Biomedical subjects

A Vardi

Publications and source records attributed to A Vardi.

At least 19 recordsLinked to original sources

PubMed2007

Fiberoptic bronchoscopy and bronchoalveolar lavage for the evaluation of pulmonary disease in children with primary immunodeficiency and cancer.

BACKGROUND: Patients with childhood cancer or primary immunodeficiencies (PID) are at high risk for developing pulmonary infections and non-infectious complications. The broad differential diagnoses and the critical condition of these patients often drive physicians to start broad-spectrum antibiotic therapy before a definite diagnostic procedure is performed. A definite diagnosis may be achieved in these situations by fiberoptic bronchoscopy (FOB) and bronchoalveolar lavage (BAL). PATIENTS AND METHODS: The records of 58 PIDs and cancer (immunocompromised group) pediatric patients who underwent 62 fiberoptic bronchoscopies between 2000 and 2004 were retrospectively reviewed and compared to 158 non-cancer patients who underwent 182 fiberoptic bronchoscopies during the same period. RESULTS: The overall diagnostic rate achieved by macroscopic inspection of purulent secretions or hemorrhage, abnormal cell count, and infectious agent isolation in the immunocompromised patients was 84%. A definite organism was recovered in 53.2% of the patients. Probable infection defined as purulent secretions or abnormal cell count without infectious agent isolation was diagnosed in another 21% of the patients. The rate of complications was 30.6%. In the control group, the overall diagnostic rate was 76.9% (n.s) and an infectious agent was demonstrated in 12.1% (P < 0.001). Probable infection was diagnosed in 24.2% (n.s) while the rate of complications was lower (15%) (P < 0.01). CONCLUSIONS: Rapid and accurate diagnoses were achieved in most procedures performed on immunocompromised patients. Although the rate of complications was higher in the immunocompromised group, they were usually very mild with no mortality. Based on these results, broncoalveolar lavage should be considered as an initial diagnostic tool in pediatric immunocompromised patients with pulmonary complications.

Adolescent↗

PubMed2005

Incoherent matter-wave solitons and pairing instability in an attractively interacting Bose-Einstein condensate.

The dynamics of matter-wave solitons in Bose-Einstein condensates (BEC) is considerably affected by the presence of a thermal cloud and the dynamical depletion of the condensate. Our numerical results, based on the time-dependent Hartree-Fock-Bogoliubov theory, demonstrate the collapse of the attractively interacting BEC via collisional emission of atom pairs into the thermal cloud, which splits the (quasi-one-dimensional) BEC soliton into two partially coherent solitonic structures of opposite momenta. These incoherent matter waves are analogous to optical random-phase solitons.

Journal Article↗

PubMed2005

Nonlinear adiabatic passage from fermion atoms to boson molecules.

We study the dynamics of an adiabatic sweep through a Feshbach resonance in a quantum gas of fermionic atoms. Analysis of the dynamical equations, supported by mean-field and many-body numerical results, shows that the dependence of the remaining atomic fraction Gamma on the sweep rate alpha varies from exponential Landau-Zener behavior for a single pair of particles to a power-law dependence for large particle number N. The power law is linear, Gamma is proportional to alpha, when the initial molecular fraction is smaller than the 1/N quantum fluctuations, and Gamma is proportional to alpha(1/3) when it is larger. Experimental data agree well with a linear dependence, but do not conclusively rule out the Landau-Zener model.

Journal Article↗

PubMed2004

Conversion efficiency of ultracold fermionic atoms to bosonic molecules via Feshbach resonance sweep experiments.

We explain why the experimental efficiency observed in the conversion of ultracold Fermi gases of 40K and 6Li atoms into diatomic Bose gases is limited to 0.5 when the Feshbach resonance sweep rate is sufficiently slow to pass adiabatically through the Landau-Zener transition but faster than "the collision rate" in the gas, and increases beyond 0.5 when it is slower. The 0.5 efficiency limit is due to the preparation of a statistical mixture of two spin states, required to enable s-wave scattering. By constructing the many-body state of the system we show that this preparation yields a mixture of even and odd parity pair states, where only even parity can produce molecules. The odd parity spin-symmetric states must decorrelate before the constituent atoms can further Feshbach scatter, thereby increasing the conversion efficiency; "the collision rate" is the pair decorrelation rate.

