Topography dependence of the metamagnetic phase transition in FeRh thin films.

The equiatomic alloy FeRh is of great scientific and technological interest due its highly unusual first-order antiferromagnetic (AF) to ferromagnetic (FM) phase transition. Here we report an exploration of the interplay between topography and phase evolution with a comprehensive magnetic force microscopy study of nominal 50 nm thick FeRh thin films and subtractively patterned wires of width 0.2 µm-2 µm. In continuous films where the surface morphology had not been optimised for smoothness, the topographical variation was observed to dominate the distribution of the magnetic transition temperatures and dictates the nucleation and growth of the magnetic phases. This observation was repeated for patterned elements, where the effects of surface morphology were more significant than those of spatial confinement. These results have clear implications for future studies of low-dimensional FeRh films, as surface topography must be considered when analysing and comparing the transition behaviour of FeRh thin films.

Substrate Induced Strain Field in FeRh Epilayers Grown on Single Crystal MgO (001) Substrates.

Equi-atomic FeRh is highly unusual in that it undergoes a first order meta-magnetic phase transition from an antiferromagnet to a ferromagnet above room temperature (Tr ≈ 370 K). This behavior opens new possibilities for creating multifunctional magnetic and spintronic devices which can utilise both thermal and applied field energy to change state and functionalise composites. A key requirement in realising multifunctional devices is the need to understand and control the properties of FeRh in the extreme thin film limit (tFeRh < 10 nm) where interfaces are crucial. Here we determine the properties of FeRh films in the thickness range 2.5-10 nm grown directly on MgO substrates. Our magnetometry and structural measurements show that a perpendicular strain field exists in these thin films which results in an increase in the phase transition temperature as thickness is reduced. Modelling using a spin dynamics approach supports the experimental observations demonstrating the critical role of the atomic layers close to the MgO interface.

Effect of rates of perfusion on dominant frequency and defibrillation energy in isolated fibrillating hearts.

This study assessed the influence of rates of reperfusion on excitability of the myocardium using dominant frequency (DF) (in Hz) of VF and the relationship of DF to the minimum defibrillation energy (MDE) (in J). Our hypothesis was that increasing flow during reperfusion increases DF that raises MDE. Initially, six Langendorff perfused swine hearts were serially fibrillated and perfusion arrested for 4 minutes followed by reperfusion and defibrillation to establish reproducibility of the model. The epicardial ECG was analyzed for DF. In subsequent studies (n = 8), no flow VF was followed by 1-minute reperfusion at normal flow or 10% flow (low flow) and shocked with increasing energy via epicardial pads until defibrillation. The DF at onset of no flow VF was 9.5 +/- 1.4 and decreased to 3.6 +/- 1.4 after 4 minutes. Reperfusion at normal flow increased the DF of VF compared to low flow after 1 minute (10.8 +/- 1.1 vs 4.5 +/- 1.1 Hz, P = 0.0002) and was associated with increased defibrillation energy requirements (13.5 +/- 5.0 vs 7.3 +/- 6.2 J, P = 0.047). In summary, defibrillation energy requirements are lower when myocardial excitability is reduced during low flow reperfusion.

Double-blind, multicenter trial to compare the efficacy of intramuscular dihydroergotamine plus hydroxyzine versus intramuscular meperidine plus hydroxyzine for the emergency department treatment of acute migraine headache.

