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R Barrera

Publications and source records attributed to R Barrera.

At least 19 recordsLinked to original sources
PubMed2006

Sample sizes for identifying the key types of container occupied by dengue-vector pupae: the use of entropy in analyses of compositional data.

A method has been developed for estimating the sample sizes needed to identify categories that comprise a large proportion of a compositional data-set. The method is to be used in the design of surveys of mosquito pupae, for identifying the key container types from which the majority of adult dengue vectors emerge. Although a finite-population correction was devised for estimating the mean of a negative binomial distribution, other complications of parametric approaches make them unlikely to yield methods simple enough to be practically applicable. The Shannon-Wiener index was therefore investigated as a more useful alternative, at the cost of theoretical generalizability, in an approach based on re-sampling methods in conjunction with the use of entropy. This index can be used to summarize the degree to which pupae are either concentrated in a few container types, or dispersed among many. An empirical relationship between the index and the repeatability of surveys of differing sample sizes was observed. A step-wise rule, based on the entropy of the cumulative data, was devised for determining the sample size, in terms of the number of houses positive for pupae, at which a pupal survey might reasonably be stopped.

Aedes↗
PubMed2006

Sample-size requirements for developing strategies, based on the pupal/demographic survey, for the targeted control of dengue.

Several methods to determine the sample size required for a reliable and practical assessment of the number of Aedes aegypti pupae in a community in Puerto Rico have been explored. Because the pupae were highly aggregated, the data were fitted to a negative binomial distribution. Classical statistical-inference methods for sample-size determination demanded the sampling of >3,000 premises for a reliable estimation of the mean number of pupae/person (with a 15% error). This number was reduced to 1,000-1,200 premises after applying a finite-population correction. Database sub-sampling simulations, with increasing sample sizes, showed that the variability in the mean relative abundance of container types and in the mean number of pupae/container substantially decreased after sampling 186 and 310 premises, respectively. Sequential sampling was applied to test the hypotheses that the number of female pupae/person was at least 0.19 (considered the dengue epidemic threshold) or no greater than 0.10 (arbitrarily set as the safe level). After sampling only 25 premises in the first survey and 125 in the second, it was determined that the densities of female pupae were above the epidemic threshold. Thus, sequential sampling provided substantial reductions in the sample size required to determine if vector control was needed. Validation of the Ae. aegypti thresholds required for dengue transmission could confer viability and efficiency to dengue-vector surveillance and control programmes.

Aedes↗
PubMed2004

Canine pyometra: a study of the urinary proteins by SDS-PAGE and Western blot.

Canine pyometra often causes glomerulonephritis by immune complex deposition in the glomeruli. Proteinuria, ranging from moderate to severe, may be present secondary to renal damage. To determine urinary protein excretion due to pyometra, sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) was conducted on urine from 15 bitches with pyometra and 10 healthy bitches. To characterize urinary immunoglobin excretion, Western blot analysis of the urine samples using antibodies to canine IgG and IgA was also performed. Nine bands were detected by electrophoresis in bitches with pyometra, while only four were detected in the healthy animals. The urinary proteins from bitches with pyometra were primarily of glomerular origin; 58% were of medium-high molecular weight (MW), and the remainder were low MW. None of the healthy dogs had IgG or IgA in their urine, whereas three bitches with pyometra had IgG in their urine and another bitch with pyometra had both IgG and IgA. The low proportion of bitches with urinary immunoglobins was probably be due to early diagnosis of the disease. Although only a limited number of dogs was used, this study is apparently the first to characterize the electrophoretic pattern of urinary proteins and to quantify urinary excretion of IgG and IgA in bitches with pyometra.

Animals↗
PubMed2001

Field testing of a vaccine against eel diseases caused by Vibrio vulnificus.

