Background: Dexmedetomidine is a sedative adjunct with sympatholytic properties. Despite many beneficial effects, hemodynamic effects limit its use.

Methods: We performed a secondary analysis of the data from TKADEX study. This single-center, double-blind, two-arm study compared intranasal dexmedetomidine premedication (1 μg kg-1) with intranasal saline in 101 planned subjects undergoing total knee arthroplasty (TKA). We analyzed the perioperative hemodynamics, oxygenation, amount of intraoperative bleeding and perioperative change in hemoglobin and thrombocytes.

Results: Compared to baseline measurements, mean arterial pressure (MAP) decreased in the dexmedetomidine group 36.3 (1.7) mmHg (95 % CI 32.9-39.7; p < 0.001) and in the placebo group 26.5 (1.7) mmHg (95 % CI 23.2-29.7; p < 0.001), and heart rate (HR) in the dexmedetomidine group 11.6 (1.3) bpm (95 % CI 9.1-14.1; p < 0.001) and in the placebo group 9.7 (1.2) bpm (95 % CI 7.3-12.2; p < 0.001) after induction of spinal anesthesia. Patients in the dexmedetomidine group had lower intraoperative MAP (maximal difference - 8.5 (2.5) mmHg; 95 % CI -13.5 - -3.5; p < 0.001) and HR (maximal difference - 6.1 (2.2) bpm; 95 % CI -10.5 - -1.7; p = 0.007) compared to the placebo group. There was higher incidence of intraoperative hypertension in the placebo group (p = 0.03). There was no difference in oxygenation, in the incidence of intraoperative bradycardia, tachycardia or hypotension, in the amount of intraoperative bleeding or in the change in perioperative blood count between the groups.

Conclusions: Intranasal dexmedetomidine appears to be hemodynamically well tolerated premedication for patients undergoing TKA under spinal anesthesia. It appears to lower the incidence of intraoperative hypertension without effects on intraoperative bleeding.