STUDY OBJECTIVE: To evaluate intramuscular dihydroergotamine in direct comparison with opioid analgesia in the treatment of acute migraine headache. METHODS: This was a prospective, multicenter, double-blind trial performed in the emergency departments of 11 general hospitals in the United States. One hundred seventy-one patients between the ages of 18 and 60 years who presented to the ED with acute migraine headache were enrolled. Patients were randomly assigned to receive either 1 mg dihydroergotamine (DHE) or 1.5 mg/kg meperidine (MEP) by intramuscular injection. The anti-nauseant hydroxyzine (H) was coadministered in both treatment groups. RESULTS: One hundred fifty-six patients were evaluable. Treatment groups were comparable in sample size, demographics, and baseline measurements of headache pain. Reduction of headache pain as measured on a 100-mm visual analog scale was 41+/-33 mm (53.5% reduction) for the DHE group, and 45+/-30 mm (55.7% reduction) for the MEP group at 60 minutes after treatment (difference=2.2%; 95% confidence interval [CI] -10%, 14.5%; P=.81). Reduction in the severity of nausea and improvement in functional ability were similar between treatment groups. Central nervous system adverse events were less common in the DHE group (DHE 23.5% versus MEP 37.6%, difference-14.1%: 95% CI -28%, 0%). In particular, dizziness was reported less commonly with DHE than MEP (2% versus 15%, difference=-13%: 95% CI -21%, -5%). CONCLUSION: In this prospective, double-blind trial of a convenience sample of ED patients randomly assigned to one of two treatment regimens, DHE and MEP were comparable therapies for acute migraine. The use of DHE avoids several problems associated with opioid analgesia, including dizziness.

Cardiopulmonary resuscitation.

Research into the physiologic changes that occur during cardiac arrest and resuscitation have led to important changes in our approach to resuscitation of the cardiac arrest victim. Methods that improve coronary perfusion pressure, coupled with direct or indirect measures of coronary perfusion, are actively being sought to improve resuscitation rates and outcomes. These studies have broadened the therapeutic options available to clinicians treating the cardiac arrest victim. Although significant improvements in hospital discharge rates and neurologic outcome have not been realized as yet, a firm basis for future studies has been established. Overall, the most significant intervention that the clinician can presently perform is early and prompt defibrillation of the patient in ventricular fibrillation.

Correlation of end-tidal CO2 measurements to arterial PaCO2 in nonintubated patients.

STUDY OBJECTIVE: To determine the accuracy of end-tidal carbon dioxide levels as a measure of arterial carbon dioxide levels in nonintubated patients presenting to an emergency department for care. DESIGN: A prospective, cross-sectional analysis. SETTING: University hospital ED. TYPE OF PARTICIPANT: Nonintubated adult patients presenting to the ED for care of a variety of problems. INTERVENTIONS: Patients who had arterial blood gas samples taken as part of their ED evaluation were asked to breathe normally through an endotracheal tube adapter or a modified nasal cannula connected to a side port sampling capnometer while a sample for arterial blood gas was drawn from the radial artery. MEASUREMENTS: End-tidal carbon dioxide levels (mm Hg) were recorded at the time of arterial blood gas sampling. The difference between end-tidal carbon dioxide and PaCO2 was tested with the paired t-test at a significance level of .05. The correlation of end-tidal carbon dioxide to PaCO2 was tested in all patients and in subgroups using simple linear regression. RESULTS: Seventy-six patients were enrolled. In all patients, end-tidal carbon dioxide was 3.5 mm Hg lower than PaCO2 and correlated well with PaCO2 (r2 = .772). In patients with hypocapnia, there was no significant difference between end-tidal carbon dioxide and PaCO2 (P = .17), and the correlation of end-tidal carbon dioxide to PaCO2 was stronger (r2 = .838). In patients with a respiratory or metabolic acidosis, the difference between end-tidal carbon dioxide and PaCO2 was 6 mm Hg (P = .005), but end-tidal carbon dioxide correlated well to PaCO2 (r2 = .899). CONCLUSION: Measurements of end-tidal carbon dioxide concentrations correlate well with PaCO2 values in nonintubated patients presenting with a variety of conditions to EDs. End-tidal carbon dioxide measurements may be sufficient measures of PaCO2 in selected patients and obviate the need for repeat arterial blood gas determination. Further study is warranted.

Evaluation and treatment of headache patients in the emergency department: a survey.

