Lack of correlation between Xenon 133 and near infrared spectroscopy/indocyanine green rCBF measurements Ralf Dirk Rothoerl, Karl Michael Schebesch, Rupert Faltermeier, Chris Woertgen and Alexander Brawanski Department of Neurosurgery, University of Regensburg, Regensburg, Germany In recent literature there are some reports describing cerebral blood ow measurements by a near infrared spectroscopy-based technique with indocyanine-green as an absorbant. To our knowledge there is no systematical study which evaluates this technique in comparison to absolute cerebral blood ow measurements. Ten patients suffering from head injury (n ˆ 9) or subarachnoid hemorrhage (n ˆ 1) were included. Twenty measurements of cerebral blood ow were performed, employing a Xenon 133 clearance technique. Near-infrared spectroscopy measurements were performed with the Somanetics 4100 System. Indocyanine-green was given at a total dose of 0.2 mg kg ¡1 bodyweight intravenously. The indocyanine- green curve was compared to cerebral blood ow measurements according to rising time and area under the curve as suggested in the literature.No correlation between the indocyanine-green clearance curve and the Xenon 133 cerebral blood ow measurements could be found. Neither the area under the curve (p ˆ 0.93) nor the rising time (p ˆ 0.75) showed a statistically signicant correlation. The near-infrared spectroscopy based indocyanine-green clearance curve measurement method of cerebral blood ow seems not to give reliable results using simple mathematical models (area under the curve and rising time). In view of our ndings, we have serious reservations in the potential of this technique. [Neurol Res 2003; 25: 528–532] Keywords: Indocyanine green; near infrared spectroscopy; cerebral blood ow INTRODUCTION Cerebral blood ow (CBF) is generally considered to be an important pathophysiological factor in critically ill patients suffering from head injury or neurovascular disease such as subarachnoid hemorrhage or stroke. Impetus has been given to cerebral blood ow measurements in these patients because tissue ischemia following critical reduction in cerebral blood ow is thought to be the main mechanism for secondary brain damage. Thus cerebral blood ow measurements are of particular interest for the intensive care clinician for its potential prognostic and therapeutic relevance. Among the several techniques available for clinical monitoring, the most widely used involve the administration of radioactive tracers or Xenon in its stable form. However these techniques require either an interhospital transport of the critically ill patient or the administration of a radioactive tracer and can therefore not be repeated arbitrarily. Thus clinicians lack a practical, simple, cost effective bedside method for swift and repeated cerebral blood ow measurements. In the recent literature there are some reports addressing this problem proposing a near infrared spectroscopy based measurement with indocyanine green as an absorbant 1–3 . To the best of our knowledge there is no systematical study in adults suffering from cerebral pathology which evaluates this technique by comparing it to absolute rCBF measure- ments. The aim of our study was to provide these data. MATERIALS AND METHODS Patients The study was performed on the neurosurgical/anesthe- siological intensive care unit. All patients were intu- bated, sedated and mechanically ventilated. The treatment of these patients was performed according to the general guidelines used in the ICU and was not inuenced by the study. Ten patients (two females and eight males, mean age 35 years) were included. Most patients were suffering from severe head injury (GCS < 9, n ˆ 9). One patient was admitted for treatment of a subarachnoid hemorrhage (Hunt and Hess IV). The measurements were performed when the clinical indica- tion for measuring CBF was given. All measurements were performed within one week of admission. A total of 20 measurements were performed. In all patients both techniques for measuring CBF were performed directly after each other. Gamma radiation detectors and NIRS detectors were placed on the same area of the head. The study was approved by the local ethics committee. Correspondence and reprint requests to: Ralf D. Rothoerl, MD, Klinik und Poliklinik fu ¨r Neurochirurgie, Klinikum der Universita ¨t Regens- burg, Franz Josef Strauss-Allee 11, 93053 Regensburg, Deutschland. [rolf.rothoerl@klinik.uni-regensburg.de] Accepted for publication March 2003. 528 Neurological Research, 2003, Volume 25, July # 2003 Forefront PublishingGroup 0161–6412/03/050528–05