Preoperative hypofibrinogenemia is associated with increased intraoperative bleeding in ruptured abdominal aortic aneurysms.

INTRODUCTION: Ruptured abdominal aortic aneurysm (rAAA) is associated with coagulopathy and intraabdominal hemorrhage. Fibrinogen acts as a key coagulation factor and has previously been suggested as a biomarker for increased perioperative bleeding in other surgical areas. The aim of the present study was to investigate fibrinogen and standard laboratory parameters and their association to preoperative hemodynamic status, intraoperative bleeding (IOB), and outcome in treatment of rAAA.
METHODS: This is a single university center retrospective cohort study of 91 consecutive patients with rAAA undergoing open surgery or endovascular aneurysm repair (EVAR) between 2008 and 2013. Patients were analyzed using the Swedish Vascular Registry (Swedvasc), and local hospital medical and laboratory records. Laboratory data analyzed included fibrinogen, hemoglobin, platelet count, prothrombin time ratio, activated partial thrombin time, and creatinine. Odds ratios (OR) with 95% confidence intervals (CI) were calculated in a logistical regression model.
RESULTS: In the study cohort (n = 91), median age was 74 (57-91) years; 80 % men; open surgical repair (n = 72; 77%); EVAR (n = 19; 23%). Median preoperative fibrinogen concentration was 1.8 g/L (IQR = 1.4) and varied significantly across bleeding groups: ≤1999 ml 2.3g/L, IQR = 1.4 (n = 35); 2000-4999 ml 1.6 g/L, IQR = 1.5 (n = 33); ≥5000 ml 1.4 g/L, IQR = 1.0 (n = 23) (P < 0.001). Preoperative fibrinogen concentration showed a linear relationship with preoperative blood pressure (r = .447, P = 0.01). When analyzing other preoperative laboratory values, only platelets showed a similar linear relationship with preoperative blood pressure (r = .247, P = 0.05). Patients with blood pressure <70 mmHg had an associated median fibrinogen concentration of less than 1.5 g/L (P = 0.001). In the multivariable logistic regression analysis, preoperative fibrinogen < 1.5 g/L [OR 10.0, CI (1.8-57.1), P = 0.009] was associated with IOB >2000 ml and preoperative blood pressure < 70 mmHg was associated with IOB >2 000 ml [OR 3.7, CI (1.1-12.6), P = 0.03] and >5000 ml [OR 5.2, CI (1.3-21.1), P = 0.02]. Low fibrinogen concentration (< 1.5 g/L) was associated with 30-day mortality in the univariate analysis but not in the multivariable logistic regression analysis.
CONCLUSION: Low preoperative fibrinogen concentration was significantly associated with preoperative hypotension and increased intraoperative bleeding in patients with rAAA. Patients in hemodynamic shock with blood pressure <70 mmHg had an associated fibrinogen concentration of less than 1.5 g/L. A fibrinogen concentration less than 1.5 g/L was associated with a ten-fold increased risk of intraoperative hemorrhage of more than 2000 ml.