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Biomedical subjects

J Ansell

Publications and source records attributed to J Ansell.

13 recordsLinked to original sources
PubMed1992

Aging and the anticoagulant response to warfarin therapy.

OBJECTIVE: To assess the effect of aging on the anticoagulant response to warfarin. DESIGN: Retrospective cohort study. SETTING: A university hospital outpatient anticoagulation clinic. PATIENTS: All patients (n = 530) monitored in the anticoagulation clinic over a 10-year period (1980 to 1990). The 530 study patients had a mean age of 61.5 (+/- 14.7) years (age range, 12 to 90 years). The patients were stratified into four age groups: younger than 50 years (n = 97); 50 to 59 years (n = 107); 60 to 69 years (n = 149); and 70 years or older (n = 177). MEASUREMENTS: For each patient, a dose-adjusted mean prothrombin time ratio was calculated by dividing the mean prothrombin time ratio by the mean daily warfarin dose. RESULTS: Older patients were more likely to be female (P less than 0.001), to have more medical problems (P less than 0.001), to be taking more medications (P less than 0.001), and to weigh less than younger patients (P less than 0.001). Across age groups, there were no significant differences in the use of medications that potentiated or inhibited the anticoagulant effects of warfarin. The prothrombin time ratio, when adjusted for dose, was significantly increased in older patients (P less than 0.001). The increased anticoagulant response to warfarin seen with increasing patient age persisted even after simultaneously controlling for relevant demographic and clinical variables in a multivariate model. Other factors significantly associated with an increased sensitivity to warfarin included use of a medication with a potentiating interactive effect with warfarin, female gender, and overall medication use. Increased body weight and duration of warfarin use exceeding 6 months were found to be inversely related to anticoagulant response. CONCLUSION: The anticoagulant response to warfarin is exaggerated with advancing age. This finding emphasizes the need for close monitoring of older patients treated with warfarin therapy.

Adolescent↗
PubMed1992

Does desmopressin acetate prophylaxis reduce blood loss after valvular heart operations? A randomized, double-blind study.

The effectiveness of prophylactic desmopressin acetate in reducing hemorrhage after cardiopulmonary bypass operations is controversial. We conducted a prospective, randomized, placebo-controlled, double-blind trial to determine its effectiveness and safety in such patients. Eighty-three evaluable patients undergoing valvular heart operations were randomized to receive desmopressin (0.3 microgram/kg) (41) or placebo (42) after cardiac bypass. Demographic characteristics were similar in both groups. There was no significant difference in total 24-hour blood loss between groups (desmopressin 1064.8 +/- 647.1 ml versus placebo 844.4 +/- 507.6 ml; p greater than 0.05), or in the requirement for red blood cell, platelet, or fresh frozen plasma transfusion, or for reexploration for control of hemorrhage. Neither was there a difference in the occurrence of thrombotic complications between groups. Analysis of factor VIII activity, von Willebrand factor, or von Willebrand factor multimers failed to show significant correlations with blood loss or differences between groups except for factor VIII activity, which was significantly higher in the desmopressin group 1 hour after operation than in the placebo group. A detailed comparative analysis of similar trials to determine the reasons for different outcomes suggests that desmopressin should not be used routinely as a prophylactic agent to reduce postsurgical hemorrhage, but that it may be beneficial when used in patients who already manifest excessive bleeding postoperatively.

Blood Loss, Surgical↗
PubMed1991

Measurement of the activated partial thromboplastin time from a capillary (fingerstick) sample of whole blood. A new method for monitoring heparin therapy.

