Effect of injection duration and local pressing duration on subcutaneous hemorrhage after the subcutaneous injection of low molecular weight heparin

Objective To investigate the effect of two different injection durations and four local pressing durations on the incidence of subcutaneous hemorrhage after low molecular weight heparin, and find a optimum injection duration and pressing time to reduce the incidence of subcutaneous hemorrhage associated with subcutaneous low molecular weight heparin. Methods 80 patients, who were deep venous thrombosis (DVT), pulmonary embolism (PE), and undergone inferior vena cava filter (IVCF) after the operation and received low molecular weight heparin (LWMH) for eight times were selected. The injection time and pressing duration after the injection were randomized into 30 s and 2 min, 30 s and 6 min, 30 s and 10 min, 30s and 14 min, 10s and 2 min, 10s and 6 min, 10 s and 10 min, 10 s and 14 min respectively. The incidence of subcutaneous hemorrhage were measured after 12 h. Single and multiple factor logistic regression analysis were used to analyze the data. Results The injection time and pressing duration after the injection were randomized into 30 s and 2 min, 30 s and 6 min, 30 s and 10 min, 30 s and 14 min, 10 s and 2 min, 10 s and 6 min, 10 s and 10 min, 10 s and 14 min respectively. The results of the incidence rate of subcutaneous hemorrhage were 46.25% (37/80), 22.50% (18/80), 23.75% (19/80), 25.00% (20/80), 71.25% (57/80), 43.75% (35/80), 50.00% (40/80), 50.00% (40/80) respectively. By the single factor test, the results showed that pressing duration and injection duration are associated with the incidence of subcutaneous hemorrhage after low molecular weight heparin. With regard to the incidence of subcutaneous hemorrhage, there was significantly difference between 2 min group and the other 3 groups (P 0.05). By multiple factors logistic regression analysis, it was revealed that pressing duration and injection duration were significant factors (P |b'(pressing duration)|=|-1.0729|). Compared with inject 10 s, there was a significantly lower incidence of bruising in inject 30 s. There was a significantly lower incidence of bruising in the longer pressing duration (b |b'(pressing duration)|). Compared with inject 10 s, there was a significantly lower incidence of bruising in inject 30 s (b<0). there was significantly difference between 2min group and the other 3 groups (P<0.01), while other adjacent groups had no significant differences. Compared with others, there was a significantly high incidence of bruising in pressing 2min and the pressing duration for at least 6 min. Conclusions It is suggested that inject 30 s with pressing for 6 min can effectively reduce the incidence of subcutaneous hemorrhage resulted from subcutaneous injection of LMWH. Key words: Low molecular weight heparin; Subcutaneous injections; Hemorrhage; Pressing duration; Injection duration