Abstract: Objective To observe the reactivity of skin temperature changes on blocked area responding to pinprick testing in ultrasound-guided transversus abdominis plane(TAP), and to explore the accuracy of the temperature changes for nerve block effect. Methods A total of 30 patients who underwent lower abdominal surgery were enrolled. Bilateral ultrasound-guided transversus abdominis plane block was performed before operation. After transversus abdominis plane was determined via ultrasound, 30 mL 0.25% ropivacaine was administered for one side. And then 4 points within the blocked area for pinprick testing were randomly selected, and the results of needle test after 10 min and skin temperature changes before and 10 min after injection were obtained. With the point analgesia(positive)as a criterion, the sensitivity and specificity to predict pain via temperature was assessed by analyzing the receiver operating characteristic curve(ROC). The correlation was assessed by calculating Pearson correlation analysis. Results The patients' ROC value of skin temperature changes on blocked area responding to the pain assessment was AUC 0. 882(95% CI 0.796-0.968). Importantly, the ROC analysis displayed that the diagnostic cut-off value was 1.25 ℃, with sensitivity being 84.4% and specificity being 79.2%. The value of Pearsons correlation coefficient was r=0.671(95% CI 0.465-0.67). Conclusion Changes of skin temperature in blocked area after transversus abdominis plane shows high accuracy responding to nerve block effect, which makes skin temperature measuring a good way in determining block success when sensory testing is impossible.

Key words: Ultrasound guided, Transversus abdominis plane, Nerve block, Analgesia, Temperature measuring