Accuracy of Laser Doppler Capillary Flow Measurements for Predicting Blood Loss from Skin Incisions in Pigs

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Abstract
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-mr−1), and lidocaine 1% plus epinephrine (5 μg-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 < 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.