A systems approach to designing effective clinical trials using simulations.

BACKGROUND: Pharmacogenetics in warfarin clinical trials have failed to show a significant benefit in comparison with standard clinical therapy. This study demonstrates a computational framework to systematically evaluate preclinical trial design of target population, pharmacogenetic algorithms, and dosing protocols to optimize primary outcomes. METHODS AND RESULTS: We programmatically created an end-to-end framework that systematically evaluates warfarin clinical trial designs. The framework includes options to create a patient population, multiple dosing strategies including genetic-based and nongenetic clinical-based, multiple-dose adjustment protocols, pharmacokinetic/pharmacodynamics modeling and international normalization ratio prediction, and various types of outcome measures. We validated the framework by conducting 1000 simulations of the applying pharmacogenetic algorithms to individualize dosing of warfarin (CoumaGen) clinical trial primary end points. The simulation predicted a mean time in therapeutic range of 70.6% and 72.2% (P=0.47) in the standard and pharmacogenetic arms, respectively. Then, we evaluated another dosing protocol under the same original conditions and found a significant difference in the time in therapeutic range between the pharmacogenetic and standard arm (78.8% versus 73.8%; P=0.0065), respectively. CONCLUSIONS: We demonstrate that this simulation framework is useful in the preclinical assessment phase to study and evaluate design options and provide evidence to optimize the clinical trial for patient efficacy and reduced risk.

Clopidogrel with or without omeprazole in coronary artery disease.

BACKGROUND: Gastrointestinal complications are an important problem of antithrombotic therapy. Proton-pump inhibitors (PPIs) are believed to decrease the risk of such complications, though no randomized trial has proved this in patients receiving dual antiplatelet therapy. Recently, concerns have been raised about the potential for PPIs to blunt the efficacy of clopidogrel. METHODS: We randomly assigned patients with an indication for dual antiplatelet therapy to receive clopidogrel in combination with either omeprazole or placebo, in addition to aspirin. The primary gastrointestinal end point was a composite of overt or occult bleeding, symptomatic gastroduodenal ulcers or erosions, obstruction, or perforation. The primary cardiovascular end point was a composite of death from cardiovascular causes, nonfatal myocardial infarction, revascularization, or stroke. The trial was terminated prematurely when the sponsor lost financing. RESULTS: We planned to enroll about 5000 patients; a total of 3873 were randomly assigned and 3761 were included in analyses. In all, 51 patients had a gastrointestinal event; the event rate was 1.1% with omeprazole and 2.9% with placebo at 180 days (hazard ratio with omeprazole, 0.34, 95% confidence interval [CI], 0.18 to 0.63; P<0.001). The rate of overt upper gastrointestinal bleeding was also reduced with omeprazole as compared with placebo (hazard ratio, 0.13; 95% CI, 0.03 to 0.56; P = 0.001). A total of 109 patients had a cardiovascular event, with event rates of 4.9% with omeprazole and 5.7% with placebo (hazard ratio with omeprazole, 0.99; 95% CI, 0.68 to 1.44; P = 0.96); high-risk subgroups did not show significant heterogeneity. The two groups did not differ significantly in the rate of serious adverse events, though the risk of diarrhea was increased with omeprazole. CONCLUSIONS: Among patients receiving aspirin and clopidogrel, prophylactic use of a PPI reduced the rate of upper gastrointestinal bleeding. There was no apparent cardiovascular interaction between clopidogrel and omeprazole, but our results do not rule out a clinically meaningful difference in cardiovascular events due to use of a PPI. (Funded by Cogentus Pharmaceuticals; ClinicalTrials.gov number, NCT00557921.).

A practical mortality risk score for emergent colectomy.

BACKGROUND: Critically ill patients requiring emergent colectomy have significant mortality risk. OBJECTIVE: A national administrative database was used to compose a simple scoring scheme for predicting in-hospital mortality risk. DESIGN: The 2007 to 2009 Nationwide Inpatient Sample was queried to identify patients requiring nonelective colectomy. Multivariable binary logistic regression analysis was used to identify predictors that increased mortality. Each predictor was given a point value, based on the corresponding logit, the sum of which constituted a risk score. The scoring system was tested by using k-partitions cross-validation. SETTINGS: This study is based on database analysis. PATIENTS: A total of 338,348 cases were identified. Mean age was 64, and 53% of the patients were women. MAIN OUTCOME MEASURES: The primary outcomes measured were mortality and risk score development. RESULTS: The overall mortality risk was 9%. Regression analysis identified the following risk factors and assigned points: acute renal failure (6), hemodialysis (6), age >65 (4), peripheral vascular disease (4), myocardial infarction (4), chronic obstructive pulmonary disease (2), cardiac arrhythmia (1), and congestive heart failure (1). The maximum score observed was 26 (of a possible 28), which corresponded to 100% mortality. Receiver operator characteristic analysis showed an area under the curve of 0.81. LIMITATIONS: This study was limited because of its retrospective nature, and because it used database data with variability in coding among participating institutions. CONCLUSIONS: With the use of a simple 8-variable scoring system, inpatient mortality estimates can be made for patients requiring emergent colectomy. When used judiciously, it can be used as a tool when counseling patients and family both before and after surgery.

