[Routine screening with APTT is not indicated before surgery]. / Rutinmässig screening med APTT är inte indicerad före operation.

Activated partial thromboplastin time (APTT) is widely practiced in preoperative screening. The value of using this test to predict the risk of perioperative bleeding is not well documented in Sweden. In this article, a literature review is performed to determine whether unselected APTT testing can predict abnormal perioperative bleeding. The current literature does not support coagulation screening with APTT in routine perioperative bleeding assessment, as preoperative screening with APTT has a low sensitivity for detection of clinically significant bleeding disorder. While a comprehensive bleeding history is crucial, the APTT test should only be performed on patients with a history of increased bleeding tendency. The conclusion of this literature review is that patients with a negative bleeding history do not require routine screening with APTT prior to surgery, which, if implemented, would lead to a more cost-effective perioperative routine.

Effects of the oral, direct factor Xa inhibitor edoxaban on routine coagulation assays, lupus anticoagulant and anti-Xa assays.

Edoxaban is an oral direct factor Xa inhibitor for prophylaxis and treatment of thromboembolic disorders. The effects on common coagulation assays are clinically valuable information and in certain clinical situations a quick assessment of the anticoagulant is wanted. Our aim was to investigate the effect of edoxaban on routine coagulation methods and evaluate anti-Xa assays, commonly used for other direct factor Xa inhibitors, for estimation of the drug concentration. Edoxaban was spiked to plasma samples from healthy subjects in the concentration range 0-742 µg/L and analyzed using different reagents for activated partial thromboplastin time (APTT) and prothrombin time (PT). Assays for antithrombin, activated protein C resistance, lupus anticoagulant (LA) and chromogenic anti-Xa assays were also included. Edoxaban displayed similar effects in vitro to other oral direct Xa inhibitors. The concentration needed to double the coagulation time varied between assays and reagents; 539-758 µg/L for the APTT and between 329 and 2505 µg/L for the PT. Edoxaban gave false high antithrombin activities in assays based on Xa-inhibition. Two integrated assays for LA, both based on activation with dilute Russell's viper venom, displayed different results. Chromogenic anti-Xa assays displayed linear dose-response curves with edoxaban up to approximately 500 µg/L. In conclusion, therapeutic concentrations of edoxaban variably affect different coagulation assays, and even different reagents within an assay group. In comparison with other oral Xa-inhibitors, the in vitro effects of edoxaban were more similar to rivaroxaban than apixaban. For measurement of edoxaban concentration in plasma, it is possible to use the chromogenic anti-Xa assays.

Effects of fibrinogen and platelet supplementation on clot formation and platelet aggregation in blood samples from cardiac surgery patients.

INTRODUCTION: Bleeding after cardiac surgery may be caused by surgical factors, impaired haemostasis, or a combination of both. Transfusion of blood products is used to improve haemostasis, but little is known about what combination is optimal. We hypothesized that addition of both fibrinogen and platelets to blood samples from cardiac surgery patients would improve clot formation and platelet aggregation to a greater extent than if the components were added separately. MATERIALS AND METHODS: Increasing doses of fibrinogen concentrate (+0.5, 1.0, and 1.5 g · l(-1)) and/or platelet concentrate (+46, 92, and 138 × 10(9) platelets l(-1)) were added to postoperative blood samples from 15 cardiac surgery patients. Clot formation was assessed with rotational thromboelastometry and platelet aggregation was assessed with multiple-electrode aggregometry before and after addition of the blood products. The effects of the different additives were compared. RESULTS AND CONCLUSIONS: Ex vivo supplementation with fibrinogen or platelet concentrate resulted in significantly shortened clotting time and improved clot strength in a dose-dependent manner. Combination of fibrinogen and platelets further improved the clotting time and strength. Platelet supplementation enhanced platelet aggregation in a dose-dependent manner while fibrinogen had no or reducing effect. Combining fibrinogen and platelets improved platelet aggregation less than the use of platelets alone. In conclusion, combined platelet and fibrinogen supplementation of blood samples from cardiac surgery patients had an additive effect on clot formation compared to the individual components, but it resulted in less platelet aggregation than with platelet supplementation alone. These results may have implications for clinical transfusion protocols.