Selective oxidative dehydrogenation of propane to propene using boron nitride catalysts.

The exothermic oxidative dehydrogenation of propane reaction to generate propene has the potential to be a game-changing technology in the chemical industry. However, even after decades of research, selectivity to propene remains too low to be commercially attractive because of overoxidation of propene to thermodynamically favored CO2 Here, we report that hexagonal boron nitride and boron nitride nanotubes exhibit unique and hitherto unanticipated catalytic properties, resulting in great selectivity to olefins. As an example, at 14% propane conversion, we obtain selectivity of 79% propene and 12% ethene, another desired alkene. Based on catalytic experiments, spectroscopic insights, and ab initio modeling, we put forward a mechanistic hypothesis in which oxygen-terminated armchair boron nitride edges are proposed to be the catalytic active sites.

Satisfaction of patients' next of kin in a 'Hub & Spoke' ICU network.

This study aimed to gauge the opinions of patients' next of kin regarding transfer of patients from the specialist 'Hub' intensive care unit, to 'Spoke' intensive care units near home. We included 213 consecutive patients with severe trauma or severe acute neurological conditions admitted to the Hub intensive care unit over a 21-month period, who were repatriated to Spoke intensive care units for ongoing intensive care. One year after admission to the Hub intensive care unit, two thirds of patients' next of kin said they would have preferred patients to have been treated only in the Hub intensive care unit, and not repatriated. They perceived Hub intensive care unit care to be important, and would have preferred that their relatives be hospitalised there until intensive treatment was completed. The next of kin's preference was associated with severe acute neurological conditions (p ≤ 0.0001). Although centralised Hub & Spoke intensive care unit networks are appropriate to ensure specialised care, repatriation to local hospitals may not be appropriate for patients with severe neurological conditions.

Classification of a traumatic brain injury: the Glasgow Coma scale is not enough.

BACKGROUND: Classifying the severity of a traumatic brain injury (TBI) solely by means of the Glasgow Coma scale (GCS) is under scrutiny, because it overlooks other important clinical signs. Clinicians treating patients with acute TBI are well placed to suggest which variables, in addition to the GCS, should concur in a new classification of TBI. METHODS: In Italy, acute TBI patients are treated by anaesthetists, and so we asked them, in a questionnaire survey, to rate the weight they give to the GCS and to other clinical variables in their approach to TBI. Because sedation may underestimate GCS scores, we also inquired whether anaesthetists select sedatives that allow drug-free GCS scores. The questionnaire was distributed to 1334 anaesthetists attending courses on neurotrauma; the response rate was 63%. RESULTS: Two thirds of the respondents believe that the definition of severe TBI should include, in addition to GCS scores, pupil reactivity to light and computer tomogram (CT) findings, the variables that guide Italian anaesthetists in TBI management. Most respondents (68.2%) administer sedation which allows prompt neurological evaluation and reliable GCS scoring. A minority of respondents (9.3%) withhold or antagonize sedation, delay tracheal intubation or allow patient-ventilator asynchrony. CONCLUSIONS: Italian anaesthetists would welcome a definition of TBI severity that includes CT findings and pupil reactivity in addition to the GCS.

Unilateral oculomotor nerve palsy: unusual sign of hydrocephalus.

We report an unusual case of hydrocephalus in which unilateral oculomotor nerve paralysis was the predominant sign. Misinterpretation of such an atypical clinical sign may lead to inappropriate therapy. We outline the role of intracranial pressure monitoring as an adjunctive diagnostic tool and we suggest a presumptive mechanism to explain the correlation between enlarged ventricles and 3(rd) nerve dysfunction. A 16-year-old boy presented with a complete left oculomotor nerve palsy associated with imaging findings of dilated ventricles and Dandy-Walker variant cystic malformation. Monitoring of intracranial pressure through a ventricular catheter was undertaken. In the first phase (no cerebrospinal fluid drainage [CSF] drainage) mean intracranial pressure (ICP) values were >0 mmHg. A second phase (with progressively longer CSF draining) further defined the diagnosis. A ventriculo-peritoneal shunt was then placed and the nerve function returned to normal within few days. Third cranial nerve dysfunction as a predominant sign of hydrocephalus is very rare and may raise doubts as to the real significance of the imaging findings of enlarged ventricles. In this ground, ICP monitoring is a safe and helpful diagnostic tool that can afford a more accurate evaluation and proper treatment. The supposed mechanism of 3(rd) nerve dysfunction was bending/stretching of the nerve.

