Abstract

In this randomized, blinded study, we sought to determine whether the vasoconstriction produced by ropivacaine after subcutaneous injection is sufficient to decrease surgical bleeding. Anesthesia was induced in seven piglets (weight, 12.2-20.4 kg) with intraperitoneal thiopental and maintained with intravenous methohexital. Five sites were injected with 10 ml of one of the following solutions: 0.25% ropivacaine, 0.25% bupivacaine, either solution plus 5 μg/ml epinephrine, or saline. Another site was left uninjected for control. Capillary blood flow was measured at each site with a laser Doppler before and ten minutes after the injections. An incision 5 cm in length was then made through the dermis, and blood loss was measured over ten minutes. We found no significant differences in capillary blood flow and blood loss between bupivacaine and ropivacaine. Addition of epinephrine decreased capillary blood flow ( p < 0.05) and tended to decrease blood loss. Capillary blood flow correlated with blood loss (r² = 0.106; p < 0.05). We conclude that, in contrast to previous studies, ropivacaine did not decrease capillary blood flow in our model. Similarly, ropivacaine did not reduce bleeding from surgical incisions. The reason for these surprising results is not clear but is unlikely to be the larger volume of solutions injected because no such effect was observed with saline alone.