Effect Of Different Doses Of Dexmedetomidine On Blood Pressure And Heart Rate Of Parturients In Cesarean Section Under Spinal Anesthesia

Objective:To observe the effect of different doses of dexmedetomidine on blood pressure and heart rate of parturients in cesarean section under spinal anesthesia.Methods:120 healthy parturients undergoing elective cesarean section were randomly divided into four groups with 30 cases in each group.D₁,D₂ and D₃groups were pumped with dexmedetomidine 0.25μg/kg,0.5/kg and 0.75μg/kg respectively,while group N were pumped with normal saline.After 15 min,D₁,D₂ and D₃ groups were maintained at a dose of 0.5μg/kg/h,while group N were maintained at the same rate of normal saline.The anesthesiologist who recorded the data did not know the grouping of parturients.After the load injection,each group of parturients was subjected to spinal anesthesia by the same anesthetist,and 10 ml/kg of hydroxyethyl starch was infused at the same time.When the measured systolic blood pressure was less than 90 mmHg once or less than 80%of the basal value twice,an intravenous injection of 50μg phenylephrine was given.In case of bradycardia（heart rate less than 60 bpm）,an intravenous injection of 0.25 mg atropine was given.Recording the SBP,HR,phenylephrine and atropine intervention cases at every minutes during the preload pumping and within 20min after spinal anesthesia.Ramsay sedation scores were recorded when four groups of parturients entered the operating room（T₀）,underwent anesthesia puncture（T₁）and took the fetus（T₂）.The number of cases of adverse reactions of reactive hypotension,chest distress,nausea,chills and oxytocin reactions in four groups of parturients were recorded.Umbilical artery and vein blood gas analyses and apgar scores at 1 minute and 5 minute were recorded in four groups.Results:The Ramsay scores of T₁ and T₂ in group N were lower than T_0,with statistically significant differences（P<0.05）.In group D₁,the T₁ Ramsay scores were lower than T₀,while T₂ were higher than T₁ and T_0,with statistically significant differences（P<0.05）.In group D₂ and group D₃,the Ramsay scores of T₂ and T₁ were higher than T₀,T₂ were higher than T_1,with statistically significant differences（P<0.05）.The Ramsay scores of T₁ in group D₃ were higher than group D₂,group D₂ were higher than group N,with statistically significant differences（P<0.05）.There were statistically significant differences about the Ramsay scores of T₂ among to group D₃,D₂,D₁ and N from high to low（P<0.05）.During the preload injection,SBP in four groups and HR in group N and group D₁ changed smoothly,while HR in group D₂ and group D₃were significantly lower than the basic value at the later stage（P<0.05）.After spinal anesthesia,SBP in group N and group D₁ fluctuated significantly,and the difference between the lowest value and the basic value was statistically significant（P<0.05）,while SBP in group D₂ and group D₃ changed smoothly.After spinal anesthesia,the fluctuation range of the first 6 min HR in group N and group D₁ was large,and the difference between the highest and lowest values was statistically significant（P<0.05）.HR changes in group D₂ and group D₃ were relatively stable,but HR in D₃ group remained at the normal low level.The number of phenylephrine intervention cases in group D₂ and group D₃ were less than that in group D₁ and group N（P<0.05）.The number of atropine intervention cases in group D₃ were more than that in other three groups（P<0.05）.The incidence of chest distress,nausea and chills in group D₂ and group D₃ were less than those in group D₁ and group N,with statistically significant differences（P<0.05）.The adverse reactions of oxytocin in D₁,D₂ and D₃groups were less than those in group N,with a statistically significant difference（P<0.05）.Conclusion:Different doses of dexmedetomidine have different effects on blood pressure and heart rate of parturients in caesarean section with spinal anesthesia.The doses of dexmedetomidine in group D₂（0.5μg/kg,0.5μg/kg/h）could significantly reduce the incidence of hypotension after spinal anesthesia,and the incidence of sinus bradycardia is low.Dexmedetomidine has the advantages of sedation,reduction of shivering rate and adverse effects of oxytocin during cesarean section under spinal anesthesia,besides there are no adverse effect on newborns.