A diagnostic flowchart, including TCD, Xe-CT and angiography, to improve the diagnosis of vasospasm critically affecting cerebral blood flow in patients with subarachnoid haemorrhage, sedated and ventilated.

The aim of this study was to prospectively evaluate a clinical protocol including transcranial doppler (TCD), Xenon-CT (Xe-CT) and angiography, for the detection of vasospasm leading to critical reductions of regional cerebral blood flow (rCBF) in both ventilated and sedated SAH patients, i.e. patients in whom clinical evaluation was not possible. Seventy-six patients were prospectively included in a surveillance protocol for daily TCD vasospasm monitoring. When TCD showed a V(mean) above 120 cm/sec in the middle cerebral artery (MCA), patients underwent Xe-CT study. If rCBF in the MCA was reduced to below 20 ml/100 g/min or if there was a reduction in the rCBF with significant asymmetry between the two MCAs, angiography was performed. Conversely, further Xe-CT and angiography were not obtained unless the TCD V(mean) values reached values above 160 cm/sec. In 35 patients, V(mean) attained values above 120 cm/sec, but only in five of them, rCBF was suggestive of vasospasm, and angiography confirmed the diagnosis in four. The protocol suggests that in sedated and ventilated patients, detection of a critical rCBF reduction due to vasospasm is possible to allow for more specific treatment and to reduce undue medical complications.

Cerebral blood flow thresholds predicting new hypoattenuation areas due to macrovascular ischemia during the acute phase of severe and complicated aneurysmal subarachnoid hemorrhage. A preliminary study.

BACKGROUND: Focal ischemia may affect patients with aneurysmal subarachnoid hemorrhage (SAH), and the potential evolution of cerebral infarction may greatly influence the patients' outcome. The aim of the study was to assess the values of regional cortical cerebral blood flow (rCBF) thresholds predictive for ischemia during the acute phase of SAH. METHODS: In 34 patients affected by poor grade or complicated SAH, 52 pairs of Xenon-CT (Xe-CT) studies of regional CBF were analyzed, in which the follow-up Xe-CT study was obtained no later than 72 hours after the baseline study. Corresponding cortical ROIs were placed in the perimeter of the cortex on both the Xe-CT studies. A blinded, experienced neuroradiologist classified for each ROI, the development of a new hypoattenuation at the unenhanced CT images included in the follow-up Xe-CT, while another independent investigator collected rCBF levels of the ROI in the baseline Xe-CT study. FINDINGS: New hypoattenuation developed in 3.94% of the ROIs in the paired follow-up Xe-CT studies, and these evolving ROIs were associated with a lower rCBF in baseline Xe-CT. However, the positive predictive value of rCBF levels for the development of new hypoattenuation was only moderately predictive (28.3%) for very low physiological values (5 ml/100gr/min). CONCLUSIONS: The results suggest that there is no absolute rCBF threshold ofischemia in severe and complicated SAH patients and that the rCBF values are only moderately predictive at levels lower than previously described.

Regional cerebral blood flow levels as measured by xenon-CT in vascular territorial low-density areas after subarachnoid hemorrhage are not always ischemic.

INTRODUCTION: The aim of this study was to assess regional cerebral blood flow (rCBV) in areas of CT hypoattenuation appearing in the postoperative period in patients treated for aneurysmal subarachnoid hemorrhage (SAH) using xenon-enhanced CT scanning (Xe-CT). METHODS: We analyzed 15 patients (5 male and 10 female; mean age 49.7+/-12.1 years) with SAH on CT performed on admission to hospital and who showed a low-density area within a well-defined vascular territory on CT scans after clipping or coiling of a saccular aneurysm. All zones of hypoattenuation were larger than 1 cm(2) and showed signs of a mass effect suggesting a subacute phase of evolution. Two aneurysms were detected in two patients. Aneurysms were located in the middle cerebral artery (n=7), in the anterior communicating artery (n=6), in the internal carotid artery (n=3), and in the posterior communicating artery (n=1). Treatments were surgical (n=8), endovascular (n=2) or both (n=1). A total of 36 Xe-CT studies were performed and rCBF values were measured in two different regions of interest (ROI): the low-density area, and an area of normal-appearing brain tissue located symmetrically in the contralateral hemisphere. RESULTS: rCBF levels were significantly lower in the low-density area than in the contralateral normal-appearing area (P<0.01). In the low-density areas, irreversible ischemia (CBF <10 ml/100 g per minute) was present in 11/36 lesions (30.6%), ischemic penumbra (CBF 10-20 ml/100 g per minute) and oligemia (CBF 20-34 ml/100 g per minute) in 8/36 lesions (22.2%), relative hyperemia (CBF 34-55 ml/100 g per minute) in 7/36 lesions (19.4%), and absolute hyperemia (CBF >55 ml/100 g per minute) in 2/36 lesions (5.6%). CONCLUSION: Our study confirmed that rCBF is reduced in new low-density lesions related to specific vascular territories. However, only about one-third of the lesions showed rCBF levels consistent with irreversible ischemia and in a relatively high proportion of lesions, rCBF levels indicated penumbral, oligemic and hyperemic areas.