Predictors of bleeding and time dependence of association of bleeding with mortality: insights from the Trial to Assess Improvement in Therapeutic Outcomes by Optimizing Platelet Inhibition With Prasugrel--Thrombolysis in Myocardial Infarction 38 (TRITON-TIMI 38).

BACKGROUND: The balance between benefit (ischemia protection) and risk (bleeding) is a key consideration in choosing the intensity of antiplatelet therapy for patients with acute coronary syndromes. The goals of this analysis were to identify baseline characteristics that independently predict bleeding and to determine how bleeding events impact the subsequent mortality in the Trial to Assess Improvement in Therapeutic Outcomes by Optimizing Platelet Inhibition With Prasugrel--Thrombolysis in Myocardial Infarction 38 (TRITON-TIMI 38). METHODS AND RESULTS: Multivariable Cox regression analyses adjusted for treatment, baseline, and procedural variables were used to determine the predictors for serious (TIMI major or minor) bleeding. To analyze the hazard ratio and time dependency of bleeding on mortality, we used iterative day-to-day landmark analyses after the bleed. From the 13 420 patients with acute coronary syndromes included in this analysis, 534 (4.0%) experienced a serious bleeding event. Variables with the highest strength of association with risk of serious bleeding were female sex, use of a glycoprotein IIb/IIIa inhibitor, duration of intervention, age, assignment to prasugrel, regional characteristics, admission diagnosis of ST-elevation myocardial infarction, femoral access for angiography, creatinine clearance, hypercholesterolemia, and arterial hypertension. Serious bleeding was associated with a significantly increased adjusted hazard ratio of 5.84 (95% confidence interval 4.11 to 8.29) for mortality. However, the hazard ratio did not differ statistically from baseline risk by 40 days after the bleeding event. CONCLUSIONS: The major predictors of serious bleeding were a combination of patient and procedural characteristics and antiplatelet therapies. Although serious bleeding was strongly associated with mortality within the first month of the bleeding event, this association was not significant beyond 40 days. CLINICAL TRIAL REGISTRATION INFORMATION: http://www.clinicaltrial.gov. Unique identifier NCT00097591.

Randomized trial of atopaxar in the treatment of patients with coronary artery disease: the lessons from antagonizing the cellular effect of Thrombin­Coronary Artery Disease Trial.

BACKGROUND: Thrombin is a key mediator of platelet activation. Atopaxar is a reversible protease-activated receptor-1 antagonist that interferes with thrombin-mediated platelet effects. The phase II Lessons From Antagonizing the Cellular Effect of Thrombin-Coronary Artery Disease (LANCELOT-CAD) trial examined the safety and tolerability of prolonged therapy with atopaxar in subjects with CAD. METHODS AND RESULTS: Subjects with a qualifying history were randomized in a double-blind fashion to 3 dosing regimens of atopaxar (50, 100, or 200 mg daily) or matching placebo for 24 weeks and followed up for an additional 4 weeks. The key safety end points were bleeding according to the Clopidogrel in Unstable Angina to Prevent Recurrent Events (CURE) and Thrombolysis in Myocardial Infarction (TIMI) classifications. Secondary objectives included platelet aggregation and major adverse cardiac events. Seven hundred and twenty subjects were randomized. Overall bleeding rates tended to be higher with atopaxar compared with placebo by CURE criteria (placebo, 0.6%; atopaxar, 3.9%; relative risk, 6.82, P=0.03; 50 mg, 3.9%; 100 mg, 1.7%; 200 mg, 5.9%; P for trend=0.01) and TIMI criteria (placebo, 6.8%; atopaxar, 10.3%; relative risk, 1.52, P=0.17; 50 mg, 9.9%; 100 mg, 8.1%; 200 mg, 12.9%; P for trend=0.07). There was no difference in major bleeding. Major adverse cardiac events were numerically lower in the atopaxar subjects. All atopaxar regimens achieved high levels of platelet inhibition. A transient elevation in liver transaminases and dose-dependent QTc prolongation without apparent complications were observed in higher-dose atopaxar treatment groups. CONCLUSIONS: In this dose-ranging study of patients with CAD, treatment with atopaxar resulted in platelet inhibition, more minor bleeding, and numerically but not statistically fewer ischemic events. Larger-scale trials are needed to determine whether these patterns translate into clinically meaningful effects. CLINICAL TRIAL REGISTRATION: URL: http://www.ClinicalTrials.gov. Unique identifier: NCT00312052.

