The present investigation was undertaken to evaluate the effect of isovolemic hemodilution with 3% albumin per se on the prevention of microvascular venous thrombosis, using an experimental model in rats mimicking the thrombotic mechanisms similar to those in clinical situations. Male Wistar rats were allocated into two groups of 15 rats each: group 1, the nonhemodiluted group, consisted of animals submitted to microsurgical procedure to induce thrombosis without previous hemodilution; group 2, the hemodiluted group, consisted of animals submitted to microsurgical procedure to induce thrombosis with previous hemodilution. The histopathological examination clearly showed that the nonhemodiluted group presented well-defined venous thrombosis in the anastomoses in 9 animals, totally occlusive in 8, and mural in 1. In contrast, in the hemodiluted group none of the anastomoses presented venous thrombosis, except for the presence of nonadherent blood clots. The clinical analysis of the anastomoses' patency, as evaluated by the empty-full test, showed a significant reduction in rate of venous occlusion in the previously hemodiluted animals as compared with the nonhemodiluted animals 20 min after microsurgical anastomosis. Forty-eight hours after anastomosis, the rate of venous occlusion was 66.7% in the nonhemodiluted group and 33.3% in the hemodiluted group; even though no significant difference could be detected during this time, the patency of anastomoses tended to be greater in the hemodiluted group than that of controls. The rate of spontaneous recanalization after 48 h was identical in both groups (16.6%) in comparison with the rates observed 20 min after the surgical procedure. In summary, moderate isovolemic hemodilution with 3% albumin was effective in reducing the rate of venous microanastomosis occlusion in rats 20 min after the surgical procedure, tending to maintain the anastomoses' patency after 48 h. In addition, 48 h after the microsurgical procedure, the rate of venous thrombosis as evaluated microscopically was significantly lower in the hemodiluted animals as compared with nonhemodiluted control animals. This points out that hemodilution with albumin could be a safe and adequate procedure to prevent thrombus formation at venous microanastomosis.
