Genetically engineered serine protease inhibitor for hemostasis after cardiac operations

A genetically engineered human Kunitz protease inhibitor with increased kallikrein inhibition in an ovine model of cardiopulmonary bypass

A recombinant human serine protease inhibitor known as Kunitz protease inhibitor (KPI) wild type has functional similarities to the bovine Kunitz inhibitor, aprotinin, and had shown a potential to reduce bleeding in an ovine model of cardiopulmonary bypass (CPB). The aim of this study was to assess KPI-185, a modification of KPI-wild type that differs from KPI-wild type in two amino acid residues and which enhances anti-kallikrein activity in a further double-blind, randomized study in an ovine model of CPB, and to compare with our previous study of KPI-wild type and aprotinin in the same ovine model. Post-operative drain losses and subjective assessment of wound 'dryness' showed no significant differences between KPI-185 and KPI-wild type, despite the significant enhancement of kallikrein inhibition using KPI-185 seen in serial kallikrein inhibition assays. These preliminary findings support the hypothesis that kallikrein inhibition is not the major mechanism by which Kunitz inhibitors such as aprotinin reduce perioperative bleeding.

Role of aprotinin in the management of patients during and after cardiac surgery

Management of patients undergoing cardiac surgery has evolved in recent years as more is understood about the physiological changes and responses that occur during and after cardiopulmonary bypass (CPB). In particular, our understanding of the mechanisms involved in haemostasis and in the inflammatory response to bypass surgery, has allowed significant refinements in patient management. Improvements in the pharmacological conservation of blood loss have been striking, particularly with the development of the serine protease inhibitor, aprotinin (Trasylol, Bayer). Aprotinin represents a significant improvement, especially for patients at high risk, since it reduces the need for allogeneic and (sometimes scarce) blood products. However, in view of its cost, making an appropriate selection of patients most at risk of serious blood loss is a major consideration in the use of aprotinin. While its mechanisms of action are not well understood, the use of aprotinin also appears to reduce inflammatory response to CPB.

Recombinant Kunitz protease inhibitor ameliorates reperfusion injury in rat lung transplantation

BACKGROUND

Recombinant Kunitz protease inhibitor (rKPI-BG022) is more homologous to human Kunitz protease inhibitor than is aprotinin. Because aprotinin has been reported to inhibit free radicals, we hypothesized that rKPI would ameliorate reperfusion injury caused by free radicals. We examined its effect and the timing of administration in an in vivo rat lung transplantation model.

METHODS

All lungs were flushed with low-potassium dextran-1% glucose solution and stored for 24 hours at 4 degrees C, then orthotopic left lung transplantations were performed. Rats were divided into 4 groups (n=6) as follows: group 1 served as control; in Group 2, rKPI was added to the flush solution (10 micromol/L); in group 3, rKPI (5 mg/kg) was administered intravenously to the recipient just after reperfusion; and in group 4, rKPI was added to the flush solution (10 micromol/L) and rKPI (5 mg/kg) was administered intravenously to the recipient just after reperfusion. Twenty-four hours after transplantation, the right main pulmonary artery and right main bronchus were ligated, and the rats were ventilated with 100% O2 for 5 minutes. Peak airway pressure, blood gas analysis, serum lipid peroxide level, tissue myeloperoxidase activity, and wet-dry weight ratio were measured.

RESULTS

The partial oxygen tension values of group 2 were higher than those of groups 1 and 4 (groups 1, 2, and 4: 104.8+/-15.8, 245.1+/-49.0, 101.4+/-4.5 mm Hg, respectively; p < 0.01). The partial carbon dioxide tension values of groups 3 and 4 were lower than those of group 1 (groups 1, 3, and 4: 74.5+/-5.7, 42.0+/-11.0, 46.0+/-8.4 mm Hg, respectively; p < 0.05). Peak airway pressures were lower in groups 2 and 3 than in groups 1 and 4 (groups 1, 2, 3, and 4: 22.5+/-0.5, 18.2+/-0.5, 19.2+/-0.8, 22.5+/-1.1 mm Hg; p < 0.01). Serum lipid peroxide levels in groups 2 and 3 were lower than those of groups 1 and 4 (groups 1, 2, 3, and 4: 0.793+/-0.037, 0.577+/-0.069, 0.560+/-0.029, and 0.785+/-0.053 nmol/mL, respectively; groups 2 and 3 vs group 1, and group 3 vs group 4: p < 0.01; group 2 vs group 4: p < 0.05). There were no differences in wet-dry weight ratio and tissue myeloperoxidase activity between the groups.

CONCLUSION

Recombinant Kunitz protease inhibitor ameliorates reperfusion injury caused by free radicals in an in vivo rat lung transplantation model. Administration of rKPI through the flush solution and intravenous injection after reperfusion were effective separately, but the combination of the two administrations was not effective.

Desmopressin and bleeding during invasive surgery

Peri-operative bleeding is associated with invasive surgery and has traditionally been compensated for by blood transfusion. Concerns about the risk of transfusion-transmitted disease have led to an increasing interest in synthetic haemostatic agents. Desmopressin (1-deamino-8-D-arginine vasopressin), a synthetic analogue of vasopressin, has been shown to be of benefit in the peri-operative management of von Willebrand's disease or mild haemophilia A. This paper addresses the role of desmopressin and bleeding during invasive surgery, particularly during cardiopulmonary bypass. Clinical trials using desmopressin in open cardiac surgery indicate that it may reduce blood loss in those with an excessive bleeding tendency. However, it is difficult to identify this group pre-operatively.