The monitoring of heparin anticoagulation is fraught with difficulties because of the need for repetitive venipunctures and the vagaries of sample handling and processing. The authors evaluated a new aPTT monitoring system with the potential to eliminate many of these difficulties. The Ciba Corning Diagnostics 512 Coagulation Monitor (CCD monitor) is a hand-held portable instrument that can measure an aPTT from a fingerstick sample of capillary whole blood. Fingerstick aPTTs from 319 subjects (including controls and individuals on heparin and/or warfarin) were compared to venipuncture-derived standard laboratory plasma aPTTs using different aPTT reagents on conventional instruments. The correlation coefficients between fingerstick and standard aPTTs (0.79-0.83) were the same as the correlation coefficient between standard laboratory aPTTs using different reagents (0.79). When venipuncture-derived whole blood was compared to fingerstick samples on the new instrument, the correlation coefficient was excellent (0.93). A high degree of precision, as demonstrated by low coefficients of variations, was shown for within-day and between-day testing using the CCD monitor and normal controls. This capillary whole blood, aPTT system is the first to provide the clinician with a means of rapidly and reliably assessing the anticoagulant response to heparin therapy at the bedside, and its use may ultimately lead to more efficient and effective therapy overall.

Blood Coagulation Tests↗
PubMed1990

Heparin-induced thrombocytopenia and arterial thrombosis: alternative therapies.

There are three distinct syndromes of heparin-induced thrombocytopenia: an acute reversible from seen immediately after intravenous bolus injection, a delayed-onset antibody-mediated form seen several days after the initiation of therapy, and an intermediate type characterized by mild thrombocytopenia developing just a few days after starting therapy. Delayed-onset heparin-induced thrombocytopenia, clinically the most important form, results from the formation of heparin-dependent antibodies that are directed against the platelet membrane. In the presence of heparin, these antibodies may induce in vitro or in vivo platelet aggregation. Consequently, the course may be complicated by arterial thromboses. Treatment of this syndrome includes the prompt cessation of heparin. Since continued or future anticoagulation is usually necessary, alternative means of anticoagulation have been explored. Oral anticoagulation is often started but requires several days to take effect. Other options include low-molecular-weight heparins, antiplatelet agents, prostacyclin analogues, and low-molecular-weight dextran. In vitro laboratory tests may be helpful in guiding alternative therapy in some, but not all cases. Unfortunately, none of these agents have proved to be uniformly effective and additional agents and clinical investigation are needed before a definitive option becomes available.

Aspirin↗
PubMed1989

pH- and time-dependent inhibition of rat kidney neutral endoprotease 24.11 by thiorphan and phosphoramidon.

The potencies of thiorphan and phosphoramidon as inhibitors of neutral endopeptidase 24.11 (NEP) are significantly affected by pH. Thiorphan and phosphoramidon are 10- and 150-fold more potent, respectively, when measured at pH 6.5 than at pH 8.5. The kinetic characteristics of these two inhibitors are different. NEP activity is readily inhibited by phosphoramidon upon mixing, while thiorphan becomes a more potent inhibitor only after preincubation with the enzyme.

Animals↗
PubMed1979

Etiology, manifestations and therapy of acute epididymitis: prospective study of 50 cases.

There were 50 patients with acute epididymitis who were evaluated prospectively by history, examination and microbiologic studies, including cultures for aerobes, anaerobes, Neisseria gonorrhoeae, Chlamydia trachomatis and Ureaplasma urealyticum. Escherichia coli was the predominant pathogen isolated from the urine of men more than 35 years old, while Chlamydia trachomatis and Neisseria gonorrhoeae were the predominant pathogens isolated from the urethra of men less than 35 years old. The etiologic role of Escherichia coli and Chlamydia trachomatis was confirmed by isolation from epididymal aspirates from a high proportion of men with positive urine or urethral cultures for these agents. Chlamydia trachomatis epididymitis accounted for two-thirds of idiopathic epididymitis in young men and often was associated with oligospermia. Of 9 female sexual partners of men with Chlamydia trachomatis infection 6 had antibody to Chlamydia trachomatis, of whom 2 had positive cervical cultures for this organism and 2 others had non-gonococcal pelvic inflammatory disease. Antibiotic therapy with tetracycline was effective for the treatment of men with Chlamydia trachomatis epididymitis and should be offered to the female sex partners.

Adolescent↗
PubMed1978

Chlamydia trachomatis as a cause of acute "idiopathic" epididymitis.

