CONTINUOUS MONITORING OF JUGULAR BULB OXYGEN-SATURATION AS A MEASURE OF THE SHUNT FLOW OF CEREBRAL ARTERIOVENOUS-MALFORMATIONS

Jugular bulb oxygen saturation (SjO(2)) was monitored during preoperat ive embolization procedures in a consecutive series of 15 patients wit h large supratentorial arteriovenous malformations (AVM's) in order to test the hypothesis that changes in the shunt now ratio can be contin uously evaluated from the SjO(2). A fiberoptic catheter was placed at the dominant jugular bulb. The SjO(2) measured using jugular blood wit hdrawn before embolization was significantly higher than the SjO(2) me asured at the end of the final embolization procedure (mean +/- standa rd deviation 84.1% +/- 12.7% vs. 74.2% +/- 10.9%, p < 0.0001), showing a positive correlation with the AVM volume (r = 0.66, p < 0.001). Con tinuous monitoring of SjO(2) via the fiberoptic catheter revealed a pr ogressive decrease in association with the embolization procedures. Mi crosurgical resection of the AVM was performed at 1 to 2 weeks after t he final embolization. Cases in which postoperative hemispheric deform ation was revealed on computerized tomography demonstrated a higher Sj O(2) at the end of embolization compared to that in the remaining case s (81.6% +/- 8.6% vs. 67.8% +/- 8.4%, p < 0.008). Hemispheric deformat ion was observed in all cases in which the SjO(2) did not decline to a level below 90% following embolization. The risk of severe hyperemic complications appeared to be greatly diminished when the SjO(2) fell t o below 80%. Assuming that the oxygen saturation of the perfusion flow (SjpO(2) ranges from 50% to 75%, the ratio of the shunt now to total now at an Sj(2) of 90% was estimated to be 0.6 to 0.8 based on the fol lowing equation: shunt flow/(perfusion flow + shunt now) = (SjO(2) - S jpO(2)/(arterial oxygen saturation - SjpO(2)). These results suggest t hat monitoring the SjO(2) provides real-time information concerning th e progress of embolization and helps to determine whether the emboliza tion has progressed sufficiently to avoid postoperative hyperemic comp lications.