Accuracy of laser Doppler capillary flow measurements for predicting blood loss from skin incisions in pigs.

This study assesses the clinical applicability of laser Doppler capillary flow measurements for predicting blood loss from a surgical incision. To produce a wide range of blood flows, we injected lidocaine 1%, lidocaine 1% plus octapressin (0.03 IU.ml-1), and lidocaine 1% plus epinephrine (5 micrograms.ml-1) subcutaneously into three separate sites on the flank of each animal (N = 6). Laser Doppler flow measurements were made before and 10 minutes after injection Subcutaneous injection of lidocaine tended to increase cutaneous blood flow (96 +/- 13 to 153 +/- 30 mV, mean +/- SE, P = 0.09). Blood flow tended to decrease after injection of lidocaine with epinephrine (101 +/- 13 to 57 +/- 10 mV, P = 0.03) or octapressin (108 +/- 20 to 58 +/- 11 mV, P = 0.08). Laser Doppler measurements were higher after the injection of plain lidocaine than after that of lidocaine with either epinephrine or octapressin (P = 0.004). A standard incision was performed at each site and blood loss measured over the subsequent 10 minutes. Laser Doppler measurements correlated with the amount of bleeding from the surgical incision (R = 0.69, P less than 0.001). We conclude that the laser Doppler is a useful tool for evaluating the ability of subcutaneously injected local anesthetics (vasodilators) or vasoconstrictors to alter bleeding from skin incisions.