Safety and tolerability of atopaxar in the treatment of patients with acute coronary syndromes: the lessons from antagonizing the cellular effects of Thrombin­Acute Coronary Syndromes Trial.

BACKGROUND: Atopaxar (E5555) is a reversible protease-activated receptor-1 thrombin receptor antagonist that interferes with platelet signaling. The primary objective of the Lessons From Antagonizing the Cellular Effects of Thrombin-Acute Coronary Syndromes (LANCELOT­ACS) trial was to evaluate the safety and tolerability of atopaxar in patients with ACS. METHODS AND RESULTS: Six hundred and three subjects were randomized within 72 hours of non-ST-elevation ACS to 1 of 3 doses of atopaxar (400-mg loading dose followed by 50, 100, or 200 mg daily) or matching placebo. The incidence of Clopidogrel in Unstable Angina to Prevent Recurrent Events (CURE) major or minor bleeding did not differ significantly between the combined atopaxar and placebo groups (3.08% versus 2.17%, respectively; P=0.63), and there was no dose-related trend (P=0.80). The incidence of CURE major bleeding was numerically higher in the atopaxar group compared with the placebo group (1.8% versus 0%; P=0.12). The incidence of cardiovascular death, myocardial infarction, stroke, or recurrent ischemia was similar between the atopaxar and placebo arms (8.03% versus 7.75%; P=0.93). The incidence of CV death, MI, or stroke was 5.63% in the placebo group and 3.25% in the combined atopaxar group (P=0.20). Dose-dependent trends for efficacy were not seen. Atopaxar significantly reduced ischemia on continuous ECG monitoring (Holter) at 48 hours compared with placebo (relative risk, 0.67; P=0.02). Transient dose-dependent transaminase elevation and relative QTc prolongation were observed with the highest doses of atopaxar. CONCLUSION: In patients after ACS, atopaxar significantly reduced early ischemia on Holter monitoring without a significant increase in major or minor bleeding. Larger trials are required to fully establish the efficacy and safety of atopaxar. CLINICAL TRIAL REGISTRATION: URL: http://www.ClinicalTrials.gov. Unique identifier: NCT00548587.

Impact of smoking on antiplatelet effect of clopidogrel and prasugrel after loading dose and on maintenance therapy.

BACKGROUND: Pharmacodynamic studies reported an amplified on-clopidogrel platelet inhibition in smokers potentially caused by an increased metabolic drug activation via induction of cytochrome P450 1A2. The aims of this analysis were to evaluate the impact of smoking on the antiplatelet effect of clopidogrel and prasugrel and to test the potential interaction of smoking with the treatment effect of these drugs. METHODS: A variety of platelet function results was analyzed from 2 large cohorts of patients undergoing coronary intervention after loading with clopidogrel 600 mg (n = 2,533 and n = 1,996), a cohort of patients undergoing dose adaptation from 75 to 150 mg according to response to clopidogrel (n = 117) and a crossover trial comparing clopidogrel 150 mg with prasugrel 10 mg (n = 87). Linear regression analyses were used to test the impact of smoking on platelet function and to identify independent predictors of on-treatment platelet reactivity. The potential interaction of smoking with the clinical effect of clopidogrel versus prasugrel was analyzed in the TRITON-TIMI 38 cohort (n = 13,608). RESULTS: No significant association of smoking with platelet reactivity on clopidogrel was seen in unadjusted and adjusted analyses. The variables most consistently associated with on-clopidogrel platelet function were age, sex, diabetes, and body mass index. There was no significant interaction of smoking status at presentation with the clinical efficacy of prasugrel versus clopidogrel (P for interaction = .39). CONCLUSIONS: Smoking does not impact on platelet reactivity in patients after loading or on different maintenance doses of clopidogrel. The clinical treatment effect of clopidogrel versus prasugrel is not affected by smoking status at presentation.

Dosing clopidogrel based on CYP2C19 genotype and the effect on platelet reactivity in patients with stable cardiovascular disease.

