Risk of cerebral vasopasm after subarachnoid hemorrhage reduced by statin therapy: a multivariate analysis of an institutional experience

Object

Impairment of endothelial nitric oxide synthase (eNOS), endothelium-dependent relaxation, and cerebrovascular autoregulation all occur in vasospastic cerebral arteries following subarachnoid hemorrhage (SAH). The 3-hy-droxy-3-methylglutaryl coenzyme A reductase inhibitors, or statins, both improve endothelial function and increase eNOS messenger RNA, protein, and enzymatic activity threefold. Increasing experimental evidence in animal models of SAH suggests that statins may ameliorate cerebral vasospasm. The authors hypothesized that patients chronically treated with statins would have a decreased risk of symptomatic vasospasm after SAH.

Methods

The authors retrospectively reviewed the charts of 115 patients with SAH who were consecutively admitted to the Neuroscience Intensive Care Unit of Duke University between 1998 and 2001. The independent association of statin therapy to symptomatic vasospasm was assessed using multivariate logistic regression analysis. Fifteen patients (13%) admitted with SAH were receiving statin therapy for at least 1 month before admission. Forty-nine patients (43%) experienced symptomatic vasospasm a mean of 5.8 ± 3 days after onset of SAH. Current statin therapy on admission (odds ratio [OR] 0.09, 95% confidence interval [CI] 0.01–0.77) was independently associated with an 11-fold reduction in the risk of symptomatic vasospasm. Fisher Grade 3 SAH (OR 2.82, 95% CI 1.50–5.71) and rupture of anterior cerebral or internal carotid artery aneurysm (OR 3.77, 95% CI 1.29–10.91) were independently associated with an increased risk of symptomatic vasospasm.

Conclusions

In this retrospective case series, patients who received statin therapy for at least 1 month demonstrated an 11-fold decrease in the risk of developing symptomatic vasospasm after SAH.

Levetiracetam is neuroprotective in murine models of closed head injury and subarachnoid hemorrhage

OBJECTIVES

Prophylactic treatment with antiepileptic drugs is common practice following subarachnoid hemorrhage (SAH) and traumatic brain injury. However, commonly used antiepileptic drugs have multiple drug interactions, require frequent monitoring of serum levels, and are associated with adverse effects that may prompt discontinuation. In the current study, we test the hypothesis that levetiracetam, an anticonvulsant with favorable interaction and adverse event profiles, is neuroprotective in clinically relevant models of SAH and closed head injury (CHI).

METHODS

A single intravenous dose of vehicle, low-dose (18 mg/kg), or high-dose (54 mg/kg) levetiracetam was administered intravenously followed CHI. Functional assessments were performed on a daily basis, and histological assessments performed at 24 hours. In a separate series of experiments, mice were randomized to receive intravenous administration of vehicle, low-dose, or high-dose levetiracetam every 12 hours for 3 days following SAH. Functional endpoints were assessed daily, followed by measurement of MCA luminal diameter on day 3.

RESULTS

A single dose of levetiracetam improved functional and histological outcomes after CHI. This effect appeared specific for levetiracetam and was not associated with fosphenytoin treatment. Treatment with levetiracetam also improved functional outcomes and reduced vasospasm following SAH.

CONCLUSION

Levetiracetam is neuroprotective in clinically relevant animal models of SAH and CHI. Levetiracetam may be a therapeutic alternative to phenytoin following acute brain injury in the clinical setting when seizure prophylaxis is indicated.