Journal Article↗

PubMed2002

Directional "superradiant" collisions: bosonic amplification of atom pairs emitted from an elongated Bose-Einstein condensate.

We study spontaneous directionality in the bosonic amplification of atom pairs emitted from an elongated Bose-Einstein condensate, an effect analogous to superradiant emission of atom-photon pairs. Using a simplified model, we make analytic predictions regarding directional effects for both atom-atom and atom-photon emission. These are confirmed by numerical mean-field simulations, demonstrating the feasibility of nearly perfect directional emission along the condensate axis. The dependence of the emission angle on the pump strength for atom-atom pairs is significantly different than for atom-photon pairs.

Journal Article↗

PubMed2002

Bose-enhanced chemistry: amplification of selectivity in the dissociation of molecular Bose-Einstein condensates.

We study the photodissociation chemistry of a quantum degenerate gas of bosonic triatomic ABC molecules, assuming two open rearrangement channels ( AB+C or A+BC). The equations of motion are equivalent to those of a parametric multimode laser, resulting in an exponential buildup of macroscopic mode populations. By exponentially amplifying a small differential in the single-particle rate coefficients, Bose stimulation leads to a nearly complete selectivity of the collective N-body process, indicating a novel type of ultraselective quantum degenerate chemistry.

Journal Article↗

PubMed2001

Bose-Einstein condensates beyond mean field theory: quantum backreaction as decoherence.

We propose an experiment to measure the slow log(N) convergence to mean field theory (MFT) around a dynamical instability. Using a density matrix formalism instead of the standard macroscopic wave function approach, we derive equations of motion which go beyond MFT and provide accurate predictions for the quantum break time. The leading quantum corrections appear as decoherence of the reduced single-particle quantum state.

Journal Article↗

PubMed2001

Acute respiratory distress syndrome in children with malignancy--can we predict outcome?

PURPOSE: The purpose of this study was to delineate early respiratory predictors of mortality in children with hemato-oncology malignancy who developed acute respiratory distress syndrome (ARDS). MATERIALS AND METHODS: We conducted a retrospective chart review of children with malignant and ARDS who needed mechanical ventilation and were admitted to a pediatric intensive care unit from January 1987 to January 1997. RESULTS: Seventeen children with ARDS and malignancy aged 10.5 +/- 5.1 years were identified. Six of the 17 children (35.3%) survived. Sepsis syndrome was present in 70.6% of all the children. Peak inspiratory pressure, positive end-expiratory pressure (PEEP), and ventilation index values could distinguish outcome by day 3. A significant relationship between respiratory data and outcome related to efficiency of oxygenation, as determined by PaO(2)/FIO(2) and P(A-a)O(2), was present from day 8 after onset of mechanical ventilation. CONCLUSIONS: Peak inspiratory pressure, PEEP, and ventilation index values could distinguish survivors from nonsurvivors by day 3. This may assist in early application of supportive nonconventional therapies in children with malignancy and ARDS.

Adult↗

PubMed2000

[The sixth vital sign: end-tidal CO2 in pediatric trauma patients during transport].

Transport of pediatric trauma victims, within as well as between medical centers, has become a frequent event and an integral activity of pediatric critical care units. Monitoring patients during transport is of utmost importance, as an unstable environment poses an increased threat to the patient's stability. The level of monitoring and care should approximate that of the critical care unit. Monitoring end-tidal CO2 (EtCO2) has become routine for many pediatric intensive care unit patients but technical problems have limited its use during transport. Our transport team uses a transportable EtCO2 monitor of the side-stream type (NPB 75), requiring very small samples; midstream sampling overcomes humidity interference. The monitor is small and lightweight, operates on a rechargeable battery and is especially designed for the demanding environment of transport. From October 1997 through January 1999, 187 pediatric patients, 62 of whom were trauma victims, were transported for a total of 45 hours, including 2 hours of in-flight transport. Age range was 3 months to 16 years. Of the 53 monitored for EtCO2, in 9 (17%) monitoring resulted in a significant, immediate change of treatment during transport. We find EtCO2 an important adjunct in monitoring pediatric trauma patients during transport. In addition to conventional monitoring of heart rate, blood pressure, respiratory rate, body temperature and blood oxygen saturation, we suggest EtCO2 as the sixth vital sign that should be monitored.

