The Effects Of Dexmedetomidine In Controlled Hypotension By Nitroglycerin

Objective:To investigate the effects of dexmedetomidine used in controlled hypotention by nitroglycerin in patients undergoing unilateral total hip replacement.Methods:Thirty ASA I or Ⅱ patients of both sexes, aged 18-65 years old, BMI18～30 kg/m2, scheduled for elective unilateral total hip replacement, were randomly assigned into 2 groups:The control group N(n=15), and the other dose dexmedetomidine group D(n=15).The group N used nitroglycerin in controlled hypotention in 3 minutes after the beginning of the surgery Dexmedetomidine was infused at a rate of 0.5μg/kg/h before the end of surgical important step (the placement of drainage tube) after a loading dose of dexmedetomidine 0.5μg/kg was infused at 10 minutes with the induction of anesthesia in group D, nitroglycerin was infused if necessary in the same way. Anesthesia was induced with target-controlled infusion of propofol (target effect-site concentraiton from 3.0μg/ml) and remifentanil (target effect-site concentraiton 3.0ng/ml). After the patients lost consciousness, cis-atracurium 0.2mg/kg was injected intravenously. The patients were mechanically ventilated after tracheal intubation. Anesthesia was maintained with target-controlled infusion of propofol、remifentanil(target effect-site concentration up to 4.0ng/ml) with end-tidal expiration sevoflurane concentration 1%--1.5%. The bispectral index(BIS) was maintained between 40-60. BIS, mean arterial pressure (MAP), systolic arterial pressure(SAP), diastolic arterial pressure(DAP), heart rate (HR) and rate pressure product (RPP) were recorded after 5 minutes entering the operating room (baseline), at 0,5 and 10 minutes after the beginning of the controlled hypotension, and at 5,10 and 15 minutes after the stopping of controlled hypotension. The operation time, anesthesia time, the total dosages of propofol, remifentanil and nitroglycerin, time for recovery of spontaneous breathing, extubation time, blood lossing, urine and the cases of intraoperative adverse reactions were recorded. Time required to reach the target values, time returned to baseline values, intraoperative increasing or decreasing in the blood pressure and lactate values before or after the the process were also needed.Results:There were no significant difference between the two groups in the operation time, anesthesia time, blood losing and urine. The total dosages of propofol, remifentanil and nitroglycerin were less in group D compared with group N (P<0.05). Compared with group N, time required to reach the target values decreased significantly in group D as with the intraoperative increasing or decreasing in blood pressure (P<0.05). HR in group D decreased significantly at T1～T6 during operation (p<0.05). Compared with group N, RPP in group D decreased significantly at T2 and T3 (P<0.05). Meanwhile, group D had lower RPP at T4 compared with T5 after the stopping of controlled hypotension (P<0.05). Lactate values were no significant between the two groups. Time for recovery of spontaneous breathing decreased significantly in group D.Conclusions:Dexmedetomidine can improve the effect of controlled hypotension by nitroglycerin, witch could make the process more stable.