Effects of a manganese (III) porphyrin catalytic antioxidant in a mouse closed head injury model

Closed head injury induces cerebral oxidative stress. The efficacy of a Mn (III) porphyrin catalytic antioxidant was assessed in a mouse closed head injury model. Mice were subjected to closed head injury and treated 15 min later with an i.v. bolus of vehicle or 3 mg/kg MnTE-2-PyP5+. Aconitase activity, Fluoro-Jade staining, glial fibrillary acidic protein immunoreactivity, and rotarod falling latencies were measured. Closed head injury altered all variables. MnTE-2-PyP5+ had no effect on any variable with the exception of attenuation of aconitase inactivation at 2 h post-closed head injury. In a second experiment, mice received 3 mg/kg or 6 mg/kg MnTE-2-PyP5+ or vehicle i.v. 15 min post-closed head injury. Rotarod and Morris water maze latencies were measured. Closed head injury altered performance in both tests. No statistically significant effect of MnTE-2-PyP5+ was observed. We conclude that single dose MnTE-2-PyP5+ does not alter outcome in this mouse closed head injury model.

A Novel apoE-Derived Therapeutic Reduces Vasospasm and Improves Outcome in a Murine Model of Subarachnoid Hemorrhage

INTRODUCTION

Recent clinical observations demonstrate that the APOE4 genotype increases the development of delayed ischemic deficit and worsens prognosis following aneurysmal subarachnoid hemorrhage (SAH). In the current study, we use targeted replacement mice expressing only human apoE3 or apoE4 to model the isoform-specific effects of apoE following SAH. We then test the hypothesis that an apoE-derived therapeutic peptide reduces vasospasm and improves functional recovery after SAH.

METHODS

Experimental SAH was induced in APOE3- and APOE4-targeted replacement mice. For 3 days following injury, daily functional assessments were made. Mice were then sacrificed and the cerebral vasculature visualized to quantify vasospasm. In a separate experiment, C57Bl/6 mice were treated with intravenous injection of vehicle, low-dose, or high-dose apoE-mimetic peptide every 12 hours for 3 days post-SAH. Functional endpoints were assessed on a daily basis, followed by measurement of middle cerebral artery diameter.

RESULTS

Mice expressing the apoE4 isoform had greater functional deficit, mortality, cerebral edema, and vasospasm as compared with their apoE3 counterparts. Mice treated with the apoE-mimetic peptide had decreased mortality, functional deficits, and histological evidence of vasospasm as compared with vehicle-treated animals.

CONCLUSION

Consistent with the clinical literature, the apoE4 isoform is associated with an increased incidence of vasospasm and poor functional recovery after experimental SAH. An apoE-derived peptide represents a novel therapeutic approach for the treatment of SAH.

Toward Solving the Sedation-Assessment Conundrum: Bispectral Index Monitoring and Sedation Interruption

The sedation-assessment conundrum is defined by two diametrically opposed goals: to maintain an appropriate level of sedation, and to obtain a comprehensive neurologic examination that most accurately reflects the patient's neurologic status. A case presentation leads to a discussion of over-sedation and under-sedation issues that impact the care of critically ill patients. This information is useful in understanding the many methods of assessing sedation and interpreting individualized patient responses to sedation. The use of bi-spectral index monitoring and periods of sedation interruption are discussed within the context of addressing the sedation-assessment conundrum.

Simvastatin reduces vasospasm after aneurysmal subarachnoid hemorrhage: results of a pilot randomized clinical trial

BACKGROUND AND PURPOSE

Cerebral vasospasm remains a major source of morbidity after aneurysmal subarachnoid hemorrhage (SAH). We demonstrate that simvastatin reduces serum markers of brain injury and attenuates vasospasm after SAH.

METHODS

Patients with angiographically documented aneurysmal SAH were randomized within 48 hours of symptom onset to receive either simvastatin (80 mg daily; n=19) or placebo (n=20) for 14 days. Plasma alanine aminotransferase, aspartate aminotransferase, and creatine phosphokinase were recorded weekly to evaluate laboratory evidence of hepatitis or myositis. Serum markers of brain injury were recorded daily. The primary end point of vasospasm was defined as clinical impression (delayed ischemic deficit not associated with rebleed, infection, or hydrocephalus) in the presence of > or =1 confirmatory radiographic test (angiography or transcranial Doppler demonstrating mean V(MCA) >160 m/sec).

