Subcutaneous heparin, plasma heparin levels and postoperative wound haematoma.

Ninety-five patients, over the age of 40, having general surgical operations, were randomly allocated to a control and test group. The test group received 5000 units of subcutaneous heparin two hours before operation and then 12-hourly for seven days. The patients in the control group received the same regimen of isotonic saline. There was a marked variation in the plasma heparin levels from patient to patient, and from day to day in the same patient. There was a significant increase in the incidence of wound haematoma in patients with a plasma heparin level greater than 0.2 units/ml. The results suggest that the increased incidence of wound haematoma previously reported is due to the increase of incidence in patients who have plasma heparin levels greater than 0.2 units/ml.