Background-This study assesses the utility of a hybrid optical instrument for noninvasive transcranial monitoring in the neurointensive care unit. The instrument is based on diffuse correlation spectroscopy (DCS) for measurement of cerebral blood flow (CBF), and near-infrared spectroscopy (NIRS) for measurement of oxy-and deoxy-hemoglobin concentration. DCS/NIRS measurements of CBF and oxygenation from frontal lobes are compared with concurrent xenon-enhanced computed tomography (XeCT) in patients during induced blood pressure changes and carbon dioxide arterial partial pressure variation.

RBCT is associated with an increase in Pbto2 in most patients with subarachnoid hemorrhage or traumatic brain injury. This mean increase appears to be independent of cerebral perfusion pressure, Sao2, and Fio2. Further study is required to determine why Pbto2 decreases in some patients after RBCT.

In patients with severe TBI and elevated ICP refractory to previous mannitol treatment, 7.5% hypertonic saline administered as second tier therapy is associated with a significant increase in brain oxygenation, and improved cerebral and systemic haemodynamics.

Background and Purpose-Lactate is central for the regulation of brain metabolism and is an alternative substrate to glucose after injury. Brain lactate metabolism in patients with subarachnoid hemorrhage has not been fully elucidated. Methods-Thirty-one subarachnoid hemorrhage patients monitored with cerebral microdialysis (CMD) and brain oxygen (PbtO 2 ) were studied. Samples with elevated CMD lactate (Ͼ4 mmol/L) were matched to PbtO 2 and CMD pyruvate and categorized as hypoxic (PbtO 2 Ͻ20 mm Hg) versus nonhypoxic and hyperglycolytic (CMD pyruvate Ͼ119 mol/L) versus nonhyperglycolytic. Results-Median per patient samples with elevated CMD lactate was 54% (interquartile range, 11%-80%). Lactate elevations were more often attributable to cerebral hyperglycolysis (78%; interquartile range, 5%-98%) than brain hypoxia (11%; interquartile range, 4%-75% Generally considered a product of anaerobic metabolism, endogenous lactate is pivotal for neuronal survival, 3,4 particularly in conditions of acute injury. 5,6 Cerebral microdialysis (CMD) enables quantification of brain metabolites in cerebral extracellular fluid and provides information about energy metabolism and the extent of aerobic versus anaerobic glycolysis. 7 Further insights can be obtained by combining CMD with brain oxygen (PbtO 2 ) monitoring to quantify the extent of brain hypoxia. 8 Brain lactate metabolism after subarachnoid hemorrhage (SAH) has not been fully elucidated. We hypothesized that elevations of brain lactate occur in poor-grade SAH patients either as the consequence of cerebral hyperglycolysis or as the consequence of brain hypoxia, and that differences in the patterns of elevated brain lactate may be associated with outcome. Patients and MethodsWe studied comatose patients with aneurysmal SAH admitted to the Division of Neurocritical Care, Hospital of the University of Pennsylvania, Philadelphia, and in the Department of Critical Care, Lausanne University Hospital, Switzerland, over a 4-year period and who underwent combined CMD-PbtO 2 monitoring. Approval was obtained by local Institutional Review Board. Patients had at least 24 hours of valid intracranial monitoring and were alive for Ͼ5 days. Intracranial monitoring was performed as part of standard care, as previously described. 9 Patients were managed according to a standard protocol in both centers; 10 therapeutic targets were set to avoid cerebral perfusion pressure Ͻ60 mm Hg and PbtO 2 Ͻ20 mm Hg. CMD catheters (CMA 70; CMA Microdialysis AB; flow rate, 0.3 L/min) and PbtO 2 probes (Licox; Integra Neurosciences) were inserted via a triple-lumen bolt and placed into visually normal white matter. CMD samples were collected every 60 minutes and analyzed for concentrations of lactate, pyruvate, and glucose. Outcome at 6 months was assessed with the modified Rankin Scale score by 1 neurologist and 1 neurointensive care nurse who were blinded to physiological data.First hour of monitored data, artifacts, and data points outside physiological ranges were excluded. Brain lactate elevations ...