RESUMEN
OBJECTIVE: To demonstrate the practicability of a tri-axial chart for the graphical and quantitative monitoring of arterial pH, arterial carbon dioxide partial pressure (PaCO2) and actual arterial bicarbonate-ion concentration (a[HCO3-]) in intensive care patients. DESIGN: Case report. SETTING: A general intensive care unit (ICU). METHODS: Using a standard mathematical transformation, a data set of pH, log PaCO2 and log a[HCO3-] values can be transformed in such a way that a graphical display of all three variables is possible while being faithful to their linear relationship. Remarkably, the graphical display closely resembles the tri-axial chart that Hastings and Steinhaus described in 1931 for studying displacements of the acid-base balance. Two new monitoring parameters based on the chart and the transformation are described. One monitors the abnormality of the acid-base status while the other monitors the rate of acid-base changes. CONCLUSIONS: With the tri-axial acid-base chart, the complete acid-base status can be faithfully monitored. Moreover, the proposed monitoring parameters provide extra information about the arterial acid-base status that, otherwise, would remain hidden.
Asunto(s)
Desequilibrio Ácido-Base/sangre , Cuidados Críticos , Registros Médicos , Arterias , Bicarbonatos/sangre , Dióxido de Carbono/sangre , Femenino , Humanos , Concentración de Iones de Hidrógeno , Cómputos Matemáticos , Persona de Mediana EdadRESUMEN
From a statistical point of view the simultaneous interpretation of multiple variables should be performed with a multivariate reference model rather than with multiple univariate reference intervals. A computer program for constructing and testing multivariate reference models is described. The use of the computer program is illustrated with a data set of total serum calcium concentrations and serum albumin concentrations from 222 2nd year medical students. Using a single univariate reference interval for total serum calcium, 17 students were classified as having an abnormal calcemic status while using a bivariate reference model for total serum calcium and serum albumin, 13 of these 17 students had in fact normal total serum calcium concentrations, taking into account their serum albumin concentrations.
Asunto(s)
Modelos Estadísticos , Análisis Multivariante , Programas Informáticos , Biometría , Calcio/sangre , Humanos , Modelos Biológicos , Valores de Referencia , Albúmina Sérica/metabolismoRESUMEN
OBJECTIVES: To determine and compare the shape and location of three data sets of arterial pH, PCO2, and BE values from intensive care patients in a new acid-base chart for the purpose of deriving multivariate reference regions. DESIGN AND METHODS: The new chart is constructed by applying a statistical technique called principal component analysis (PCA). Three different data sets, each comprised of 1500 arterial pH, PCO2, and BE values, were subjected to PCA. The 3 data sets were collected in a respiratory intensive care unit (ICU) of a University Hospital, in a general ICU of a District Hospital, and in a neonatal ICU of a Children's Hospital. RESULTS: The outlines of the resulting charts are similar for all 3 data sets, but the representations of the three distributions in the new chart are highly dissimilar, both in shape and in location. CONCLUSIONS: PCA can be used to derive a patient-based reference region for arterial pH, PCO2, and BE values. Furthermore, the new chart may be useful for the graphical monitoring of acid-base data because distances between consecutive observations are faithfully represented.
Asunto(s)
Desequilibrio Ácido-Base/sangre , Arterias/fisiología , Dióxido de Carbono/sangre , Modelos Estadísticos , Análisis de Varianza , Humanos , Concentración de Iones de Hidrógeno , Lactante , Recién Nacido , Unidades de Cuidados Intensivos , Análisis Multivariante , Valores de ReferenciaRESUMEN
Monitoring the arterial acid-base status of ICU patients is done by measuring and calculating the acid-base variables pH, the partial pressure of carbon-dioxide (PCO2) and the bicarbonate-ion concentration ([HCO-3]). Univariate normal reference ranges exist for these values. However, it is well known that an exact linear relationship exists between pH, the logarithm of PCO2 and the logarithm of [HCO-3] values. We developed a computer program for the multivariate evaluation and graphical monitoring of these values in an intensive care setting that takes this intrinsic two-dimensionality into account. A composite index is introduced for the monitoring of all three laboratory values. Moreover, using this index, a multivariate statistical reference region based on an unselected population of ICU patients was derived.