CONTEXT: Variants in the CYP2C19 gene influence the pharmacologic and clinical response to the standard 75-mg daily maintenance dose of the antiplatelet drug clopidogrel. OBJECTIVE: To test whether higher doses (up to 300 mg daily) improve the response to clopidogrel in the setting of loss-of-function CYP2C19 genotypes. DESIGN, SETTING, AND PATIENTS: ELEVATE-TIMI 56 was a multicenter, randomized, double-blind trial that enrolled and genotyped 333 patients with cardiovascular disease across 32 sites from October 2010 until September 2011. INTERVENTIONS: Maintenance doses of clopidogrel for 4 treatment periods, each lasting approximately 14 days, based on genotype. In total, 247 noncarriers of a CYP2C19*2 loss-of-function allele were to receive 75 and 150 mg daily of clopidogrel (2 periods each), whereas 86 carriers (80 heterozygotes, 6 homozygotes) were to receive 75, 150, 225, and 300 mg daily. MAIN OUTCOME MEASURES: Platelet function test results (vasodilator-stimulated phosphoprotein [VASP] phosphorylation and VerifyNow P2Y(12) assays) and adverse events. RESULTS: With 75 mg daily, CYP2C19*2 heterozygotes had significantly higher on-treatment platelet reactivity than did noncarriers (VASP platelet reactivity index [PRI]: mean, 70.0%; 95% CI, 66.0%-74.0%, vs 57.5%; 95% CI, 55.1%-59.9%, and VerifyNow P2Y(12) reaction units [PRU]: mean, 225.6; 95% CI, 207.7-243.4, vs 163.6; 95% CI, 154.4-173.9; P < .001 for both comparisons). Among CYP2C19*2 heterozygotes, doses up to 300 mg daily significantly reduced platelet reactivity, with VASP PRI decreasing to 48.9% (95% CI, 44.6%-53.2%) and PRU to 127.5 (95% CI, 109.9-145.2) (P < .001 for trend across doses for both). Whereas 52% of CYP2C19*2 heterozygotes were nonresponders (≥230 PRU) with 75 mg of clopidogrel, only 10% were nonresponders with 225 or 300 mg (P < .001 for both). Clopidogrel, 225 mg daily, reduced platelet reactivity in CYP2C19*2 heterozygotes to levels achieved with standard clopidogrel, 75 mg, in noncarriers (mean ratios of platelet reactivity, VASP PRI, 0.92; 90% CI, 0.85-0.99, and PRU, 0.94; 90% CI, 0.84-1.04). In CYP2C19*2 homozygotes, even with 300 mg daily of clopidogrel, mean VASP PRI was 68.3% (95% CI, 44.9%-91.6%) and mean PRU, 287.0 (95% CI, 170.2-403.8). CONCLUSION: Among patients with stable cardiovascular disease, tripling the maintenance dose of clopidogrel to 225 mg daily in CYP2C19*2 heterozygotes achieved levels of platelet reactivity similar to that seen with the standard 75-mg dose in noncarriers; in contrast, for CYP2C19*2 homozygotes, doses as high as 300 mg daily did not result in comparable degrees of platelet inhibition. TRIAL REGISTRATION: clinicaltrials.gov Identifier: NCT01235351.

Otamixaban for the treatment of patients with non-ST-elevation acute coronary syndromes (SEPIA-ACS1 TIMI 42): a randomised, double-blind, active-controlled, phase 2 trial.

BACKGROUND: Otamixaban is an intravenous direct factor Xa inhibitor. We aimed to assess its efficacy and safety in non-ST-elevation acute coronary syndromes and to identify the optimum dose range for further assessment in a phase 3 study. METHODS: In this double-blind, phase 2 trial undertaken in 196 sites in 36 countries, 3241 patients with non-ST-elevation acute coronary syndromes were randomly assigned via a central, telephone-based interactive voice response system to one of five doses of otamixaban (0.08 mg/kg bolus followed by infusions of 0.035 [n=125], 0.070 [676], 0.105 [662], 0.140 [658], or 0.175 [671] mg/kg/h) or to a control of unfractionated heparin (60 IU/kg intravenous bolus followed by an infusion of 12 IU/kg/h) plus eptifibatide (180 microg/kg intravenous bolus followed by an infusion of 1.0-2.0 microg/kg/min [n=449]). Both investigators and patients were unaware of treatment allocation. Enrolment into the lowest dose group was stopped early at the recommendation of the Data Monitoring Committee. The primary efficacy endpoint was a composite of death, myocardial infarction, urgent revascularisation, or bailout glycoprotein IIb/IIIa inhibitor use up to 7 days. The primary safety endpoint was TIMI major or minor bleeding not related to coronary-artery bypass grafting. Efficacy analyses were by intention to treat; safety analyses were in treated patients. This study is registered with ClinicalTrials.gov, number NCT00317395. FINDINGS: Rates of the primary efficacy endpoint in the five otamixaban doses were 7.2% (nine of 125) with 0.035 mg/kg/h, 4.6% (31/676) with 0.070 mg/kg/h, 3.8% (25/662) with 0.105 mg/kg/h, 3.6% (24/658) with 0.140 mg/kg/h, and 4.3% (29/671) with 0.175 mg/kg/h (p=0.34 for trend). In the control group, the rate was 6.2% (28/449), yielding relative risks for the five otamixaban doses of 1.16 (95% CI 0.56-2.38), 0.74 (0.45-1.21), 0.61 (0.36-1.02), 0.58 (0.34-1.00), and 0.69 (0.42-1.15), respectively. Rates of the primary safety endpoint in the five otamixaban doses were 1.6% (two of 122), 1.6% (11/669), 3.1% (20/651), 3.4% (22/651), and 5.4% (36/664), respectively (p=0.0001 for trend); the rate in the control group was 2.7% (12/448). INTERPRETATION: In patients with non-ST-elevation acute coronary syndromes, otamixaban infusions of 0.100-0.140 mg/kg/h might reduce ischaemic events and have a safety profile similar to unfractionated heparin plus eptifibatide. Further testing in a phase 3 trial is warranted. FUNDING: Sanofi-Aventis.

