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Biomedical subjects

G J Kost

Publications and source records attributed to G J Kost.

At least 19 recordsLinked to original sources
PubMed1998

Multicenter study of oxygen-insensitive handheld glucose point-of-care testing in critical care/hospital/ambulatory patients in the United States and Canada.

OBJECTIVES: Existing handheld glucose meters are glucose oxidase (GO)-based. Oxygen side reactions can introduce oxygen dependency, increase potential error, and limit clinical use. Our primary objectives were to: a) introduce a new glucose dehydrogenase (GD)-based electrochemical biosensor for point-of-care testing; b) determine the oxygen-sensitivity of GO- and GD-based electrochemical biosensor test strips; and c) evaluate the clinical performance of the new GD-based glucose meter system in critical care/hospital/ambulatory patients. DESIGN: Multicenter study sites compared glucose levels determined with GD-based biosensors to glucose levels determined in whole blood with a perchloric acid deproteinization hexokinase reference method. One site also studied GO-based biosensors and venous plasma glucose measured with a chemistry analyzer. Biosensor test strips were used with a handheld glucose monitoring system. Bench and clinical oxygen sensitivity, hematocrit effect, and precision were evaluated. SETTING: The study was performed at eight U.S. medical centers and one Canadian medical center. PATIENTS: There were 1,248 patients. RESULTS: The GO-based biosensor was oxygen-sensitive. The new GD-based biosensor was oxygen-insensitive. GD-based biosensor performance was acceptable: 2,104 (96.1%) of 2,189 glucose meter measurements were within +/-15 mg/dL (+/-0.83 mmol/L) for glucose levels of < or = 100 mg/dL (< or = 5.55 mmol/L) or within +/-15% for glucose levels of > 100 mg/dL, compared with the whole-blood reference method results. With the GD-based biosensor, the percentages of glucose measurements that were not within the error tolerance were comparable for different specimen types and clinical groups. Bracket predictive values were acceptable for glucose levels used in therapeutic management. CONCLUSIONS: The performance of GD-based, oxygen-insensitive, handheld glucose testing was technically suitable for arterial specimens in critical care patients, cord blood and heelstick specimens in neonates, and capillary and venous specimens in other patients. Multicenter findings benchmark the performance of bedside glucose testing devices. With the new +/-15 mg/dL --> 100 mg/dL --> +/-15% accuracy criterion, point-of-care systems for handheld glucose testing should score 95% (or better), as compared with the recommended reference method. Physiologic changes, preanalytical factors, confounding variables, and treatment goals must be taken into consideration when interpreting glucose results, especially in critically ill patients, for whom arterial blood glucose measurements will reflect systemic glucose levels.

Adult↗
PubMed1995

Guidelines for point-of-care testing. Improving patient outcomes.

Whole-blood biosensors and point-of-care testing created a unique paradigm in medical diagnostics in the 1980s, when liver and heart transplant centers, as well as operating rooms and other critical care areas implemented whole-blood analysis to provide rapid test results in 2 to 5 minutes. Rising expectations, patient-focused hospitals, and managed care intensify the need for immediate decisions at the point of care. The guidelines promote consensus priorities, multidisciplinary teamwork, fiscal coordination, and collaborative practice during this phase of rapid change. Four primary principles and accompanying guideline objectives are optimization (patient outcomes, medical linkages, integrated diagnostic synthesis, therapeutic turnaround time, test clusters, and critical limits), hybridization (strategic modalities, economic effectiveness, and testing --> monitoring), quality (quality improvement, clinical performance, risk reduction and academics and accreditation), and consistency (results communication and error minimization, and reference intervals and standardization). Whole-blood analysis and point-of-care testing help facilitate temporal optimization, optimize diagnostic-therapeutic processes, and improve patient outcomes in critical care.

Blood Chemical Analysis↗
PubMed1995

The current and future status of critical care testing and patient monitoring.

