Effects of Dexmedetomidine on the Heart Rate Variability in Patients Undergoing Lower Limbs Operations with Application of Tourniquet / 中国医科大学学报

ABSTRACT

Objective To evaluate the effects of dexmedetomidine on the hemodynamics and the heart rate variability(HRV)in patients under-going lower limbs operations with application of tourniquet. Methods Forty patients undergoing lower limbs operations with application of tourni-quet were randomized assigned to dexmedetomidine group(group D,n=20)or control group(group C,n=20). After combined spinal-epidural anesthesia,group D received a continuous infusion of dexmedetomidine(0.5μg/kg for 10 min for loading dose and followed by 0.2μg·kg-1·h-1) until tourniquet deflation. The control group received normal saline instead. Mean arterial pressure(MAP),heart rate(HR),saturation of pulse ox-imetry(SpO2),low frequency power(LF),high frequency power(HF)and LF to HF ratio(LF/HF)were recorded at regular time pointsimme-diately before loading dose(T0),before tourniquet inflation(T1),15 min after tourniquet inflation(T2),30 min after tourniquet inflation(T3),45 min after tourniquet inflation(T4),60 min after tourniquet inflation(T5),1 min after tourniquet deflation(T6),5 min after tourniquet deflation (T7)and 10 min after tourniquet deflation(T8). Results Compared with T0,the MAP of group D significantly decreased at T6-T8(P0.05). Compared with T2-T5,the MAP of group C significantly decreased at T6(P0.05). Compared with T0,the HF of group D significantly increased and the LF/HF of group D significantly decreased at T1-T4(P<0.05). Compared with group C,the HF of group D significantly increased and the LF/HF of group D significantly decreased at T1-T4(P<0.05). Conclusion The appropriate dose of dexmedetomidine(loading dose 0.5μg/kg and maintenance dose 0.2μg · kg-1 · h-1)can significantly increase vagal tone and improve cardiac sympathetic and parasympathetic balance during tourniquet appli-cation.