The Effect of Sex on median effective concentration of ropivacaine for ultrasound-assisted caudal block in the elderly undergoing Anorectal Surgery

BACKGROUND: Caudal block is widely employed in pediatric lower abdominal surgeries and adult anorectal surgical by its simplicity of operation, reliable efficacy, and high safety. Previous studies have found that the dose of ropivacaine for Caudal block in adults exhibits gender differences. However, it remains unclear whether such differences in the median effective concentration (EC50) of ropivacaine also exist in the elderly population . METHODS: This is a double-blind, prospective study, We enrolled patients aged 60-80 years with ASA physical status I-? who were scheduled for anorectal surgery under caudal anesthesia, and allocated them to 2 study groups according to their gender. Each p