Adolescent↗

PubMed1999

Programmed cell death of the dinoflagellate Peridinium gatunense is mediated by CO(2) limitation and oxidative stress.

The phytoplankton assemblage in Lake Kinneret is dominated in spring by a bloom of the dinoflagellate Peridinium gatunense, which terminates sharply in summer [1]. The pH in Peridinium patches rises during the bloom to values higher than pH9 [2] and results in CO(2) limitation. Here we show that depletion of dissolved CO(2) (CO(2(dis))) stimulated formation of reactive oxygen species (ROS) and induced cell death in both natural and cultured Peridinium populations. In contrast, addition of CO(2) prevented ROS formation. Catalase inhibited cell death in culture, implicating hydrogen peroxide (H(2)O(2)) as the active ROS. Cell death was also blocked by a cysteine protease inhibitor, E-64, a treatment which stimulated cyst formation. Intracellular ROS accumulation induced protoplast shrinkage and DNA fragmentation prior to cell death. We propose that CO(2) limitation resulted in the generation of ROS to a level that induced programmed cell death, which resembles apoptosis in animal and plant cells. Our results also indicate that cysteine protease(s) are involved in processes that determine whether a cell is destined to die or to form a cyst.

Animals↗

PubMed1999

[Head injuries in children--clinical characteristics as prognostic factors].

An unselected series of 200 consecutive cases of major head trauma in children aged 6 months to 16 years, seen during 4 years, was studied. Injuries were due to road accidents (40%), falls (30.5%) and other causes (29.5%), and were assessed clinically and by cranial CT. On admission the Glasgow Coma Score ranged from 4.72-11.65 and in addition to pupillary responses and brain stem reflexes, was a significant predictor of outcome. Brain edema, midline shift, intracranial hemorrhage and also hyperglycemia, hypokalemia and coagulopathy, were associated with poor outcome. While 17% died, 53% were discharged in good functional condition. Early identification of clinical features related to prognosis can help the caring team provide maximal support for patient and family.

Accidental Falls↗

PubMed1999

[Intrahospital transport of critically ill children].

Prospective evaluation of intrahospital transportation of 33 critically ill children to and from the pediatric intensive care unit was conducted over the course of a month. Factors contributing to risk of transport were assessed. There were 33 children (25 boys and 8 girls), 3 days to 15 years of age. Reasons for admission included: disease and trauma in 19, and status post operation in 11. The pretransport PRISM score was 4.84. 22 children (66.6%) were being mechanically ventilated and 10 (30.3%) were being treated with amines. Transport time ranged from 8-150 minutes. 15 of the transports (45.4%) were urgent and a special intensive care team escorted 22 (66.6%). Equipment mishaps and physiological deterioration occurred in 12 (36.3%) and 11 (30.3%) of the cases, respectively. The use of amines, mechanical ventilation, longer transport time and high PRISM score were all associated with physiological deterioration on transport.

Adolescent↗

PubMed1999

CT diagnosis of delayed presentation of congenital diaphragmatic hernia simulating massive pleuropneumonia.

A case of an 11-month-old infant with a delayed presentation of congenital diaphragmatic hernia is reported. Incarceration of the herniated colon caused a misleading appearance on the chest X-ray which was interpreted as massive pleuropneumonia. Computed tomography, performed because of continuing deterioration in the clinical condition, showed fluid-filled bowel loops in the chest and dilated bowel loops with air-fluid levels in the abdomen, suggesting the correct diagnosis.

Colon↗

PubMed1999

Invasive meningococcal disease: patient and strain characteristics set new challenge for prevention and control.