Diagnostic impact of the spectrum of ischemic cerebral blood flow thresholds in sedated subarachnoid hemorrhage patients.

OBJECTIVE: Ischemia is the main cause of secondary damage in subarachnoid hemorrhage (SAH). Cerebral blood flow (CBF) measurement is useful to detect critical values. We analyzed the diagnostic impact of CBF ischemic thresholds to predict a new low attenuation area on computed tomography (CT) due to failure of large vessel perfusion. METHODS: We analyzed 48 xenon CT (Xe-CT) studies from 10 patients with SAH. CBF measurements were obtained by means of Xe-CT and cortical regions of interest (ROls). The ROIs which appeared in a hypoattenuation area were recorded. Cortical CBF was tested for specificity and sensitivity as a predictor of hypoattenuation by means of a receiver operating characteristic curve. RESULTS: Mean age was 58 (SD +/- 12.4) years. The median Fisher score and Hunt and Hess scale were 2 and 3, respectively. The area under the receiver operating characteristic curve was 0.912 (CI 0.896 to 0.926). The cut-off value for best accuracy was 6 mL/ 100 g/min, with a likelihood ratio of 37. CONCLUSION: The present study suggests a threshold of 6 mL/100 g/ min as a predictor of a new low attenuation area. However, each clinician should choose the most useful threshold according to pre-test probability and the cost/effectiveness ratio of the applied therapies.

Evaluation of acute perihematomal regional apparent diffusion coefficient abnormalities by diffusion-weighted imaging.

In this study, we investigated 40 patients (18 male, 22 female; mean age = 64.5 +/- 11.0; GCS = 9 to 14) with acute supratentorial spontaneous intracerebral hemorrhage (SICH) at admission by using a 1-tesla magnetic resonance imaging (MRI) unit equipped for single-shot echo-planar spin-echo isotropic diffusion-weighted imaging (DWI) sequences. All DWI studies were obtained within 48 hours after symptom onset. Regional apparent diffusion coefficient (rADC) values were measured in 3 different regions of interest (ROIs) drawn freehand on the T2-weighted images at b 0 s/mm2 on every section in which hematoma was visible: 1) the perihematomal hyperintense area; 2) 1 cm of normal appearing brain tissue surrounding the perilesional hyperintense rim; 3) an area mirroring the region including the clot and perihematomal hyperintense area placed in the contralateral hemisphere. rADC mean values were higher in perihematomal hyperintense and in contralateral than in normal appearing areas (p < 0.001), with increased rADC mean levels in all regions examined. Our findings show that rADC values indicative of vasogenic edema were present in the perihematomal area and in normal appearing brain tissue located both ipsilateral and contralateral to the hematoma, with lower levels in non-injured areas located in the T2 hyperintense rim around the clot.

Reperfusion of low attenuation areas complicating subarachnoid hemorrhage.

