The effect of hydroxyethyl starch (HES) on different fibrinogen quantification methods in elective neurosurgery.

Sammanfattning: Background: Fibrinogen, a plasma protein essential for clot formation, can reach critically low levels during bleeding. The most commonly used method to determine fibrinogen is the photometric Clauss method. Intravenous colloid fluids can lead to falsely high values of fibrinogen when measured with the photometric Clauss method in comparison to an immunologic method. The main objective of this study was to investigate the effect of hydroxyethyl starch colloid on three different fibrinogen determination methods during elective neurosurgery. A secondary aim was to compare rotational thromboelastometry, which assess clot structure, with the immunologic fibrinogen method and compare these methods with intraoperative blood loss. Methods: Blood was collected from arterial catheters prior to surgery, after 1000 ml of starch, at end of surgery, and 3, 6 and 12 hours after surgery. A total of 30 patients scheduled for intracranial tumour extirpation were included after signed consent. Three different laboratory plasma fibrinogen quantification methods were assessed; two Clauss methods with photometric end-point determination using two different reagents (Multifibren U and Dade Thrombin) and one immunological assay (Zymutest Fibrinogen kit). Thromboelastometry was assessed with Maximum Clot Firmness. Results: 14 of 30 patients who received 1000ml starch were statistically evaluated in this preliminary report. Plasma fibrinogen concentrations, measured with the photometric Clauss method (Dade Thrombin reagent) were higher preoperatively as compared to the immunologic measured fibrinogen. Starch infusion did not increase this difference during or after surgery. Maximum Clot Firmness in the thromboelastometry correlated with the immunologic method (r=0.76); preoperatively only thromboelastometry predicted intraoperative bleeding (r=-0.37). Conclusion: In this first report on in vivo hydroxyethyl starch infusion effects on different photometric plasma-fibrinogen methods, no effect of starch was seen as compared to an immunologic assay. These results do not corroborate previous in vitro studies. Thromboelastometry correlated to the immunologic fibrinogen method, but better predicted blood loss.