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Biomedical subjects

K L Carlson

Publications and source records attributed to K L Carlson.

At least 19 recordsLinked to original sources
PubMed2000

Sonography of the glenoid labrum: a cadaveric study with arthroscopic correlation.

OBJECTIVE: We assessed the usefulness of sonography in evaluating the glenoid labrum in cadaveric specimens using arthroscopy as a standard of reference. MATERIALS AND METHODS: Eighty labral quadrants in 20 cadaveric shoulders were examined by two musculoskeletal radiologists using 5- to 7-MHz linear and curvilinear transducers. Agreement was reached by consensus. After sonography, arthroscopy was performed by an experienced orthopedic surgeon. Each labral quadrant was classified at the time of sonography and arthroscopy as normal, degenerated, or torn. RESULTS: Concordance between sonography and arthroscopy was 86% (69/80 quadrants). In differentiating abnormal labrum (tear or degeneration) from normal labrum using sonography, sensitivity was 63%, specificity was 98%, positive predictive value was 94%, negative predictive value was 86%, and accuracy was 88%. In differentiating labral tears from other labral conditions (degeneration or normality), sensitivity was 67%, specificity was 99%, positive predictive value was 67%, negative predictive value was 99%, and accuracy was 98%. CONCLUSION: Sonography has a promising role in the evaluation of the glenoid labrum, particularly in excluding labral tears when the labra appear normal on sonography. Further studies are required using normal and symptomatic patients to determine the usefulness of sonography in the diagnosis of labral abnormalities.

Aged↗
PubMed1999

Relationship between mammographic screening intervals and size and histology of ductal carcinoma in situ.

OBJECTIVE: The objective of this study was to determine how the length of time between mammographic screenings is related to the size, grade, and histology of mammographically detected ductal carcinoma in situ (DCIS). MATERIALS AND METHODS: We retrospectively reviewed 166 consecutive mammograms of women evaluated for DCIS with (n = 24) and without (n = 142) microinvasion. The size of the DCIS was determined by the maximum diameter as measured on the mammogram. After pathologic analysis, DCIS was classified by histologic architecture, nuclear grade, presence of microinvasion, and presence of multifocality. Four screening intervals were defined: annual (6-17 months), biennial (18-29 months), triennial (> or = 30 months), and first time. Patients were grouped according to screening intervals. The average age of all groups was 55 years. RESULTS: The annual group (mean size of DCIS, 1.69 cm) had significantly smaller DCIS than did the biennial (mean size, 2.27 cm), triennial (mean size, 3.49 cm), or first time groups (mean size, 3.29 cm) (p = .003). Comedo histology was more frequently observed in patients screened biennially (73.7%) than in those screened annually (46.8%) (p = .05). High-grade nuclear histology was more commonly seen in the biennial (76.3%) than in the annual (48.1%) screening group (p = .008). We found no significant correlation between screening interval and the incidence of microinvasion and multifocality. CONCLUSION: Small, low-grade noncomedo DCIS was more common in the annual mammographic screening group than in the biennial screening group. A direct relationship was found between DCIS size and length of screening interval: DCIS detected at annual screening was smaller than that found at biennial screening, which in turn was smaller than DCIS revealed at triennial screening. This study provides inferential support for annual screening mammography for DCIS detection and management.

Breast↗
PubMed1996

Neonatal pain: from concept to research questions and a role for the advanced practice nurse.

The assessment and treatment of neonatal pain remain inconsistent in spite of scientific evidence and agreement among practitioners that neonates do experience pain. In fact, pain forms the basis for many subsequent maturational events and may mediate future responses to pain. The article outlines the concept of pain in the neonate, provides suggestions for future research, and discusses the instrumental role of the advanced practice nurse in the recognition and treatment of neonatal pain.

Humans↗
PubMed1992

Effect of orthostatic stress on umbilical Doppler waveforms in normal and hypertensive pregnancies.

