Bedside monitoring of cerebral blood flow in patients with acute hemispheric stroke

Objective: To test the practicability of a new double indicator dilution method for bedside monitoring of cerebral blood flow (CBF) and to assess the clinical value of CBF monitoring as a prognostic tool for outcome and in therapy of elevated intracranial pressure (ICP) in patients with acute hemispheric stroke. Design: Prospective study. Clinical evaluation of a new method. Setting: Neurological intensive care unit of a university hospital. Patients: Ten patients with acute complete middle cerebral artery territory- or hemispheric infarctions. Interventions: Two combined fiberoptic thermistor catheters were placed in the right jugular bulb and in the thoracic aorta. Central venous injections of ice-cold indocyanine green dye were performed. CBF was estimated by calculating the mean transit times of the cold bolus and dye. Measurements and Main Results: A total of 104 reproducible CBF measurements were obtained. No complications associated with the method were observed. Twelve pairs of measurements were performed within 30 mins with unchanged clinical conditions. The standard deviation of repeated measurements was 2.7 mL/100g/min; the interrater reliability was between 0.95 and 0.99. The median CBF in patients who died (n = 4) was lower (27 mL/100g/min) than in those who survived (n = 6) (45 mL/100g/min). Patients who died more frequently had low CBF values of <30 ml./100g/min (22 of 38; 58%) than patients who survived (10 of 54; 19%). A total of 37 CBF measurements were done during ICP elevation of >20 mm Hg. In patients who survived, ICP elevations were only associated with low CBF values in 5 of 26 events; whereas in patients who died, ICP elevations were associated with low CBF values in 8 of 11 events. Conclusions: The new double indicator dilution technique may be suitable for serial bedside CBF measurement. It is easy to perform and can be rapidly repeated in the ICU environment. Validation of the method by comparison with standard methods is needed. The preliminary data indicate that bedside monitoring of CBF may give prognostic information for outcome and may guide therapy of elevated ICP in patients with malignant hemispheric infarction.