The effect of acute haemorrhage and of delayed blood replacement on wound healing: an experimental study.

Haemorrhage whether untreated or with volume replacement delayed for 1 h has been shown by other workers to result in weaker scars 7-10 days after wounding. Studies have been carried out 6 weeks and 3 months after median laparotomy in three groups of Wistar rat: control, bled 10 ml/kg without replacement and bled 10 ml/kg with replacement of heparinized shed blood after 1 h. At 6 weeks the burst pressure of the laparotomy scar was significantly less (Mann-Witney U) in both the haemorrhage group (n = 6; 181.7 +/- 30.5 mmHg s.e.m.; P = 0.026) and the replacement group (n = 6; 207.8 +/- 27.4 mmHg s.e.m.; P = 0.037) than in the control animals (n = 7; 301.9 +/- 42.0 mmHg s.e.m.) At 3 months there were no significant differences between the groups. On histology there was no difference in cellularity between the groups, but in both the haemorrhage and replacement animals collagen was less abundant and less well organized. These differences also had disappeared by 3 months. Neigher collagen nor the fibroblast ultrastructure showed significant differences between groups, all animals showing patchy vacuolation of endoplasmic reticulum of fibroblasts at 6 weeks. It is concluded that oligaemia slows wound healing but does not affect the ultimate strength of the scar.