RESULTS

There were no significant differences in laboratory-defined transaminitis or myositis between groups. No patients developed clinical symptoms of myopathy or hepatitis. Plasma von Willebrand factor and S100beta were decreased 3 to 10 days after SAH (P<0.05) in patients receiving simvastatin versus placebo. Highest mean middle cerebral artery transcranial Doppler velocities were significantly lower in the simvastatin-treated group (103+/-41 versus 149+/-47; P<0.01). In addition, vasospasm was significantly reduced (P<0.05) in the simvastatin-treated group (5 of 19) compared with those who received placebo (12 of 20).

CONCLUSIONS

The use of simvastatin as prophylaxis against delayed cerebral ischemia after aneurysmal SAH is a safe and well-tolerated intervention. Its use attenuates serum markers associated with brain injury and decreases the incidence of radiographic vasospasm and delayed ischemic deficit.

A novel therapeutic derived from apolipoprotein E reduces brain inflammation and improves outcome after closed head injury

Although apolipoprotein E4 (APOE4) was initially identified as a susceptibility gene for the development of Alzheimer's disease, the presence of the APOE4 allele is also associated with poor outcome after acute brain injury. One mechanism by which apoE may influence neurological outcome is by downregulating the neuroinflammatory response. Because it does not readily cross the blood-brain barrier, the apoE holoprotein has limited therapeutic potential. We demonstrate that a single intravenous injection of a small peptide derived from the apoE receptor binding region crosses the blood-brain barrier and significantly improves histological and functional outcomes after traumatic brain injury (TBI). The development of an apoE-based intervention represents a novel therapeutic strategy in the management of acute brain injury.

Accurate patient history contributes to differentiating diabetes insipidus: a case study

This case study highlights the important contribution of nursing in obtaining an accurate health history. The case discussed herein initially appeared to be neurogenic diabetes insipidus (DI) secondary to a traumatic brain injury. The nursing staff, by reviewing the patient's health history with his family, discovered a history of polydipsia and long-standing lithium use. Lithium is implicated in drug-induced nephrogenic DI, and because the patient had not received lithium since being admitted to the hospital, his treatment changed to focus on nephrogenic DI. By combining information from the patient history, the physical examination, and radiologic and laboratory studies, the critical care team demonstrated that the patient had been self-treating his lithium-induced nephrogenic DI and developed neurogenic DI secondary to brain trauma. Thus successful treatment required that nephrogenic and neurogenic DI be treated concomitantly.

Correlation of serum brain natriuretic peptide with hyponatremia and delayed ischemic neurological deficits after subarachnoid hemorrhage

OBJECTIVE

Serum brain natriuretic peptide (BNP) is elevated after subarachnoid hemorrhage (SAH), causes diuresis and natriuresis (cerebral salt wasting), and may exacerbate delayed ischemic neurological deficits. We examined the temporal relationship between serum BNP elevation, hyponatremia, and the onset of delayed ischemic neurological deficits and determined whether serum BNP levels correlated with the 2-week outcome after SAH.

METHODS

Serum BNP and sodium were measured prospectively every 12 hours for 14 days in 40 consecutive patients admitted with SAH. All patients remained euvolemic, underwent transcranial Doppler assessment every 48 hours, and underwent angiography at the onset of delayed neurological deficits. New-onset neurological deficits were attributed to vasospasm only in the absence of other causes and when supported by transcranial Doppler or cerebral angiography.

