Minimum effective volume of ropivacaine for ultrasound-guided supra-inguinal fascia iliaca compartment block

Supra inguinal fascia iliaca compartment block (FICB) is increasingly used in elderly patients with hip fractures. However, the minimum effective volume of local anesthetics required for ultrasound-guided supra-inguinal FICB has not been determined. With ethical committee approval and written informed consent from patients, we studied 21 consecutive patients of ASA physical status I–III undergoing surgery for hip fracture who met the inclusion criteria. Blocks were performed before going to the operation room. We determined the injection volumes of 0.25% ropivacaine for consecutive patients from the preceding patient's outcome. The initial volume was 30 ml. The testing interval was set at 10 ml, and the lowest volume was 5 ml. An effective block was defined as loss of sensation of pinprick in the territory of the femoral nerve and lateral cutaneous nerve of the thigh 30 min after the injection. The aim of this study was to determine the 50% effective volume (EV(50)) and the 95% effective volume (EV(95)) of 0.25% ropivacaine for ultrasound-guided supra-inguinal FICB using Logistic regression analysis. EV(50) and EV(95) of 0.25% ropivacaine for ultrasound-guided supra-inguinal FICB calculated with logistic regression analysis were 15.01 ml (95% confidence interval, 6.53–22.99 ml) and 26.99 ml (95% confidence interval, 20.54–84.09 ml), respectively. EV(50) and EV(95) of 0.25% ropivacaine for ultrasound-guided supra-inguinal FICB were 15.01 ml and 26.99 ml, respectively. Clinical trial number: UMIN000027277 (URL https://www.umin.ac.jp/ctr/index-j.htm).