TITLE: ACT MEASUREMENT WITH HEPCON/HMS^® DUE TO BLOOD SAMPLE DILUTION

AUTHORS: Doi Yumiko, MD, Makoto Kosaka, MD, Kiyoshi Morita, MD, Masahisa Hirakawa, MD
AFFILIATION: Okayama University, Okayama, Japan.

INTRODUCTION: We measured activated coagulation time (ACT) with three different devices Hemochron^® (Hem), Sono-clot(Son)^® and Hepcon/HMS^® (Hep) in 14 cardiopulmonary bypass (CPB) cases of pediatric congenital heart surgery (Age:1 month to 8 years, Body Weight:10.4±5.43 kg). We found that, after heparin administration, ACTs of many samples were markedly prolonged (>999 sec.): 4 cases with Hem, 5 cases with Son and 9 cases with Hep. The 9 cases with Hep still displayed prolonged ACT (>999 sec.) after the protamine reversal period. The purpose of this study is to evaluate the influence of hemodilution on measurement of ACT with the above three devices.
METHODS: Blood samples were offered by five healthy adult volunteers (Age:31.8±7.52 years, Body Weight:68.2±12.37 kg).The blood samples were diluted with lactate Ringer's solution. The dilution rates of blood to solution were 1:1,1:3,1:4,1:7. Control samples (undiluted blood) and the diluted samples were measured with the above three devices. The plasma fibrinogen concentration was measured with Du Pont(r) aca star(tm).
RESULTS: The ACT for undiluted blood samples was 130.1 ±11.72 sec. (mean±SD) and there were no significant differences between the ACTs of the three devices. For dilution rates greater than 1:1,the plasma fibrinogen concentration decreased below 50 mg/dl. Of the three devices, only Hep showed prolonged ACTs (>999 sec.): 1 case at dilution 1:3, 3 cases at dilution 1:4 and 5 cases at dilution 1:7.
DISCUSSION: In the testing cuvette of Hep, 0.4 ml of blood sample is mixed with 0.1 ml of buffer liquid. This causes even more dilution in the blood samples, which have already been excessively diluted by CPB solution in pediatric cardiac surgery. This is the reason why Hep is less able to detect coagulation than the other two devices.