Using galvanic skin response (GSR) value to measure peripheral block efficiency

OBJECTIVE: Successful brachial nerve blockade is determined by local vasodilation, increased local blood flow, increased skin temperature, and evaluation of sensory and motor functions due to sympathetic fiber blockade. However, these clinical findings may not appear quickly enough to confirm the adequacy of nerve blockade, especially before or during intensive operating room conditions, and may not be used in clinical decision. Traditional methods are time consuming and require patient cooperation to assess block success. We aimed to show that the Galvanic Skin Response (GSR) value, which is a non-invasive method that does not require patient cooperation for the success of the block, can be a reliable and objective method to evaluate the adequacy of peripheral nerve blocks. METHODS: It was planned as a prospective observational study. Fifty patients, ASA 1-2, aged 18-65 years, who underwent orthopedic surgery to the proximal upper extremity elbow were included in the study. Demographic data (age, gender, weight, height), laboratory parameters (hemoglobin, hematocrit, platelet, Na, K+, Ca+), hemodynamic parameters (HR, NIAB, SpO2) of the patients were recorded. The GSR values of the patients before and after the block at 0, 5, 10, 15, 30 minutes and postoperative 0, 15, 30 minutes were recorded from the 2nd and 3rd fingers of both hands on the arm with and without infraclavicular block. After the block, pinprick, cold sense test and modified bromage scale were evaluated. The patients were taken to the operating table at 30 minutes. RESULTS: Pinprick test was measured as %84 positive in an average of 6,33±1,56 minutes. The mean GSR value for which the Pinprick test was positive was calculated as 383,32±70,79. The hot cold sense test was %88 positive in an average of 5,27±1,06 minutes. The mean GSR value for which the hot-cold sense test was positive was calculated as 339,35±88,82. The modified bromage scale test stage-2 was positive at 6,40±1,33 minutes and the mean GSR value measured in this period was calculated as 395,74±49. The modified bromage scale test stage-3 was positive at 11,65±1,60 minutes, and the mean GSR value measured in this period was calculated as 365,96±61,92. As a result of the ROC analysis, a statistically significant difference was found in predicting the success of the block as a result of the pinpyric test and the modified bromage scale test, while no significant difference was found in the hot cold test. CONCLUSION: With this study, it was concluded that GSR can be a reliable and rapid indicator of successful sympathetic blockade when compared with traditional methods. As a non-invasive monitor with easy clinical applicability, GSR has the potential to improve procedural accuracy and efficiency during the performance of brachial blocks. KEYWORDS: Galvanic Skin Response (GSR), Sympathetic block, Infraclavicular block