Differences in the course of invasive meningococcal disease, in prevalence, case-to-carrier ratio, geographical pattern, age distribution and antibiotic resistance have been related to major serogroups and their serotypes. The relationships between Neisseria meningitidis serogroups and clinical manifestation, outcome and patient characteristics are assessed. All hospitalized patients in six major hospitals in central Israel with a verified meningococcal disease during 1990-1994 were included (n = 66). Their personal and clinical data and the results of bacteriological and serological tests of their blood and cerebrospinal fluid (CSF) were recorded. Meningococci were isolated from both blood and CSF, from blood alone, and from CSF alone in 60.6%, 18.2%, and 21.2% of the cases, respectively. The highest proportion of isolations were from infants < 1 year (34.8%), followed by children aged 1 to 5 years (25.8%). Serogroup B prevailed in 62.1%, while groups C and W135 accounted for 28.8% and 9.1%, respectively. Serogroup B predominated in children < 1 year, while in patients aged 5-22 years, C strains were the major pathogen (P < 0.001). Serogroup B accounted for 93% of the cases of meningitis, 58% of meningococcemia and 42% of fulminant meningococcemia, while group C strains were the major cause of fulminant meningococcemia (50%). The overall case fatality rate was 7.6%: fulminant meningococcemia 8.3%, and meningococcemia 10%. It was concluded that N. meningitidis group C continues to account for almost a third of the cases of meningococcal disease and is the major cause of fulminant meningococcemia.

Adolescent↗

PubMed1999

Adapting prognostic respiratory variables of ARDS in children to small-scale community needs.

PURPOSE: The clinical literature on the incidence and subsequent mortality of adult respiratory distress syndrome (ARDS) has come primarily from the experiences of large tertiary referral centers, particularly in Western Europe and North America. Consequently, very little has been published on the incidence, management, and outcome of ARDS in smaller community-based intensive care units. We aimed to delineate early clinical respiratory predictors of death in children with ARDS on the modest scale of a community hospital. MATERIALS AND METHODS: A retrospective chart review of children with ARDS needing conventional mechanical ventilation admitted to our pediatric intensive care unit from 1984 to 1997. The diagnosis of ARDS was based on acute onset of diffuse, bilateral pulmonary infiltrates of noncardiac origin and severe hypoxemia defined by partial pressure of oxygen <200 mm Hg during positive end-expiratory pressure (PEEP) of 6 cm H2O or greater for a minimum of 24 hours. Demographic, clinical, and physiological data including PaO2/ FIO2, A-aDo2, and ventilation index were retrieved. RESULTS: Fifty-six children with ARDS aged 8 +/- 5.5 years (range, 50 days to 21 years) were identified. The mortality rate was 50%. Early predictors of death included the peak inspiratory pressure (PIP), ventilation index, and PEEP on the third day after diagnosis: Nonsurvivors had significantly higher PIP (35.3 +/- 10.5 cm H2O vs 44.4 +/- 10.7 cm H2O, P < .001), PEEP (8 +/- 2.8 cm H2O vs 10.7.0 +/- 3.5 cm H2O, P < .01), and ventilation index (49.14 +/- 20.4 mm Hg x cm H2O/minute vs 61.6 +/- 51.1 mm Hg cm H2O/minute) than survivors. In contrast, PAO2/FIO2 and A-a DO2 were capable of predicting outcome by day 5 and thereafter. CONCLUSIONS: A small-scale mortality outcome for ARDS is comparable to large tertiary referral institutions. The PIP, PEEP, and ventilation index are valuable for predicting outcome in ARDS by the third day of conventional therapy. The development of a local risk profile may assist in decision-making of early application of supportive therapies in this population.

Adolescent↗

PubMed1999

Pharmacokinetics of endobronchial tolazoline administration in dogs.

Tolazoline is a potent vasodilator of arteries and veins and has a powerful effect on the pulmonary vasculature, reducing hypoxic pulmonary vasoconstriction and lowering pulmonary artery pressure. Intravenous tolazoline lowers the mean pulmonary arterial pressure and resistance and increases the cardiac index when given to infants with persistent pulmonary hypertension (PPHN). Endotracheally administered tolazoline decreases mean pulmonary arterial pressure and pulmonary vascular resistance, and improves oxygenation without the harmful decline in the systemic arterial pressure. The purpose of our study was to examine the pharmacokinetic and pharmacodynamic characteristics of endobronchial tolazoline to determine the relationship between endobronchial tolazoline administration, plasma concentration, and its effects on the cardiovascular and respiratory systems. Tolazoline was administered endobronchially to seven dogs, and its serum concentration and the hemodynamic parameters were monitored for 270 min postdelivery. It was found that 15 sec after dosing, tolazoline plasma concentrations started to increase significantly above baseline levels, reaching a maximum of 9.3+/-8.0 microg x mL(-1) The volume of distribution was 1657+/-321 mL x kg(-1) after 1 2.4+/-1 6.6 min. The extent of tolazoline absorption was 319+/-38 microg x min(-1) mL(-1). The total body clearance was 10.9 +/-4.8 mL x min(-1) x Kg(-1) and the elimination half-life was 156+/-81 min. Endobronchial tolazoline produced an initial short-lived decrease in the mean blood pressure in all the dogs, but thereafter the blood pressure increased gradually above baseline levels. Immediately following endobronchial tolazoline a significant tachycardia developed, peaking at 90 min. Subsequently, the heart rate gradually decreased and stabilized at values above baseline for 200 min. We conclude that an endobronchial bolus dose of tolazoline is effectively absorbed, produces measurable pharmacological effects, and may be beneficial in the therapy of persistent pulmonary hypertension of the newborn.

