Bedside monitoring of cerebral blood flow by transcranial thermo-dye-dilution technique in patients suffering from severe traumatic brain injury or subarachnoid hemorrhage

Bedside measurement of cerebral blood flow (CBF) represents an important fe ature in monitoring of neurointensive care patients which is hard to establ ish. Therefore, we adopted a recently described thermo-dye-dilution-based a pproach for monitoring CBF in patients suffering from severe cerebral insul ts, that is, traumatic brain injury (TBI) or subarachnoid hemorrhage (SAH). Combined fiberoptic-thermistor catheters were placed in one jugular venous bulb and in the abdominal aorta of 16 patients. Following central venous i njection of a 50-mL bolus of precooled indocyanine green (ICG) solution, CB F was determined as a function of the mean transit times of coldness and dy e. In addition, measurements of CBF using stable xenon-enhanced computerize d tomography (sXe-CT) were simultaneously performed in 10 patients. A total of 272 thermo-dye-dilution measurements yielded 196 valid results, with CB F ranging from 26.2 to 144.8 mL 100 g(-1) min(-1). Reproducibility was fair ly good, with the standard deviation within sets of repeated measurements b eing 6.3 mL 100 g(-1) min(-1) and 9.4 as the mean coefficient of variation. Simultaneously obtained values with sXe-CT displayed a good correlation (r = 0.843, p < 0.01); however, the thermo-dye-dilution method consistently o verestimated CBF. Data analysis using the Bland and Altman methodology reve aled a large bias of 45.7 mL 100 g(-1) min(-1) with a +/-2 SD range of 37 m L 100 g(-1) min(-1), indicating a rather poor agreement. The thermo-dye-dil ution method proved a reasonably reproducible technique, enabling repeated long-term bedside measurements of CBF in neurointensive care patients with a minimum of time effort. However, a high failure rate was also noted, and consistent overestimation of perfusion was observed in comparison to sXe-CT measurements. Although the thermo-dye-dilution technique has been successf ully validated in patients with normal neurovascular function, its applicab ility for bedside monitoring of CBF appears uncertain in patients suffering from severe TBI or SAH.