Hypoattenuation areas shown on brain CT scans after subarachnoid hemorrhage (SAH) are believed to be associated with persistent ischemia. The aim of this study was to evaluate regional cerebral blood flow (rCBF) in hypoattenuation areas and its evolution over time by means of Xenon CT (Xe-CT). We enrolled 16 patients with SAH who developed a hypoattenuation area in the middle cerebral artery territory. Patients were studied at time zero (the first Xe-CT), within 24 to 96 hours, and 96 hours after the initial Xe-CT. We analyzed 19 hypoattenuation areas caused by vascular distortion, vasospasm, or post-surgical embolization in 48 Xe-CT studies. Areas of hypoattenuation were divided in 2 groups according to initial rCBF. In the first group (n = 15), rCBF was initially above 6 mL/100 gr/min but only 2 were still ischemic (rCBF < 18 mL/ 100 gr/min) 96 hours after the first Xe-CT, while 7 (58%) were hyperemic. Conversely, in the second group with severe ischemia (rCBF < 6 mL/100 gr/min; n = 4) mean rCBF increased (p = 0.08) but still remained below the ischemic threshold. In severely ischemic lesions, rCBF reperfusion occurs but is probably marginally relevant. Conversely, in lesions not initially severely ischemic, residual CBF gradually improved and frequently became hyperemic. The functional recovery of these zones remains to be evaluated.

An Italian survey of severe head trauma management during extracranial surgery.

BACKGROUND AND OBJECTIVE: Anaesthetic drugs and procedures interfere with secondary brain injury following severe head trauma, yet studies regarding the anaesthetic management of these patients are lacking. We investigated the behaviour of Italian anaesthetists regarding this topic. METHODS: A questionnaire investigating the approach to a patient with severe head trauma requiring an urgent splenectomy for ruptured spleen was sent to 250 Italian anaesthetists. Questions regarded the pre-, intra- and postoperative phases, and concerned the rationale use and availability of specific monitoring systems, and indications for invasive procedures and use of drugs, fluids and blood products. RESULTS: There were 162 (64.8%) responders. Seventy-five percent believed that early tracheal intubation within the emergency room was necessary, while 25% postponed it to the operating room. Basic monitoring was defined as essential by all responders, 147 (90.7%) considered invasive arterial pressure monitoring to be essential. Fifty-seven (84%) anaesthetists working in hospitals without neurosurgical facilities would have transferred the patient after splenectomy. Prophylactic hyperventilation was frequently used (36%). Sixty-eight percent of responders would have preferred in intracranial pressure monitoring inserted before laparotomy, but only 35% actually had this possibility. In case of acute intraoperative arterial hypotension after splenectomy, 54% of the responders advocated the use of blood or blood products to optimize peripheral oxygen transport. CONCLUSIONS: More widespread knowledge of certain areas of severe head trauma management such as early tracheal intubation, avoidance of prophylactic hyperventilation, adequate invasive monitoring, appropriate use of blood products, and timing of transfer to hospitals with neurosurgical facilities is needed.

Estimated cerebral respiratory quotient and arteriovenous differences of CO2 in the ultra early detection of global ischemia in severe head injury.

The specificity of jugular bulb saturation (SjO2) and arteriovenous oxygen difference (AVDO2) to detect global cerebral ischemia remains controversial. An absolute increase in the arteriovenous difference of carbon dioxide tension (AVDpCO2) and, more specifically, the estimated respiratory quotient (eRQ = AVDpCO2/AVDO2) may indicate anaerobic CO2 production. We compared these variables with SjO2 to predict global cerebral ischemia. We selected 36 patients from a cohort of 69 consecutive patients suffering from severe traumatic brain injury. All patients had jugular bulb sampling within 6 hours after injury. Brain death at 48 hours was used as a surrogate index of irreversible ischemia to build a receiver operating characteristics (ROC) curve analysis. The mean (+/- standard deviation) eRQ in the 13 patients who died early (3.7 +/- 3.2 mmHg/ml/dl) was higher than the survivors (1.78 +/- 0.45 mmHg/ml/dl, P = 0.03). There was no differences in SjO2 between groups. The area under the ROC curves for eRQ, but not that of AVDpCO2, was greater (P = 0.04) than that of SjO2. The eRQ, more than AVDpCO2, appears to be a potentially more informative index of global cerebral ischemia than SjO2.

Cerebral blood flow in mean cerebral artery low density areas is not always ischemic in patients with aneurysmal subarachnoid hemorrhage--relationship with neurological outcome.

