1. A comparison of cerebral and venous microdialysis during experimental hypothermic antegrad cerebral perfusion. Authors: Jonsson O, Tovedal T, Zemgulis V, Lennmyr F, Hillered L, Thelin S. Department of Cardiothoracic surgery and anesthesiology Department of Neuroscience, Neurosurgery Uppsala University Uppsala University Hospital, Sweden

2. SACP Selective Antegrade Cerebral Perfusion A Carotis communis Aortic cannula Clamps

3. Microdialysis Lactate/pyruvate Lactate/glucose

4. Background To encircle any signs of energy metabolic crisis and cellular distress during SACP flows between 6 ml/kg/min and 4 ml/kg/min. Can intravenous microdialysis in the sagittal sinus reveal global cerebral metabolic changes not detected by the brain microdialysis catheter.

5. Aims To investigate the effects of two SACP flow levels (6 and 4 ml/kg/min) on the development of cerebral ischemia. To evaluate the agreement and correlation between microdialysis markers harvested from the brain and the sagittal sinus.

6. Method Randomized study 3 groups 18 pigs (0 excluded) Microdialysis (Cerebral, Sinus sagittal) NIRS (Near infrared spectroscopy) Cooling temperature 20 o C

7. Experimental protocol Group 1(○) SACP 4 ml/kg/min increased to 6 ml/kg/min/ Group 2 (∆) SACP 6 ml/kg/min decreased to 4 ml/kg/min Group 3 (●) Control

8. Results NIRS tissue oxygen index (TOI)

9. Results Microdialysis from the brain

10. Results Microdialysis from the sagittal sinus Probably the effect of circulatory arrest

11. Results Bland Altman

12. Results Correlation and Agreement Table 3. Spearman’s correlation, bias, and limits of agreement between cerebral and sagittal sinus MD samples (n=119). ComparisonCorrelation (r)BiasLimits of agreementp value Glucose 0.41 - 3.8- 9.2to+ 1.6<0.01 Lactate 0.25 - 2.1- 6.6to+ 4.50.08 Pyruvate- 0.02 - 35.7-179.4to+ 108.00.87 Urea 0.32 - 0.7- 2.2to+ 0.80.02 L/P ratio- 0.02 - 5.8-49.0to+ 37.40.88 L/G ratio 0.15 2.0 - 6.3to+ 10.40.30 Glutamate 0.11 - 49.0-152.9to+ 54.90.45 Glycerol 0.03 80.9-71.4to+ 233.30.85

13. Conclusion An SACP flow of 6 ml/kg/min preserves cerebral metabolism according to cerebral microdialysis and NIRS. An SACP flow of 4 ml/kg/min induces early signs of disturbed energy metabolism. Microdialysis from the sagittal sinus is a feasible methode for monitoring biomarkers of global cerebral perturbations, But in the present model correlation with parenchymal measurements were poor and no agreement could be demonstrated.