Thermography in Anesthetic Peripheral Nerve Blocks When Using Different Local Anesthetics

Background: Peripheral nerve blocks in regional anesthesia are operator skill dependent and are not always successful, which leads to patient discomfort and post-operative pain. The methods of determining a failed nerve block are based on subjective feelings of the patient - loss of sensation and motor functions, which take time to set in and can be often misleading. This study examines thermography, an objective, quantitative method for determining the success of a nerve block and extrapolates the practical meaning of our findings for clinical practice. Methods: In this study, done in Hospital of Traumatology and Orthopedics in Riga, 55 patients undergoing N.Ischiadicus block with different local anesthetics in equipotent doses were enrolled. Three different local anesthetics for nerve blocks were used - lidocaine, bupivacaine and ropivacaine, all in equipotent doses. After the nerve block, the region anesthetized was pictured with a thermography camera for 45 minutes for detection of temperature changes. Results: After analyzing the data, we concluded, that there is no practical significant difference between various local anesthetics and time for skin temperature changes, at least 15 minutes must pass before judging the success of a nerve block, this method is less reliable in acute bone fractures, the lower the initial temperature, the faster observable temperature increase.