RESULTS

Sixteen patients (40%) experienced symptomatic cerebral vasospasm after SAH. A more than threefold increase in admission serum BNP was associated with the onset of hyponatremia (P < 0.05). Mean BNP levels were similar between vasospasm and nonvasospasm patients fewer than 3 days after SAH (126 +/- 39 pg/ml versus 154 +/- 40 pg/ml; P = 0.61) but were elevated in the vasospasm cohort 4 to 6 days after SAH (285 +/- 67 pg/ml versus 116 +/- 30 pg/ml; P < 0.01), 7 to 9 days after SAH (278 +/- 72 pg/ml versus 166 +/- 45 pg/ml; P < 0.01), and 9 to 12 days after SAH (297 +/- 83 pg/ml versus 106 +/- 30 pg/ml; P < 0.01). BNP level remained independently associated with vasospasm adjusting for Fisher grade and Hunt and Hess grade (odds ratio, 1.28; 95% confidence interval, 1.1-1.6). In patients in whom vasospasm developed, mean serum BNP increased 5.4-fold within 24 hours after vasospasm onset and 11.2-fold the first 3 days after vasospasm onset. Patients with increasing BNP levels from admission demonstrated no change (0 +/- 3) in Glasgow Coma Scale score 2 weeks after SAH versus a 3.0 +/- 2 (P < 0.05) improvement in Glasgow Coma Scale score in patients without increasing serum BNP levels.

CONCLUSION

Increasing serum BNP levels independently were associated with hyponatremia, significantly increased the first 24 hours after onset of delayed ischemic neurological deficits, and predicted the 2-week Glasgow Coma Scale score.

Effects of Isoflurane Versus Fentanyl–Nitrous Oxide Anesthesia on Long-term Outcome from Severe Forebrain Ischemia in the Rat

Background

This study examined long-term outcome from severe forebrain ischemia in the rat, as a function of anesthetic given during the ischemic injury.

Methods

Rats were subjected to 10 min of near-complete forebrain ischemia while anesthetized with either 1.4% isoflurane or 70% nitrous oxide-fentanyl. Neurologic and histologic outcomes were measured at 5 days, 3 weeks, or 3 months after ischemia.

Results

At 5 days, isoflurane-anesthetized rats had less damage than did fentanyl-nitrous oxide-anesthetized rats (mean +/- SD, percent alive hippocampal CA1 neurons = 58+/-29 vs. 20+/-16, respectively; P = 0.011). This was accompanied by improved motor function in the isoflurane group (P = 0.002). At 3 weeks, there was no difference between groups for either outcome variable (percent alive CA1 neurons = 35+/-26 and 36+/-28 for isoflurane and fentanyl-nitrous oxide, respectively). Similarly, at 3 months, there was no difference between groups (percent alive CA1 neurons = 56+/-27 and 60+/-27 for isoflurane and fentanyl-nitrous oxide, respectively). Morris water maze performance at 3 months was similar between anesthetic groups and was also similar to sham performance. The percent alive CA1 neurons in the fentanyl-nitrous oxide group increased with duration of recovery (P = 0.004). There were no differences among isoflurane groups over time (5 days vs. 3 weeks, P = 0.26; 5 days vs. 3 months, P = 0.99; 3 week vs. 3 months, P = 0.32).

Conclusions

This study found no change in the percent alive CA1 hippocampal neurons as a function of duration of recovery from severe forebrain ischemia in isoflurane anesthetized rats. In contrast, the percent alive CA1 neurons in fentanyl-nitrous oxide-anesthetized rats tripled over 3 months of recovery. The natural history of long-term responses to forebrain ischemia requires further study before conclusions can be drawn with respect to the permanence of isoflurane neuroprotection.

Novel diagnostic test for acute stroke

BACKGROUND AND PURPOSE

The absence of a widely available and sensitive diagnostic test for acute cerebral ischemia remains a significant limitation in the diagnosis and management of stroke. The objective of this study was to examine the feasibility of developing a diagnostic panel of blood-borne biochemical markers of cerebral ischemia.

METHODS

Serial blood samples were obtained from patients (n=65 with suspected ischemic stroke, n=157 control subjects) presenting to an academic medical center emergency department. We analyzed 26 blood-borne markers believed to play a role in the ischemic cascade and created a 3-variable logistic regression model to predict the clinical diagnosis of stroke, defined as persistent neurological symptoms of cerebral ischemia lasting >24 hours.

