Administering heparin subcutaneously: an evaluation of techniques used and bruising at the injection site.

This experimental study tested the effects of four different subcutaneous injection techniques on bruising at the injection site. The independent variables of aspiration of the syringe prior to injecting heparin and pressure on the site following injection, and the dependent variable of size of bruising were studied. Aspiration of the syringe had little effect on bruising. After the first injection, fewer subjects who received pressure following the injection had bruising, the difference being significant for females. However analysis of subsequent injections did not support the conclusion that pressure reduces the probability of bruising.