Chronic subdural haematoma after snowboard head injury.

Two cases of chronic subdural haematoma following a snowboard head injury are reported. Although such cases are rare in sport, the risk in snowboarders is higher than expected. Evaluation of a snowboarder with a history of head injury, albeit mild, who complains of headaches should include computed tomography or magnetic resonance imaging to allow rapid identification of any intracranial pathology.

Effects of edaravone on experimental brain injury in view of free radical reaction.

The purpose of this study is to clarify the influence of a novel free radical scavenger edaravone on experimental brain injury. Male Wistar rats were anesthetized with 1-2% halothane. Brain injury was produced using a controlled cortical impact injury device. Experimental rats were divided into 2 groups. In the edaravone group, edaravone (3 mg/kg) was twice administered intravenously for 30 minutes. In the saline group, saline solution was administered in the same way. This administration of edaravone or saline solution made it possible to evaluate the relative effects of edaravone by assessment of free radical reaction and water content. As a result, the level of oxygen free radicals at 50 minutes after brain injury was significantly lower in the edaravone group than in the saline group. The water content in the injured brain at 180 minutes was significantly lower in the edaravone group than in the saline group. Therefore, we propose that edaravone may be effective for treatment in head injury.

Comparison of jugular venous oxygen saturation and brain tissue Po2 as monitors of cerebral ischemia after head injury.

OBJECTIVE: To compare the characteristics of jugular venous oxygen saturation (Sjvo2) and brain tissue Po2 (Pbto2) as monitors for cerebral ischemia after severe head injury. Sjvo2 has been useful as a monitor for cerebral ischemia, but it is limited by its inability to identify regional cerebral ischemia. Pbto2 may be superior to Sjvo2 for this purpose, because oxygenation in localized areas of the brain can be monitored. DESIGN: Sjvo2 and Pbto2 were successfully monitored in 58 patients with severe head injury. The changes in Sjvo2 and Pbto2 were compared during ischemic episodes. SETTING: Neurosurgical intensive care unit of a level I trauma center. MEASUREMENTS AND MAIN RESULTS: During the monitoring period, which averaged 90 hrs/patient, there were 54 episodes during which Sjvo2 decreased to <50% and/or Pbto2 decreased to <8 torr. Two of these episodes were caused by an infarction in the area of the Po2 probe, leaving 52 episodes of global hypoxia/ischemia that were identified by one of the two monitors. The sensitivities of the two monitors for detecting ischemia, using the thresholds of 50% and 8 torr for Sjvo2 and Pbto2, respectively, were similar. The Sjvo2 catheter detected 69.7% of the episodes and the Pbto2 catheter detected 63.5% of the episodes. In most of the remaining episodes, both probes reflected a decrease in oxygenation, but not to levels below the defined thresholds. The major differences in the two measures of oxygenation included the following: a) Sjvo2 more consistently reflected a reduction in oxygenation during hyperventilation; b) Pbto2 was affected more by changes in arterial Po2; and c) during severe global ischemia, Pbto2 decreased to 0 and remained at 0, whereas Sjvo2 initially decreased but then increased again as cerebral blood flow ceased, and the only blood in the jugular bulb was of extracerebral origin. CONCLUSIONS: The two monitors provide complimentary information, and neither monitor alone identifies all episodes of ischemia. The best strategy for using these monitors is to take advantage of the unique features of each monitor. Sjvo2 should be used as a monitor of global oxygenation; but Pbto2 should be used as a monitor of local oxygenation, ideally with the catheter placed in an area of the brain that is vulnerable to ischemia but that may be salvageable with appropriate treatment.

Prevention of secondary ischemic insults after severe head injury.

OBJECTIVE: The purpose of this study was to compare the effects of two acute-care management strategies on the frequency of jugular venous desaturation and refractory intracranial hypertension and on long-term neurologic outcome in patients with severe head injury. DESIGN: Randomized clinical trial. SETTING: Level I trauma hospital. PATIENTS: One hundred eighty-nine adults admitted in coma because of severe head injury. INTERVENTIONS: Patients were assigned to either cerebral blood flow (CBF)-targeted or intracranial pressure (ICP)-targeted management protocols during randomly assigned time blocks. In the CBF-targeted protocol, cerebral perfusion pressure was kept at >70 mm Hg and PaCO2 was kept at approximately 35 torr (4.67 kPa). In the ICP-targeted protocol, cerebral perfusion pressure was kept at >50 mm Hg and hyperventilation to a PaCO2 of 25-30 torr (3.33-4.00 kPa) was used to treat intracranial hypertension. MEASUREMENTS AND MAIN RESULTS: The CBF-targeted protocol reduced the frequency of jugular desaturation from 50.6% to 30% (p = .006). Even when the frequency of jugular desaturation was adjusted for all confounding factors that were significant, the risk of cerebral ischemia was 2.4-fold greater with the ICP-targeted protocol. Despite the reduction in secondary ischemic insults, there was no difference in neurologic outcome. Failure to alter long-term neurologic outcome was probably attributable to two major factors. A low jugular venous oxygen saturation was treated in both groups, minimizing the injury that occurred in the ICP-targeted group. The beneficial effects of the CBF-targeted protocol may have been offset by a five-fold increase in the frequency of adult respiratory distress syndrome. CONCLUSIONS: Secondary ischemic insults caused by systemic factors after severe head injury can be prevented with a targeted management protocol. However, potential adverse effects of this management strategy may offset these beneficial effects.

