ALTERATIONS IN INTRACRANIAL VOLUME FOLLOWING CROSS-CLAMPING OF THE DESCENDING THORACIC AORTA IN PIGS - AN EXPERIMENTAL-STUDY USING MRI

Objectives: To determine whether alterations in intracranial volume oc curred following cross-clamping of the descending thoracic aorta in pi gs. Design and setting: Laboratory animal study. Materials: Eight pigs undergoing cross-clamping of the descending thoracic aorta for 30 min . Chief outcome measures: A Philips Gyroscan T5-II Release 3 (0.5 T) w as used to obtain intracranial images before cross-clamping during cro ss-clamping and after declampinng. The ventricular volume was measured on Spin Echo T2-weighted images. The signal intensity of the cerebral tissue was measured on Spin Echo T2-weighted images. Increased signal intensity of the cerebral tissue relative to an external reference wa s used as an indicator of cerebral oedema. Main results: The ventricul ar volume decreased to 89% (p < 0.01) of the baseline value after 5 mi n of cross-clamping At 5 min after declamping the ventricular volume d ecreased further to 71% (p < 0.01). At 25 min after declamping the ven tricular volume had returned to the baseline value. The signal intensi ty of the cerebral tissue did not differ from baseline values followin g aortic cross-clamping. Conclusions: In this study, ventricular volum e decreased following cross-clamping of the descending thoracic aorta. Since no cerebral oedema was observed the decrease of ventricular vol ume was most likely due to increased intracranial blood volume.