Aneurysmal subarachnoid hemorrhage (SAH) can be complicated by reduction of regional cerebral blood flow (rCBF) from large conductance vessels leading to focal edema appearing as an area of hypoattenuation on CT. In this study we included 29 patients with SAH due to aneurysmal rupture, having 36 CT low density areas within the middle cerebral artery territory in whom a total of 56 Xenon-CT (Xe-CT) studies were performed. Collectively, we evaluated 70 hypoattenuated areas. rCBF levels were measured in two different regions of interest drawn manually on the CT scan, one in the low density area and the other in a corresponding contralateral area of normal-appearing brain tissue. In the low density area (22.6 +/- 22.7 ml/100 gr/min) rCBF levels were significantly lower than in the contralateral area (32.8 +/- 17.1 7 ml/100 gr/min) (p = 0.0007). In the injured areas deep ischemia (CBF < 6 ml/ 100 g/min) was present in only 25.7% of Xe-CT studies, suggesting that hypodense areas are not always ischemic, whereas in 43.7% of the lesions/Xe-CT studies we found hyperemic values. Patients with a better outcome had hyperemic lesions, suggesting brain tissue recovery in injured areas.

Cerebral blood flow mapping in two different subtypes of intraparenchymal hemorrhagic traumatic lesions.

The pathogenesis and the viability of edematous tissue may be different in traumatic hematomas and traumatic contusions. We tested the hypothesis that mapping of regional Cerebral Blood Flow (rCBF) was different in these two subtypes of traumatic intraparenchymal lesions. We evaluated rCBF by means of Xenon-enhanced computerized tomography (Xe-CT) in 59 traumatic intracerebral lesions from 43 patients with severe head injury. One-hundred-nine intracerebral lesions/Xe-CT CBF measurements were obtained. The rCBF was measured in the hemorrhagic core, in the intralesional oedematous low density area and in a 1 cm rim of apparently normal perilesional parenchyma of both lesion subtypes. Not statistically significant lower rCBF levels were found in the edematous area of traumatic contusions. In traumatic hematomas rCBF levels were lower in the core than in the low density area, suggesting that rCBF in edematous area is marginally involved in the initial traumatic injury and that edema is probably influenced by the persistence of the hemorrhagic core. Conversely, in the traumatic contusions a difference in rCBF values was found between core, low density area and perilesional area, indicating that rCBF of the low density area is related to a concentrical distribution of the initial injury.

Assessment of acute spontaneous intracerebral hematoma by CT perfusion imaging.

A single-section deconvolution-derived computerized tomographic perfusion imaging was performed in 45 patients (22 male and 23 female; mean age=69.89+/-10.07 years) with acute supratentorial spontaneous intracerebral hemorrhage. Mean rCBF and rCBV were lower in the hemorrhagic core than in the perihematomal low density area (p<0.001), and in the perihematomal low density area than in normal appearing brain parenchyma (p<0.001). Mean rMTT values were higher in perihematomal low density area than in normal appearing area (p<0.01) and in both hemorrhagic and perihematomal area than in controlateral ROI (p<0.001). There were no differences in rMTT mean values between hemorrhagic core and perihematomal area, as well as between normal appearing and controlateral areas. We found a concentric distribution of all CT perfusion parameters characterized by an improvement from the core to the periphery, with low perihematomal rCBF and rCBV values suggesting edema formation.

Time course of CT evolution in traumatic subarachnoid haemorrhage: a study of 141 patients.

BACKGROUND: Evidence of tSAH on an admission CT scan seems to be an early predictor of evolving posttraumatic lesions. Detection of these changes requires serial CT scanners. The goal of our study was to determine the optimal timing of follow-up CT scans in head injured patients with traumatic subarachnoid haemorrhage (tSAH). METHOD: We reviewed the initial and follow-up CT scans in 141 patients with closed head injuries and evidence of tSAH on the initial CT scan. We used the Marshall classification to determine diffuse and focal injuries. The "worst CT scan", defined as the CT examination in which midline shift, cistern compression and/or intracranial focal lesions were greater, was also determined. Any worsening of the admission CT findings, occurring when the "worst CT examination" did not correspond to the initial CT study, was considered as a "CT evolution". Any "CT evolution" associated with a variation from a lower to a higher score in the Marshall classification score was indicated as a "significant CT evolution". FINDINGS: The median time between injury and the first CT scan was 1.3 (IQR 1.5) hours. A CT evolution was found in 83/141 (58.9%) patients in whom the median time between the initial and worst CT scans was 27.7 hours (IQR 69.2 hours). The worst CT studies were seen more often at 12-24 hours and at 24-48 hours after the admission CT scan than in later studies. A similar temporal profile was observed when the timing of the "worst CT scan" was evaluated in 38/83 (45.8%) subjects with a "significant CT evolution". INTERPRETATION: Our findings show that an early admission CT scan did not represent the full extent of the posttraumatic damage in more than half of our patients. They also suggest that to identify these changes in head injured patients with tSAH, CT scans should be repeated at 12-24 and possibly also at 24-48 hours from the admission CT examination to allow early detection and evacuation of evolving intracranial lesions.