Extracellular lactate and glucose alterations in the brain after head injury measured by microdialysis.

OBJECTIVE: To study cerebral glucose and lactate metabolism in head-injured patients using microdialysis. DESIGN: Prospective, nonrandomized, clinical study. SETTING: Neurosurgical intensive care unit in a university-affiliated county hospital. PATIENTS: One hundred twenty-six head-injured patients. INTERVENTIONS: Cerebral cortical neurochemical monitoring using microdialysis coupled with systemic hemodynamic and oxygenation monitoring, measurement of cerebral perfusion pressure and intracranial pressure, and measurement of global cerebral oxygenation using jugular venous oxygen saturation in all 126 patients. In selected cases, cerebral blood flow was also measured using cortical thermodilution probes in 33 patients, and regional cerebral oxygenation was measured using PO2 probes in 65 patients. MEASUREMENTS AND MAIN RESULTS: Elevated extracellular lactate, reduced glucose, and an elevated lactate/glucose ratio were observed with cerebral hypoxia and ischemia. Elevated lactate and an increased lactate/glucose ratio strongly correlated with death. Other more subtle alterations of lactate and glucose were seen early after injury that may reflect compensatory alterations in cerebral metabolism. CONCLUSIONS: Clinical neurochemical monitoring of glucose and lactate levels in the extracellular space of the cerebral cortex is technically feasible and provides insight into the bioenergetic status of the brain. Increased lactate and decreased glucose, indicating accelerated glycolysis, commonly occurred with cerebral ischemia or hypoxia, and increased anaerobic glycolysis in this setting is associated with a poor outcome.

Evaluation of a new fiberoptic catheter for monitoring jugular venous oxygen saturation

OBJECTIVE: The purpose of this study was to evaluate three modified, fiberoptic, oxygen saturation catheters as monitors of jugular venous oxygen saturation (SjvO2). METHODS: Three modified fiberoptic catheters, designated Catheters 1, 2, and 3, were evaluated. After preinsertion calibration, the catheters were inserted in the dominant jugular vein of patients with severe head injuries. The catheter reading for SjvO2 was compared with the SjvO2 value measured in a blood sample drawn through the catheter, at intervals up to 72 hours. RESULTS: Catheter 3 (a modified version of the pediatric Swan-Ganz catheter) showed significantly better performance than the other two catheters. Both the initial calibration of the catheter and the calibration with time were significantly better for Catheter 3 than for the other two catheters tested. The Catheter 3 value for SjvO2 was more than 4% different from the co-oximeter value in only 6% of the 4-hour calibration checks, compared with 26% and 29% for Catheters 1 and 2, respectively. CONCLUSION: Catheter 3, which is now being marketed as the Opticath P540-H catheter, represents a significant improvement in performance and may make SjvO2 monitoring in the intensive care unit more practical.

Simultaneous measurement of cortical potassium, calcium, and magnesium levels measured in head injured patients using microdialysis with ion chromatography.

Potassium, calcium and magnesium were measured in 3717 microdialysate samples in 43 patients with head injury experiencing refractory increased ICP, episodes of jugular venous oxygen desaturation and brain death. Cation analysis was performed with 'ion chromatography'. Potassium levels remained stable until severe physiological deterioration occurred, whereupon they increased 100-400%, usually associated with release of amino-acids including glutamate, aspartate, and taurine into the extracellular space. The magnesium and calcium levels remained unchanged, regardless of the severity of physiological deterioration.

Relationship of brain tissue PO2 to outcome after severe head injury.

OBJECTIVE: To determine thresholds of brain tissue PO2 (PbtO2) that are critical for survival after severe head injury. DESIGN: Prospective data collection. SETTING: Neurosurgical intensive care unit of Ben Taub General Hospital, a comprehensive academic neurosurgical facility and Level I trauma center. PATIENTS: Forty-three severely head-injured patients who were not obeying commands on presentation or whose condition deteriorated to this level shortly after admission. INTERVENTIONS: Intracerebral placement of Licox (n=39) or Paratrend (n=4) PO2 probes during craniotomy or in the intensive care unit. MEASUREMENTS AND MAIN RESULTS: PbtO2 monitoring continued for an average of 84.6+/-41.8 hrs. The probes were calibrated before insertion according to the manufacturer's specifications. After removal, probes were tested in room air and in blood gas standard calibration solutions. PbtO2 data were analyzed by comparing the average time that PbtO2 was below the values of 20, 15, 10, 8, 6, 4, and 2 torr (2.7, 2.0, 1.3, 1.0, 0.8, 0.5, and 0.3 kPa, respectively) in patients who were living 3 mos after injury vs. those who died. A Tobit regression analysis using maximum likelihood methods was utilized. Both Licox and Paratrend probes functioned well in room air and in the Level I control. However, in the zero-oxygen solution, the Paratrend probes gave an average reading of 7.0+/-1.4 torr (0.9+/-0.2 kPa), compared with 0.3+/-0.3 torr (0.04+/-0.04 kPa) for the Licox probes. CONCLUSIONS: Analysis of the PbtO2 monitoring data suggested that the likelihood of death increased with increasing duration of time at or below a PbtO2 of 15 torr (2.0 kPa) or with the occurrence of any PbtO2 values of < or =6 torr (< or =0.8 kPa).