Patients with headache represent a common diagnostic and treatment challenge for health care providers in the emergency department. The therapeutic options continue to grow, yet many studies imply that narcotics continue to be a frequently chosen treatment. In this retrospective cross-sectional survey, the evaluation and treatment patterns of patients presenting to an academic medical center emergency department with a primary diagnosis of headache were analyzed. Headache disorders accounted for 1.7% of all visits to the emergency department. Migraine headache was the most common headache diagnosis representing 60% of headache visits followed by headache of no obvious source at 25%. Narcotics were the most common treatment employed (180 patient-visits) in all patients and non-steroidal anti-inflammatory agents were the second most common agent used (86 patient visits). Narcotics were also the most common therapy in migraine headache patients (152 patient-visits) while ergotamines were used in less than one-third of patient-visits (36 patient-visits). Therapy of headache patients in the emergency department continues to rely on narcotics. Methods of interrupting the dependence on narcotics need to be explored if newer non-narcotic therapies are to be successful.

A randomized clinical trial of high-dose epinephrine and norepinephrine vs standard-dose epinephrine in prehospital cardiac arrest.

OBJECTIVE: To determine the relative efficacy of high- vs standard-dose catecholamines in initial treatment of prehospital cardiac arrest. DESIGN: Randomized, prospective, double-blind clinical trial. SETTING: Prehospital emergency medical system of a major US city. PATIENTS: All adults in nontraumatic cardiac arrest, treated by paramedics, who would receive epinephrine according to American Heart Association advanced cardiac life support guidelines. INTERVENTIONS: High-dose epinephrine (HDE, 15 mg), high-dose norepinephrine bitartrate (NE, 11 mg), or standard-dose epinephrine (SDE, 1 mg) was blindly substituted for advanced cardiac life support doses of epinephrine. MAIN OUTCOME MEASURES: Restoration of spontaneous circulation in the field, admission to hospital, hospital discharge, and Cerebral Performance Category score. RESULTS: Of 2694 patients with cardiac arrests during the study period, resuscitation was attempted on 1062 patients. Of this total, 816 patients met study criteria and were enrolled. In the entire cardiac arrest population, 63% of the survivors were among the 11% of patients who were defibrillated by first responders. The three drug treatment groups were similar for all independent variables. Thirteen percent of patients receiving HDE regained a pulse in the field vs 8% of those receiving SDE (P = .01), and 18% of HDE patients were admitted to the hospital vs 10% of SDE patients who were admitted to the hospital (P = .02). Similar trends for NE were not significant. There were 18 survivors; 1.7% of HDE patients and 2.6% of NE patients were discharged from the hospital compared with 1.2% of SDE patients, but this was not significant (P = .37; beta = .38). There was a nonsignificant trend for Cerebral Performance Category scores to be worse for HDE (3.2) and NE patients (3.7) than for SDE patients (2.3) (P = .10; beta = .31). No significant complications were identified. High-dose epinephrine did not produce longer hospital or critical care unit stays. CONCLUSIONS: High-dose epinephrine significantly improves the rate of return of spontaneous circulation and hospital admission in patients who are in prehospital cardiac arrest without increasing complications. However, the increase in hospital discharge rate is not statistically significant, and no significant trend could be determined for neurological outcome. No benefit of NE compared with HDE was identified. Further study is needed to determine the optimal role of epinephrine in prehospital cardiac arrest.

Potential complications of high-dose epinephrine therapy in patients resuscitated from cardiac arrest.

Adults resuscitated from nontraumatic cardiac arrest who received intravenous epinephrine in doses chosen by the treating physician and who survived at least 6 hours were studied to determine if high-dose epinephrine produced more complications than standard-dose. A total of 68 patients were enrolled and evaluated for postresuscitation complications attributable to epinephrine, using a two-tailed t test, and contingency analysis. The 33 patients receiving high-dose epinephrine and 35 patients receiving standard-dose epinephrine were similar in demographics and variables known to affect outcome. There was no difference in potential complications between groups except serum calcium, which was 1.97 mmol/L (SD, 0.20) in the high-dose epinephrine group and 2.10 (SD, 0.20) in the standard-dose group. Hospital discharge rates (18% in the high-dose vs 30% in the standard-dose group) and neurological status on discharge were not significantly different. High-dose epinephrine did not produce increased direct complications in this cardiac arrest population compared with standard-dose epinephrine.

Subarachnoid hemorrhage presenting as acute chest pain: a variant of le coup de poignard.

