Reconfigurable infrared hyperbolic metasurfaces using phase change materials.

Metasurfaces control light propagation at the nanoscale for applications in both free-space and surface-confined geometries. However, dynamically changing the properties of metasurfaces can be a major challenge. Here we demonstrate a reconfigurable hyperbolic metasurface comprised of a heterostructure of isotopically enriched hexagonal boron nitride (hBN) in direct contact with the phase-change material (PCM) single-crystal vanadium dioxide (VO2). Metallic and dielectric domains in VO2 provide spatially localized changes in the local dielectric environment, enabling launching, reflection, and transmission of hyperbolic phonon polaritons (HPhPs) at the PCM domain boundaries, and tuning the wavelength of HPhPs propagating in hBN over these domains by a factor of 1.6. We show that this system supports in-plane HPhP refraction, thus providing a prototype for a class of planar refractive optics. This approach offers reconfigurable control of in-plane HPhP propagation and exemplifies a generalizable framework based on combining hyperbolic media and PCMs to design optical functionality.

Prospective evaluation of short-term, high-volume isovolemic hemofiltration on the hemodynamic course and outcome in patients with intractable circulatory failure resulting from septic shock.

OBJECTIVE: To evaluate the effects of short-term, high-volume hemofiltration (STHVH) on hemodynamic and metabolic status and 28-day survival in patients with refractory septic shock. DESIGN: Prospective, interventional. SETTING: Intensive care unit (ICU), tertiary institution. PATIENTS: Twenty patients with intractable cardiocirculatory failure complicating septic shock, who had failed to respond to conventional therapy. INTERVENTIONS: STHVH, followed by conventional continuous venovenous hemofiltration. STHVH consisted of a 4-hr period during which 35 L of ultrafiltrate is removed and neutral fluid balance is maintained. Subsequent conventional continuous venovenous hemofiltration continued for at least 4 days. MEASUREMENTS AND MAIN RESULTS: Cardiac index, systemic vascular resistance, pulmonary vascular resistance, oxygen delivery, mixed venous oxygen saturation, arterial pH, and lactate were measured serially. Fluid and inotropic support were managed by protocol. Therapeutic endpoints were as follows during STHVH: a) by 2 hrs, a > or =50% increase in cardiac index; b) by 2 hrs, a > or =25% increase in mixed venous saturation; c) by 4 hrs, an increase in arterial pH to >7.3; d) by 4 hrs, a > or =50% reduction in epinephrine dose. Patients who attained all four goals (11 of 20) were considered hemodynamic "responders"; patients who did not (9 of 20) were considered hemodynamic "nonresponders." There were no differences in baseline hemodynamic, metabolic, and Acute Physiology and Chronic Health Evaluation and Simplified Acute Physiology Scores between responders and nonresponders. Survival to 28 days was better among responders (9 of 11 patients) than among nonresponders (0 of 9). Factors associated with survival were hemodynamic-metabolic response status, time interval from ICU admission to initiation of STHVH, and body weight. CONCLUSIONS: These data suggest that STHVH may be of major therapeutic value in the treatment of intractable cardiocirculatory failure complicating septic shock. Early initiation of therapy and adequate dose may improve hemodynamic and metabolic responses and 28-day survival.

Effects of filter pore size on efficacy of continuous arteriovenous hemofiltration therapy for Staphylococcus aureus-induced septicemia in immature swine.