RESULTS

Of the 26 blood-borne markers analyzed, univariate logistic analysis revealed that 4 were highly correlated with stroke (P<0.001): a marker of glial activation (S100beta), 2 markers of inflammation (matrix metalloproteinase-9 and vascular cell adhesion molecule), and 1 marker of thrombosis (von Willebrand factor). When the outcome level was set to a cutoff of P=0.1, our logistic model provided a sensitivity and specificity of 90% for predicting stroke.

CONCLUSIONS

A panel of blood-borne biochemical markers may be helpful in identifying patients with acute cerebral ischemia who could benefit from urgent care. Such a test may also be helpful in identifying stroke patients in the prehospital setting so that they could be fast-tracked to an institution equipped to care for patients with acute stroke.

APOE genotype and an ApoE-mimetic peptide modify the systemic and central nervous system inflammatory response

Human apolipoprotein E is the major apolipoprotein expressed in the brain and exists as three isoforms, designated E2, E3, and E4. Although evidence suggests that apolipoprotein E plays an important role in modifying systemic and brain inflammatory responses, there is little data investigating apoE isoform-specific effects in vivo. In this study, we compared the inflammatory responses of targeted-replacement mice expressing the human APOE3 and APOE4 genes after intravenous administration of lipopolysaccharide. Animals expressing the E4 allele had significantly greater systemic and brain elevations of the pro-inflammatory cytokines TNFalpha and IL-6 as compared with their APOE3 counterparts, suggesting an isoform-specific effect of the immunomodulatory properties of apoE. Furthermore, intravenous administration of a small apoE-mimetic peptide derived from the receptor-binding region of the apoE holoprotein (apoE-(133-149)) similarly suppressed both systemic and brain inflammatory responses in mice after lipopolysaccharide administration. These results suggest that apoE plays an isoform-specific role in mediating the systemic and brain inflammatory responses. Moreover, because exogenous administration of this apoE mimetic peptide is effective at suppressing both systemic and brain inflammation, it may represent a novel therapeutic strategy for diseases characterized by systemic or central nervous system inflammation, such as septic shock, multiple sclerosis, and traumatic brain injury.

Leukocytosis as an independent risk factor for cerebral vasospasm following aneurysmal subarachnoid hemorrhage

OBJECT

The identification of patients at an increased risk for cerebral vasospasm after subarachnoid hemorrhage (SAH) may allow for more aggressive treatment and improved patient outcomes. Note, however, that blood clot size on admission remains the only factor consistently demonstrated to increase the risk of cerebral vasospasm after SAH. The goal of this study was to assess whether clinical, radiographic, or serological variables could be used to identify patients at an increased risk for cerebral vasospasm.

METHODS

A retrospective review was conducted in all patients with aneurysmal or spontaneous nonaneurysmal SAH who were admitted to the authors' institution between 1995 and 2001. Underlying vascular diseases (hypertension or chronic diabetes mellitus), Hunt and Hess and Fisher grades, patient age, aneurysm location, craniotomy compared with endovascular aneurysm stabilization, medications on admission, postoperative steroid agent use, and the occurrence of fever, hydrocephalus, or leukocytosis were assessed as predictors of vasospasm. Two hundred twenty-four patients were treated for SAH during the review period. One hundred one patients (45%) developed symptomatic vasospasm. Peak vasospasm occurred 5.8 +/- 3 days after SAH. There were four independent predictors of vasospasm: Fisher Grade 3 SAH (odds ratio [OR] 7.5, 95% confidence interval [CI] 3.5-15.8), peak serum leukocyte count (OR 1.09, 95% CI 1.02-1.16), rupture of a posterior cerebral artery (PCA) aneurysm (OR 0.05, 95% CI 0.01-0.41), and spontaneous nonaneurysmal SAH (OR 0.14, 95% CI 0.04-0.45). A serum leukocyte count greater than 15 x 10(9)/L was independently associated with a 3.3-fold increase in the likelihood of developing vasospasm (OR 3.33, 95% CI 1.74-6.38).

