Effects Of Hypothermia On Cerebral Oxygen Metabolism In Adult During Cardiopulmonary Bypass

Backgroung and Objective:The brain is the most active energy metabolism and the largest oxygen metabolism in the organ of the body The blood supply to the brain is rich Even in the stationary state, cerebral oxygen consumption accounts for 20% -25% of human body oxygen consumption Cerebral oxygen supply and demand balance is the key point of this study during cardiopulmonary bypass in cardiac surgeryAutoregulation of cerebral blood flow is a sensitive mechanism,which can be impaired by various pathological conditions.As its disruption makes cerebral blood flow mainly dependent on pressure,.Thus, the knowledge about possible changes in cerebral autoregulation may have an impact on various aspects of perioperative management of patients undergoing open heart surgery. Although the influence of such methods of CPB conduct, as pH-stat vs alpha-stat approach of pH management on the cerebral autoregulation was studied extensively, scarce data exist concerning changes in cerebral autoregulation in the postoperative period.We avoided hypercapnia, hypotension, and the use of inhalation agents; all these factors are known to affect cerebral autoregulation. However, increased brain uptake of oxygen in the blood, which did not still fully compensate for the oxygen supply, cerebral oxygen consumption will be reduced, anaerobic metabolism of lactate will increase Hypothermia is widely used for cerebral protection during cardiopulmonary bypass By measuring arterial blood oxygen saturation and arterial blood oxygen pressure did not fully reflect the above characteristics herefore, we hope that by measuring the internal jugular vein bulb oxygen saturation (SjvO₂), calculating the rate of cerebral oxygen uptake (ERO₂) may better reflect the situation in cerebral oxygen metabolism, providing a basis for clinical work.In this experiment, the object is adult cardiac patients. To observe hypothermia on cerebral oxygen metabolism in adults and choose the right temperature of the brain ,which provide the basis for cerebral protection MethodsThirty patients, ASA gradedâ…¡-â…£, without history of hypertension, diabetes mellitus, lung disease, and without severe dysfunction of liver and kidney, underwent cardiac operation during cardiopulmonary bypass under general anesthesia were divided in group A(shallow hypothermia 30℃) B(deep hypothermia 20℃) By monitoring the artery, jugular vein and mixed venous oxygen content and lactate concentration, calculation of systemic and cerebral arteriovenous oxygen content difference, oxygen uptake rate and the arteriovenous lactate concentration difference Intramuscular injection of morphine 0.1mg/Kg, scopolamine 0.01mg/Kg prior to anesthesia All the patients into the operating room followed to monitor blood pressure (BP), heart rate (HR), oxygen saturation (SpO₂). All the patients accepted right radial artery catheter puncture in Lidocaine local anesthesia to monitor blood pressure and mean arterial pressure (MAP) through pressure transducer Induction of anesthesia: midazolam 0.1mg·kg^-1, etomidate 0.15mg·kg^-1, vecuronium 0.1mg·kg^-1, sufentanil 0.75μg·kg^-1, followed by slow intravenous Note. Three minutes after injection, rapid tracheal intubation, endotracheal intubation and monitoring of respiratory parameters and end-tidal carbon dioxide partial pressure (PETCO₂), Respiratory parameter settings: tidal volume (VT) as 10ml/kg, respiratory rate (RR) 12 times / min, inspiratory to expiratory ratio (I:E) 1:2, the oxygen flow rate 2.0L·min^-1. Maintain PETCO₂ at 30 35mmHg. After anesthesia, jugular vein catheterization to prepare and monitor central venous pressure forces blood transfusion (CVP) Maintenance of anesthesia: endotracheal intubation: infusion of fentanyl 0.1μg·kg^-1·min^-1, an additional vecuronium 0.03mg·kg^-1, during the operation: five minutes prior to incision , continuouing infusion fentanyl 0.2μg·kg^-1·min^-1, vecuronium 0.03mg·kg^-1·min^-1, 1 to 2% inhaled sevoflurane anesthesia. Cardiopulmonary bypass with a Stockert CPB machine method, application Medtronic membrane oxygenation. Priming for the Ringer solution 1500 2000ml,plasma substitue 500ml Flow rate of 60⁸0mg·kg^-1·min^-1. Moderate hemodilution (HCT 0.18⁰.22). A group, temperature control in 30℃, B group in 20℃. Aortic root infusion of cold crystalloid cardioplegia circulatory arrest. ACT remained at more than 400s. The water temperature and nasopharyngeal temperature difference is less than 10℃during rewarming Temperature to nasopharyngeal temperature-based, before turning machine when the temperature is 36℃(T1), when the temperature reaches the required temperature and time stability of ten min (T2), rewarming to 36℃(T3)and time stability of ten min when stoping machine To take the radial artery and internal jugular venous blood to monitor blood gas withαrespectively, According to blood gas, monitoring arterial blood oxygen saturation(SaO₂) and jugular venous oxygen saturation(SjvO₂) values, arterial blood lactate (AL), jugular venous blood lactate concentration (VL) By the following formula ,calculating artery and internal jugular venous oxygen content (CaO₂, CjvO₂), arterial and jugular venous oxygen content difference(Ca-jvO₂) and cerebral oxygen extraction rate(ERO₂), cerebral lactate production (ADVL) CaO₂=(Hb×1.36×SaO₂)+(0.003×PaO₂); SaO₂: arterial oxygen saturation; PaO₂: arterial oxygen CjvO₂=(Hb×1.36×SjvO₂)+(0.003×PjvO₂); SjvO₂: jugular venous oxygen saturation; PjvO₂: jugular venous oxygen partial pressure Ca-jvO₂=CaO₂-CjvO₂=Hb×1.36×(SaO₂-SjvO₂)+0.003×(PaO₂-PjvO₂) ERO₂=(CaO₂-CjvO₂)/CaO₂×100% ADVL= AL-VLResults CaO₂,CjvO₂and ERO₂ of the two groups were significantly reduced(P<0.01, P<0.05) after initiation of hypothermia In groupA, Ca-jvO₂ and ERO₂ were higher(P<0.05, P<0.01) than those in group B at the T2 time point. The lactate concentration increased in both groups during CPB, but ADVL in arterial and jugular vein blood in two groups did not change significantly(P>0.05) at the same time points. Ca-jvO₂ at the T1 time point was both higher(P<0.01) than that at the T3 time point in the two groupsConclusions Total cerebral oxygen balance of the two groups patients is maintained during CPB. But lactate will further increased after CPB termination. However, whether hypothermia have impact on cerebral oxygen metablism, should be studied further...