803 Study of Coagulation Factors in Patients with Mild Prolongation of Prothrombin Time: Implications for Neurosurgical Patients

Abstract

INTRODUCTION: The published data do not provide evidence-based guidance for use of preprocedure plasma therapy in patients with mild to moderate abnormalities of coagulation tests. The international normalized ratio (INR) is calculated from prothrombin time (PT) and is used to monitor coumadin therapy. However, it is frequently used erroneously to assess bleeding risk in patients who are not on coumadin. The purpose of this study was to correlate the levels of relevant clotting factors in patients with mild abnormalities of PT (INR). METHODS: Thirty-six patients with a mild prolongation of PT at 12.5 to 15 seconds (normal = 9–12.5 s; INR = 1.3–1.5) and normal partial thromboplastin time (PTT) (normal = 23–35 s) were treated by the Neurosurgery Service at Parkland Memorial Hospital between September 2003 and January 2004. Plasma levels of Factors (F) II, VII, and VIII (normal hemostatic levels >50%) were measured when requests for fresh-frozen plasma were received. The PT (INR) and PTT were correlated with factor levels. RESULTS: The median PT was 13.6 seconds (mean, 13.8 s), median INR was 1.38 (mean, 1.3), and median PTT was 30.5 seconds (mean, 32.8 s; range, 19.3–37.9 s). The median FII level was 66% (mean, 68%; range, 34 to 107%) The median FVII level was 51% (mean, 53%; range, 28 to 124%). There was no correlation between PT or INR with FVII levels (P ≤0.5). All patients had FVII levels greater than the 15–25% typically recommended as safe for surgery. FII, the precursor of thrombin, was also hemostatically normal, whereas median FVIII levels were elevated at 126% (mean, 156%; range, 55–547%). FVIII is an acute-phase reactant and a strong procoagulant factor, which is associated with shortened PTT in many patients. CONCLUSION: In patients with a mild prolongation of PT (INR), plasma levels of Factor II and VII were hemostatically normal, whereas FVIII was increased. Aggressive correction of mild elevation of PT (INR up to 1.5) may be unnecessary in patients with no evidence of continued bleeding. This may lead to fewer transfusion-related morbidities and help to conserve valuable blood products.