McEvoy, A.W.; (2005) Haemostatic studies in subarachnoid haemorrhage. Doctoral thesis , University of London.

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Abstract

Object. The primary objective of this thesis was to establish the pattern of change in haemostatic systems in patients following a subarachnoid haemorrhage (SAH). I hypothesise that following a SAH there is an undefined period of increasing hypercoagulability, which if present would predispose to ischaemic stroke. Methods. This was a prospective, observational study on 67 consecutive patients admitted with a primary diagnosis of SAH. There were 24 males, median age 47.5 years (25-75) and 43 females, median age 53 years (23- 80). Blood was taken at 4 time periods (<48hours, 4-5, 9-10 and 15-16 days) following the ictus depending on the day of hospital admission, and on regular intervals during the hospital stay. In addition, a sample was taken at 3 months from the ictus. A Thromboelastograph (TEG) profile performed at 37 C, and the routine coagulation studies, International Normalised Ratio (INR) and Activated Partial Thromboplastin Time Ratio (APTR) were obtained at each of these time points. In addition a full blood count, biochemical profile, and plasma for coagulation and fibrinolytic assays was also taken. Results. The results demonstrated that SAH patients were hypercoagulable immediately following the ictus, when compared with the blood sample taken 3 months later. In addition we observed the development of an increasingly hypercoagulable state for the first 21 days following the ictus. This increase in coagulation was demonstrated against a background of haemodilution during this time. Conclusions. This highly significant data demonstrates that SAH patients become increasingly hypercoagulable over time (maximum 21 days) following the ictus. This prothrombotic tendency has reversed by 3 months. This may provide a new direction in the treatment of symptomatic vasospasm. In addition, an in-vitro study using TEG has been performed in 20 volunteer subjects to assess whether haemodilution 'per se' has an intrinsic affect on coagulation specific to the dilutent itself. This study demonstrates that haemodilution does alter coagulation profiles measured using TEG. Different crystalloid and colloid fluids used to achieve haemodilution produce qualitatively consistent but quantitatively very different effects on coagulation in-vitro.

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