Cerebral blood flow and oxygen metabolism during cardiopulmonary bypass with moderate hypothermic selective cerebral perfusion

Effect of resuscitation after selective cerebral ultraprofound hypothermia on expressions of nerve growth factor and glial cell line-derived neurotrophic factor in the brain of monkey

OBJECTIVE

To investigate the expression of nerve growth factor (NGF) and glial cell line-derived neurotrophic factor (GDNF) in monkeys of resuscitation after selective cerebral ultraprofound hypothermia and blood flow occlusion.

METHODS

The monkeys were immediately removed brain after death in operation of group A (identical temperature perfusion group) and group B (ultraprofound hypothermia perfusion group). Immunohistochemical technique was used to determine frontal cellular expression of NGF and GDNF. Statistics were analyzed by ANOVA analyses with significance level at P < 0.05.

RESULTS

The expressions of NGF and GDNF in the group B were significantly higher than those in the group A (P < 0.05).

CONCLUSION

NGF and GDNF increased significantly in the monkeys of resuscitation after selective cerebral ultraprofound hypothermia and blood flow occlusion. It may be a protective mechanism for neuron survival and neural function recovery.

Simulation study of a selective cerebral perfusion system with a single centrifugal pump

We previously successfully developed a simple nonroller extracorporeal circulation system (NRECC). In aortic arch surgery, more than two pumps are generally used for systemic perfusion and selective cerebral perfusion (SCP); we developed a new pressure-dependent perfusion system for SCP based on our NRECC and operated by a single centrifugal pump. The cerebral perfusion line was branched from the main perfusion line, and one 15 French and two 12 French cannulae were used for SCP. The perfusion pressure was regulated with a tube occluder. Afterload was changed from 30 to 80 mm Hg, the pressure of the SCP line was increased from 80 to 200 mm Hg, and flow volume was measured. When the afterload was set at 50 mm Hg, according to the increase of perfusion from 80 to 200 mm Hg, the flow volume of the 15 French cannula increased from 280 to 950 ml/min. Under the same conditions, flow volume of the 12 French cannula increased from 160 to 560 ml/min. Sufficient flow volume of the SCP lines was obtained when the SCP line pressure was over 80 mm Hg. As a result of the increased perfusion pressure, the flow volume showed a direct increase. These findings suggest that aortic arch surgery is possible using this SCP system.

The effect of prior hypothermia on the physiological response to norepinephrine

OBJECTIVE

this study determines the effect of prior hypothermia on the cardiovascular responses to norepinephrine (NE) after rewarming.

METHODS

the experiment was a 2x2 controlled design with four groups of feline animals. The two variables were the presence or absence of previous cooling, and the use or non-use of NE after rewarming. During the 'cooling' phase, animals were either cooled using an external arterial-venous femoral shunt to 30 degrees C or maintained at 37 degrees C. After 'rewarming' animals were stratified to receive either NE at rates to deliver 0.2, 1.0 or 5 microg/kg per h or normal saline infusions. Animals were instrumented to measure mean arterial pressure (MAP) and cardiac output (CO) and systemic vascular resistance (SVR) was calculated.

RESULTS

there were no differences between groups at baseline and low dose NE (0.2 microg/kg per min). At 1.0 microg/kg per min, NE caused a significant increase in CO (P<0.01) and no effect of MAP or SVR in the rewarmed animals when compared with normothermic controls. In rewarmed animals 5.0 microg/kg per min NE caused a significant increase in CO (P<0.01) and no effect on MAP or SVR. In normothermic controls there was a significant increase in SVR (P=0.02) and MAP (P=0.05) and no effect on CO.

CONCLUSION

this study shows that the effect of prior hypothermia on cardiovascular responses to moderate and high doses of NE is an improved CO with no affect on SVR and MAP. This could alter the clinical utility of NE in this situation.