OBJECTIVE: To evaluate the effect of hemofilter pore size on the efficacy of continuous arteriovenous hemofiltration (CAVH) in improving morbidity and mortality in an immature swine model of Staphylococcus aureus-induced septicemia. DESIGN: Prospective, randomized study with age-matched controls. SETTING: Biomedical research facility. SUBJECTS: Fourteen 4 to 8-wk-old, weaned Poland-China swine, weighing 5 to 10 kg. INTERVENTIONS: Spontaneously breathing, ketamine-sedated swine (4 to 8 wks of age) were given an intravenous lethal dose of live S. aureus. Animals were then filtered with either a 50-kilodalton (kD) pore size filter (control) or a 100-kD pore size filter (experimental). No animals received antibiotics. MEASUREMENTS AND MAIN RESULTS: Physiologic, biochemical, and hematologic parameters were measured in all animals every 1 to 3 hrs. Animals were monitored continuously and survival time (hr) was recorded (permanent survival = 168 hrs/7 days). Animals filtered with the 100-kD filter survived significantly longer than control animals (103 +/- 18 [SEM] vs. 56 +/- 9 hrs). The 100-kD-filtered group had one permanent survivor (168 hrs). Protein concentration of the ultrafiltrate obtained from the 100-kD-filtered animals was eight-fold higher than control ultrafiltrate. The protein removed did not contain a high percentage of albumin (as determined by autoanalyzer methods). No significant differences were seen in any of the other measured parameters. CONCLUSIONS: CAVH significantly improved survival in swine with S. aureus-induced sepsis. The superior performance of the 100-kD filter vs. the 50-kD filter suggests that higher molecular weight mediators that are not removed efficiently by the 50-kD filter may be responsible for the morbidity and mortality seen in this model of sepsis. These mediators may be removed in greater proportion by our customized (100-kD pore size) filter.

Continuous arteriovenous hemofiltration therapy for Staphylococcus aureus-induced septicemia in immature swine.

OBJECTIVES: The goals of this study were: a) to evaluate the efficacy of controlled, continuous arteriovenous hemofiltration in improving morbidity and mortality rates in an immature swine model of Staphylococcus aureus-induced septicemia; b) to determine if ultrafiltrate from septic animals contained mediators that produce pathophysiologic changes observed in untreated S. aureus septic pigs. DESIGN: Prospective, randomized, controlled study with age-matched controls. SETTING: U.S. Department of Agriculture-licensed biomedical research facility. SUBJECTS: Sixty-five weaned Poland-China swine (4 to 6 wks of age; 5 to 10 kg). INTERVENTIONS: Part 1: Animals received a lethal dose of live S. aureus (8 x 10(9) colony-forming units/kg) over 1 hr. The three treatment groups included: hemofiltration group 1 (eight filtered, eight nonfiltered animals), plasma filtration fraction = 5.5%; hemofiltration group 2 (six filtered, six nonfiltered animals), filtration fraction = 16.6%; and hemofiltration group 3 (six filtered, six nonfiltered animals), filtration fraction = 33.4%. A control, nonseptic group of animals (n = 4) was filtered to obtain "clean" ultrafiltrate (hemofiltration group 4). Part 2: Sterile ultrafiltrate concentrate batches obtained from each group of filtered, septic animals were concentrated and infused into healthy, nonseptic pigs (reinfusion groups 1 through 3). MEASUREMENTS AND MAIN RESULTS: Physiologic, biochemical, and hematologic variables were measured in all animals every 1 to 3 hrs. Overall length of survival was also recorded. In hemofiltration groups 1 through 3, filtered animals survived significantly longer than matched, nonfiltered (sham-filtered) animals. Increments in survival time increased directly with filtration fraction. Ultrafiltrate concentrate from septic pigs produced death (LD41) and disease similar to those rates observed in untreated S. aureus-septic pigs. Infusion of clean ultrafiltrate concentrate produced no response. CONCLUSIONS: Continuous arteriovenous hemofiltration significantly improved survival rates in swine with S. aureus-induced sepsis. Resultant ultrafiltrate concentrate contained mediators responsible for some pathophysiologic responses observed in this animal model.

Delayed detection of coarctation in infancy: implications for timing of newborn follow-up.

During a recent 5-year period, 74 patients younger than 6 months of age were diagnosed with coarctation of the aorta. Coarctation was correctly diagnosed in only 22% of patients prior to referral despite readily apparent femoral pulse abnormalities in 86%. Infants whose symptoms were detected between 5 and 14 days of age were significantly more ill than infants outside this age range and had a high mortality rate (25%). The number of associated cardiac defects was not related to the severity of clinical illness in this group, suggesting that closure of the ductus arteriosus is the primary determinate of disease severity. Observations in two patients suggested that a detectable pulse discrepancy occurs between 3 and 5 days postnatally. Upper extremity hypertension was found commonly in infants after 5 days of age despite the presence of congestive heart failure. Earlier detection of coarctation in the newborn requires a diligent cardiovascular and peripheral pulse examination between 3 and 7 days of life, upper extremity and lower extremity blood pressure measurement, and a high index of suspicion.