Comparative determinants of 4-year cardiovascular event rates in stable outpatients at risk of or with atherothrombosis.

CONTEXT: Clinicians and trialists have difficulty with identifying which patients are highest risk for cardiovascular events. Prior ischemic events, polyvascular disease, and diabetes mellitus have all been identified as predictors of ischemic events, but their comparative contributions to future risk remain unclear. OBJECTIVE: To categorize the risk of cardiovascular events in stable outpatients with various initial manifestations of atherothrombosis using simple clinical descriptors. DESIGN, SETTING, AND PATIENTS: Outpatients with coronary artery disease, cerebrovascular disease, or peripheral arterial disease or with multiple risk factors for atherothrombosis were enrolled in the global Reduction of Atherothrombosis for Continued Health (REACH) Registry and were followed up for as long as 4 years. Patients from 3647 centers in 29 countries were enrolled between 2003 and 2004 and followed up until 2008. Final database lock was in April 2009. MAIN OUTCOME MEASURES: Rates of cardiovascular death, myocardial infarction, and stroke. RESULTS: A total of 45,227 patients with baseline data were included in this 4-year analysis. During the follow-up period, a total of 5481 patients experienced at least 1 event, including 2315 with cardiovascular death, 1228 with myocardial infarction, 1898 with stroke, and 40 with both a myocardial infarction and stroke on the same day. Among patients with atherothrombosis, those with a prior history of ischemic events at baseline (n = 21,890) had the highest rate of subsequent ischemic events (18.3%; 95% confidence interval [CI], 17.4%-19.1%); patients with stable coronary, cerebrovascular, or peripheral artery disease (n = 15,264) had a lower risk (12.2%; 95% CI, 11.4%-12.9%); and patients without established atherothrombosis but with risk factors only (n = 8073) had the lowest risk (9.1%; 95% CI, 8.3%-9.9%) (P < .001 for all comparisons). In addition, in multivariable modeling, the presence of diabetes (hazard ratio [HR], 1.44; 95% CI, 1.36-1.53; P < .001), an ischemic event in the previous year (HR, 1.71; 95% CI, 1.57-1.85; P < .001), and polyvascular disease (HR, 1.99; 95% CI, 1.78-2.24; P < .001) each were associated with a significantly higher risk of the primary end point. CONCLUSION: Clinical descriptors can assist clinicians in identifying high-risk patients within the broad range of risk for outpatients with atherothrombosis.

Efficacy and safety of a potent and selective peroxisome proliferator activated receptor alpha agonist in subjects with dyslipidemia and type 2 diabetes mellitus.

The weak peroxisome proliferator activated receptor-alpha (PPAR-alpha) agonists gemfibrozil and fenofibrate achieve only small increases in high-density lipoprotein (HDL) cholesterol. CP-778,875 is a more potent PPAR-alpha agonist developed to produce greater HDL cholesterol increases. This randomized, multicenter, double-blinded, placebo-controlled study evaluated the efficacy and safety of CP-778,875 in subjects with mixed dyslipidemia and type 2 diabetes. Eight-six subjects with low HDL cholesterol (< or =45 mg/dl for men and < or =55 mg/dl for women) and increased triglycerides (150 to 500 mg/dl) who had coexisting type 2 diabetes were randomized. Subjects received CP-778,875 doses of 0.5, 2, or 6 mg/day or placebo for 6 weeks. Any other lipid-altering therapy was stopped at screening. The primary end point was percent change in HDL cholesterol from baseline. The 2-mg/day dose of CP-778,875 significantly increased HDL cholesterol by 14%. The 2-mg dose also increased concentrations of apolipoprotein (apo) A-I, HDL(2) cholesterol, and HDL(3) cholesterol by 13%, 12%, and 19%, respectively. An unusual dose-response pattern was observed in that at 6 mg/day CP-778,875 only increased HDL cholesterol by 3% and decreased HDL(2) cholesterol by 24%. Fasting triglyceride levels were significantly decreased to a similar extent (26%) by all 3 doses of CP-778,875. CP-778,875 significantly increased homocysteine levels. There was no significant relation between change in homocysteine and change in apoA-I or HDL cholesterol. No subjects developed myopathy. In conclusion, CP-778,875 2 mg/day significantly increased HDL cholesterol, significantly lowered fasting triglycerides, and increased apoA-I and HDL subfractions. The clinical relevance of the increase in homocysteine levels is unknown.