A 39-year-old woman presented to the emergency department with symptoms of acute knifelike chest pain and was discharged with a diagnosis of musculoskeletal pain syndrome. One day later, she returned with a complaint of persistent chest pain. Physical examination disclosed meningismus, this led to a lumbar puncture and the subsequent diagnosis of subarachnoid hemorrhage. Angiography later revealed findings consistent with dissection of the vertebral artery. This case illustrates an unusual presentation and cause of spinal subarachnoid hemorrhage, a potentially treatable emergency condition.

Aortic dilation, dissection, and rupture in patients with Turner syndrome.

We report two patients with Turner syndrome who had aortic dissection and rupture, one with prior repair of coarctation. We also note the high incidence (8.8%) of unrecognized aortic root dilation in a group of 57 patients with Turner syndrome whom we prospectively evaluated by echocardiography. Our analysis and review of previously reported cases suggests that multiple risk factors may exist for aortic dissection, including coarctation, bicuspid aortic valve, and systemic hypertension, but that these need not be present. Aortic root dilation may be an additional finding that suggests the patient with Turner syndrome is also at risk. When it is present, magnetic resonance imaging visualizes the entire aorta and allows quantification of the site and degree of dilation. In patients with dissection, the aorta often exhibits pathologic evidence of cystic medial necrosis similar to the finding in patients with Marfan syndrome. Therapeutic methods to decrease risk, such as those directed toward prevention of bacterial endocarditis, blood pressure control, and perhaps prophylactic beta blockade or surgical reconstruction, may need to be considered. Patients with Turner syndrome, their families, and the physicians who care for them should be aware of the significance of unexplained chest pain, dyspnea, or hypotension as potential manifestations of aortic dissection or rupture.

Two-dimensional and Doppler echocardiographic features of left circumflex coronary artery to right ventricle fistula: case report and literature review.

We report the case of a seven-month-old infant with a clinical diagnosis of patent ductus arteriosus whose two-dimensional and Doppler echocardiographic examinations were consistent with a coronary artery fistula. At angiography, a left circumflex coronary artery to right ventricle fistula was diagnosed. Echo-Doppler techniques for the noninvasive diagnosis of this lesion are discussed and the literature is reviewed.

Value of treadmill exercise test in pre- and postoperative children with valvular aortic stenosis.

To determine the utility of graded treadmill exercise test (ETT) in estimating severity of obstruction in postoperative patients with aortic stenosis, we compared results to a nonoperated aortic stenosis group. Cardiac catheterization was performed in all patients. The interval between surgery and ETT in the postoperative group was 7.5 years (range 1.1-12.9). Mean and range values for postoperative versus nonoperative aortic stenosis groups respectively were: age 14.5 (7.9-20.8) versus 12.5 years (5.9-19.7); peak left ventricular pressure 150 (101-190) versus 144 mmHg (100-183); peak systolic ejection gradient (PSEG) 41 (15-75) versus 38 mmHg (14-80); left ventricular end-diastolic pressure (LVEDP) 13.4 (7-20) versus 13.5 mmHg (8-20); and cardiac index 3.7 (2.4-5.6) versus 3.8 liters/min/m2 (2.6-4.9) (p for each = NS). ETT in the nonoperated patients correctly identified all those with PSEG greater than or equal to 50 mmHg (sensitivity 100%), but specificity was 56%, (i.e., the proportion correctly identified with PSEG less than 50 mmHg). By contrast, sensitivity and specificity for postoperative aortic stenosis patients were 67% and 63%, respectively. Furthermore, among nonoperated aortic stenosis patients ST depression on ETT identified those with increased left ventricular end-diastolic pressure. For LVEDP greater than or equal to 12 mmHg, sensitivity was 75% and specificity 100%, corresponding values for postoperative aortic stenosis patients were 45% and 33%, respectively. In the nonoperated aortic stenosis group with a PSEG greater than or equal to 50 mmHg, sensitivity and specificity for ETT-induced change in systolic blood pressure of less than or equal to 30 mmHg were 100% and 56%, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)