['Percutaneous tunneling (hydrodissection) in the neck and anterior chest in patients undergoing robotic thyroidectomy leads to significant hemodynamic responses such as increases in blood pressure and heart rate. We evaluated whether a single preoperative dexmedetomidine injection attenuated hemodynamic responses to hydrodissection by reducing the half-maximal effective concentration (EC50) of remifentanil needed to maintain hemodynamic stability during hydrodissection.', "Forty-one patients undergoing robot-assisted endoscopic thyroidectomy were randomly allocated to one of the two groups-group D (n\xa0=\xa022) and group C (n\xa0=\xa019) patients received dexmedetomidine 1\xa0µg/kg and normal saline for 10\xa0min before anesthetic induction, respectively. The EC50 of remifentanil for hemodynamic stability during hydrodissection was determined using Dixon's up-and-down method with initial dose (4\xa0and 5\xa0ng/mL in groups D and C, respectively). The concentration of remifentanil for consecutive patients in each group was determined by the response of the previous patient, using increments or decrements of 0.5\xa0ng/mL. Hemodynamic stability during hydrodissection was defined as increased systolic blood pressure <20\xa0% of baseline.", 'The EC50 of remifentanil for maintaining hemodynamic stability during hydrodissection was 0.8\xa0ng/mL in group D and 7.3\xa0ng/mL in group C (p\xa0=\xa00.002).'] Does preoperative dexmedetomidine attenuate hemodynamic responses to hydrodissection in patients undergoing robotic thyroidectomy?