Patterns of energy substrates during ischemia measured in the brain by microdialysis.

The purpose of this study was to examine the patterns of change in microdialysate concentrations of glucose, lactate, pyruvate, and glutamate in the brain during periods of hypoxia/ischemia identified by monitoring brain tissue pO2 (PbtO2). Of particular interest was a better understanding of what additional information could be obtained by the microdialysis parameters that was not available from the PbtO2. Fifty-seven patients admitted with severe traumatic brain injury who had placement of both a brain tissue pO2 (PbtO2) and microdialysis probe were studied. The microdialysis probe was perfused with Ringer's solution at 0.3 microL/min and dialysate was collected at 1-h intervals. The concentration of glucose, pyruvate, lactate, and glutamate were measured in each dialysate sample. Changes in the microdialysis parameters were examined during episodes where the PbtO2 decreased to below 10 mm Hg. Ten episodes of tissue hypoxia/ischemia identified by a decrease in PbtO2 below 10 mm Hg were observed during the period of monitoring. The concentration of the dialysate glucose closely followed the PbtO2. The dialysate pyruvate concentration was more variable and in some patients transiently increased as the PbtO2 dropped below 10 mm Hg. The dialysate concentration of lactate was significantly increased as the PbtO2 decreased to less than 10 mm Hg. Dialysate glutamate was significantly elevated only when PbtO2 decreased to very low levels. Although changes in the PbtO2 provided the earliest sign of hypoxia/ischemia, the microdialysis assays provided additional information about the consequences that the reduced tissue pO2 has on brain metabolism, which may be helpful in managing these critically ill patients.

The role of endothelial nitric oxide synthase in the cerebral hemodynamics after controlled cortical impact injury in mice.

Traumatic brain injury causes a reduction in cerebral blood flow, which may cause additional damage to the brain. The purpose of this study was to examine the role of nitric oxide produced by endothelial nitric oxide synthase (eNOS) in these vascular effects of trauma. To accomplish this, cerebral hemodynamics were monitored in mice deficient in eNOS and wild-type control mice that underwent lateral controlled cortical impact injury followed by administration of either L-arginine, 300 mg/kg, or saline at 5 min after the impact injury. The eNOS deficient mice had a greater reduction in laser Doppler flow (LDF) in the contused brain tissue at the impact site after injury, despite maintaining a higher blood pressure. L-Arginine administration increased LDF post-injury only in the wild-type mice. L-Arginine administration also resulted in a reduction in contusion volume, from 2.4 +/- 1.5 to 1.1 +/- 1.2 mm(3) in wild-type mice. Contusion volume in the eNOS deficient mice was not significantly altered by L-arginine administration. These differences in cerebral hemodynamics between the eNOS-deficient and the wild-type mice suggest an important role for nitric oxide produced by eNOS in the preservation of cerebral blood flow in contused brain following traumatic injury, and in the improvement in cerebral blood flow with L-arginine administration.

Clinical trials in head injury.

Traumatic brain injury (TBI) remains a major public health problem globally. In the United States the incidence of closed head injuries admitted to hospitals is conservatively estimated to be 200 per 100,000 population, and the incidence of penetrating head injury is estimated to be 12 per 100,000, the highest of any developed country in the world. This yields an approximate number of 500,000 new cases each year, a sizeable proportion of which demonstrate significant long-term disabilities. Unfortunately, there is a paucity of proven therapies for this disease. For a variety of reasons, clinical trials for this condition have been difficult to design and perform. Despite promising pre-clinical data, most of the trials that have been performed in recent years have failed to demonstrate any significant improvement in outcomes. The reasons for these failures have not always been apparent and any insights gained were not always shared. It was therefore feared that we were running the risk of repeating our mistakes. Recognizing the importance of TBI, the National Institute of Neurological Disorders and Stroke (NINDS) sponsored a workshop that brought together experts from clinical, research, and pharmaceutical backgrounds. This workshop proved to be very informative and yielded many insights into previous and future TBI trials. This paper is an attempt to summarize the key points made at the workshop. It is hoped that these lessons will enhance the planning and design of future efforts in this important field of research.

Dynamic autoregulatory response after severe head injury.

