Cateterización venosa central guiada por ecografía: estudio randomizado controlado

RESUMEN Antecedentes: en nuestro medio no hay estudios en cuidados críticos o anestesia que analicen la utilidad de la ecografía para la cateterización venosa central. Objetivo: comparar el grado de dificultad en la colocación de vías venosas centrales (VVC) con y sin ecografía y la incidencia de complicaciones. Establecer si el grado de entrenamiento del operador o la anatomía del cuello influyen en los resultados. Métodos: se estudiaron 257 pacientes que se dividieron según la experiencia del operador: “experto=E” (más de 70 accesos centrales realizados previos al estudio) y “no entrenamiento=NE”. El grupo “E” realizó 152 accesos venosos y 105 el grupo “NE”. Se incluyeron todos los pacientes que requirieron VVC a partir del inicio del período de estudio en el CCE y sala de operaciones del Hospital Central de las Fuerzas Armadas (HCFFAA). Los procedimientos se randomizaron en “sin ecografía=S/E” (80-“E” y 54-“NE”) y “con ecografía=C/E” (72-“E” y 51-“NE”). Resultados: en el grupo “E” existieron más aciertos en la colocación de las VVC que en el grupo “NE” (88% versus 79%; p 0,04). También existieron más aciertos en el grupo “C/E” que en el grupo “S/E” (91% versus 78%; p=0,005). No hubo diferencia significativa en el acierto relacionado al tipo de cuello (p=0,06). La incidencia global de complicaciones fue de 11,7%. No existe diferencia entre los grupos “C/E” (8,1%) y “S/E” (14,9%); p=0,09. Sin embargo, al discriminar entre el grupo de “E” Y “NE”, el segundo grupo sí presenta ventajas en cuanto a la disminución de las complicaciones con el uso de ecografía: 7,8% C/E versus 24% S/E (p=0,03).

SUMMARY Background: in our country, there are no studies on critical care or anesthesia that analyze the usefulness of ultrasound guidance for central venous catheterization. Objective: to compare the degree of difficulty of central venous line (CVL) placement with or without ultrasound guidance and the incidence of complications and to determine whether the level of training of the operator or the neck anatomy affects the results. Methods: there were studied 257 patients, classified according to the experience of the operator: "experienced=E" (over 70 central accesses carried out before trial) and "non-experienced =NE". Group "E" performed 152 venous accesses and group "NE" 105. All patients who required CVL in the CCE and operation room of the HCFFAA as from the beginning of the trial were included. Procedures were randomized as per "without ultrasound=Wo/U" (80-"E" and 54-"NE") and "with ultrasound=W/U" (72-"E" and 51-"NE"). Results: there were more correct placements of CVLs in group "E" than in group "NE" (88% vs.79%; p 0.04). There were also more correct placements in group "W/U" than in group "Wo/U" (91% vs. 78%; p=0.005). No significant difference existed in correct placement related to the type of neck (p=0.06). General incidence of complications was 11.7%. There is no difference between groups "W/U" (8.1%) and "Wo/U" (14.9%); p=0.09. However, when comparing groups "E" and "NE", the second group presented advantages in terms of reduction of complications using ultrasound guidance: 7.8% W/U vs. 24% Wo/U (p=0.03).

RESUMO Antecedentes: em nosso meio não há estudos em terapia intensiva ou anestesia que analise a utilidade da ecografia para a cateterizacão venosa central. Objetivo: comparar o grau de dificuldade na obtenção de via venosa central (VVC) com ou sem ecografia e a incidência de complicações. Estabelecer se o grau de treinamento do operador ou a anatomia do pescoço influi nos resultados. Métodos: estudou-se 257 pacientes que foram divididos de acordo com a experiência do operador. "expert" =E" (mais de 70 acessos centrais realizados previamente ao estudo) e "em treinamento=NE". O grupo "E" realizou 152 acessos venosos e o grupo "NE" 105. Foram incluídos todos os pacientes que requeriam VVC a partir do inicio do período do estudo no CCE e sala de cirurgia do HCFFAA. Os procedimentos se randomizaram em " sem ecografia=S/E" (80 "E" e 54 "NE") e "com ecografia=C/E" (72 "E" e 51 "NE"). Resultados: no grupo "E" se obteve mais acertos na colocação das VVC que no grupo "NE" (88% VS. 79%; p 0.04). Também se obteve mais acertos no grupo "C/E" que no grupo "S/E" (91% vs. 78%; p=0.005). Não houve diferenças significativas no acerto relacionado ao tipo de pescoço (p=0.06). A incidência global de complicações foi de 11,7%. Não existem diferenças entre os grupos "C/E" (8,1%) e "S/E" (14,9%);p=0.09. Entretanto, ao segregar os grupos "E" e "NE", o segundo grupo apresentou vantagem quanto a diminuição das complicações com o uso de ecografia; 7,8% C/E vs. 24% S/E (p=0.03).

