Effect Of Different Controlled Hypo-Tension Methods On The Blood Flow Of The Vertebral Muscle And Cerebral Metabolism In Rabbits

Objective:To explore the effect of different controlled hypotension methods on the blood flow of the vertebral venous and the cerebral metabolism in rabbits.Methods:Eighteen New Zealand rabbits were randomly divided into three groups:group A(with no CH), group B(with CH by nitroglycerin+ esmolol) and group C((with CH by sodium nitroprusside+ esmolol). After propofol intravenous anesthesia and separation of the left femoral artery, connect the femoral artery to blood Pressure gauge. Group A with 20 ml/h of the rate of continuous infusion of Physiological saline. Group B with nitroglycerin 0.5μg/ (kg·min) and esmolol 2.5μg/(kg·min) (nitroglycerin:esmolol is 1:5) as the initial starting antihypertensive, and gradually increase the dose until the blood Pressure to reach the intended target, and according to the heart rate and blood Pressure to adjust the dose. Group C with nitroglycerin 0.5μg/(kg·min) and esmolol 2.5μg/(kg·min) (nitroglycerin:esmolol is 1:5) as the initial starting antihypertensive, and gradually increase the dose until the blood Pressure to reach the intended target, and according to the heart rate and blood Pressure to adjust the dose.(The target blood Pressure is about 70% of basal blood Pressure). The target blood Pressure was reduced from 10 to 15 min in each group, and the decompression speed was less than 10 mmHg/min. After that, the dosage was adjusted according to the change of blood Pressure, and the target blood Pressure was maintained 1h. After all this operation and kept the blood Pressure steadily for 15min and when the MAP achieved to the target blood Pressure, adjusted the dose of each drug to maintain the blood Pressure. Tested the vertebral venous blood flow by ultrasonic measurement system for all these rabbits, measured average for rabbits was the paraspinal muscle blood flow at this time. Rabbit venous blood was used to detect the content of S100B Protein (astrocytes derived Protein) through ELSIA in order to assess the rabbit brain damage.Detected the apoptosis of CA1 neurons in the hippocampus CA1 area in rabbits by TUNEL.Results:1. In group B (64.00±7.772) mmHg and group C (66.00±6.099) mmHg, the blood pressure decreased significantly after controlled hypotension when compared with group A (89.83±4.665) mmHg, P<0.05.2. Compared with group A (0.297±0.070) ml/min, the blood flow in group B and group C were significantly reduced, P<0.05. The blood flow in group B (0.122±0.050) ml/min was significantly reduced when compared with group C (0.148±0.038) ml/min, P<0.05.3. Compared with group A (0.436±0.102) μg/L and group C (0.467±0.163)μg/L, the levels of S100B protein in the serum of the group B (0.768±0.227)μg/L was significant increased, P<0.05.4. Compared with group A(35.67±10.053)%, the apoptotic index of the hippocampus CA1 area in group B(46.50±6.221)% and group C(39.17±12.481)% changed no significantly, P>0.05.Conclusion:Controlled hypotension by nitroglycerin+ esmolol and nitroprusside+ esmolol all can reduce vertebral venous blood flow in rabbits,and controlled hypotension by nitroglycerin+ esmolol can ruduce more blood flow than by nitroprusside+ esmolol;Controlled hypotension by nitroglycerin may cause the damage of brain in rabbits; Controlled hypotension by nitroprusside+ esmolol may be the better choice for spinal surgery.