The Effect Of Acute Hypervolemic Hemodilution Combined With Controlled Hypotension With Nitroglycerin On Cerebral Oxygen Metabolism In Patients Undergoing Spinal Surgery

Objective: To observe the effect of acute hypervolemic hemodilution (AHH) combined with controlled hypotension (CH) with nitroglycerin on cerebral oxygen metabolism and investigate whether AHH&CH can change the balance of cerebral oxygen metabolism.Methods: Thirty ASA I～Ⅱpatients scheduled for internal fixation surgery of thoracic/lumbar vertebrae under general anesthesia were divided randomly into three groups: control group(groupâ… ),AHH(groupâ…¡and AHH&CH(groupâ…¢). In groupâ…¡,patients was infused 6% HES (130/0．4, Voluven) in speed of 50ml·min^-1 and with volume of 15 ml·kg^-1 after induction and before operation . In groupâ…¢,during AHH ,CH was initiated before incision and terminated at 45 minutes prior to the end of surgery, induced with nitroglycerin to maintain MAP at 65%～75% of the basic MAP. Radial artery and right internal jugular vein was cannulated for pressure monitoring and blood sampling. Blood transfusion was considered when Hct<25% or the intraoperative blood loss >20% of blood volume. HR,MAP,CVP,PetCO₂,BIS,TEMP were continuously monitored throughout the operation. Arterial and right internal jugular venous blood samples were taken for measuring CaO₂,CjvO₂,CEO₂,VADL at five time points: T₀(after induction and before AHH/AHH&CH), T₁ (15 minutes after AHH/AHH&CH), T₂(60 minutes after AHH/AHH&CH), T₃(60 minutes before the end of surgery),T₄(at the end of surgery). Hb and Hct must be monitored every 30 minutes during the operation.Result: The intraoperative blood loss was more lower in groupâ…¢than in groupâ…¡and groupâ… (P<0．05) . The intraoperative blood transfusion was more lower in groupâ…¢than in groupâ…¡(P<0．05 ), and more markedly lower than in group I (P<0．01) . In group III and groupâ…¡, Hct after AHH at T₁ T₂ T₃ T₄ was more lower than T₀(P<0．05) . There were no significantly differences between groupâ…¢and groupâ…¡on Hct. Hct at T₄was no differences among three groups and all exceeded 25%. There were no significantly changes among three groups on HR in the study. CVP was markedly increased at T₁ T₂ T₃ in groupâ…¡(P<0．05 ), but all in normal; MAP was markedly decreased at T₁ T₂ T₃ in groupâ…¢(P<0．05) , but all in normal. Differences on MAP and CVP weren't to exist among three groups at T₄．SjvO₂ in groupâ…¡was increased with statistical significance at T₁ T₂ T₃ (P<0．05) , but it isn't in groupâ…¢and groupâ… . In groupâ…¡, SjvO₂ only for two persons exceeded 75% , and it was to recover the original level at the end of opration . In groupâ…¢and groupâ…¡, CEO₂ and Da-jvO₂ were decreased at T₁ T₂ T₃ T₄, while all with statistical significance(P<0．05) , they were also decreased in groupâ… , but statistical significance was to exist at T₃ T₄ (P<0．05) . Markedly differences on VADL wasn't to exist and all in normal among three groups. Conclusions: This study suggests that during AHH the balance of cerebral oxygen metabolism can be well maintained in most patients, but cerebral hyperperfusion might occur in a few patients. It also indicates that cerebral anoxia and cerebral hyperperfusion didn't occur during AHH&CH, AHH&CH can't change the balance of cerebral oxygen metabolism.