Ex vivo and in vivo biosensor-based systems for patient monitoring now augment in vitro point-of-care testing, a paradigm currently in the explosive phase. As new technologies arise, so do opportunities for laboratory professionals. First, the laboratory consultant or clinical pathologist can contribute substantially to our understanding of temporal optimization and the role of diagnostic testing in optimizing diagnostic-therapeutic processes. Clarification of these facilitates wise selection of alternative testing modalities, test clusters, and instrument formats. Second, the laboratory professional is a natural member of a performance team that can help optimize outcomes and assure the quality of point-of-care testing. Explicit site-specific performance criteria for accuracy, precision, response time, and test clusters are essential and can only be established and accomplished jointly with clinicians. Third, clinical integration requires practice guidelines and care paths. These can help determine how, when, and where point-of-care testing should be implemented. Finally, global outcomes optimization calls for the input of those professionals who are most familiar with the economics of diagnostic testing, the challenges of point-of-care testing, and the best clinical benefits of in vitro, ex vivo, and in vivo biosensor-based systems in critical care and other settings.

Biosensing Techniques↗
PubMed1994

Are age-related differences in response to myocardial ischemia and cardioplegia pH dependent?

Phosphorus-31 nuclear magnetic resonance and left ventricular pressure development (dP/dt) were used to test the hypothesis that age-related differences in myocardial functional recovery after ischemia and cold crystalloid cardioplegia (CCC) are the result of an inverse relationship between recovery and the decrease in intracellular pH (pHi) during ischemia. Neonatal (3-8 days) and adult rabbit hearts were Langendorff perfused using two protocols: (1) control--30 min perfusion, 30 min global ischemia, 2 h reperfusion; (2) CCC--the same except ischemia was initiated after a 4-min infusion of cold hyperkalemic solution. Analysis of variance and the Tukey test showed the following significant differences between the protocols (p < 0.05). CCC decreased inorganic phosphate (Pi) during ischemia in both age groups, but more in adult hearts, and decreased Pi during reperfusion in adult hearts. CCC increased pHi during ischemia and ATP during ischemia and reperfusion in both age groups but more in adult hearts. CCC increased dP/dt during reperfusion only in adult hearts. The results are consistent with the hypothesis.

Adenosine Triphosphate↗
PubMed1994

Multisite point-of-care potassium testing for patient-focused care.

In the past two decades, a dominant paradigm has been the main laboratory, which is often located far from the patient and characterized by slow response times. The invention of whole blood biosensors and the innovation of point-of-care testing have initiated a paradigm shift in diagnostic medicine that supports the trend toward patient-focused care. The objective of this study was to compare point-of-care potassium testing performed with a handheld potassium analyzer (STAT K, PDx Technologies Inc, Westlake Village, Calif) in the cardiac and intensive care units with potassium measurements obtained similarly in the main laboratory. Two critical care nurses performed point-of-care testing for critically ill patients. In a series of 56 specimens, the mean +/- SD potassium levels were 3.91 +/- 0.53 and 3.94 +/- 0.57 mmol/L when testing was performed at the bedside and in the main laboratory, respectively. The mean paired difference, -0.03 mmol/L, between point-of-care and main laboratory results was not statistically or clinically significant. Point-of-care potassium testing is accurate and precise, as well as clinically efficient for use in patient-focused care settings.

Delivery of Health Care↗
PubMed1993

New whole blood analyzers and their impact on cardiac and critical care.

Miniaturized whole blood biosensors, patient-focused hospitals, and rising expectations of patients and physicians are shifting laboratory diagnostics to the point of care. Expanding transplantation and intensive care are increasing the need for rapid test results. Whole blood analysis improves accuracy, eliminates centrifugation, reduces response time, and conserves blood volume. Several hand-held, and over 20 portable or transportable whole blood instruments are now available. Criteria for instrument evaluation include test menus, point-of-care features, analysis time, on-site performance, and information integration. Whole blood analyzers measure several vital indicators (pO2, pCO2, pH, hematocrit, K+, Ca2+, Na+, Cl-, glucose, and lactate) simultaneously in less than 2 min with less than 200 microliters of whole blood. Other in vitro tests are available (Mg2+, osmolality, CO2 content, urea nitrogen, beta-hydroxybutyrate, hemoglobin, coagulation) or under development (HCO3- phosphorus). Some can be monitored in vivo (O2 saturation, pO2, pCO2, pH, glucose) or ex vivo. The clinical impact is demonstrated by ionized calcium, now established in importance for cardiac and neurologic problems, and ionized magnesium, a promising new measurement. The hybrid laboratory (a composite of conventional clinical laboratory and patient-focused testing), performance maps, and quality paths facilitate implementation of new whole blood analyzers for optimal support of cardiac and critical care, and improved patient outcomes (prospects).

