Bedside assessment of cerebral blood flow by double-indicator dilution technique

Background: Currently, quantitative measurement of global cerebral blood fl ow (CBF) at bedside is not widely performed. The aim of the present study w as to evaluate a newly developed method for bedside measurement of CBF base d on thermodilution in a clinical setting. Methods: The investigation was performed in 14 anesthetized patients before coronary bypass surgery. CBF was altered by hypocapnia, normocapnia, and h ypercapnia. CBF was measured simultaneously by the Kety-Schmidt inert-gas t echnique with argon and a newly developed transcerebral double-indicator di lution technique (TCID). For TCID, bolus injections of ice-cold indocyanine green were performed via a central venous line, and the resulting thermo-d ye dilution curves were recorded simultaneously in the aorta and the jugula r bulb using combined fiberoptic thermistor catheters. CBF was calculated f rom the mean transit times of the indicators through the brain. Results: Both methods of measurement of CBF indicate a decrease during hypo capnia and an increase during hypercapnia, whereas cerebral metabolic rate remained unchanged. Bias between CBFTCID and CBFargon was --7.1 +/- 2.2 (SE M) mi min-l 100 g(-1); precision (+/- 2.SD of differences) between methods was 26.6 ml.min(-1).100 g(-1). Conclusions: In the clinical setting, TCID was feasible and less time-consu ming than alternative methods. The authors con-elude that TCID is an altern ative method to measure global CBF at bedside and offers a new opportunity to monitor cerebral perfusion of patients.