Anticoagulant activity and operative blood loss after intrapulmonary heparin

The safety and efficacy of heparin given by the intrapulmonary route are further assessed in this study. A single dose of heparin (2000 units/kg) was given by intratracheal instillation in dogs and measurements of plasma heparin concentration, whole blood clotting time and partial thromboplastin time made at intervals for 48 h. These values rose progressively and in parallel for 7 h and remained elevated for 48 h. A series of operations was performed on dogs within 3 h of a single dose of intrapulmonary heparin (1500 units/kg). Operations involving minimal dissection (small bowel resection) and extensive dissection (resection of muscle) were performed in two separate groups. Within each group the animals were randomly given heparin or saline. In the limited dissection group there were no differences in operative blood loss, wound healing, or sequential haemoglobin and haematocrit measurements. In the group subjected to muscle resection there was increased postoperative wound drainage and a slightly greater fall in haemoglobin and haematocrit in those given heparin. It is concluded that heparin is absorbed from the lung causing significant changes in coagulation parameters. Even with the relatively high dose of 1500 units/kg, operations were performed with minimal hazard. Intrapulmonary heparin may have important clinical applications after further investigation.