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Biomedical subjects

D Scheidegger

Publications and source records attributed to D Scheidegger.

At least 73 records · Page 4Linked to original sources
PubMed1987

Thermodilution determination of right ventricular volume and ejection fraction: a comparison with biplane angiography.

In 13 patients without tricuspid incompetence, we compared the values of right ventricular ejection fraction (RVEF) and right ventricular end-diastolic volume (RVEDV) obtained with biplane angiography and thermodilution at end-inspiration. A modification of Simpson's rule was used to measure angiographic volumes, and a new pulmonary artery catheter equipped with a rapid response thermistor was used to measure the ejection fraction by the Holt plateau method. The correlation between the two methods was acceptable (r = 0.83 for RVEF, r = 0.71 for RVEDV) despite the limitations of both angiography and thermodilution. Thermodilution underestimated RVEF and overestimated RVEDV when compared to angiography. The variation coefficient with thermodilution for five measurements of the RVEF per patient was 12 +/- 5%. In addition to pressure and cardiac output measurements, monitoring of RVEF and RVEDV in the ICU should be possible with such a catheter. Further work is needed to assess the clinical relevance of these added data and their use for optimizing the therapy of right ventricular failure in acutely ill patients.

Adult↗
PubMed1986

The hemodynamic effects of heparin and their relation to ionized calcium levels.

Heparin complexes calcium in vitro and possesses vasodilating properties when given as an intravenous bolus. To investigate the possibility that these hemodynamic effects could be related to the ability of heparin to induce hypocalcemia in vivo, we studied the response to a bolus of heparin, 300 IU/kg, in 20 patients undergoing cardiopulmonary bypass for cardiac operations. Ionized calcium decreased significantly after heparin administration, as did mean arterial pressure and systemic vascular resistance. In a further nine patients, 125 mg of calcium chloride was given immediately before the heparin bolus. It induced a small rise in calcium levels and maintained the mean arterial pressure at unchanged values. Our data confirm the vasodilating effect of an intravenous bolus of heparin and show that it is related to an acute lowering of ionized calcium levels. When calcium levels are not allowed to drop, the blood pressure is maintained at stable values. We advise slow injection of the heparin bolus and special attention to the ionized calcium levels before cardiopulmonary bypass.

Aged↗
PubMed1985

A sensitive and quantitative microassay for the detection of mycoplasma contamination: inhibition of IL-2 dependent cell line proliferation.

A simple, rapid and sensitive microassay for mycoplasma detection in cell culture is reported. The assay is based on the fact that culture supernatants from contaminated cells inhibit [3H]thymidine incorporation by an IL-2 dependent mouse cytotoxic T cell line (CTLL). The mechanism of inhibition is related to the production by several mycoplasma strains of a pyrimidine-specific nucleoside phosphorylase which can degrade the radiolabelled thymidine used for the measurement of DNA synthesis. These strains were the commonest contaminants in cultures of 24 cell lines from 5 different sources. To establish the sensitivity of the test to detect mycoplasmas we have also used the inhibition assay to monitor the clearance of mycoplasma from 2 contaminated cell lines.

Cell Division↗
PubMed1985

Isolation and characterization of Ni-specific T cell clones from patients with Ni-contact dermatitis.

Ni-specific T lymphocyte clones (TLC) were isolated from two patients with Ni-contact dermatitis. All of the isolated TLC required both histocompatible antigen-presenting cells (APC) and Ni for induction of proliferation. By using a panel of HLA-typed Epstein Barr virus-transformed B cells (EBV-B cells) as APC and monoclonal anti-DR antibody, the clones were shown to recognize Ni in the context of HLA class II determinants. All of the clones that were isolated are OKT3+, OKT4+, OKT8-. In the presence of Ni, they polyclonally activate autologous B cells, and in the presence of Ni and autologous EBV-B cells, they produce IL 2 and very high levels of IFN-gamma. The Ni-specific clones should be helpful in the identification of the Ni-induced antigen which is recognized by T cells.

Antigen-Presenting Cells↗
PubMed1985

Facilitated determination of ionized calcium.

Using a calcium-containing heparin preparation for anticoagulation, we determined [Ca2+], the mean concentration of ionized calcium, in whole blood of 120 healthy blood-donors to be 1.23 (SD 0.04) mmol/L. Similarly, for 50 intensive-care patients selected without conscious bias, the correlation between [Ca2+] in serum (mean 1.15, SD 0.10 mmol/L) and in whole-blood samples anticoagulated with the same heparin preparation (mean 1.15, SD 0.09 mmol/L) was very good (r = 0.95). Storing samples anaerobically on ice for as long as 2 h did not alter whole-blood [Ca2+]. On the other hand, various concentrations of calcium-free heparin preparations all induced a significant decrease in measured [Ca2+]. By using whole-blood samples, rather than plasma or serum, for [Ca2+] determination with a calcium-selective electrode, repetitive measurements can be made with simple handling procedures, facilitating rapid implementation of appropriate therapeutic measures for critically ill patients.

Adult↗
PubMed1982

Acute hemodynamic effects of intravenous tiapamil in patients with coronary artery disease.