Comparison of brain tissue oxygen tension to microdialysis-based measures of cerebral ischemia in fatally head-injured humans.

This study investigated the relationship between brain tissue oxygen tension (PbtO2) and cerebral microdialysate concentrations of several compounds in five patients with refractory intracranial hypertension after severe head injury. The following substances were assayed: lactate and glucose; the excitatory amino acids glutamate and aspartate; and the cations potassium, calcium, and magnesium. Glucose concentrations did not correlate with PbtO2, but lactate increased as PbtO2 decreased. The lactate/glucose ratio exhibited a close relationship to PbtO2, increasing sharply only when oxygen tension reached zero. Although glucose and oxygen eventually reached very low levels and zero, respectively, in these fatally head-injured patients, the terminal decrease in PbtO2 slightly preceded that of glucose in four of the five patients. This time lag is the cause of the poor correlation between glucose and PbtO2. Glutamate and aspartate concentrations both demonstrated a close relationship to PbtO2, with sharp increases not occurring until PbtO2 was zero. Concentrations of these amino acids exhibited a similar pattern in response to decreasing glucose concentrations. Potassium concentrations began increasing at a PbtO2 of 35 mm Hg, which is not generally considered indicative of hypoxia. Sharper increases began occurring once PbtO2 dropped below 15 mm Hg, with a slight rise in the minimum potassium concentrations recorded at these low PbtO2 values. Calcium and magnesium concentrations did not vary in response to PbtO2. In summary, the most robust biochemical indicators of cerebral anoxia were elevations in the lactate/glucose ratio and in the concentrations of lactate and of the excitatory amino acids glutamate and aspartate. Furthermore, the fact that glucose concentrations continue to decrease for a short period after oxygen levels reach zero suggests that cells continue to utilize glucose anaerobically for such functions as maintenance of cellular integrity, with collapse of the cell membrane as evidenced by increases of extracellular glutamate and aspartate not occurring until both oxygen and glucose concentrations reach zero.

Metabolic changes in the brain during transient ischemia measured with microdialysis.

Forty-four patients with severe head injury were monitored for episodes of cerebral ischemia using jugular venous oxygen saturation (sjvO2), brain tissue pO2 (ti-pO2), and a microdialysis probe. The concentration of lactate and glucose were measured in the microdialysate. A total of 10 episodes of global ischemia were observed. The characteristic pattern of a simultaneous decrease in sjvO2 and brain ti-pO2 with an increase in the concentration of lactate occurred in all 10 patients. In addition, 3 episodes of regional ischemia were observed. Although brain ti-pO2 decreased to very low values and the concentration of lactate increased in the microdialysate, sjvO2 remained unchanged. Brain ti-pO2 adds another dimension to our cerebral monitoring by allowing the detection of regional cerebral ischemia.

Brain temperature exceeds systemic temperature in head-injured patients.

OBJECTIVE: To identify the temperature differences in readings taken from the brain, jugular bulb, and core body in head-injured patients. DESIGN: Prospective, observational study. SETTING: Neurosurgical intensive care unit of a university-affiliated county hospital. PATIENTS: Thirty patients with severe head injuries had measurements of brain and core body temperatures. Fourteen patients also had measurements of jugular venous blood at the level of the jugular bulb. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Brain temperature was increased an average of 2.0 degrees F (1.1 degrees C) over the core body temperature. In individual patients, the average brain temperature increase over the core body temperature ranged from -0.5 degrees to 3.8 degrees F (-0.30 degrees to 2.1 degrees C). Jugular vein and core body temperatures were similar. The difference in the brain and body temperatures increased when cerebral perfusion pressure decreased to between 20 and 50 mm Hg. The difference in the brain and body temperatures decreased in those patients treated with barbiturate coma. CONCLUSIONS: Direct measurement of temperature in head-injured patients is a safe procedure. Temperatures in the brain are typically increased over the core body temperature and the jugular bulb temperatures. Jugular vein temperature measurement is not a good measurement of brain temperature since it reflects body, not brain temperature. These findings support the potential importance of monitoring brain temperature and the importance of controlling fever in severely head-injured patients since brain temperature may be higher than expected.

Comparative study of magnetic resonance and CT scan imaging in cases of severe head injury.

The distribution, frequency, and appearance of head injuries were evaluated with MRI and CT in a prospective study of 155 patients with acute (n = 124) and chronic (n = 31) head injuries. MRI was significantly more sensitive than CT in the detection of intraaxial injury at any stage. In severe cases, central structure lesions were detected in approximately 80% of patients. Severity on admission was compatible with MR findings. However it was difficult to decide on neurobehavioural prognosis from initial MRI findings only.