CONCLUSIONS

During this 7-year period, spontaneous nonaneurysmal SAH and ruptured PCA aneurysms decreased the odds of developing vasospasm sevenfold and 20-fold, respectively. The presence of Fisher Grade 3 SAH on admission or a peak leukocyte count greater than 15 x 10(9)/L increased the odds of vasospasm sevenfold and threefold, respectively. Monitoring of the serum leukocyte count may allow for early diagnosis and treatment of vasospasm.

Protective effect of apolipoprotein E-mimetic peptides on N-methyl-D-aspartate excitotoxicity in primary rat neuronal-glial cell cultures

Apolipoprotein E (apoE) is a 34-kD protein with multiple biological properties. Recent clinical and preclinical observations implicate a role for apoE in modifying the response of the brain to focal and global ischemia. One mechanism by which apoE might exert these effects is by reducing glutamate-induced excitotoxic neuronal injury associated with ischemic insults. We demonstrate that human recombinant apoE confers a mild neuroprotective effect in primary neuronal-glial cultures exposed to 100 microM N-methyl-D-aspartate. Furthermore, a peptide derived from the receptor-binding region of apoE (residues 133-149) maintained a significant helical population as assessed by circular dichroism, and completely suppressed the neuronal cell death and calcium influx associated with N-methyl-D-aspartate exposure. Neuroprotection was greatest when the peptide was added concurrently with N-methyl-D-aspartate; however, a significant protection was observed when peptide was preincubated and washed off prior to N-methyl-D-aspartate exposure. These results suggest that one mechanism by which apoE may modify the CNS response to ischemia is by partially blocking glutamate excitotoxicity. Moreover, small peptide fragments derived from the receptor-binding region of apoE have enhanced bioactivity compared with the intact holoprotein, and may represent a novel therapeutic strategy for the treatment of brain ischemia.

Simvastatin increases endothelial nitric oxide synthase and ameliorates cerebral vasospasm resulting from subarachnoid hemorrhage

BACKGROUND AND PURPOSE

Endothelial nitric oxide synthase (eNOS) activity is decreased after subarachnoid hemorrhage (SAH). Simvastatin increases eNOS activity. We hypothesized that simvastatin would increase eNOS protein and ameliorate SAH-induced cerebral vasospasm.

METHODS

Mice were treated with subcutaneous simvastatin or vehicle for 14 days and then subjected to endovascular perforation of the right anterior cerebral artery or sham surgery. Three days later, neurological deficits were scored (5 to 27; 27=normal), and middle cerebral artery diameter and eNOS protein were measured. The study was repeated, but simvastatin treatment was started after SAH or sham surgery.

RESULTS

In SAH mice, simvastatin pretreatment increased middle cerebral artery diameter (SAH-simvastatin=74+/-22 micro m, SAH-vehicle=52+/-18 micro m, P=0.03; sham-simvastatin=102+/-8 micro m, sham-vehicle=105+/-6 micro m). Pretreatment reduced neurological deficits (SAH-simvastatin=25+/-2, SAH-vehicle=20+/-2, P=0.005; sham-simvastatin and sham-vehicle=27+/-0). Simvastatin pretreatment also increased eNOS protein. Simvastatin posttreatment caused a modest increase in middle cerebral artery diameter in SAH mice (SAH-simvastatin=56+/-12 micro m, SAH-vehicle=45+/-4 micro m, P=0.03; sham-simvastatin=92+/-13 micro m, sham-vehicle=99+/-10 micro m) and reduced neurological deficits (SAH-simvastatin=21+/-1, SAH-vehicle=19+/-2, P=0.009). Simvastatin posttreatment did not significantly increase eNOS protein.

