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Biomedical subjects

M F Burritt

Publications and source records attributed to M F Burritt.

At least 37 records · Page 2Linked to original sources
PubMed1992

Abnormalities in circadian patterns of bone resorption and renal calcium conservation in type I osteoporosis.

We compared changes over 24 h in 15 postmenopausal normal women (mean [+/- SD] age, 64 +/- 7 yr) with those in 15 postmenopausal women with type I osteoporosis and vertebral fractures (mean age, 64 +/- 5 yr). The serum osteocalcin concentration, a sensitive index of bone formation, increased by about 5% at night in both groups. Urinary deoxypyridinoline excretion, a sensitive index of bone resorption, increased by 48% at night (P less than 0.01) in the normal women, whereas in the osteoporotic women it was 62% higher overall (P less than 0.05), and the increase persisted into the morning. At night, urinary fractional excretion of calcium decreased by 20% (P less than 0.001) in the normal women, but was unchanged in the osteoporotic women; this circadian pattern differed between groups (P less than 0.05). The serum ionized calcium concentration did not change at night in either group. There was a trend (P = 0.07) for blunting of the nocturnal increase in the serum intact PTH level in osteoporotic women. Thus, the nocturnal serum ionized calcium level is maintained by decreased urinary calcium excretion and increased bone resorption in postmenopausal normal women, but almost entirely by increased resorption in postmenopausal osteoporotic women. This greater dependence on bone resorption during the nocturnal fast may account in part for the greater bone loss in osteoporotic women.

Amino Acids↗
PubMed1992

Skeletal responsiveness to endogenous parathyroid hormone in postmenopausal osteoporosis.

To test the hypothesis that increased sensitivity of bone to PTH may be a major cause of bone loss in postmenopausal osteoporosis, we induced acute calcium deprivation and measured bone responsiveness to endogenous PTH under physiological conditions. Eighteen osteoporotic and 17 normal postmenopausal women with similar dietary calcium intakes were studied before and after 4 days of calcium deprivation (dietary calcium 230 mg/day and treatment with a calcium-binding agent). Despite decreased serum PTH values, the baseline indices of bone turnover (serum osteocalcin level and 24-h urinary excretions of total deoxypyridinoline/creatinine and pyridinoline/creatinine corrected for total body bone mineral content), were higher in the osteoporotic women. During calcium deprivation, the changes in bone markers from baseline were similar in both groups, except for serum osteocalcin and serum type I procollagen carboxy-terminal propeptide. Changes in the normal and the osteoporotic women were, respectively: serum ionized calcium concentration decreased 3.3% and 2.1%; serum intact PTH increased 65% and 56%; plasma 1,25-dihydroxyvitamin D3 increased 29% and 39%; pyridinoline/creatinine increased 12% and 11%; and deoxypyridinoline/creatinine increased 27% and 12%. Serum osteocalcin increased 2.3% and serum procollagen carboxy-terminal propeptide decreased 9.4% in the normal women but did not change in the osteoporotic women. We conclude that women with postmenopausal osteoporosis do not have increased skeletal responsiveness to PTH compared with age-comparable normal postmenopausal women. Therefore, the higher bone turnover in postmenopausal osteoporosis, despite lower serum intact PTH concentration, must be due to other factors. Assessment of acute changes in bone turnover during physiological alterations in endogenous PTH secretion is a useful test in metabolic bone diseases.

Bone Density↗
PubMed1991

Portable blood glucose meters. Teaching patients how to correctly monitor diabetes.

Self-monitoring of blood glucose is an important component of treatment in patients with diabetes. Recent improvements in glucose meters have made patient self-testing more reliable and less dependent on user technique. However, success of the process depends on the training, reassessment, and support of the patient by the healthcare team.

Blood Glucose Self-Monitoring↗
PubMed1991

Circadian variation in ionized calcium and intact parathyroid hormone: evidence for sex differences in calcium homeostasis.