To assess the etiologic role of C. trachomatis and other micro-organisms in "idiopathic" epididymitis, 23 men underwent microbiologic studies, including cultures of epididymal aspirates in 16. Eleven of 13 men under the age of 35 years had C. trachomatis infection whereas eight of 10 over 35 had coliform urinary-tract infection. Cultures of epididymal aspirates yielded C. trachomatis alone in five of six men under 35, and coliform bacteria alone in five of 10 over 35. These results suggest that C. trachomatis is the major cause of "idiopathic" epididymitis, and coliform bacteria the major cause of epididymitis in older men. Expressible urethral discharge and inguinal pain were more common in the chlamydial cases, whereas concurrent genitourinary abnormality and scrotal edema and erythema occurred more commonly in the coliform cases. The morbidity attributable to C. trachomatis is as serious as that attributable to Neisseria gonorrhoeae.

Acute Disease↗
PubMed1976

Patterns of lactic dehydrogenase isozymes in mouse embryos over the implantation period in vivo and in vitro.

Following blastocyst implantation, or outgrowth in vitro, the LDH isozyme pattern changes from that of the maternally inherited B subunit isozyme form (LDH-1) to a pattern dominated by A subunits (Auerbach & Brinster, 1967, 1968). In preimplantation embryos we have observed additional isozyme bands, as yet unidentified. An analysis of the pattern of newly synthesized LDH isozymes and specific activity of LDH in different regions of early postimplantation embryos suggests that there is a sequantial activation of A and B subunits, and that activity first appears in ICM- (inner cell mass) derived tissues and then in trophoblast-derived tissues. In vitro, in the absence of ICM cells, the transition of LDH-isozyme pattern does not occur in outgrowing trophoblast giant cells. This suggests a possible inductive interaction between ICM and trophoblast.

Animals↗
PubMed1975

Maternal immunization to paternal antigens in multiparous mice.

Mice of the CBA strain which had given birth to five litters sired by males of a different H-2 type (C57BL/10) showed evidence of immunization to paternal antigens, in that the numbers of lymphocytes forming alloclusters with paternal erythrocytes were significantly elevated. On the other hand, the graft-versus-host responsiveness of maternal splenic lymphocytes to paternal antigens remained virtually unchanged, showing only a slight increase at Day 8 of the assay.

Animals↗
PubMedDate not supplied

Risk-benefit assessment of anticoagulant therapy.

Thromboembolic disease is a common medical condition which, if untreated, carries a significant risk of morbidity and mortality. Treatment with anticoagulant therapy, while clearly beneficial, may expose patients to potentially serious side effects. A thoughtful risk-benefit assessment is therefore crucial before initiating therapy. Thromboembolic disease involves syndromes of both the venous and arterial circulation, and its pathogenesis is best understood by considering the elements of Virchow's Triad. This model defines the risk factors for venous thromboembolism and allows us to classify surgical and medical patients into low, moderate and high risk groups. Similar analysis allows risk assessment for patients prone to cardiogenic embolism resulting from nonvalvular atrial fibrillation, ischaemic heart disease, rheumatic heart disease and valvular prostheses. All anticoagulant therapy is prophylactic. Primary prophylaxis involves instituting anticoagulant therapy in patients at risk, before thromboembolism occurs, while secondary prophylaxis involves treating patients with established disease. The 2 major anticoagulants, heparin and warfarin, differ in their mechanism of action, mode of administration and methods of monitoring. Either may be used as primary or secondary prophylaxis. Heparin, because it acts immediately, is the drug of choice for the short term treatment of thromboembolic disease. Warfarin is the drug of choice for long term oral maintenance therapy. The principal complication of heparin therapy is haemorrhage, although thrombocytopenia and osteoporosis may also occur; the complications of warfarin include haemorrhage and skin necrosis. The risks of complications vary with the underlying thromboembolic disease. After the benefits of treatment are weighed against the risks of complications, recommendations for therapy can be established. The use of anticoagulants in pregnancy is especially complex. Here heparin is probably the preferred agent since, unlike warfarin, it does not cross the placenta and is nonteratogenic.

Adult↗