The field results of a vaccination programme against Vibrio vulnificus serovar E (biotype 2) in a Spanish eel farm are reported. A total of 9.5 million glass eels were vaccinated from January 1998 to March 2000 by prolonged immersion followed by 2 subsequent reimmunisations after 12 to 14 and 24 to 28 d, respectively. The acquired protection and the immune response against serovar E were estimated over a period of 6 mo after vaccination. A similar vaccination schedule was conducted with elvers in a Danish eel farm. In this case, the acquired protection and the immune response against serovar E and the new eel-pathogenic serovars, recently described in Denmark, were evaluated over a short term. The overall results show that the vaccine against V. vulnificus serovar E induces a satisfactory protective immunity during the main growth period of eels (around 6 mo) with a relative percentage survival of 62 to 86% and protects them against the new eel-pathogenic serovars. Vaccination of eels by immersion seems to be the best strategy to prevent diseases caused by V. vulnificus.

Animals↗
PubMed2001

Nutritional support in critically ill patients with cancer.

Nutritional depletion is a common problem seen in critically ill patients with cancer and is associated with increased morbidity and mortality. Infection and injury activate a cascade of metabolic events that leads to a poor nutritional state and wasteful energy consumption. The goals of nutritional support entail minimizing starvation, preventing nutrient deficiencies, supporting or improving immune function, and facilitating tissue repair and wound healing. Further understanding of the metabolic changes of illness will improve effective regulation of the inflammatory events occurring in critically ill patients. Multiple clinical parameters are available to assess the nutritional status in critically ill patients, but no standard recommendations can be made at this time. The use of these parameters can be appropriate, provided that their limitations are understood clearly. The development and standardization of objective parameters to identify patients at risk or with subclinical malnutrition are needed. Enteral and parenteral feedings are safe and effective methods to deliver nutrients to critically ill patients with cancer who are unable to ingest adequate amounts orally. Early nutritional support should be instituted in the appropriate clinical setting. Specialized nutritional solutions and supplements require careful consideration in patients with renal, hepatic, cardiac, or pulmonary disorders. The unselective use of nutritional support is not indicated in well-nourished patients with cancer undergoing surgery, chemotherapy, or radiotherapy in whom adequate oral intake is anticipated. Nutritional support remains an important adjunctive therapy in the overall management of critically ill patients. Continued clinical investigations in nutrition are necessary to identify other groups of patients who can benefit from nutritional interventions.

Critical Illness↗
PubMed2001

Accuracy of predictions of survival at admission to the intensive care unit.

PURPOSE: The purpose of this study was to compare the accuracy of outcome predictions made on the day of intensive care unit (ICU) admission by critical care physicians, critical care fellows, and primary team physicians. PATIENTS AND METHODS: Fifty-nine consecutive patients admitted to a Medical-Surgical ICU were included in the study. Two ICU attending physicians and two critical care fellows, not involved in medical management, evaluated each new ICU patient at admission and after 48 to 72 hours. Altogether six ICU attendings and six fellows were involved in the study. Each investigator separately assigned probability to each patient of being discharged alive from the ICU and the hospital. On the day of admission the primary service was also asked to estimate the likelihood of successful outcome. All values are expressed in percentiles. Statistical analysis was performed by a logistic regression procedure with a binary outcome. Data are presented as mean +/- SD. RESULTS: Fifty-nine patients were surveyed. Twenty-six (44%) patients died in the ICU, 3 (5%) died in the hospital wards, and 30 (51%) were discharged alive from the hospital. ICU attendings most reliably and accurately estimated patient outcome on admission compared with critical care fellows and primary team physicians. ICU attendings were more consistent than ICU fellows at predicting outcome at 48 and 72 hours. Clinical predictions were better for patients at the extremes of disease severity, and the accuracy of predictions in these patients was highest. Accuracy was diminished in patients with moderate compromise of clinical status. CONCLUSION: ICU attendings predicted most accurately and consistently the final outcome of patients, and ICU fellows estimated outcome more reliably than the primary service. For the most part, the primary service tended to overestimate the probability of favorable outcome of patients for whom ICU admission had been requested. Additionally, clinical accuracy of survival or mortality was best for those patients at the extremes of clinical compromise: this point seems to confirm the validity of using clinical judgement as a guide to restricting ICU resources for those severely compromised or mildly compromised.This study also indicates that predictions of outcome in critically ill patients made within days of admission are statistically valid but not sufficiently reliable to justify irrevocable clinical decisions at present.