Biosensing Techniques↗
PubMed1993

The significance of ionized calcium in cardiac and critical care. Availability and critical limits at US medical centers and children's hospitals.

The clinical use of ionized calcium has increased since the recognition of its importance in cardiac and critical care medicine. However, more than half the general medical centers in the United States do not provide immediate testing of ionized calcium levels in patients in critical care settings, although indications for this test indicate that they should. The following objectives were used in this study: (1) to determine the availability of ionized calcium testing; (2) to document appropriate critical limits; and (3) to describe the significance of ionized hypocalcemia in cardiac and critical care. The participants were 100 medical centers and 40 children's hospitals in the United States. At medical centers, mean (+/- SD) critical limits were as follows: low, 0.82 +/- 0.14 mmol/L (3.29 +/- 0.56 mg/dL); and high, 1.55 +/- 0.19 mmol/L (6.21 +/- 0.76 mg/dL). At children's hospitals, mean critical limits were as follows: low, 0.85 +/- 0.13 mmol/L (3.41 +/- 0.52 mg/dL); and high, 1.53 +/- 0.11 mmol/L (6.13 +/- 0.44 mg/dL). In the past decade, the availability of ionized calcium testing increased dramatically. Now, 57%, 86%, 95%, and 100% of general hospitals, heart transplant centers, children's hospitals, and pediatric heart transplant centers, respectively, perform testing in house. Collective experience indicates that: (1) aggressive monitoring of ionized calcium prevents cardiac (and neurologic) catastrophes, (2) appropriate levels optimize cardiac function, and (3) calcium repletion is safest when based on acute trends measured directly in whole blood. Hospitals should provide rapid response testing needed during transplantation and massive transfusion and for the diagnosis and treatment of acute ionized hypocalcemia.

Calcium↗
PubMed1992

Age-related response of rabbit heart to normothermic ischemia: a 31P-MRS study.

The age-related response of the myocardium to 30 min of 37 degrees C global ischemia and 120 min of 37 degrees C reperfusion, measured by phosphorus-31 magnetic resonance spectroscopy and the recovery of isovolumic function, was evaluated by using perfused neonatal (3-8 days old, n = 10), immature (24-30 days old, n = 10), and adult (2-4 mo old, n = 5) rabbit hearts. Basal intracellular pH (pHi) was highest in neonatal hearts and decreased with age. The basal phosphocreatine (PCr)-to-ATP ratio differed in each group, increasing with age. Rapid depletion of PCr occurred in all groups during ischemia; ATP retention was greater in adults than in neonates. Reperfusion resulted in no measurable recovery of ATP in any group. Postischemic pHi stabilized above preischemic values in neonatal and immature hearts and below preischemic values in adult hearts. Recovery of PCr and cytosolic Pi (Pcyi) content, heart rate, and coronary flow during reperfusion was greater in neonatal and immature than in adult hearts. During the final 20 min of ischemia, pHi was lower in immature than in neonatal or adult hearts. Postischemic recovery of left ventricular maximum rate of pressure rise (+dP/dtmax) was depressed in immature compared with neonatal and adult hearts. These results demonstrate increased tolerance of the neonatal heart and increased susceptibility of the immature heart to unprotected normothermic ischemic injury relative to the adult heart and suggest that maturational changes in myocardial pHi regulation may be responsible for the observed age-related response.

Adenosine Triphosphate↗
PubMed1992

Creatine kinase and its MB isoenzyme in the third trimester and the peripartum period.

Forty-nine normal pregnant women were recruited late in the third trimester for serial determinations of creatine kinase (CK) and its MB isoenzyme fraction (CK-MB) at four different times: (1) on recruitment between 36 and 40 weeks' gestation, (2) on admission in active labor, (3) immediately after delivery, and (4) on the first postpartum day. In the patients with vaginal delivery (n = 43) total CK was significantly elevated at time 4 compared with times 1, 2 and 3 (P value < .0001). CK-MB fraction was also significantly elevated at time 4 compared with times 1, 2 and 3 (P value < .0001). In 35.7% of the patients at time 4, CK-MB was sufficiently elevated to give the laboratory interpretation of "borderline" or "consistent with a myocardial infarction," even though none of the patients had cardiac symptoms or complications. A review of the literature shows that CK-MB is found not only in myocardium but also in uterus and placenta. The implication of this study is that elevations in total CK and CK-MB should be used with caution during the peripartum period to diagnose myocardial ischemia or infarction.