Absorption↗

PubMed1999

Early prediction of neurological outcome after falls in children: metabolic and clinical markers.

Falls are the foremost reason for non-fatal injuries and are second only to motor vehicle accidents in causing accidental death. The purpose of this study was to identify the clinical and metabolic predictors of the outcome of head injury caused by falls from a height. Medical records of 61 children who had been admitted to the paediatric intensive care unit from 1990 to 1993 after falling from a height were reviewed retrospectively. Outcomes were categorised as good, moderate, severe, and poor. Glasgow coma scores, pupillary responses, brain oedema, and midline shift are significantly associated with poor outcome (p < 0.05). Metabolic markers associated with poor outcome included hyperglycaemia and hypokalaemia. Children with a poor outcome had, at admission, significantly higher glucose concentrations compared with children with good outcomes (mean SD): 20.0 (7.1) v 9.31 (4.0) mmol/l, p < 0.01), and lower potassium concentrations compared with children with good, moderate, and severe outcomes (mean (SD): 2.8 (0.4) v 3.7 (0.4) mmol/l, p < 0.001, 3.5 (0.3) mmol/l, p < 0.01, and 3.41 (0.3) mmol/l, p < 0.05, respectively). These findings allow for an early allocation of effort and resources to children injured from such falls.

Accidental Falls↗

PubMed1999

Acute respiratory distress syndrome in children: a 10 year experience.

BACKGROUND: Acute respiratory distress syndrome is a well-recognized condition resulting in high permeability pulmonary edema associated with a high morbidity. OBJECTIVES: To examine a 10 year experience of predisposing factors, describe the clinical course, and assess predictors of mortality in children with this syndrome. METHODS: The medical records of all admissions to the pediatric intensive care unit over a 10 year period were evaluated to identify children with ARDS. Patients were considered to have ARDS if they met all of the following criteria: acute onset of diffuse bilateral pulmonary infiltrates of non-cardiac origin and severe hypoxemia defined by < 200 partial pressure of oxygen during > or = 6 cm H2O positive end-expiratory pressure for a minimum of 24 hours. The medical records were reviewed for demographic, clinical, and physiologic information including PaO2/forced expiratory O2, alveolar-arterial O2 difference, and ventilation index. RESULTS: We identified 39 children with the adult respiratory distress syndrome. Mean age was 7.4 years (range 50 days to 16 years) and the male:female ratio was 24:15. Predisposing insults included sepsis, pneumonias, malignancy, major trauma, shock, aspiration, near drowning, burns, and envenomation. The mortality rate was 61.5%. Predictors of death included the PaO2/FIO2, ventilation index and A-aDO2 on the second day after diagnosis. Nonsurvivors had significantly lower PaO2/FIO2 (116 +/- 12 vs. 175 +/- 8.3, P < 0.001), and higher A-aDO2 (368 +/- 28.9 vs. 228.0 +/- 15.5, P < 0.001) and ventilation index (43.3 +/- 2.9 vs. 53.1 +/- 18.0, P < 0.001) than survivors. CONCLUSIONS: Local mortality outcome for ARDS is comparable to those in tertiary referral institutions in the United States and Western Europe. The PaO2/FIO2, A-aDO2 and ventilation index are valuable for predicting outcome in ARDS by the second day of conventional therapy. The development of a local risk profile may allow early application of innovative therapies in this population.

Acute Disease↗