The rate of bone loss with age and the incidence of osteoporosis are greater in women than men, which led us to question whether subtle sex differences may occur in the circadian variation of serum ionized calcium (iCa) and PTH. We measured iCa hourly and intact PTH every 2 h for 26 h in 25 women (21-69 yr) and 24 men (20-67 yr) consuming self-selected diets. Urine was collected at 0800-1600, 1600-2400, and 2400-0800 h. Serum iCa levels followed a circadian rhythm in both sexes (P less than or equal to 0.01), and the patterns differed between sexes, notably during early morning, when serum iCa levels were lower in women (P = 0.02). Urinary calcium excretion and fractional excretion of calcium declined in both sexes at night (2400-0800 h), but the decline in men was significantly greater (P = 0.02). Similarly, the percent reduction in urinary calcium excretion at night was greater in men than in women (34% vs. 17%; P less than or equal to 0.05). In women, 26-h mean serum iCa values correlated significantly with total daily calcium intake (r = 0.44; P = 0.03). Serum intact PTH levels showed a significant circadian pattern in both sexes (P less than or equal to 0.001). The patterns of serum intact PTH differed between the sexes (P = 0.05), with an earlier and greater increase at night in men. This blunted nocturnal rise in PTH in women may explain the poor nocturnal adaptation to fasting found in women who, despite lower calcium intake, did not reduce urinary calcium loss at night as effectively as men.

Adult↗
PubMed1990

Pediatric reference intervals for 19 biologic variables in healthy children.

We defined age- and sex-specific reference intervals for 19 biologic variables in serum samples from healthy children, 1 to 22 years of age, using common laboratory equipment. Upper and lower reference intervals were defined as the estimated 2.5 and 97.5 percentiles of the distribution. For variables (y) that varied with age, the relationship of y to age was modeled with polynomial regression. Parametric percentile estimates specific to each age were then calculated as the predicted y value +/- 1.96 . SD, in which SD = the standard deviation of the residuals. For variables not associated with age, the nonparametric 2.5 and 97.5 sample percentiles were used to define the reference intervals. No significant age or sex differences were found for serum sodium, total protein, glucose, direct bilirubin, or albumin. Potassium, chloride, and urea showed constant values in children that were higher than adult values in the case of potassium and chloride and lower than adult values in the case of urea. No sex-related differences were seen for these analytes. Creatinine, uric acid, and bicarbonate showed an upward trend in values with increasing age, whereas aspartate aminotransferase, phosphorus, and total and ionized calcium showed a downward trend with increasing age. Sex-related differences were noted for these analytes. The immunoglobulins (IgG, IgA, and IgM) showed an upward trend with increasing age, with no sex-related differences except for IgM in children.

Adolescent↗
PubMed1990

Current analytical approaches to measuring blood analytes.

In recent years, laboratory testing in the critical-care setting has increased, a trend due, in part, to the evolution of electrochemical sensors. Various innovations have extended sensor lifetimes, reduced sensor maintenance, and led to the development of single-use and unit-use disposable sensors. These sensor technologies allow the accurate and precise determination, either at or near the bedside, of several analytes including pO2, pCO2, pH, Na, K, Cl, ionized calcium, hematocrit, total hemoglobin, and glucose. Use of these new systems, however, has raised new issues regarding sensor calibration and sample handling and collection. The number of direct-reading analyzers for electrolyte determinations has also increased dramatically. Issues regarding calibration of ion-selective electrodes (ISEs) for Na/K have also been raised after demonstrations of between-instrument variation. Recently, collaborative efforts between eight ISE instrument manufacturers and the National Institute of Standards and Technology resulted in the development of a Standard Reference Material, SRM 956, for the purpose of standardizing direct-reading Na/K ISEs to the flame photometer. Other widely used technologies that provide noninvasive, continuous monitoring include pulse oximetry and transcutaneous gas electrodes. These trends are expected to continue and to produce a new generation of electrochemical and optical sensors.

Autoanalysis↗
PubMed1989

Anesthesia approach to hepatic transplantation.

Anesthesia support for patients undergoing orthotopic liver transplantation can be complicated because of multiple medical problems in such patients and rapid hemodynamic, metabolic, and coagulation changes intraoperatively. Preoperative assessment should include careful review of the cardiovascular, respiratory, and hematologic systems. Use of isoflurane as the main anesthetic agent will minimize toxicity to the liver. During liver transplantation, hemodynamic monitoring and immediate laboratory studies should be available. In our experience during the first 100 liver transplantations performed at our institution, use of a rapid infusion pump and venovenous bypass has helped normalize hemodynamic and renal function.

Anesthesia, General↗
PubMed1989

Hemodynamic and metabolic changes in hepatic transplantation.

In this study, we retrospectively analyzed the intraoperative hemodynamic, laboratory, and coagulation data on the first 83 patients who underwent an initial liver transplantation procedure at our institution. The major hemodynamic changes at the time of reperfusion of the donor liver were significant decreases in arterial blood pressure, systemic vascular resistance, and pulmonary artery temperature and significant increases in cardiac output and pulmonary capillary wedge pressure. The alterations in laboratory values reflected intraoperative therapeutic manipulations. Citrate toxicity is a concern, and the amount of calcium chloride administered reflected the volume of blood transfused. On reperfusion, the fibrinogen concentration decreased and both the prothrombin time and the activated partial thromboplastin time increased. This coagulopathy was also evident in the thromboelastographic values. Aggressive monitoring and prompt intervention are necessary to maintain hemodynamic and metabolic homeostasis in these patients.

