Effects of total plasma protein concentration on plasma sodium, potassium and chloride measurements by an indirect ion selective electrode measuring system.

OBJECTIVE: Ion selective electrodes (ISE) measure electrolytes by two different technologies, direct and indirect. We wished to investigate the effect of total plasma protein concentration on the plasma sodium, potassium and chloride measurements by indirect ISE compared with measurements by direct ISE. METHODS: The evaluation of the objective was performed in a tertiary care hospital on patient blood samples sent to the pathology laboratory for general chemistry analysis. To determine the degree of difference between the two ISE measurements, 195 lithium heparin plasma samples were measured and the results were separated into three groups (65 samples in each group) depending on the protein concentration (e.g. total plasma protein concentration less than, greater than and within the reference range between 62-83 g/L). The samples were analysed over a 40 day period on a Hitachi Modular ISE system - indirect ISE (Roche Australia) and Bayer Rapidlab 865 Blood Gas Analyser - direct ISE (Bayer Diagnostics, Australia). RESULTS: Using indirect ISE, low plasma protein concentrations caused a 'pseudohyper' effect in all 3 analytes and a 'pseudohypo' effect with high plasma protein concentrations. The variation in total protein concentration had the greatest effect on plasma sodium measurement. The relationship was non-linear and no accurate predictive value could be calculated for the plasma electrolytes with changes in plasma protein concentrations. CONCLUSIONS: The plasma sodium, potassium and chloride measurements are effected by changes in plasma protein concentration when measured by indirect ISE systems. Clinicians must be aware that differences exist between the ISE technologies and in border-line clinical situations, the direct ISE systems provide a more accurate estimate of plasma sodium, potassium, chloride, anion gap, osmolality and strong ion difference calculations, and should be used for clinical decision-making.

Prospective independent validation of APACHE III models in an Australian tertiary adult intensive care unit.

Evaluation of the performance of the APACHE III (Acute Physiology and Chronic Health Evaluation) ICU (intensive care unit) and hospital mortality models at the Princess Alexandra Hospital, Brisbane is reported. Prospective collection of demographic, diagnostic, physiological, laboratory, admission and discharge data of 5681 consecutive eligible admissions (1 January 1995 to 1 January 2000) was conducted at the Princess Alexandra Hospital, a metropolitan Australian tertiary referral medical/surgical adult ICU ROC (receiver operating characteristic) curve areas for the APACHE III ICU mortality and hospital mortality models demonstrated excellent discrimination. Observed ICU mortality (9.1%) was significantly overestimated by the APACHE III model adjusted for hospital characteristics (10.1%), but did not significantly differ from the prediction of the generic APACHE III model (8.6%). In contrast, observed hospital mortality (14.8%) agreed well with the prediction of the APACHE III model adjusted for hospital characteristics (14.6%), but was significantly underestimated by the unadjusted APACHE III model (13.2%). Calibration curves and goodness-of-fit analysis using Hosmer-Lemeshow statistics, demonstrated that calibration was good with the unadjusted APACHE III ICU mortality model, and the APACHE III hospital mortality model adjusted for hospital characteristics. Post hoc analysis revealed a declining annual SMR (standardized mortality rate) during the study period. This trend was present in each of the non-surgical, emergency and elective surgical diagnostic groups, and the change was temporally related to increased specialist staffing levels. This study demonstrates that the APACHE III model performs well on independent assessment in an Australian hospital. Changes observed in annual SMR using such a validated model support an hypothesis of improved survival outcomes 1995-1999.

Errors in the estimation of the distance of fall and angles of impact blood drops.

This paper presents derived equations for the estimation of the variances in the estimated distance of fall and the estimated angle of impact for blood droplets. The derived equation for the variance of the estimated distance of fall predicts that as the blood drop size approaches that of a blood droplet falling at terminal velocity, the variance of the estimate grows without limit. The derived equation for the variance in the estimated angle of impact shows that as the angle of impact approaches 90 degrees, the variance grows without limit. The validity of the equation for the estimated variance of the angle of impact was tested for five angles of impact (15, 30, 45, 60 and 75 degrees); the equation correctly predicted the observed variance up to an angle of 60 degrees.

Laryngoceles and saccular cyst.

Laryngoceles and saccular cysts, while relatively rare, occur more often than the literature would suggest. In the past, most were diagnosed clinically in a symptomatic patient. Today, however, more patients suspected of head and neck cancer are being diagnosed with diagnostic radiographic procedures. Of 2,068 patients studied at M.D. Anderson Hospital and Tumor Institute for suspected laryngeal or hypopharyngeal cancer, 87 (4.2%) had laryngoceles. There are three types of laryngoceles currently recognized: internal, external, and mixed/combined. Saccular cysts are divided into two categories: anterior and lateral. Both may be congenital, or acquired, and may occur at any age. This article reviews current evidence regarding classification, anatomy, clinical symptoms, etiology, pathogenesis, diagnostic techniques, and treatment of these two disorders.

Intentional replantation: report of a successful case.

Irreversible iatrogenic damage sometimes occurs during dental treatment. In certain cases, intentional extraction, repair, and replantation can be used to save the damaged tooth. This case report describes the successful replantation of a premolar that had sustained a large root perforation.

Stress relaxation techniques for the dental practitioner.

The practice of dentistry can be quite stressful, and dentists need to know how to relieve their own stress. Both psychologic and physiologic stress should be alleviated so as not to become disabling. The stress of life and the stress of dental practice should be understood by practitioners. If used properly, simple relaxation techniques that can be performed several times a day will help relieve these life-threatening stresses.

Isolation of Pasteurella pneumotropica from rodents in South Africa.

Four thousand, five hundred and sixteen rodents of 27 species were captured in widely separated localities in South Africa over a period of ten years. Samples of spleen, lung, heart, liver and rectal tissue with faeces were tested for the presence of zoonotic bacteria and 109 isolations of Pasteurella pneumotropica were made from 11 species. Latent infection with the organism was found to be widespread although there were temporal fluctuations in prevalence. Field and laboratory evidence suggest that P. pneumotropica may be associated with, but not the primary cause of, rodent epizootics in the wild.

Migration and species diversity in the tropics.

If the young of a dominant species are subjected to disproportionately heavy predation, this, together with a limitation on food, can promote a high species diversity. This is seen among tropical birds, which are simultaneously exposed to both conditions to a far greater degree than are Temperate Zone species. Migration to the Temperate Zones during the spring provides a release from these restraints, while also precluding breeding in the Tropics.