OBJECTIVE: Our study examined the effects of orthostatic stress and maternal hemodynamics on umbilical systolic/diastolic ratios in normal and hypertensive pregnancies. STUDY DESIGN: Eighteen normal and 20 hypertensive third-trimester pregnancies were examined in the left lateral recumbent, sitting, and standing positions. Measurements included umbilical systolic/diastolic ratio, maternal blood pressure, maternal cardiac output, and maternal total peripheral resistance. RESULTS: All patients demonstrated a fall in cardiac output and a rise in total peripheral resistance with standing. No change in systolic/diastolic ratio occurred with change to the upright position in patients with normotension. Patients with hypertension exhibited a significant increase in umbilical systolic/diastolic ratio with postural change. The increase was more marked in women who had hypertension with elevated peripheral resistance. CONCLUSION: Patients with hypertension are at increased risk of elevation of systolic/diastolic ratio with postural change; women with high-resistance hypertension may be at highest risk.

Diastole↗
PubMed1992

The maternal hemodynamic effect of indomethacin in normal pregnancy.

The vasodilation of pregnancy is thought by many to be due to increased endothelial production of prostacyclin, a vasodilatory prostanoid. Indomethacin, a potent inhibitor of prostaglandin synthesis, is known to increase the maternal blood pressure response to angiotensin II infusion. We sought to measure directly the hemodynamic effects of a short course of indomethacin. Twenty-three healthy pregnant women with uncomplicated pregnancies between 26-32 weeks' gestation completed the study. Using Doppler technology, we determined cardiac output, stroke volume, and total peripheral resistance before and after three 25-mg doses of indomethacin. Although blood pressure did not change, peripheral resistance rose and stroke volume fell following indomethacin administration. Our findings support the hypothesis that indomethacin interferes with tonic prostaglandin-induced vasodilation in pregnancy. However, the increase in vascular resistance was very slight, suggesting that other vasodilators are also at work in pregnancy. We recommend that indomethacin be used judiciously in hypertensive pregnant patients until more information concerning possible adverse hemodynamic effects becomes available.

Blood Pressure↗
PubMed1991

Maternal hemodynamics in pregnancies complicated by hyperthyroidism.

The hemodynamics of six pregnant women with hyperthyroidism were studied before and after therapy. Cardiac output was measured by Doppler technique, and blood pressure by automated cuff. When compared with values in euthyroid pregnant women, blood pressure (83.6 mmHg, P less than .001), heart rate (89.2 beats per minute, P less than .001), cardiac output (11.2 L/minute, P less than .001), and stroke volume (123 mL, P less than .001) were significantly elevated. Total peripheral resistance was significantly reduced (609 dyne.second.cm-5, P less than .001). Despite normalization of thyroid indices after therapy, cardiac output remained markedly elevated (9.7 L/minute, P less than .001) and vascular resistance remained reduced (708 dyne.second.cm-5, P = .01). Although the hemodynamics of pregnant thyrotoxic women normalize with therapy, they remain significantly hyperdynamic.

Echocardiography, Doppler↗
PubMed1990

Measurement of cardiac output in pregnancy by Doppler technique.

Doppler technique of measuring cardiac output was evaluated during pregnancy. In a study of accuracy Doppler technique correlated well with thermodilution, (r = 0.95, y = 1.05x - 0.35). In a study of interoperator variability, the technique was found to be reproducible, (r = 0.92, y = 0.91x + 0.74).

Aorta↗
PubMed1990

Isolation and structural identification of 9hydroxy-9desmethyl-cyclosporine.

A metabolite of cyclosporine has been isolated and its structure identified through use of HPLC and tandem mass spectroscopy. Fast atom bombardment mass spectrometry of an HPLC fraction co-eluting with 1 eta hydroxy-cyclosporine (M17) indicated that the mass of this metabolite was 2 Da greater than that of cyclosporine. Further isolation by HPLC yielded a pure fraction, which we analyzed with tandem mass spectrometry. Linear acyl fragment ions originating from the metabolite under collision-induced dissociation were consistent with the difference in mass being associated with amino acid 9 in the cyclosporine backbone. We propose a nomenclature system for future discussion of cyclosporine metabolites.