CONCLUSIONS

Simvastatin treatment before or after SAH attenuated cerebral vasospasm and neurological deficits in mice. The mechanism may be attributable in part to eNOS upregulation.

Serum von Willebrand factor, matrix metalloproteinase-9, and vascular endothelial growth factor levels predict the onset of cerebral vasospasm after aneurysmal subarachnoid hemorrhage

OBJECTIVE

Endothelial damage and intimal proliferation occur in vasospastic cerebral arteries after subarachnoid hemorrhage (SAH). In the peripheral vasculature, endothelial damage increases intimal matrix metalloproteinase-9 (MMP-9) and vascular endothelial growth factor (VEGF) levels, causing neointimal proliferation. We hypothesized that serum von Willebrand factor (vWF) (a marker of endothelial cell death), MMP-9, and VEGF levels could serve as prognostic markers in predicting the occurrence of cerebral vasospasm.

METHODS

Venous serum vWF, MMP-9, and VEGF levels were prospectively measured daily, for 12 days or until the onset of vasospasm, for 45 consecutive patients admitted with SAH (n = 38) or admitted for elective aneurysm clipping (control subjects, n = 7). The development of transcranial Doppler flow velocities of more than 180 cm/s and/or new focal neurological deficits with angiographically confirmed vasospasm was considered the onset of vasospasm. To establish whether these markers were specific for vasospasm versus ischemia, blood samples were obtained from a concurrent group of 42 patients within 24 hours after stroke onset unrelated to SAH.

RESULTS

Fifty-seven percent of patients (22 of 38 patients) developed vasospasm, 4 to 11 days after SAH (median, 7 d). Mean peak serum vWF, MMP-9, and VEGF levels were increased in the SAH prevasospasm cohort, compared with the SAH nonvasospasm cohort (vWF, 5526 +/- 929 versus 4934 +/- 599 ng/ml, P = 0.01; MMP-9, 705 +/- 338 versus 438 +/- 154 ng/ml, P = 0.006; VEGF, 0.12 +/- 0.06 versus 0.06 +/- 0.06 ng/ml, P = 0.023). Mean peak vWF, MMP-9, and VEGF levels for the focal ischemia cohort (vWF, 4645 +/- 875 ng/ml, P = 0.01; MMP-9, 250 +/- 308 ng/ml, P = 0.001; VEGF, 0.03 +/- 0.04 ng/ml, P = 0.001) were markedly lower in comparison with the SAH prevasospasm cohort and were unchanged in comparison with the control cohort. vWF levels of more than 5500 ng/ml, VEGF levels of more than 0.12 ng/ml, and MMP levels of more than 700 ng/ml each independently increased the odds of subsequent vasospasm (18-, 20-, and 25-fold, respectively).

CONCLUSION

The development of cerebral vasospasm after SAH was preceded by increases in serum vWF, MMP-9, and VEGF levels. Increased serum vWF, MMP-9, and VEGF levels could accurately predict the onset of cerebral vasospasm after SAH. These factors were not elevated by SAH alone or in a separate cohort of patients with ischemic stroke, suggesting that these factors might play a role in the pathogenesis of human cerebral vasospasm.

Apolipoprotein E affects the central nervous system response to injury and the development of cerebral edema

Apolipoprotein E has been implicated in modifying neurological outcome after traumatic brain injury, although the mechanisms by which this occurs remain poorly defined. To investigate the role of endogenous apolipoprotein E following acute brain injury, noninvasive magnetic resonance imaging was performed on anesthetized mice following closed head injury. Effacement of the lateral ventricle was used as a radiographic surrogate for cerebral edema. At 24 hours following injury, apolipoprotein E-deficient animals had a greater degree of cerebral edema as compared to matched controls. In addition, the brains of apolipoprotein E-deficient animals had a significantly greater upregulation of tissue necrosis factor alpha messenger ribonucleic acid as compared to controls as early as 1-hr post injury. Thus, modulation of the endogenous central nervous system inflammatory response may be one mechanism by which apolipoprotein E affects outcome following acute brain injury.

