The effects of heparin and low molecular weight dextran on survival after fibrinopurulent peritonitis

A surgical model of fibrinopurulent peritonitis in the rabbit was developed by producing ischemic necrosis of the rabbit appendix by 95 percent appendiceal ligation and total devascularization of the organ. Four days after the procedure, mortality due to intra-abdominal sepsis was 95 per cent; however, when appendectomy was performed 18 hours after ligation and devascularization, the four day mortality was reduced to 57 per cent. Using this model of appendiceal ligation followed 18 hours later by appendectomy, heparin and low molecular weight dextran were tested to determine if these agents improved peritoneal bacterial clearance and, thus, enhanced survival from peritonitis. Heparin at the time of appendectomy and low molecular weight dextran on days 1 to 4 were used for their anticoagulant and rheologic properties, respectively. Four day survival after appendectomy was significantly increased after high dose heparin. Low dose heparin did not affect survival time when compared with that for the control rabbits. Low molecular weight dextran improved survival of rabbits with peritonitis; however, this was not statistically significant. Long term surviving rabbits that received high dose heparin had fewer intra-abdominal abscesses and adhesions than did the surviving control rabbits. To determine a possible mechanism for the effects seen in the heparin group, fibrinolytic activity of the peritoneal tissue was measured to see if a correlation existed between increased survival and fibrinolytic activity. Peritonitis significantly decreased peritoneal fibrinolytic activity; however, heparin did not reverse this depression. The beneficial effect of heparin may be through diminished fibrin deposition rather than increasing its breakdown.