Amino Acid Sequence↗
PubMed1989

Antihypertensive therapy in pregnancy directed by noninvasive hemodynamic monitoring.

Invasive and noninvasive investigations suggest that the hemodynamics of pregnant hypertensive patients are heterogeneous. Nineteen pregnant patients were evaluated before changes in antihypertensive therapy. Cardiac output was measured by Doppler technique. Blood pressure was measured by automated cuff. Systemic vascular resistance was calculated. Two distinct groups were identified on the basis of differences in cardiac output (p less than 0.0001) and systemic vascular resistance (p less than 0.0001). Those with high resistances were treated with hydralazine. A modest antihypertensive effect was achieved (-6.9 mmHg, p = 0.01), but systemic vascular resistance was dramatically reduced, (-534 dyne.sec.cm-5, p less than 0.0001) and was associated with a compensatory increase in cardiac output (2.0 liters/min, p less than 0.0001). Those with a high cardiac output were treated with atenolol. An antihypertensive effect was achieved, (-17.0 mm Hg, p = 0.008), which was associated with a reduction in cardiac output (-2.8 liters/min, p less than 0.0001).

Atenolol↗
PubMed1989

Measurement of cardiac output in pregnancy by thermodilution and impedance techniques.

To assess the value of impedance cardiography in pregnancy, simultaneous measurements of cardiac output were made with impedance and thermodilution techniques in 10 patients who required pulmonary artery catheterization. The methods correlated poorly (r = 0.17). The discrepancy between methods was particularly pronounced in hypertensive patients. Impedance cardiography does not measure cardiac output accurately in hypertensive pregnant women.

Cardiac Output↗
PubMed1989

Contact pressures from an instrumented hip endoprosthesis.

A pressure-measuring Moore-type endoprosthesis was implanted in a seventy-three-year-old patient who had sustained a displaced fracture of the femoral neck. The measurement and telemetry of contact pressures in the hip began in the operating room, and data were acquired periodically for more than thirty-six months. Unexpectedly high localized contact pressures between the acetabular cartilage and the prosthesis were recorded. Early in the period of recovery, activities such as using a bedpan or performing isometric exercise produced pressures that were close to those recorded during normal walking. The highest pressure, eighteen megapascals, was recorded one year postoperatively, while the patient was rising from a chair. High pressures occurred in the superior and posterior aspects of the acetabulum.

Acetabulum↗
PubMed1986

Contact pressures in the human hip joint measured in vivo.

The pressures on human articular cartilage have been measured in vivo. An instrumented femoral head prosthesis that telemeters interarticular pressure at 10 discrete locations 253 times per second was implanted in apposition to natural acetabular cartilage. Data were acquired during surgery, recovery, rehabilitation, and normal activity, for longer than 1 year after surgery. Pressure magnitudes were synchronized with body-segment kinematic data and foot-floor force measurements so as to locate transduced pressure areas on the natural acetabulum and correlate movement kinematics and dynamics with local cartilage pressures. The data reveal very high local (up to 18 MPa) and nonuniform pressures, with abrupt spatial and temporal gradients, that correlate well both in magnitude and distribution with in vitro data and computer simulations of synovial joint mechanics. Peak pressures in vivo are, however, considerably higher than pressures measured in vitro under the putative forces experienced by the joint in life, particularly in normal movements where cocontraction occurs in agonist and antagonist muscles across the hip joint. Thus, extant gait-analysis studies which apply inverse Newtonian calculations to infer joint forces establish the lower limit on such forces, since such analyses include only the net muscular torques about the joint and cannot account for the contribution of the increment in joint force due to muscular cocontraction. Our data also contribute to the understanding of normal synovial joint tribology and the possible role of mechanical factors in the deterioration evident in osteoarthritis. Further, design criteria for both partial and total hip replacement prostheses and specific aspects of rehabilitation protocols following hip surgery (e.g., the extent to which crutches and canes unload the hip joint) warrant reconsideration in light of the extraordinary high pressures measured during the activities of daily living.

Biomechanical Phenomena↗