The Application Of Dexmedetomidine As A Supplement To Cervical Plexus Block For Thyroidectomy

OBJECTIVE:To observe the effect of dexmedetomidine infusion as a supplement to cervical plexus block for thyroidectomyMETHODS:60 sub-total or total thyroidectomy patients ASAⅠ-Ⅱ, All patients were treated with 0.375% ropivacaine plus 1%lidocaine for unilateral deep cervical plexus and bilateral superfical cervical plexus anesthesia.and the patients were divided randomly into four groups according to the different drugs during operation and 15 patients for each.Group A, patients for intraoperative contions infusion of 0.9% saline as contral after anesthesia.Group B, patient for intravenous infusion of mixture of fentanyl and droperidol auxiliarily. Group C, patients for a loading dose of 1μg kg-1 h-1 of dexmedetomidine give over 10 min,then 0.2μg kg-1 h-1 intravenous dexmedetomidine was maintained until the start of skin closure.Group D patients for a loading dose of dexmedetomidine give over 10 min,then 0.7μg kg-1 h-1 intravenous dexmedetomidine was maintained until the start of skin closure.The changes of SBP, DBP,HR,SPO2 Ramsay sedation scale were monitored. The above parameters were recored at time before cervical plexus(T0),5 minute later(T1),10min later(T2),and at incision (T3), separation of thyroid upper extreme(T4) and suture(T5).VAS score were monitored at T3,T4,T5 to evaluated the pain sense lever. Venous blood sample were taken at T0,T3,T4,T5 for monitor of glucose and determination of plasma concentration of cortisol.The incidence and degree of advese effect suas as repiratory depression, hypotension or bradycardia were recored.The normal distribution data were analyzed by Paied -Sample T test and ANOVA.Significance was established at P<0.05.Result:There were no significant differences of SBP,DBP,HR at T0 among four groups。The value of SBP,DBP,HR were showed significant higher at T2,T3,T4, T5 than T0 in group A and B(P<0.05), In group C and D,SBP,DBP,HR presented a bi-directional changes, SBP, DBP at T2,T3 were higher than at T0,HR at T3 and SBP,DBP,HR at T4,T5 in group C and D showed a decrease tendancy.In group D,the SBP,DBP,HR at T5 were significant lower than at T0(P<0.05).there was no significant differences of SBP,DBP,HR in group A and B at the same time.the values of SBP,DBP,HR were higher in group A and B than in group C and D at T4,T5 (P<0.05).Compared group C and D,the SBP,DBP,HR in group D were lower than in group D at T5(P<0.05).Respiratory depression was discovered in two patients in group B, and rescovery quickly.The values of SPO2 had no statistical significance in four groups in all time point.The Ramsay scales among the four groups are comparable.In time points of T3,T4,T5 the Ramsay scales in group C and group D were higher than in group A and B.(P<0.05),but no differences between group C and D(P>0.05). The pain scores at the incision moment showed no significant differences among the four groups (P>0.05).At the time of separation of thyroid upper extreme(T4),the pain scores of group A and B were significant higher than in group C and D(P<0.05), but there were no significant differences between group A and B(P>0.05),also no significant differences between group C and D(P>0.05).The content of blood glucose and cortisol showed no significant differences at T0 among groups. But the content of glucose and cortisol were higher at T3,T4,T5 than T0 in each group. At T4,T5compared to group A and B, the content of glucose and cortisol in group C and D were lower(P<0.05).but in group A and in group C and D,there was no significant difference(p>0.05).During perioperative time, the BP of 2 patients increased over 160/100mmHg and the HR of 4 patients increased more than 100 bpm in group A.2 patients sufferred respiratory depression at T4 in group B,2 patients had bradycardia in group D.Conclusion:Dexmedetomidine as a supplement to cervical plexus block for thyroidectomy, After a loading dose followed by a maintenance infusion of 0.2p,g kg-1 h-1 or 0.7μg kg-1 h-1 can effectively decrease haemodynamics stress reaction, provide disirable blunting of blood pressure and heart rate undergoing thyroidectomy under cervical plexus block, without respiratory depression,and produce better sedation and analgesia,reduce the content of blood glucose and cortisol. But followed by a maintenance infusion of 0.7μg kg-1 h-1 dexmedetomidine,we should be careful the incidences of adverse effects such as hypotension and bradycardia.