Cancer Care Facilities↗
PubMed2001

Outcome of direct percutaneous endoscopic jejunostomy tube placement for nutritional support in critically ill, mechanically ventilated patients.

PURPOSE: Gastrointestinal function is adversely affected in critically ill mechanically ventilated patients. The most common abnormality is delayed gastric emptying. Among the options for postpyloric feeds, direct percutaneous endoscopic jejunostomy (PEJ) provides a permanent, reliable, and direct access to the small bowel and can be used for full enteral feedings, thus eliminating the need for parenteral nutrition. PATIENTS AND METHODS: All patients who underwent direct PEJ tube placement while mechanically ventilated in the intensive care unit (ICU) were evaluated. For each patient the following factors were identified: age, indication for ICU admission and PEJ placement, nutritional support before and after PEJ placement, calories received, complications, and outcome. RESULTS: Seventeen patients underwent the procedure. All had successful placement of direct PEJ tube. There was a single complication. Within 24 hours of PEJ placement, 16 of 17 patients tolerated jejunal feedings. All patients progressed to their established nutritional goals. There were no cases of aspiration of enteral feedings. In the 16 patients, total parenteral nutrition (TPN) was not required once PEJ tubes were placed. Thirteen patients were discharged home or to a rehabilitation facility with jejunal feedings. CONCLUSIONS: Direct PEJ placement is a safe and reliable device that can be successfully placed in critically ill, mechanically ventilated patients. With this procedure, all patients can meet their nutritional requirements and eliminate the need for TPN.

Adult↗
PubMed2001

Determination of metabolic monitor errors and precision under clinical conditions.

BACKGROUND & AIMS: Metabolic monitoring devices used in the critical care setting are subject to a range of conditions that may compromise their accuracy. We sought to investigate the error and precision of the Deltatrac metabolic monitor under these conditions. METHODS: A modified version of the funnel burner, described by Miodownik et al. (8), was ventilated by a mechanical ventilator. This was used to examine the performance of the Deltatrac metabolic monitor over a wide range of inspired oxygen concentrations, minute ventilation, and positive end expiratory pressure at different levels of oxygen consumption and carbon dioxide production. RESULTS: The Deltatrac measured V(O(2)) with a mean error+/-precision of 9.4%+/-19.5% (range, 9.3%+/-1.9%-72.6%+/-13.6%). The mean V(CO(2)) error+/-precision was 1.2%+/-3.1% (range-2.0%+/-1.2%-5.4%+/-3.1%). Error was significantly affected by oxygen concentration and minute ventilation but was largely independent of positive and expiratory pressure. CONCLUSIONS: The methodology of Miodownik et al. permits the expression of metabolic device errors over a wide range of simulated clinical conditions.

Calorimetry, Indirect↗
PubMed2001

Characterization of enzootic foci of Venezuelan equine encephalitis virus in western Venezuela.

