Articles: prothrombin-time.
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Hypothermic patients commonly develop coagulopathy, but the effects of hypothermia on coagulation remain unclear because clinical laboratories routinely perform clotting tests only at 37 degrees C. Measurements of activated partial thromboplastin times (APTT), prothrombin times (PT), and thrombin times (TT) were performed on plasma from normothermic and hypothermic rats at a range of temperatures (25 degrees-37 degrees C) to assess the effects of hypothermia on apparent clotting factor levels and clotting factor activities. In general, clotting times were more severely prolonged when test temperatures were hypothermic than when body temperatures were hypothermic. ⋯ These findings reveal the observed disparity between clinically evident hypothermic coagulopathy and near-normal clotting studies. Clotting studies performed at 37 degrees C will not confirm hypothermic coagulopathy. These results indicate that the appropriate treatment for hypothermia-induced coagulopathy is rewarming rather than administration of clotting factors.
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To determine the relation of bleeding to prothrombin times and important remediable lesions in outpatients treated with warfarin. ⋯ Our results provide a valid quantitative basis for estimating the odds of bleeding in relation to the prothrombin time and the yield of diagnostic evaluation in patients with bleeding.
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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.
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The activated partial thromboplastin time (APTT) and prothrombin time (PT) have three principal uses. In screening for coagulation disorders (or increased risk of postoperative hemorrhage), the tests add no information to the preoperative care of patients without clinical findings indicative of increased bleeding risk. Furthermore, the prevalence of asymptomatic congenital coagulopathies is so low that false-positive test results greatly outnumber true-positive results. ⋯ In evaluating abnormal bleeding, these tests are sufficiently sensitive that if both are negative, further investigation of the coagulation system is obviated. If one or both tests are positive, the pattern of results directs further attention to limited segments of the coagulation sequence. In monitoring anticoagulation therapy, the APTT and PT tests appear to contribute to the safety and effectiveness of heparin and warfarin therapies, respectively.
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Preoperative tests of coagulation function have been suggested to detect patients who are likely to have abnormal bleeding during and after surgery. A study was designed to determine the yield of prothrombin time (PT) and partial thromboplastin time (PTT), both in discovering patients who are at risk for abnormal bleeding and in inducing changes in patient care or outcome. Of 750 patients on three surgical services, 611 (81%) patients had no indication of a bleeding disorder on history or physical examination. ⋯ One (0.2%) of the 480 patients might have benefited from the test result (this patient required a second operation to control arterial bleeding). The prolonged PT or PTT was of no apparent clinical importance in the remaining 12 patients without indications of bleeding disorders preoperatively. The low yield of the PT and PTT in detecting unsuspected bleeding disorders preoperatively was further obscured by the larger number of apparently false-positive results.