Dexmedetomidine Controlled Hypotension Is Used In The Research Of Brain Protection In Spinal Surgery

Objective:To observe the safety of dexmedetomidine（DEX）on controlled hypotension in spinal surgery and its effect on cerebral oxygen extration rate,POCD and inflammatory factors.This study aims to investigate the tole of DEX on cerebral protection and its potential mechanism.Methods:Forty patient which received posterior approach lumbar interbody fusion surgery under general anesthesia were randomly divided into two groups:twenty patients received DEX（D group）and other twenty patients received nitroglycerin（N group）.All patients applied the same anesthesia induction with controlled hypotension ten minutes before operation.The load dose of DEX was 1.0μg·kg^-1 of computerized infusuion pump for10 mins,then applied a maintained dose of 0.2μg·kg^-1·h^-1 in D group;While for N group,the patients recieved intravenous injection of nitroglycerin at a dose of 2μg·kg^-1,at the beginning of operation,the two groups were injected with a maintained dose of 0³μg·kg^-1·min^-1.The aim of experiment was to lower the mean arterial pressure（MAP）20-25%compared to base pressure.MAP and hear rate（HR）were recorded in both groups at different time points,blood-oxygen difference of artery-jugular vein（Da-jv0₂）and cerebral oxygen extration rate（CER0₂）were recorded as well.The levels of inflammatory factors（IL-6,TLR-4,TNF-α）were measured with blood from jugular vein at different time points too.Results:MAP was significantly decreased in both groups（P<0.05）while There was no difference of MAP 15 mins after controlled hypotension;HR in D group was significantly decreased 15 mins after controlled hypotension and 15 mins after the termination of controlled hypotension compared to N group（P<0.05）;there is no statistical significance between two groups of Fromme and blood loss during operations（P>0.05）;nitroglycerin dose in D group is significantly decreased compared to N group（P<0.05）;BIS index in D group 15 minutes after administration decreases,and lowered compared to N group,significance exists（P<0.05）,no significance exists when compared to other group timings（P>0.05）.Da-jv0₂ and CER0₂ were significantly decreased in D group at insion,key procedure and accomplishment of operation（P<0.05）.TNF-αand TLR4 increased at T2time point,reached peak at T5 time point and started to decrease at T7in both groups.Significance existed at T3,T4,T5,T7 time points compared to T1 in the same group（P<0.05）;IL-6 started increase at T2,reached peak at T7 in both groups,IL-6 level at T3,T4,T5,T7 time points was significantly increased compared to T1 in the same group（P<0.05）;IL-6、TLR4 and TNF-αlevels were significantly lowered at T3,T4,T5,T7time points in D group compared to N group respectively（P<0.05）;Score of MMSE and POCD cases are significantly lowered compared to those of N group（P<0.05）.Conclusions:DEX is safe to be applied in controlled hypotension in spinal surgery,haemodynamics is stable during operation.DEX is better in controlled hypotension compared to nitroglycerin.DEX could decrease the use of nitroglycerin and other drugs,and decrease the expression of TLR4、IL-6、TNF-αso as to lower inflamatory response.DEX could decrease cerebral oxygen extration rate and lower mental dysfunction rate after surgery.DEX exhibits its neuro-protection role by decreasing inflamatory response and POCD incidence rate.