Hierarchical clustering of monoclonal antibody reactivity patterns in nonhuman species.

Monoclonal antibodies (Mab) are an important resource for defining molecular expression and probing molecular function. The characterization of Mab reactivity patterns, however, can be costly and inefficient in nonhuman experimental systems. To develop a computational approach to the pattern analysis of Mab reactivity, we analyzed a panel of 128 Mab recognizing sheep antigens. Quantitative single parameter flow cytometry histograms were obtained from five cell types isolated from normal animals. The resulting 640 histograms were smoothed using a Gaussian kernel over a range of bandwidths. Histogram features were selected by SiZer--an analytic tool that identifies statistically significant features. The extracted histogram features were compared and grouped using hierarchical clustering. The validity of the clustering was indicated by the accurate pairing of externally verified molecular reactivity. We conclude that our computational algorithm is a potentially useful tool for both Mab classification and molecular taxonomy in nonhuman experimental systems.

Feature-guided clustering of multi-dimensional flow cytometry datasets.

BACKGROUND: Flow cytometry produces large multi-dimensional datasets of the physical and molecular characteristics of individual cells. The objective of this study was to simplify the cytometry datasets by arranging or clustering "objects" (cells) into a smaller number of relatively homogeneous groups (clusters) on the basis of interobject similarities and dissimilarities. RESULTS: The algorithm was designed to be driven by histogram features; that is, the relevant single parameter histogram features were used to guide multidimensional k-means clustering without an a priori estimate of cluster number. To test this approach, we simulated cell-derived datasets using protein-coated microspheres (artificial "cells"). The microspheres were constructed to provide 119 populations in 40 samples. The feature-guided (FG) approach accurately identified 100% of the predetermined cluster combinations. In contrast, an approach based on the partition index (PI) cluster validity measure accurately identified 83.2% of the clusters. Direct comparisons of the two methods indicated that the FG method was significantly more accurate than PI in identifying both the number of clusters and the number of objects within the clusters (p<.0001). CONCLUSION: We conclude that parameter feature analysis can be used to effectively guide k-means clustering of flow cytometry datasets.

Structural mapping of immunoglobulin subclasses using multiplexed bead flow cytometry.

Monoclonal hybridomas secrete immunoglobulin molecules with a single specificity and distinct class/subclass structure. The determination of immunoglobulin structure can be used to facilitate hybridoma colony management and predict monoclonality. In this report, we used multiplexed bead flow cytometry to define hybridoma class/subclass. The assay was sufficiently sensitive to detect 50 ng/mL of antibody. The multiplexed bead assay efficiently defined traditional class/subclass determinants as well as more subtle patterns of crossreactivity. Further, the assay was combined with Poisson statistics to provide a numerical estimate of hybridoma monoclonality. The sensitivity and flexibility of this approach suggests the utility of multiplexed bead flow cytometry in the early management of immunoglobulin-secreting hybridomas.

Melittin-induced membrane permeability: a nonosmotic mechanism of cell death.

Derived from honeybees, melittin is a 26-amino acid, alpha-helical, membrane-attack protein that efficiently kills mammalian cells. To investigate the contribution of colloid-osmotic effects to the mechanism of cell death, we studied the effect of melittin on lymphocyte membrane permeability and cell volumes. Melittin concentrations of 0.5 to 2.0 microM induced release of membrane permeability markers without total disruption of the cell membrane. At these melittin concentrations, electrical-impedance cytometry demonstrated melittin-induced changes in red blood cell volumes (P<0.01), but no change in lymphocyte cell volumes (P>0.05). Streaming video microscopy, obtaining images of melittin-treated lymphocytes at 80-ms intervals, demonstrated a loss of optical density (P<0.001) suggesting a flattening of the cell but no significant increase in cell perimeter (P>0.05). Real-time multiparameter flow cytometry of melittin-treated lymphocytes confirmed simultaneous loss of the cytoplasmic marker, calcein, and uptake of the DNA dye, ethidium homodimer, but demonstrated no increase in forward light scatter. Transmission-electron microscopy of melittin-treated lymphocytes showed normal cell volumes but discontinuities in the cell membrane suggesting direct membrane toxicity. We conclude that melittin causes lymphocyte death by a "leaky patch" mechanism that is independent of colloid-osmotic effects.