The distribution of the sylvatic subtype ID Venezuelan equine encephalitis (VEE) viruses in the lowland tropical forests of western Venezuela was investigated using remote sensing and geographic information system technologies. Landsat 5 Thematic Mapper satellite imagery was used to study the reflectance patterns of VEE endemic foci and to identify other locations with similar reflectance patterns. Enzootic VEE virus variants isolated during this study are the closest genetic relatives of the epizootic viruses that emerged in western Venezuela during 1992-1993. VEE virus surveillance was conducted by exposing sentinel hamsters to mosquito bites and trapping wild vertebrates in seven forests identified and located by means of the satellite image. We isolated VEE viruses from 48 of a total of 1,363 sentinel hamsters in two of the forests on six occasions, in both dry and wet seasons. None of the 12 small vertebrates captured in 8,190 trap-nights showed signs of previous VEE virus infection. The satellite image was classified into 13 validated classes of land use/vegetation using unsupervised and supervised techniques. Data derived from the image consisted of the raw digital values of near- and mid-infrared bands 4, 5, and 7, derived Tasseled Cap indices of wetness, greenness, and brightness, and the Normalized Difference Vegetation Index. Digitized maps provided ancillary data of elevation and soil geomorphology. Image enhancement was applied using Principal Component Analysis. A digital layer of roads together with georeferenced images was used to locate the study sites. A cluster analysis using the above data revealed two main groups of dense forests separated by spectral properties, altitude, and soil geomorphology. Virus was isolated more frequently from the forest type identified on flat flood plains of main rivers rather than the forest type found on the rolling hills of the study area. The spatial analysis suggests that mosquitoes carrying the enzootic viruses would reach 82-97% of the total land area by flying only 1-3 km from forests. We hypothesize that humans within that area are at risk of severe disease caused by enzootic ID VEE viruses. By contrast, equines could actually become naturally vaccinated, thus preventing the local emergence of epizootic IC VEE virus strains and protecting humans indirectly.

Animals↗
PubMed2001

Unusual freshwater near-drowning syndrome in a hospitalized postlobectomy patient.

Near-drowning syndrome depends on the duration of submersion, the amount of fluid aspirated, and the severity of hypoxia. We report a case in which a patient developed ARDS shortly after undergoing a left upper lobectomy and a chest wall resection for a lung carcinoma. On further investigation, the ARDS was caused by near-drowning in a basin of freshwater: the patient's face was submerged by the patient's companion as part of a cultural tradition of trying to clean his lung. We believe that this case presents the etiology of freshwater near-drowning syndrome due to an ethnogenic practice not previously reported.

Aged↗
PubMed2001

Spatial dispersion of adult mosquitoes (Diptera: Culicidae) in a sylvatic focus of Venezuelan equine encephalitis virus.

We studied the spatial localization of mosquitoes in sylvatic focus of Venezuelan equine encephalitis virus in western Venezuela to identify mosquito species potentially involved in the hypothesized transport of viruses out of enzootic foci. The following criteria were used to identify species with potential for virus export: (1) common in the forest and surrounding area, (2) feeding on a wide range of vertebrates; (3) long dispersal capabilities, and (4) established vectorial competence for enzootic or epizootic VEE viruses. CDC traps baited with light/CO2 were operated for four and 12-h intervals to collect mosquitoes at four stations along two forest/open area transects from September to November 1997. We collected 60,444 mosquitoes belonging to 11 genera and 34 species. The most common species were Aedes serratus (Theobald), Ae. scapularis (Rondani), Ae. fulvus (Wiedmann), Culex nigripalus Theobald, Cx, (Culex) "sp", Cx. mollis Dyar & Knab, Cx. spissipes (Theobald), Cx. pedroi Sirivanakarn and Belkin, Psorophora ferox (Humboldt), Ps. albipes (Theobald), and Ps. cingulata (F.). Very few mosquitoes were captured during the (day in the open area outside the forest, suggesting that any virus export from the forest may occur at night. The following mosquitoes seemed to be mostly restricted to the forest habitat: Ae. serratus, Ps. ferox, Ps. albipes, sabethines, Cx. spissipes, Cx. pedroi, Cx. dunni Dyar, and Ae. fulvus. The main species implicated its potential virus export were Cx. nigripalpus, Ae. scapularis, and Mansonia titillans (Walker).

Aedes↗
PubMed2001

Genetic diversity and relationships among Venezuelan equine encephalitis virus field isolates from Colombia and Venezuela.

