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Biomedical subjects

R Schaffer

Publications and source records attributed to R Schaffer.

At least 37 records · Page 2Linked to original sources
PubMed1991

Multiple-dose evaluation of intravenous hydromorphone pharmacokinetics in normal human subjects.

We measured the pharmacokinetics of hydromorphone in normal volunteers given three doses of the drug (10, 20, and 40 micrograms/kg) as intravenous 45-s injections on different days. Concentrations of hydromorphone in plasma from serial blood samples were measured by a high-performance liquid chromatography method specific for hydromorphone with a detection limit of 0.1 ng/mL. In all cases, plasma hydromorphone concentration versus time data for individual subjects were best described by a triexponential (instead of mono- or biexponential) function. Furthermore, we found that the pharmacokinetics of hydromorphone was independent of dose across the range studied. Averaged across doses, the distribution and terminal elimination half-lives were 1.27 min (t1/2 pi), 14.7 min (t1/2 alpha), and 184 min (t1/2 beta), respectively. Average values for systemic clearance, initial dilution volume, and steady-state volume of distribution were 1.66 L/min (Cl), 24.4 L (Vc), and 295 L (Vdss). Our results indicate that hydromorphone pharmacokinetic parameters are linear across a fourfold range of doses that are usually employed clinically and that previously reported pharmacokinetic values for hydromorphone (based on radioimmunoassay measurements) deserve reconsideration.

Adult↗
PubMed1989

A study of children with learning disabilities and sensorimotor problems or let's not throw the baby out with the bathwater.

The 1986 position statement by the Board of Trustees fo the Council for Learning Disabilities called for a moratorium on the measurement and training of perceptual and perceptual-motor function as a part of services for children with learning disabilities (LD). Estimates in the literature, however, indicate that approximately 13% of children with LD exhibit motor deficits. Such children with motor or perceptual-motor problems are of ten referred to occupational therapy and found to have sensory integrative (SI) dysfunction; subsequently, they are treated with techniques aimed at remediating perceptual or sensorimotor dysfunction. Because the results of research concerned with the efficacy fo sensorimotor therapy are inconclusive and incomplete at this time, the position statement may be premature. Occupational therapists, however, must be aware of the statement and respond appropriately. In order to respond, they must have a better understanding of the nature of this subgroup of children with LD who have motor problems. the purpose fo this study was to assist in the definition of this population. Eighty children with LD between 5 years and 8 years 11 months were examined. They had been referred for occupational therapy at six centres in Southern Ontario. Results indicated that these children were similar to other children with LD in terms of gender and IQ distribution, developmental history, and academic achievement. The study population, however, tended to have less generalized emotional/behavioral disorder than the general population with LD. As expected, these children also had major deficits in gross and fine motor performance. A focus of the paper is on the importance of sensorimotor deficit for learning and self-concept in the child. Implications for both the position statement and practice and research in occupational therapy are discussed.

Journal Article↗
PubMed1989

The National Reference System for Cholesterol.

The NRS/CHOL is a reality that is progressively becoming the way in which accuracy of cholesterol results is being ensured. Proof of traceability to NRS/CHOL within each segment of the clinical laboratory, now an expectation, will soon be the norm that makes a sound conceptual reference system into an everyday reality that reaches into the many thousands of working sites that measure cholesterol in serum on patient samples.

Cholesterol↗
PubMed1985

Relationship of ultrasound findings after cesarean section to operative morbidity.

Postcesarean section febrile morbidity remains a common problem on obstetric services. Although a few preliminary studies have reported on the use of ultrasound to assess the postcesarean section patient, they have not compared sonographic findings with either intraoperative or postoperative events. These reports have noted fluid collections around the incision site. In this report of 100 postcesarean section patients, it is noted that echo-free areas anterior to the incision site, which correspond to the described fluid collections, were present in 29% of patients and were more frequently found in patients with excess blood loss at surgery. Patients whose echo-free areas were greater than or equal to 3.5 cm were significantly more likely to have postoperative morbidity. The significance of these findings and the role of ultrasound in the evaluation of the postcesarean section patient are discussed.

Abscess↗
PubMed1985

Candidate reference method for determination of total bilirubin in serum: development and validation.

This candidate Reference Method for measuring total bilirubin in serum is based on the Jendrassik-Gróf principle (Clin Chem 29: 297-301, 1983). Standard Reference Material no. 916 bilirubin (National Bureau of Standards) is used as the standard. Bilirubin standard solutions may be prepared either in human serum or in 40 g/L albumin solution (human or bovine), because we found the molar absorptivity of the azopigment at 598 nm to be identical in these media. The absorptivities of the unconjugated and conjugated azopigments appear to be identical, but the conjugated azopigment is completely hydrolyzed in the final reaction mixture. Bilirubin added to serum from adults or neonates was quantitatively accounted for. Interference by hemoglobin (up to 2 g/L), ascorbic acid (up to 20 mg/L), or zinc (at physiological concentrations) is negligible. Of the therapeutic drugs we tested, only L-dopa and alpha-methyldopa interfere. We established normal adult reference values for total bilirubin and examined the intraindividual variation in 19 subjects.

Adult↗
PubMed1984

Multiple pancreatic pseudocyst disease.

