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Articles by N Rahe Meyer
Total Records ( 2 ) for N Rahe Meyer
  N Rahe Meyer , M Pichlmaier , A Haverich , C Solomon , M Winterhalter , S Piepenbrock and K. A. Tanaka
  Background

Bleeding diathesis after aortic valve operation and ascending aorta replacement (AV–AA) is managed with fresh-frozen plasma (FFP) and platelet concentrates. The aim was to compare haemostatic effects of conventional transfusion management and FIBTEM (thromboelastometry test)-guided fibrinogen concentrate administration.

Methods

A blood products transfusion algorithm was developed using retrospective data from 42 elective patients (Group A). Two units of platelet concentrate were transfused after cardiopulmonary bypass, followed by 4 u of FFP if bleeding persisted, if platelet count was ≤100x103 µl–1 when removing the aortic clamp, and vice versa if platelet count was >100x103 µl–1. The trigger for each therapy step was ≥60 g blood absorbed from the mediastinal wound area by dry swabs in 5 min. Assignment to two prospective groups was neither randomized nor blinded; Group B (n=5) was treated according to the algorithm, Group C (n=10) received fibrinogen concentrate (Haemocomplettan® P/Riastap, CSL Behring, Marburg, Germany) before the algorithm-based therapy.

Results

A mean of 5.7 (0.7) g fibrinogen concentrate decreased blood loss to below the transfusion trigger level in all Group C patients. Group C had reduced transfusion [mean 0.7 (range 0–4) u vs 8.5 (5.3) in Group A and 8.2 (2.3) in Group B] and reduced postoperative bleeding [366 (199) ml vs 793 (560) in Group A and 716 (219) in Group B].

Conclusions

In this pilot study, FIBTEM-guided fibrinogen concentrate administration was associated with reduced transfusion requirements and 24 h postoperative bleeding in patients undergoing AV–AA.

  D Bolliger , F Szlam , R. J Molinaro , N Rahe Meyer , J. H Levy and K. A. Tanaka
  Background

Replacement of fibrinogen is presumably the key step in managing dilutional coagulopathy. We performed an in vitro study hypothesizing that there is a minimal fibrinogen concentration in diluted whole blood above which the rate of clot formation approaches normal.

Methods

Blood samples from six healthy volunteers were diluted 1:5 v/v with saline keeping haematocrit at 24% using red cell concentrates. We measured coagulation factors and thrombin generation in plasma at baseline and after dilution. Thromboelastometry was used to evaluate (i) speed and quality of clot formation in diluted samples supplemented with fibrinogen 50–300 mg dl–1 and (ii) clot resistance to fibrinolysis. Diluted and undiluted samples with no added fibrinogen served as controls.

Results

Coagulation parameters and platelets were reduced by 74–85% after dilution. Peak thrombin generation was reduced by 56%. Adding fibrinogen led to a concentration-dependent improvement of all thromboelastometric parameters. The half maximal effective concentration (EC50) for fibrinogen replacement in haemodiluted blood was calculated to be 125 mg dl–1. Adding tissue plasminogen activator, 0.15 µg ml–1, led to a decrease of clot firmness and lysis time.

Conclusions

The target plasma concentration for fibrinogen replacement was predicted by these in vitro results to be greater than 200 mg dl–1 as only these concentrations optimized the rate of clot formation. This concentration is twice the level suggested by the current transfusion guidelines. Although improved, clots were prone to fibrinolysis indicating that the efficacy of fibrinogen therapy may be influenced by co-existing fibrinolytic tendency occurring during dilutional coagulopathy.

 
 
 
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