During field studies of enzootic Venezuelan equine encephalitis (VEE) viruses associated with epizootic emergence, a large number of virus isolates were made in sylvatic foci of Venezuela and Colombia. To rapidly characterize these isolates, antigenic subtypes were determined by means of immunofluorescence and by single-strand conformational polymorphism (SSCP) analysis by use of an 856-bp fragment from the P62 gene, which we used to distinguish genetic variants. Representative isolates were sequenced to assess the sensitivity of SSCP to detect genetic differences. The SSCP analysis distinguished isolates differing by as little as 1 nucleotide; overall, differences of > or = 1 nucleotide were recognized 89% of the time, and the sensitivity to distinguish strains that differed by only 1 or 4 nucleotides was 17 and 57%, respectively. Phylogenetic analyses of representative sequences showed that all recent isolates from the Catatumbo region of western Venezuela and the middle Magdalena Valley of Colombia were closely related to epizootic subtype IAB and IC strains; strains from Yaracuy and Miranda States were more distantly related. Cocirculation of the same virus genotype in both Colombian and Venezuelan foci indicated that these viruses are readily transported between enzootic regions separated by > 300 km. The SSCP analysis appears to be a simple, fast, and relatively efficient method of screening VEE virus isolates to identify meaningful genetic variants.

Aedes↗
PubMed2000

Seasonal adaptation modulates the expression of the protein kinase CK2 beta subunit gene in the carp.

Carp fish seasonal acclimatization induces a cyclical transcriptional modulation of several genes. Its most dramatic expression results in a concomitant structural rearrangement of the nucleolar components that phenotypically represents profound shifts in the level of ribosomal RNA synthesis. In connection with the recent studies that implicate CK2 in the control of rRNA synthesis in vertebrates, we characterized the cDNA of carp protein kinase CK2beta subunit and assessed its transcriptional behavior in winter- and summer-acclimatized fish. We found a remarkable differential gene expression of CK2beta subunit between summer- and winter-acclimatized carp which correlates with the modulatory pattern observed in rRNA transcription.

Acclimatization↗
PubMed2000

Ionized magnesium supplementation in critically ill patients: comparing ionized and total magnesium.

PURPOSE: The purpose of this study was to assess the effect of magnesium supplementation on total magnesium, ionized magnesium, ionized calcium, potassium, and pH in critically ill cancer patients and to compare the validity of the measurements. MATERIALS AND METHODS: Thirty-three consecutive critically ill patients receiving magnesium supplementation were placed in this prospective observational study at the Comprehensive Cancer Center, University Hospital. One gram (4.1 mmol) magnesium in 50 mL D5W was administered to critically ill patients, and the following were measured: total magnesium, ionized magnesium, ionized calcium, potassium, albumin, pH, BUN, creatinine, creatinine. RESULTS: Total magnesium and ionized magnesium increased by a mean of .11 +/- .02 and .05 +/- .01 mmol/L, respectively, after supplementation with 4.1 mmol of magnesium sulfate (P = .0001). Total magnesium, ionized magnesium, albumin, ionized calcium, potassium, and pH did not change significantly by the administration of 1 g of magnesium sulfate. CONCLUSION: The mean ionized magnesium (IMg+2) relationship to total magnesium (TMg) cannot be predicted before the supplementation with the available technology. After supplementation of 4.1 mmol/L the ionized magnesium level increased by .05 +/- .01 mmol/L. Magnesium supplementation had no significant effect on ionized calcium, potassium, and pH. TMg and IMg+2 should be followed independently.

Adult↗
PubMed2000

The effect of varying inspiratory flow waveforms on pulmonary mechanics in critically ill patients.