In an effort to determine the incidence of multiple pseudocyst disease and establish the optimal approach to this problem, the records of 91 consecutive patients diagnosed during a 36-month period as having pancreatic pseudocyst disease by sonography or computerized tomographic scanning were reviewed. Thirteen patients (14.3%) had multiple cysts; all received sonograms and six had CT scans. The combined false negative and false positive rate with sonography was 9%. Spontaneous resolution occurred involving five cysts (18%) up to 6.5 cm in size. The diagnosis of cyst multiplicity was confirmed at operation in seven cases; two of the seven operations were excisional and the remaining patients received drainage procedures. There were no operative deaths; complications included one patient who required chronic enzyme replacement therapy after excision and another patient who developed a subphrenic abscess after attempted percutaneous drainage. The incidence of multiple pseudocyst disease in our series is just over 14%. The possibility of multiplicity should be carefully investigated in each patient with pseudocyst disease. In light of the rate of spontaneous resolution, not all patients with multiple pseudocysts may require operative therapy. Because of the 7.7% false negative diagnoses with sonography, CT scanning is especially helpful when the diagnosis of multiple pseudocysts is suspected or in preoperative preparation of pseudocyst drainage. If an operation becomes necessary, a drainage procedure rather than excision should be used whenever possible to maximize gland salvage.

Adult↗
PubMed1983

Sonography of tuberculous kidney.

Sonography of 8 patients with renal tuberculosis is reported and collated with 3 additional cases reported in the literature. The patterns of hydronephrosis versus granuloma formation are presented and the differential diagnoses at sonography reviewed.

Diagnosis, Differential↗
PubMed1983

Sonography of vesical and perivesical abnormalities in children.

Pelvic sonograms of 40 children who had abnormalities related to the bladder and perivesical region were reviewed. The lesions detected were categorized into three groups, intramural, intravesical, and perivesical; in each category, conditions not related to vesical or perivesical anomalies that could mimic such anomalies were encountered. Real-time ultrasonography was most helpful in identifying ectopic ureteroceles. Aperistaltic loops of bowel were found to mimic perivesical cysts.

Adolescent↗
PubMed1982

The accurate determination of serum glucose by isotope dilution mass spectrometry--two methods.

Two isotope dilution mass spectrometric methods have been developed for the determination of D-glucose in human serum. Each uses a uniformly labeled (13C)glucose as the internal standard. The first method involves conversion of glucose into 1,2:5,6-di-O-isopropylidene-alpha-D-glucofuranose and an extensive clean-up, followed by quantitation using packed column gas chromatography mass spectrometry. In the second method, glucose is converted into alpha-D-glucofuranose cyclic 1,2:3,5-bis(butylboronate)-6-acetate. The wet chemistry work-up is simpler, but analysis by capillary gas chromatography mass spectrometry is required. Both methods exhibit excellent precision (coefficients of variation less than 0.3%) and provided mean values that agree within 1% for all serum pools tested.

Blood Glucose↗
PubMed1982

Comparison of two isotope dilution/mass spectrometric methods for determination of total serum cholesterol.

Isotope dilution/mass spectrometric methods for total serum cholesterol, developed separately at the Karolinska Institutet (KI) and the National Bureau of Standards (NBS), were compared by applying them to a common set of serum pools. A search for the cause of a systematic difference of a few percent in results from the two methods revealed that the KI cholesterol standard contained lathosterol, which interfered with the calibration of the method. With NBS Standard Reference Material cholesterol used for new analyses at the KI, the average difference in mean values dropped to 0.2%. The NBS results are more precise. This is attributed to the protocols NBS used for sample preparation and mass spectrometry. However, these protocols make the NBS method more complex and time-consuming. A recent critical article on the use of this technique for total cholesterol is also examined.

Cholesterol↗
PubMed1982

A candidate reference method for uric acid in serum. II. Interlaboratory testing.

We describe the interlaboratory testing of a candidate Reference Method (Part I) for uric acid in serum. The method is based on the ultrasound spectrophotometric quantitation of uric acid before and after incubation with uricase. A comprehensive investigation involving 12 laboratories was organized to document the transferability, intra- and interlaboratory precision, and general reliability of the candidate Reference Method. The interlaboratory CV with this method was about 2 to 6% for uric acid concentrations ranging from 0.12 to 0.60 mmol/L. The results detailed here demonstrate that the method can be successfully duplicated among different laboratories.

Evaluation Studies as Topic↗
PubMed1981

A candidate reference method for determination of total protein in serum. I. Development and validation.

We developed a candidate Reference Method for measuring total serum protein by use of the biuret reaction. The method involves a previously described biuret reagent (Clin. Chem. 21: 1159, 1975) and Standard Reference Material (SRM) 927 bovine albumin (National Bureau of Standards) as the standard. At 25 degrees C, color development for 30 or 60 min provides identical serum protein values. Glucose (up to 10 g/L) and bilirubin (up to 300 mg/L) do not interfere. Hemoglobin, at 3 g/L, increases apparent serum protein by 0.4 g/L. The presence of dextran in serum causes easily detected turbidity, but this interference can be eliminated by centrifuging the reaction mixture. Therapeutic concentrations of ampicillin, carbenicillin, penicillin, oxacillin, nafcillin, chloramphenicol, cephalothin, and methicillin in blood do not interfere, nor do triglycerides up to 10 g/L. Within-run and day-to-day standard deviations of the method are 0.1 and 0.4 g/L, respectively.

Bilirubin↗
PubMed1981

A candidate reference method for determination of total protein in serum. II. Test for transferability.

The transferability of the candidate Reference Method for total serum protein was tested in eight laboratories in the United States and Europe. National Bureau of Standards SRM 927 (bovine serum albumin) was used in each analytical run as the calibration standard. The mean absorptivity value obtained for this material was 0.2983 L g-1 cm-1. Four serum pools prepared at the Centers for Disease Control were analyzed on each of 15 days. Within-run variation of the protein values (expressed as CV) in the eight laboratories ranged from 0.1 to 2.5% and day-to-day (total) variation in six of the laboratories ranged from 0.4 to 1%.

Biuret Reaction↗