Relationship between Temperature and Pain Sensation Following a Peripheral Ulnar Block: An Exploratory Pilot Study

Objectives In recent years, measuring skin temperature has been studied as a potential method for predicting the success of peripheral nerve blocks. However, additional research is needed. This study aimed to explore the temperature course following a peripheral Ulnar Nerve Block (UNB). Methods An exploratory observational study was conducted in which an ulnar nerve block at the wrist was performed on healthy volunteers using 1% lidocaine (1 ml). Skin temperature was measured using probes and analyzed in relation to pinprick testing, with detailed temperature profiles depicted as graphs to allow visual analysis of temperature variations. Additionally, temperature at specific time points was analyzed based on changes in pinprick testing and/or temperature. Results Ten UNBs were performed on five subjects. The temperature profiles revealed an increase in temperature in all 10 cases, with a median temperature of 34.2°C (range 33.7–34.7) during the plateau phase. A gradual decrease in temperature was observed in nine out of ten UNBs before the return of pain sensation, with a median duration of 20.0 minutes (range 5–43) and a median decrease of 1.1°C (range 0.5–4.1). Conclusion The temperature course following a peripheral ulnar nerve block was analyzed in this study. Based on the results, skin temperature is suggested to serve as an indicator of a successful nerve block. Additionally, it is suggested that the temperature decreases prior to the return of pain sensation, which could be used to infer a declining block in clinical practice.