An elevated blood viscosity could lead to increased venous stasis and a higher incidence of post-operative deep vein thrombosis. Immediately preoperatively we have measured, using a Contraves low shear 2 viscometer, blood yield stress and viscosity at high and low shear rate in 28 general surgical patients. These patients were then screened by the standard I125 fibrinogen technique to detect the development of deep vein thrombosis post-operatively.13 patients developed a deep vein thrombosis. These patients had a significantly higher blood yield stress, corrected to a standard haemoerit of 45%, than the others (P < 0.01 students t). All other viscosity parameters were normal in these patients. Patients with malignant disease had a very high incidence of thrombosis (90%: 30%) and significantly higher yield stress values (mean 0.26 dynes/cm2: mean 0.194 dynes/cm2, P < 0.0005 students t) compared to patients with benign disease.We conclude that a high blood yield stress could be an important aetiological factor in thrombosis and the high values obtained in patients with malignant disease could partly explain the high incidence in these patients.
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