Postoperative deep vein thrombosis caused by intravenous fluids during surgery

Using a new method of measuring whole blood clotting time, we have confirmed the findings of others, that blood clots faster when diluted with saline. A prospective trial was designed to test the hypothesis that intravenous saline peroperatively causes hypercoagulation and increases the risk of venous thrombosis. Sixty patients admitted for routine laparotomy were randomly allocated to either a group receiving intravenous fluids during or after operation (Wet), or a group receiving no intravenous fluids (Dry). The Wet patients became significantly more haemodilute and hypercoagulable than the Dry (P < 0.001), and these changes correlated. A postoperative deep vein thrombosis occurred in 30 per cent of the Wet patients, but in only 7 per cent of the Dry (P < 0.05). The need for intravenous fluids during uncomplicated surgery is probably unproved, and their greater use may have contributed to the increasing prevalence of venous thromboembolism.