PURPOSE: Ten mechanically ventilated patients were evaluated to determine the effect of three different inspiratory flow patterns on pulmonary mechanics. MATERIALS AND METHODS: Ten consecutive mechanically ventilated critically ill patients with acute respiratory failure admitted to the intensive care unit were evaluated to assess the effects of decelerating, square, and sine waveforms on pulmonary mechanics. The variables measured were peak airway pressure (PaW), pleural pressure (Ppl), change in peak airway pressure (dPaW), inspiration time/total ventilation cycle time (Vi/tot), dynamic compliance (Cdyn), respiratory rate (RR), minute ventilation (Ve), and work of breathing (WOB). RESULTS: The PaW, Ppl, and dPaW (cm H2O) were significantly lower using the decelerating inspiratory flow waveform (P<.05) compared with sine or square waveform patterns. Ti/Ttot was also lower with the decelerating waveform (P<.05) with better dynamic compliance compared with the other waveforms (P<.10). CONCLUSIONS: These results indicate that critically ill mechanically ventilated patients show improved respiratory mechanics with decelerating inspiratory waveform that may have beneficial clinical implication.

Adult↗
PubMed2000

[Stratification of a hyperendemic city in hemorrhagic dengue].

Any effort to control dengue hemorrhagic fever (DHF) faces a number of challenges. Among these are the great environmental heterogeneity of homes and neighborhoods in urban centers where the primary dengue vector, Aedes aegypti, breeds, as well as shortages of resources and of personnel trained in mosquito control. Adequate epidemiological surveillance could serve as a basis to begin to stratify urban communities and identify the areas in them where control efforts should be focused. In this study we stratified Maracay, Venezuela, a city with hyperendemic dengue hemorrhagic fever, using a geographic information system and analyzing the persistence, incidence, and prevalence of dengue, by means of clinical diagnoses reported from 1993 through 1998. Maracay has around one million inhabitants living in some 349 neighborhoods in the six communities that make up the greater Maracay metropolitan area. During that 1993-1998 period the Maracay area reported 10,576 cases of dengue, 2,593 cases of DHF, and 8 deaths. The incidence of DHF was related to the incidence of dengue, the number of inhabitants in an area, and population density. The spatial pattern of dengue incidence was stable over the years that were studied, and significant, positive relationships were found between pairs of years and the incidence of dengue by neighborhood. The persistence of dengue was related directly to monthly incidence by neighborhood. These spatial patterns helped to divide the city into three strata: 68 neighborhoods without apparent dengue, 226 neighborhoods with low persistence and prevalence, and 55 neighborhoods with high persistence and prevalence. We recommend giving the highest priority for control efforts to these 55 neighborhoods, which make up just 35% of the Maracay urban area but had 70% of all the reported dengue cases.

Aedes↗
PubMed1999

Flow triggering added to pressure support ventilation improves comfort and reduces work of breathing in mechanically ventilated patients.

PURPOSE: The purpose of this study was to measure the effect of flow triggering (FT), added to pressure support ventilation (PSV), during spontaneous breathing in intubated patients. MATERIALS AND METHODS: A prospective observational study was conducted at a Comprehensive Cancer Center, University Hospital. Fourteen consecutive critically ill, mechanically ventilated patients on PSV with positive end-expiratory pressure were studied. Flow triggering was added to PSV in spontaneously breathing ventilated patients. RESULTS: Respiratory rate (f), minute ventilation (Vepsilon), patient work of breathing (WOBp), respiratory drive (P0.1), rapid shallow breathing index (f/Vt), tidal volume (Vt) and a visual analog scale of breathing effort and comfort all improved. There was a large decrease in WOBp and P0.1 when flow triggering was added to PSV (P<.001). There was a moderate decrease in f/V1 during the same procedure (P<.01). Twelve patients felt subjectively better with the intervention. CONCLUSIONS: Flow triggering offers an excellent complement to PSV because it improves patient comfort and reduces the magnitude of the inspiratory effort as well as the delay time between inspiratory muscle contraction and gas flow. It augments gas exchange at no metabolic cost to the patient while reducing the work of breathing.

Adult↗