Septic shock: principles of management in the emergency department.

Bacteremia is a potentially serious event which must be recognized early and treated aggressively to prevent progression to septicemia and septic shock. The pathophysiology of septicemia and shock includes inadequate tissue perfusion and oxygenation. Expansion of intravascular volume and pharmacologic cardiovascular support are designed to minimize resulting end-organ injury. Initial antibiotic therapy must be individualized and should include an agent or agents active against the common pathogens encountered in the specific clinical setting. Once the causative organism is isolated, therapy is targeted more narrowly. Despite the availability of a variety of newer antibiotics, the morbidity and mortality of septicemia and septic shock remain unacceptably high. Development of new pharmacologic agents active against the mediators of shock may offer future promise.

Diphenylhydantoin-induced hypersensitivity reaction with interstitial nephritis.

A 10-year-old black girl had an episode of diphenylhydantoin(DPH)-induced exfoliative dermatitis, lymphadenopathy, hepatitis, peripheral eosinophilia, and transient renal failure. The findings of specific lymphocyte sensitization of DPH, a clinically typical delayed hypersensitivity reaction, multinucleated histiocytes in the renal interstitium, and negative renal immunofluorescence studies for immune reactants indicate that the child's renal injury was at least partially cell-mediated.

Effects of inhibition of prostaglandin synthesis on fetal renal function.

The role of renal prostaglandin production on the control of renal blood flow (RBF) and renal function was studied in eight chronically catheterized fetal lambs during the last trimester of gestation by using indomethacin as an inhibitor of prostaglandin synthesis. Following administration of indomethacin, RBF decreased significantly (-7.44 +/- 2.04 ml/min) whereas significant increases in filtration fraction (+3.92 +/- 0.85%) and renal vascular resistance (+ 0.41 +/- 0.13 mm Hg . ml-1 . min-1) were observed. Significant changes in glomerular perfusion rate were observed only in the inner portion of the cortex. No changes in GFR were demonstrated. Following administration of indomethacin, significant increases in fetal urinary sodium (+22.2 +/- 7.03 micro E/min) and chloride excretion (+18.2 +/- 6.26 micro E/min) were found despite a decrease in RBF. No changes in potassium excretion were seen. A significant increase in Uosm (+100 +/- 25.9 mOsm/kg H2O) not associated with significant changes in urinary flow rate was also demonstrated following indomethacin. Finally, fetal administration of indomethacin produced a significant decrease in plasma renin activity (-2.70 +/- 0.65 ng/ml/hr) not associated with changes in plasma aldosterone concentration. The present data are consistent with the idea that prostaglandins are important modulators of RBF and renin secretion during fetal life. The inability of indomethacin to render the urine hypertonic indicates that the inability of the fetal kidney to concentrate is probably not due to endogenous activity of the renal prostaglandin system. The increase in sodium chloride excretion with a concomitant reduction of RBF is a pattern not previously reported following inhibition of prostaglandin production. In addition to their effects on RBF and renin release, renal prostaglandins in the fetal kidney may have tubular effects on sodium and chloride absorption that are opposite to those generally ascribed to adult kidneys.

Anemia of chronic renal failure.

Anemia is one of the most characteristic and visable manifestations of chronic renal failure. Investigators in the past decade have provided a better understanding of this anemia. The etiology of the anemia of chronic renal failure has three facets: first is reduced erythropoietin production by damaged kidneys; second is the presence of inhibitors to red blood cell (RBC) production in uremic serum; and third is red blood cell hemolysis. Unfortunately, transfusion therapy with its expense and risk of transmissable viral disease remains the mainstay of management for symptomatic anemia. Other modalities include dialysis, androgens, histidine supplementation, and erythropoietin replacement.

Interaction of minoxidil and captopril in the treatment of refractory hypertension.

A case of severe hypertension resistant to multiple drug therapy was controlled with minoxidil, captopril, and propranolol hydrochloride after treatment with these drugs alone or in other combinations had failed. Hyperreninemic hypoaldosteronism with hyperkalemia and acidosis developed after captopril administration was started.