Articles: partial-thromboplastin-time.
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An increased incidence of thrombosis has been reported in patients with a prolonged activated partial thromboplastin time (APTT) due to a lupus anticoagulant (LA), which is an antibody to negatively charged phospholipids. The antiphospholipid antibodies can be quantitated in an enzyme-linked immunoabsorbent assay (ELISA) that utilizes cardiolipin as the antigen. With the development of the ELISA, two major areas of controversy have arisen. First, the correlation between assay results for LA and for the ELISA has varied widely among laboratories. Second, some investigators have described a correlation between high levels of anticardiolipin antibodies (ACA) and thrombotic disorders, whereas others have found no association between ACA levels and thrombosis in a general population of medical patients. To explore these issues further, the present study determined the sensitivity and specificity of an LA assay for detecting ACA in medical patients with a prolonged APTT. The association between the isotype and titer of ACA and thrombosis was examined in those patients positive for LA. ⋯ A test for LA in medical patients with a prolonged APTT can be sensitive and specific for ACA. Determination of ACA levels in patients who have LA that is not induced by medication or infection may define those patients at increased risk for thrombosis.
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J Cardiothorac Anesth · Dec 1989
Activated partial thromboplastin time-protamine dose relation in the presence and absence of heparin.
A protamine titration is one of the methods to determine the protamine dose necessary to neutralize heparin. The protamine dose response was studied with the activated partial thromboplastin time (APTT) in the presence of a known amount of heparin and in the absence of heparin, using freshly prepared human plasma. When heparin was present in the plasma, APTT values plateaued between a minimal neutralizing dose of protamine and a protamine dose five times greater. ⋯ The increases in APTT values caused by an increase of 50 micrograms/mL of protamine were significantly greater without heparin than they were in the presence of heparin. These results suggest that protamine has a wide safety range when neutralizing heparin without exerting its own anticoagulant action. Although the mechanisms are under speculation, the heparin-protamine complex may inhibit the anticoagulant action of protamine in vitro.
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Comparative Study
Relationship between arterial and venous activated partial thromboplastin time values in patients after percutaneous transluminal coronary angioplasty.
This quasi-experimental study was conducted to determine whether reliable activated partial thromboplastin time (APTT) values could be obtained from samples taken from indwelling arterial catheter lines. The 30 subjects, who were receiving heparin infusions after a percutaneous transluminal coronary angioplasty (PTCA), had femoral intraarterial lines. With use of a counterbalanced design, APTT values determined in two serial samples of venous and arterial blood were compared for the 30 subjects. ⋯ The histogram indicated that three of the 30 subjects had arterial-venous APTT differences that exceeded 19 seconds when four times the discard volume was used. In the samples where six times the discard volume were used, only one person had an APTT reading greater than 8 seconds. Paired t tests revealed statistically significant differences between the arterial and venous APTT values (t = 2.95, df = 29, p less than 0.01) for discards of four times the catheter dead space volume, whereas no statistically significant difference was found between the arterial and venous APTT values (t = 2.62, df = 28, p greater than 0.01) for discards of six times the dead space volume.(ABSTRACT TRUNCATED AT 250 WORDS)
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Warfarin provides effective prophylaxis against postoperative venous thromboembolic complications in adults undergoing elective hip surgery, but at the risk of increased bleeding complications. Although patients on this drug are routinely monitored by prothrombin time (PT), mild elevations of the partial thromboplastin time (PTT) have been reported with warfarin therapy. In a prospective study of 194 patients undergoing elective hip surgery, the authors assessed the incidence of elevation of the PTT above 50 seconds while the patient was receiving warfarin prophylaxis and the effect of this elevation on bleeding complications. ⋯ Major postoperative bleeding complications occurred in 26.3% of group 1 patients, versus 4.5% of group 2 (P less than .01). This subset of patients with an abnormal PTT elevation despite appropriate control of the PT is at a significantly increased risk of major postoperative bleeding. This observation may also prove valuable in reducing bleeding complications from warfarin use in nonsurgical patients.
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Int. J. Pediatr. Otorhinolaryngol. · Oct 1987
An assessment of preoperative coagulation screening for tonsillectomy and adenoidectomy.
Preoperative coagulation studies are commonly employed in order to try to identify the 2-4% of all patients undergoing tonsillectomy/adenoidectomy surgery who experience hemorrhagic complications. In an atmosphere of increasing cost consciousness, evaluation of the efficacy of screening tests is warranted. The records of 994 out of 1050 patients consecutively scheduled for tonsillectomy, adenoidectomy or T&A over a 2.5-year period were retrospectively reviewed in order to determine the usefulness of partial thromboplastin (PTT) and prothrombin time (PT) screening in predicting surgical and postsurgical bleeding. ⋯ The purpose of any screening test is to identify disease early enough for therapeutic intervention to be effective. Although preoperative PT/PTT will occasionally identify an unsuspected von Willebrand's or other coagulopathy, the prevalence of bleeding disorders in patients with negative history and examination is low enough that PT/PTT has essentially a zero predictive value for surgical bleeding. Screening PT/PTT should therefore be reserved for patients with known or suspected coagulopathies.