Clinica chimica acta; international journal of clinical chemistry
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Anion gap (AG) is a calculated value commonly used in clinical practice. It approximates the difference between the concentration of unmeasured anions (UA) and unmeasured cations (UC) in serum. At present, the reference range of anion gap has been lowered from 8-16 to 3-11 mmol/l because of the changes in technique for measuring electrolyte. ⋯ If one finds high incidence of increased anion gap (>24 mmol/l) or decreased anion gap (<2 mmol/l), one should check the quality control of electrolyte and whether the patients were hypoalbuminemia or hyperglobulinemia. An anion gap exceeding 24 mmol/l will suggest the presence of metabolic acidosis. It is very rare to find anion gap with the negative sign.
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Comparative Study
Analytical performance of a portable critical care blood gas analyzer.
The portable blood gas analyzer OPTI Critical Care Analyzer was evaluated in comparison to routine laboratory assays using heparinized blood samples of adults and newborns. Within-run imprecision studies were performed with native blood using tonometry to adjust blood gas concentrations. ⋯ The coefficients of variation for the within-run imprecision were below 1.1% for sodium and hemoglobin, and below 2.6% for all other parameters, except for pCO(2) with coefficients of variation up to 3.6% at low calibration gas concentrations. Due to this analytical performance and its portability, the OPTI system is well suited for low to medium test frequencies and immediate use in emergency rooms, intensive care or surgery units.
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Point-of-care testing (POCT) has economic and medical benefits in the areas of immediate medical management, resource utilization and time management. Starting with bedside glucose, the Mount Sinai Medical Center has, over the past 11 years, implemented 23 POC tests, spanning complexity from blood gas/electrolyte testing to occult blood, in compliance with all regulatory and accreditation requirements. QC data are reviewed on a daily and weekly basis and all patient results are in the electronic medical record. ⋯ In 1999, over 1300 individuals performed over 440,000 POC tests within the institution. A formalized continuous quality improvement (CQI) program for the POCT program was developed in the fall of 1999. All testing sites are reviewed on a monthly basis for various quality indicators that cover QC performance, maintenance performance, proficiency testing, patient identification, and alert value confirmations.
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In response to clinical demand some point-of-care analysers now provide blood lactate measurements, but recently concern has been expressed about the value and interpretation of these measurements. We undertook this study to evaluate blood lactate measurements in patients with acute renal failure undergoing haemofiltration (HF) with lactate replacement fluid. At baseline, 27 patients had base deficits of >5 mmol/l and 14 (52%) had blood lactates of >3.5 mmol/l. ⋯ Of the remaining 12 patients with improved base deficit (+2 to +20), 10 (83%) survived. Lactate tolerance was compromised in patients with co-incidental liver disease, those on inotropic support, and in patients with initial blood lactate measurements of >10 mmol/l and large base deficits. The data suggest that blood lactate and simultaneous acid-base response measurements during HF help to assign correct buffer replacement and should be performed on all patients.
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Neonates represent a group with unusual sample characteristics and tend to have high hematocrits (Hct). The critically ill patient is also far from ideal with respect to sample type, being prone to either hemodilution or hemoconcentration. Prior to the selection of a point-of-care testing (POCT) analyser for blood gases and electrolytes, we therefore undertook a careful evaluation of some of the performance characteristics of selected instruments. ⋯ It also showed an important bias for pO(2) at levels that are clinically significant. The possibility of operator-related effects on test results has to be eliminated. In terms of ease of use and client satisfaction, the system was well received.