Normal jugular bulb oxygen saturation.

BACKGROUND: Normal values of the jugular bulb oxygen saturation were obtained in 1942 and in 1963. Correct catheter positioning was not confirmed radiologically. OBJECTIVES: To replicate the measurements during angiographic catheterisation of the jugular bulb. METHODS: Oxygen saturation in the jugular bulb (SjO(2)), inferior petrosal sinus (SipsO(2)), and internal jugular vein was bilaterally measured in 12 patients with Cushing's syndrome undergoing selective bilateral catheterisation of the inferior petrosal sinus. In addition, data from the two old series were reanalysed for comparison. RESULTS: SjO(2) values (44.7%) were significantly lower than in the two old series, particularly concerning the normal lower limit (54.6% and 55.0% respectively). Comparative analysis suggests that contamination with the extracerebral blood of the facial veins and inferior petrosal sinuses was responsible for falsely high SjO(2) values in the two old series. CONCLUSIONS: The normal lower SjO(2) limit is lower than previously recognised. This may have practical implications for treating severe head trauma patients.

Mixed dishomogeneous hemorrhagic brain contusions. Mapping of cerebral blood flow.

The aim of the study was to verify whether regional cerebral blood flow (rCBF) was distributed centrifugally in traumatic hemorrhagic contusions with multiple cores within an oedematous area. Seventeen traumatic brain contusions, from 14 patients with severe head injury (GCS < 9), were analyzed during 39 Xenon-enhanced computerized tomography (Xe-CT) studies. The CBF was measured in 3 concentric regions of interest (ROls): the hemorrhagic core, the intracontusional oedematous low density area and a 1 cm rim of pericontusional normal-appearing brain tissue surrounding the contusion. Differences between rCBFs in the three ROIs were found (p < 0.0001). rCBF in both the hemorrhagic core (21.4 +/- 19.4 ml/ 100gr/min) and the intracontusional low density area (28.4 +/- 19 ml/100gr/min) were lower than rCBF in pericontusional normal-appearing area (41.9 +/- 16 ml/100gr/min) (p < 0.0001). No significant differences were found between rCBF measured in the hemorrhagic core and intracontusional low density area (p = 0.184). Our study suggests that in the mixed density contusions with multiple hemorrhagic cores, the CBF is concentrically distributed, improving from the core to the periphery.

Induced acute arterial hypertension and regional cerebral flow in intracontusional low density area.

Traumatic brain contusions have been associated with regional ischemia. We aimed to measure the effect of induced supra-normal values of cerebral perfusion pressure (CPP) on regional cerebral blood flow (rCBF) in the intracontusional low density area surrounding the contusional hemorrhagic core. In 7 severely head injured patients (GCS < or = 8) harbouring a contusion larger than 2 cm, the rCBF levels were measured, by means of Xenon-enhanced CT, in: 1) the intracontusional low density area: 2) contralaterally, in a normal brain symmetric area. CBF studies were performed at a baseline CPP of 65.3 mmHg +/- 7 and after 20 minutes of norepinephrine-induced CPP supernormal values (88.3 mmHg +/- 10.5) (p = 0.0013). A "paradoxical" reduction of rCBF levels was observed in both the intracontusional low density area (p = 0.07) and the contralateral "normal" area (p = 0.08). In particular, this decrease of rCBF in the intracontusional low density area (-25.7 + 10 ml/100gr/min) (p = 0.0009) was present in only 4 cases, having a mean rCBF at baseline of 25 +/- 16 ml/100gr/min. In the remaining 3 cases in which rCBF at baseline was abnormally low (12 +/- 7 ml/ 100gr/min), rCBF values improved slightly (3.6 +/- 2 ml/100gr/min) (p = 0.61). An acute increase of CPP seems to marginally affect rCBF in the intracontusional low density area having critically reduced initial values, but may greatly reduce rCBF in subjects starting from non-critical baseline values.