Adult↗
PubMed1991

Critical limits for emergency clinician notification at United States children's hospitals.

Critical results demand rapid patient evaluation, possibly followed by life-saving intervention. A national survey of children's hospitals determined the critical limits used for emergency notification of critical laboratory results. Mean low and high critical limits for children for the tests listed most frequently were as follows (millimoles per liter): glucose, 2.6 and 24.7; potassium, 2.8 and 6.4; calcium, 1.62 and 3.17; and sodium 121 and 156. For newborns, significantly different (P less than .01) critical limits were glucose, 1.8 and 18.2; and potassium, 7.8. Hematology mean critical limits for children included hemoglobin, 69 and 208 g/L; platelets, 53 and 916 x 10(9)/L; hematocrit, 0.20 and 0.62 L/L; and white blood cell counts, 2.1 and 42.9 x 10(9)/L. Critical limits for pH were 7.21 and 7.59; for PCO2, 21 and 66 mm Hg; and for PO2, 45 and 124 mm Hg. Important qualitative critical results included blasts on the blood smear and abnormal cerebrospinal fluid findings. In comparison with other medical centers, children's hospitals maintained tighter critical limits for surveillance of renal function, hemostasis dysfunction, and newborn hypokalemia. Use of these results to eliminate outliers can help reduce unnecessary statim notification and improve resource utilization for the acute diagnosis and treatment of critically ill newborns and children.

Chemistry, Clinical↗
PubMed1990

Critical limits for urgent clinician notification at US medical centers.

A national survey determined critical limits used by trauma and medical centers in the United States. Mean low and high critical limits for the most frequently listed tests were the following values: glucose, 2.6 and 26.9 mmol/L; potassium, 2.8 and 6.2 mmol/L; calcium, 1.65 and 3.22 mmol/L; sodium, 120 and 158 mmol/L; hematocrit, 0.18 and 0.61; hemoglobin, 66 and 199 g/L; platelets, 37 x 10(9)/L and 910 X 10(9)/L; and white blood cell count, 2.0 X 10(9)/L and 37.0 X 10(9)/L. The high critical limit for prothrombin time was 27 seconds. Critical limits for PCO2 were 19 and 67 mm Hg; and for pH, 7.21 and 7.59. The low critical limit for PO2 was 43 mm Hg; no high critical limit was listed. The noncritical span for free calcium was 0.80 mmol/L. Important qualitative critical results included the presence of blasts on the blood smear, a Gram's stain or culture from blood or cerebrospinal fluid with positive results, and an elevated white blood cell count in the cerebrospinal fluid. A product of 15 years of collective medical judgment, these data should help physicians improve the quality and efficiency of acute patient care.

Blood Gas Analysis↗
PubMed1990

pH standardization for phosphorus-31 magnetic resonance heart spectroscopy at different temperatures.

Intracellular pH typically is measured by NMR using the calibrated chemical shift of the inorganic phosphate peak in phosphorus-31 spectra. Heart spectroscopy experiments often require measurements of intracellular pH at temperatures from 5 to 37 degrees C. This paper provides NMR pH calibrations for this range of temperatures, a summary of calibration data reported to date, and a discussion of the factors influencing pH standardization.

Hydrogen-Ion Concentration↗
PubMed1990

New whole-blood testing for laboratory support of critical care at cardiac transplant centers and US hospitals.

Whole-blood analytical techniques include ion-specific, substrate-specific, amperometric, and impedance electrodes. These allow direct measurement of critical analytes simultaneously in whole blood without centrifugation, resulting in a response time of 2 to 5 minutes. Cardiac transplantation centers rely heavily on whole-blood instruments to provide rapid response tests essential for cardiovascular management. A survey of 81 blood gas laboratories in 25 cardiac transplantation centers and 73 blood gas laboratories in 36 general hospitals showed an increase in testing for potassium, free calcium, and glucose by blood gas laboratories since 1982 and extensive use of satellite laboratories near areas serving critically ill patients. The following three recent developments are improving the availability of laboratory results: (1) direct whole-blood measurement is gaining acceptance, (2) instrumentation designed specifically for rapid critical care profiling is being used extensively, and (3) testing is moving closer to patients. These trends suggest a significant change in laboratory support of critical care in the United States.

Blood Chemical Analysis↗