a weak urinary loss (only non conjugated Hb), and a plasmatic half-disappearance time close to 7h. Results from haemorrhagic shocks to a final hematocrit < 0.10 l/l and total and isovolemic exchange transfusions seem to prove a real oxygen-carrying capacity of this new Hb solution.

Histocompatibility assessment of 70 g/l stroma-free hemoglobin solutions pyridoxylated or not, and purified or not, was carried out using vascular perfusion of the intestine of rats. Mechanical and ultrastructural changes in the organ and the arteriovenous difference of P02 were compared to those obtained with albumin, gelatine and dextran.Overlapping epithelium conserves its structure in the presence of hemoglobin, whereas it is partially or totally destroyed with the plasma substitutes. Nevertheless, with non pyridoxylated hemoglobin there is a strong detachment of the epithelium from the lamina propria. The intestine, irrigated by the hemoglobin solutions shows efficient peristalsis, but this totally disappears with plasma substitutes. For similar arterial P02, for all the solutions, the arteriovenous difference was of 100 mmHg for the hemoglobin solutions, whereas they never exceeded 60 mmHg for the plasma substitutes. Hemoglobin pyridoxylation led to an arteriovenous difference significantly superior (p < 0,001) to those obtained using non modified hemoglobin. With their O2 supply hemoglobin solutions appear able to limit the development of hypoxia in the tissue. The continuation of peristalsis and the weak ultrastructural modifications confirm the slight histological improvement gained when using pyridoxylated hemoglobin. Nevertheless an extravasation appeared constantly, as well as flow reduction during perfusion with the hemoglobin solutions.