Blood Chemical Analysis↗
PubMed1987

Macroenzyme as a cause of unexplained elevation of aspartate aminotransferase.

Aspartate aminotransferase (AST) can exist as a macroenzyme by forming a complex with an immunoglobulin. This immunoglobulin-complexed macromolecule can cause an elevation in serum AST activity, which may be detected on routine blood chemistry analysis and erroneously considered to indicate the presence of liver disease. Clinicians should be aware of this phenomenon so patients are not subjected to unnecessary procedures. In patients with unexplained AST elevation, liver and muscle disease can be biochemically excluded by the finding of normal serum levels of alanine aminotransferase and creatine kinase. The presence of macro-AST can be determined by exclusion chromatography, electrophoresis, and activation assays with pyridoxal 5-phosphate. The elevated AST values can persist for many years.

Aged↗
PubMed1987

Ionized calcium monitoring during liver transplantation.

Ionized calcium concentration was measured in five patients undergoing liver transplantation. Varying degrees of decreased ionized calcium were observed in all cases and can be attributed to the chelation of calcium by the citrate added during blood transfusions, the inability of the patient to metabolize citrate by the liver during the anahepatic phase of the transplant, and hemodilution of the blood volume with the perfusion prime during venovenous bypass. Calcium chloride was administered when necessary as guided by ionized calcium measurements to restore concentrations to levels that maintain adequate cardiac output. Because of the serious hemodynamic consequences of severe hypocalcemia, regular monitoring of ionized calcium concentration is necessary during this procedure. Total calcium levels are not reliable for this because they do not reflect the extent of anion binding.

Calcium↗
PubMed1984

The sensitivity and specificity of nutrition-related variables in relationship to the duration of hospital stay and the rate of complications.

We assessed the nutritional status at the time of hospital admission of 74 patients who were admitted for elective gynecologic or urologic operations. Nutritional assessment included measurement of serum albumin, thyroxine-binding prealbumin, retinol-binding protein, weight-change history, estimate of daily protein and total calorie intake, and a global estimate of nutritional risk. The sensitivity, specificity, false-positive rate, likelihood ratio, and positive predictive value of these nutrition-related variables were analyzed in patients who stayed in the hospital for longer than 10 days and in those patients with recognized complications. In the analysis of patients who remained in the hospital longer than 10 days, the finding of a low serum protein concentration or a low protein intake was most sensitive, and a low serum albumin concentration was the most specific. A receiver-operating-characteristic diagram that depicts the sensitivity and false-positive rates for the single variables and the combinations of variables is probably the most clinically useful summary of our study. Using the information in such a diagram, a clinician might choose variables that are more sensitive to identify hospitalized patients who should receive special nutritional attention in comparison with another clinician who might need fewer false-positive results for a prospective study of nutritional intervention.

Adult↗
PubMed1984

Laboratory assessment of nutritional status.

Malnutrition is one of the major causes of increased morbidity and mortality among hospitalized patients. The availability of nutritional therapy for these patients has made clinicians aware of the need for reliable methods of nutritional assessment. A variety of anthropometric, biochemical, and immunologic parameters has been used as indicators of protein-calorie malnutrition. Recently, the concentration of several rapid-turnover visceral proteins (transferrin, thyroxine-binding prealbumin and retinol-binding protein) has been shown to be a very sensitive parameter for indicating both the efficiency of nutritional therapy and conditions of borderline protein intake in apparently healthy children. Likewise, several immunologic parameters (including T cells, delayed hypersensitivity response, and complement components) have been shown to correlate with morbidity, mortality risk, sepsis, and death.

Avitaminosis↗
PubMed1982

Artifactual hypercalcemia in multiple myeloma.

A calcium-binding IgG K monoclonal protein in a patient with multiple myeloma and asymptomatic hypercalcemia was recognized, isolated, and characterized. In addition to binding by the whole IgG molecules, calcium was bound by purified Fab fragments and recombined heavy and light chains. In a competitive binding study, the isolated myeloma protein did not bind magnesium. Recognition of calcium-binding myeloma proteins is important in order to avoid therapy for hypercalcemia.

Adult↗