Apolipoprotein E modulates glial activation and the endogenous central nervous system inflammatory response

Apolipoprotein E (apoE) is a 299 amino acid protein that is associated with risk of developing Alzheimer's Disease (AD) and outcome after acute brain injury. To investigate the possibility that apoE modulates glial activation we studied the effect of endogenous apoE on inflammatory gene regulation in vitro and in vivo. Our results indicate that apoE downregulates CNS production of TNFalpha, Il-1beta, and Il-6 mRNA following stimulation with lipopolysaccharide (LPS). This effect of endogenous apoE on inflammatory gene regulation appears to be specific, and may account for the biological role that apoE plays in acute and chronic human neurological disease.

Quantitative level of protection offered to workers by ACGIH threshold limit values occupational exposure limits

The details of the example or modeling methodologies used herein are not critical to the general point of this article, which advises the estimation of residual risk at the OEL by using some quantitative modeling structure. Specifically, the authors believe that an explicit attempt to gauge the level of residual risk at the OEL based on conceptual stochastic models with transparent and testable assumptions could be seen as an important enhancement to the process. This is especially true in sharing the OEL deliberations and explaining OEL decisions to the stakeholders. Indeed, if this approach is used, it is critically important to understand and continually communicate that this "cloud of uncertainty" represents model estimates in which the true risk would most likely be less than worst case estimates and could possibly be zero. It is also possible but highly unlikely that it could be higher than the worst case upper-bound estimate. The above quantitative estimation scheme represents a possible improvement that could provide a reasoned attempt on the part of the risk assessors to use rational science (i.e., conceptual models with transparent and testable assumptions) to inform all of the OEL users and stakeholders of their meaning.

Survival and outcome after endotracheal intubation for acute stroke

OBJECTIVE

To assess survival and functional outcome in patients endotracheally intubated after ischemic stroke (IS) or spontaneous intracerebral hemorrhage (ICH).

BACKGROUND

Endotracheal intubation is both a necessary life support intervention and a measure of severity in IS or ICH. Knowledge of associated clinical variables may improve the estimation of early prognosis and guide management in these patients.

METHODS

We reviewed 131 charts of patients with IS or ICH who were admitted to the Neurosciences Intensive Care Unit at Duke University Medical Center between July 1994 and June 1997 and required endotracheal intubation. Stroke risk factors, stroke type (IS or ICH) and location (hemispheric, brainstem, or cerebellum), circumstances surrounding intubation, neurologic assessment (Glasgow Coma Score [GCS] and brainstem reflexes), comorbidities, and disposition at discharge were documented. Survivors were interviewed for Barthel Index (BI) scores.

RESULTS

Survival was 51% at 30 days and 39% overall. Variables that significantly correlated with 30-day survival in multivariate analysis included GCS at intubation (p = 0.03) and absent pupillary light response (p = 0.008). Increase in the GCS also correlated with improved functional outcome measured by the BI (p = 0.0003). In patients with IS, age and GCS at intubation predicted survival, and in patients with ICH, absent pupillary light response predicted survival.

CONCLUSIONS

Predictors for mortality differ between patients with IS and ICH; however, decreased level of consciousness is the most important determinant of increased mortality and poor functional outcome. Absent pupillary light responses also correspond with a poor prognosis for survival, but further validation of this finding is needed.

Hospital closure: an efficiency analysis

Logistic regression analysis was used to test the hypothesis that market forces have led to recent hospital closures. Specifically, inefficient and underutilized hospitals in competitive markets were hypothesized to be at greater risk for closure. While past studies used crude measures of hospital efficiency to predict closure, this study used data envelopment analysis to construct an efficiency index. Mixed support was found for the market forces hypothesis; however, contrary to expectations, inefficient hospitals were not shown to be at increased risk for closure. In fact, efficiency proved to be a weak, but positive, predictor of closure.