OBJECT: The purpose of this study was to evaluate the extent and timing of impairment of cerebral pressure autoregulation after severe head injury. METHODS: In a prospective study of 122 patients with severe head trauma (median Glasgow Coma Scale Score 6), dynamic tests of pressure autoregulation were performed every 12 hours during the first 5 days postinjury and daily during the next 5 days. The autoregulatory index ([ARI] normal value 5 +/- 1.1) was calculated for each test. The changes in the ARI over time were examined and compared with other physiological variables. The ARI averaged 2.8 +/- 1.9 during the first 12 hours postinjury, and continued to decrease to a nadir of 1.7 +/- 1.1 at 36 to 48 hours postinjury. At this nadir, in 87% of the patients the value was less than 2.8. This continued deterioration in the ARI during the first 36 to 48 hours postinjury occurred despite an increase in cerebral blood flow ([CBF], p < 0.05) and in middle cerebral artery blood flow velocity ([BFV], p < 0.001), and could not be explained by changes in cerebral perfusion pressure, end-tidal CO2, or cerebral metabolic rate of O2. A marked decrease in cerebrovascular resistance ([CVR], p < 0.001) accompanied this deterioration in the ARI. Patients with a relatively higher BFV on Day 1 had a lower CVR (p < 0.05) and more impaired pressure autoregulation than those with a lower BFV. CONCLUSIONS: The inability of cerebral vessels to regulate CBF normally may play a role in the vulnerability of the injured brain to secondary ischemic insults. These studies indicate that this vulnerability continues and even increases beyond the first 24 hours postinjury. Local factors affecting cerebrovascular tone may be responsible for these findings.

Dynamic TIMI risk score for STEMI.

BACKGROUND: Although there are multiple methods of risk stratification for ST-elevation myocardial infarction (STEMI), this study presents a prospectively validated method for reclassification of patients based on in-hospital events. A dynamic risk score provides an initial risk stratification and reassessment at discharge. METHODS AND RESULTS: The dynamic TIMI risk score for STEMI was derived in ExTRACT-TIMI 25 and validated in TRITON-TIMI 38. Baseline variables were from the original TIMI risk score for STEMI. New variables were major clinical events occurring during the index hospitalization. Each variable was tested individually in a univariate Cox proportional hazards regression. Variables with P<0.05 were incorporated into a full multivariable Cox model to assess the risk of death at 1 year. Each variable was assigned an integer value based on the odds ratio, and the final score was the sum of these values. The dynamic score included the development of in-hospital MI, arrhythmia, major bleed, stroke, congestive heart failure, recurrent ischemia, and renal failure. The C-statistic produced by the dynamic score in the derivation database was 0.76, with a net reclassification improvement (NRI) of 0.33 (P<0.0001) from the inclusion of dynamic events to the original TIMI risk score. In the validation database, the C-statistic was 0.81, with a NRI of 0.35 (P=0.01). CONCLUSIONS: This score is a prospectively derived, validated means of estimating 1-year mortality of STEMI at hospital discharge and can serve as a clinically useful tool. By incorporating events during the index hospitalization, it can better define risk and help to guide treatment decisions.

Evaluation of NT-proBNP and high sensitivity C-reactive protein for predicting cardiovascular risk in patients with arthritis taking longterm nonsteroidal antiinflammatory drugs.

OBJECTIVE: Patients with arthritis frequently are at increased risk for future cardiovascular (CV) events. We investigated the performance of the cardiac biomarkers N-terminal pro-B-type natriuretic peptide (NT-proBNP) and high sensitivity C-reactive protein (hsCRP) for predicting CV events in patients with arthritis taking chronic nonsteroidal antiinflammatory drugs (NSAID). METHODS: We evaluated 2-year CV outcomes in a prospective, nested biomarker study among patients (N = 6273) with rheumatoid arthritis and osteoarthritis treated with NSAID in the MEDAL (Multinational Etoricoxib and Diclofenac Arthritis Long-term) trial. Patients were stratified by quartiles of baseline NT-proBNP and established cutpoints of NT-proBNP and hsCRP. RESULTS: NT-proBNP demonstrated a strong graded relationship with CV outcomes, including CV death (p for trend < 0.0001), myocardial infarction (MI) (p for trend = 0.02), heart failure (HF) (p for trend < 0.0001), and a composite of thrombotic events (CV death, MI, stroke) or HF (p for trend < 0.0001). Baseline levels of hsCRP were not associated with CV events (CV death/MI/stroke/HF; p for trend = 0.65). NT-proBNP remained strongly predictive of CV events after adjustment for age, sex, diabetes, hypertension, hyperlipidemia, smoking, type of arthritis, body mass index, creatinine clearance, history of CV disease, and hsCRP (CV death/MI/stroke/HF: Q4 vs Q1 hazard ratio 3.53, 95% CI 1.89-6.58). Patients with a NT-proBNP level below 100 pg/ml had a 0.94% rate of thrombotic events or heart failure at 2 years. CONCLUSION: NT-proBNP is a simple and robust noninvasive indicator of CV risk in patients with arthritis. Risk stratification based on NT-proBNP may facilitate identification of patients with arthritis who are at low CV risk during chronic NSAID treatment.