The acute hemodynamic effects of intravenous tiapamil were studied during heart catheterization in 19 patients with coronary artery disease (age range 41-66 years, mean 52.4 years). 10 subjects received an initial intravenous loading dose of 1 mg/kg followed by intravenous infusion of 50 micrograms/kg/min for 15 min. The other 9 patients received an initial intravenous dose of 1.5 mg/kg which was followed by an intravenous infusion of 75 micrograms/kg/min for 15 min. Tiapamil had little effect on heart rate, intracardiac pressures and left ventricular dp/dtmax. The ejection fraction increased, but not significantly. The most striking findings were an increase in cardiac output and a decrease in systemic vascular resistance. The overall results are consistent with the drug's propensity to produce peripheral vasodilatation which outweighs its intrinsic negative inotropic property due to calcium antagonism in myocardial tissues.

Adult↗
PubMed1981

[Hemodynamic changes in acute respiratory insufficiency: the role of the right ventricle].

Acute respiratory failure, particularly if associated with sepsis, results in diffuse changes in pulmonary vascular geometry and the afterload characteristics against which the right ventricle must perform. Therapy in these patients frequently requires replacement of intravascular volume which, if pulmonary vascular resistance is abnormally elevated, may cause a substantial enlargement in right ventricular (RV) end-diastolic volume. The low compliance characteristics of the RV invalidate the use of filling pressure (CVP) as a guide to RV size. We have examined RV volume in critically ill patients by means of the gated 99TAc scan and noted a substantial increase in RV volume despite filling pressure in the upper normal range. This enlargement appears to encroach upon LV function because the ejection fraction of the LV remained high despite elevation of pulmonary capillary wedge pressure (PCWP). Older patients with "silent" right coronary artery disease may become hemodynamically limited during therapy for acute respiratory failure and sepsis due to RV enlargement, increased wall tension and RV ischemia, a condition not readily diagnosed at the bedside with the usual monitoring techniques.

Animals↗
PubMed1980

[Hemodynamics monitoring: correlations of clinical and invasive methods].

Cardiac failure is the main in-hospital cause of death in acute myocardial infarction. The present review demonstrates the possibilities and advantages of invasive monitoring. The Swan-Ganz catheter offers the possibility of measuring cardiac pressures, particularly pulmonary wedge pressure, cardiac O2 saturations and cardiac output. The main indications are severe left heart failure, right heart failure, complicated myocardial infarction, severe hypovolemia and vasodilator therapy.

Blood Pressure↗
PubMed1980

Role of the systemic vasculature in the hemodynamic response to changes in plasma ionized calcium.

Hemodynamic consequences of sustained (one hour) hypocalcemia and hypercalcemia (plasma ionized calcium concentration [Ca++] maintained approximately 60% below or above normal, encompassing the clinical range) were studied and the influence of beta blockade on these hemodynamic alterations examined in 16 anesthetized, closed-chest dogs. Alterations in [Ca++] were associated with directionally similar changes in mean arterial pressure, whereas on the average cardiac output remained unchanged. Thus, the peripheral vasculature played an important role in the hemodynamic response to alterations in [Ca++]. The state of beta adrenergic activity was an important determinant of the hemodynamic response to hypocalcemia. Prior to beta blockade, hypocalcemia was associated with decreased systemic vascular resistance, whereas after beta blockade with propranolol hydrochloride, systemic vascular resistance was not different from control except at the five-minute observation period, and cardiac output and stroke volume fell.

Adrenergic beta-Antagonists↗
PubMed1980

Production of monoclonal antibodies: strategy and tactics.

A myeloma line has been developed which produces no globulin chains of its own, has a duplication of 8.7 h, fuses effectively with B-lymphoblasts and produces stable hybrids. An enhancing effect of macrophages on hybridoma yields has been observed. Among the fusing agents tested, PEG of mol.wt. 4000 gave the best results, 20 degrees C being the optimum working temperature. The maintenance medium of choice has been found to be Iscove's with 10% FCS. Direct exposure of fusion cultures to a selective medium with hypoxanthine, aminopterine and thymidine reduced the labor involved and increased the yield. A mechanical device for changing the medium has been designed. The replacement of standard trays by microtrays resulted in a higher frequency of surviving hybrids. By using a feeder layer, the spleen cell input can be reduced 50-fold. At such low multiplicities the positive cultures arise predominantly from single hybrids, eliminating the need for subsequent cloning. The hybrids can be labelled and will yield in serum-free medium. Since at least a third of them inherit the fast growth rate of their myeloma parent and keep producing over 2000 antibody molecules per second, readaptation to ascitic growth is also superfluous. A simplified technique of producing monoclonal antibodies is given in detail, together with the experimental evidence prompting modifications of the classical method of Köhler and Milstein (1975, 1976).

Animals↗
PubMed1979

Haemodynamic consequences of citrate infusion in the anaesthetized dog: comparison between two citrate solutions and the influence of beta blockade.

We have compared the effects of a solution of acid--citrate--dextrose (ACD) with those of a solution of citrate--phosphate--dextrose (CPD), infused at equal rates, on blood calcium ion concentration and different indices of haemodynamic performance in 17 dogs. The influence of beta adrenergic blockade on these changes was examined. The effects of ACD and CPD were studied in five dogs and were similar. Peripheral vascular changes were the principal cause of arterial hypotension. In six dogs, propranolol 0.5 mg kg-1 intensified the hypocalcaemia-induced left ventricular dysfunction.

Animals↗