Asunto(s)
Equilibrio Ácido-Base , Monitoreo Fisiológico/métodos , Programas Informáticos , Dióxido de Carbono/análisis , Gráficos por Computador , Humanos , Concentración de Iones de Hidrógeno , Unidades de Cuidados Intensivos , Modelos Biológicos , Análisis MultivarianteRESUMEN
The acid-base status of intensive care patients is monitored on the basis of three quantities. The graphical representation which may be of help for the monitoring task is therefore cumbersome. The classical Siggaard-Andersen acid-base chart is such a representation, but it is only suited for evaluating one acid-base status at a time and not for representing acid-base paths. A new representation, obtained after a principal components transformation is presented. It is shown that the representation is characteristic for the laboratory instrument used. Its most attractive feature is that it is distortionless with respect to the three-dimensional configuration.
Asunto(s)
Desequilibrio Ácido-Base/sangre , Gráficos por Computador , Cuidados Críticos , Modelos Biológicos , Monitoreo Fisiológico , Acidosis/sangre , Algoritmos , Alcalosis/sangre , Bicarbonatos/sangre , Dióxido de Carbono/sangre , Humanos , Concentración de Iones de Hidrógeno , Sistemas en Línea , Estándares de Referencia , Valores de Referencia , Programas InformáticosRESUMEN
Restriction fragment length polymorphism haplotyping of mutated and normal phenylalanine hydroxylase (PAH) alleles in 49 Dutch phenylketonuria (PKU) families was performed. All mutant PAH chromosomes identified by haplotyping (n = 98) were screened for eight of the most predominant mutations. Compound heterozygosity was proven in 40 kindreds. Homozygosity was found for the IVS/2nt1 mutation in 5 families, and for the R158Q and IVS10nt546 mutations in one family each. All patients from these families suffer from severe PKU, providing additional proof that these mutations are deleterious for the PAH gene. Genotypical heterogeneity was evident for mutant haplotype 1 (n = 27) carrying the mutations R261Q (n = 12), E280K (n = 4, P281L (n = 1) and unknown (n = 10), and likewise for mutant haplotype 4 (n = 30) carrying the mutations R158Q (n = 13), Y414C (n = 1) and unknown (n = 16). Mutant haplotype 3 (n = 20), in tight association with mutation IVS12nt1, appeared to be in strong linkage disequilibrium (LDE) with its normal counterpart allele (n = 4). Mutant haplotype 6 (n = 4), in tight association with the IVS10nt546 mutation, showed moderate LDE with its counterpart allele (n = 1). The distribution of the mutant PAH haplotypes 1, 3 and 4 among the Dutch PKU population resembles that in other Northern and Western European countries, but it is striking that mutant haplotype 2 and its associated mutation R408W is nearly absent in The Netherlands, in strong contrast to its neighbouring countries.
Asunto(s)
Análisis Mutacional de ADN , Haplotipos , Fenilalanina Hidroxilasa/genética , Fenilcetonurias/genética , Polimorfismo de Longitud del Fragmento de Restricción , Secuencia de Bases , Heterocigoto , Homocigoto , Humanos , Datos de Secuencia Molecular , Países Bajos , Fenilcetonurias/enzimología , Fenilcetonurias/etnologíaRESUMEN
Phenylketonuria (PKU), due to a defect in phenylalanine hydroxylase (PAH), is presented as a model system for computer-aided DNA diagnosis of genetic diseases. Eight different restriction fragment length polymorphism (RFLP) markers have been localized within the introns of the 90 kb PAH gene (located on chromosome 12). These RFLPs can be combined in 384 different ways and each combination has been defined as a particular haplotype. A special computer program has been developed to calculate the possible haplotype combinations in a PKU core family (index patient and parents), with the goal to derive unambiguously both the PAH and PKU alleles. Taking into account that participation of other members of the family (grandparents or brothers/sisters) is sometimes necessary, haplotyping by itself is sufficient to establish (or exclude) the PKU status of an individual in approximately eight out of ten PKU families.