Metabolic effects of a late hypotensive insult combined with reduced intracranial compliance following traumatic brain injury in the rat.

INTRODUCTION: Traumatic brain injury makes the brain vulnerable to secondary insults. Post-traumatic alterations in intracranial dynamics, such as reduced intracranial compliance (IC), are thought to further potentiate the effects of secondary insults. Reduced IC combined with intracranial volume insults leads to metabolic disturbances in a rat model. The aim of the present study was to discern whether a post-traumatic hypotensive insult in combination with reduced IC caused more pronounced secondary metabolic disturbances in the injured rat brain. MATERIALS AND METHODS: Rats were randomly assigned to four groups (n = 8/group): 1) trauma with hypotension; 2) trauma and reduced IC with hypotension; 3) sham injury with hypotension; and 4) sham injury and reduced IC with hypotension. A weight drop model of cortical contusion trauma was used. IC was reduced by gluing rubber film layers on the inside of bilateral bone flaps before replacement. Microdialysis probes were placed in the perimeter of the trauma zone. Hypotension was induced 2 h after trauma. Extracellular (EC) levels of lactate, pyruvate, hypoxanthine, and glycerol were analyzed. RESULTS: The trauma resulted in a significant increase in EC dialysate levels of lactate, lactate/pyruvate ratio, hypoxanthine, and glycerol. A slight secondary increase in lactate was noted for all groups but group 2 during hypotension, otherwise no late effects were seen. There were no effects of reduced IC. DISCUSSION: In conclusion, reduced IC did not increase the metabolic disturbances caused by the post-traumatic hypotensive insult. The results suggest that a mild to moderate hypotensive insult after initial post-traumatic resuscitation may be tolerated better than an early insult before resuscitation.

Low intracranial compliance increases the impact of intracranial volume insults to the traumatized brain: a microdialysis study in a traumatic brain injury rodent model.

OBJECTIVE: The vulnerability of the brain is considered to be increased after trauma. The present study was undertaken to determine whether intracranial volume insults in the posttraumatic period led to increased metabolic disturbances if intracranial compliance was decreased. METHODS: A weight drop technique with a brain compression of 1.5 mm was used for injury. Intracranial compensatory volume was decreased 60 microl by placing rubber film between the dura mater and the bone. Intracranial volume insults were induced using the Bolus injection technique. Microdialysis was used to measure interstitial lactate, pyruvate, hypoxanthine, and glycerol. Fifty-two rats were allocated to trauma and sham groups with 0 to 3 layers of rubber film with and without intracranial volume insults. RESULTS: In the groups with reduced intracranial volume exposed to intracranial volume insults, the time course of metabolic markers showed higher increases and slower recovery rates than for the other groups. Reduced intracranial volume or intracranial volume insults alone did not cause any changes compared with controls. CONCLUSION: These results support the hypothesis that decreased intracranial compliance increases the vulnerability of the brain for secondary volume insults even with intracranial pressure at low levels between the insults. This finding has important clinical implications in that it stresses the need to identify patients with low intracranial compliance so that their treatment can be optimized.

Community consultation in emergency research.

CONTEXT: Recent federal regulations allow for emergency research without prospective consent provided that additional protections for the subjects are provided. One of these is community consultation. OBJECTIVE: To determine how to feasibly consult the community and what to do with the findings. DESIGN, SETTING, AND PARTICIPANTS: In connection with an ongoing study of l-arginine for brain injury at a public hospital's trauma center, we consulted three sets of community representatives using different methods. To sample the entire population of the county, we conducted a random-digit dialing survey (456 residents). To sample individuals served by the hospital, we interviewed a convenience sample of 566 patients and individuals in the waiting area. To sample particularly interested individuals, we conducted a series of public meetings (114 participants). In each case, the same instrument was used to ascertain their attitudes toward the study in general and toward its major features (randomization, waiver of consent, location, risks/benefits). To control for framing effects, items were randomly presented in a positive or negative fashion. RESULTS: All methods proved feasible, but telephone surveys were most efficient and guaranteed the desired demography. Even for a very low-risk study, only 79.75% of respondents would be willing to participate. The rate of approval for the major features was lower, with only 67.78% approving of the risk/benefit ratio, 53.7% approving of randomization, 57.66% approving of the consent waiver, and 44.45% approving of the location. The most significant factors affecting the rate of approval were the method of consultation and the framing of items (both p < .001), age, ethnicity, and previous research participation (all p < .01). CONCLUSIONS: Community consultation is feasible, but its results depend heavily on method of consultation, framing of questions, and choice of community. It may well demonstrate unexpectedly substantial opposition. There needs to be a better definition of the process and a better understanding of how to respond to its results.