Impedance plethysmography in the diagnosis of asymptomatic deep vein thrombosis in hip surgery. A venography-controlled study.

We prospectively evaluated the accuracy of computerized impedance plethysmography (CIP) in the diagnosis of asymptomatic deep vein thrombosis (DVT) in 246 consecutive high-risk patients scheduled for hip surgery, with bilateral venography used for comparison. The CIP was performed as a surveillance program every third day. If the CIP remained negative, bilateral venography was performed on postoperative day 10 +/- 1 or on day of treatment 14 +/- 1 in nonoperated-on patients. If the CIP became positive, venography was performed within 24 hours. The sensitivity and specificity of CIP for proximal and distal DVT were 19% (confidence interval [CI], 13% to 24%) and 91% (CI, 87% to 94%), respectively. The positive and negative predictive values were 52% (CI, 38% to 65%) and 70% (CI, 65% to 74%), respectively. The sensitivity and specificity of CIP for proximal DVT were 24% (CI, 13% to 34%) and 90% (CI, 87% to 94%), respectively; the positive and negative predictive values were 31% (CI, 20% to 51%) and 87% (CI, 83% to 90%), respectively. We conclude that, because of its low sensitivity, CIP cannot be used in the surveillance of DVT in high-risk patients or for outcome measurements in clinical trials on DVT prophylaxis.

Clinical outcome of orthopaedic patients with negative lower limb venography at discharge.

Pharmacological prophylaxis for postoperative venous thromboembolism is generally restricted to the hospital stay. A high incidence of deep vein thrombosis (DVT) and pulmonary embolism presenting after hospital discharge has been reported and thus it has been claimed that pharmacological prophylaxis should be continued after discharge. The aim of this study was to perform a prospective survey to assess the prevalence of clinically overt thromboembolic events in hip surgery patients discharged with a negative venography without further pharmacological prophylaxis. We followed-up 213 patients with negative venography at discharge (105 elective hip replacement and 108 hip fracture patients). 186 patients (87.3%) were re-examined as outpatients one to two months after discharge. Five patients reported symptoms of DVT but the diagnosis was not confirmed by objective testing. The remaining 27 patients (12.7%) were followed up through their family doctor or by telephone call; in these patients the follow-up period ranged from 60 days to 2 years. Twenty-two patients (10.3%) were still alive and reported no signs or symptoms of venous thromboembolism. Three patients (1.4%) died for reasons not correlated with venous thromboembolism. Two patients could not be traced due to geographical inaccessibility; they were still alive after 1 year according to the records of their health care district. The results of our study suggest that in hip surgery patients with negative venography the prevalence of clinically overt thromboembolic events after hospital discharge ranges from 0 to 2.2% (95% C.I.). It is conceivable that the majority of late presenting postoperative DVT actually develop during the hospital stay and become symptomatic after hospital discharge.

A randomised, double-blind, placebo-controlled trial of dermatan sulphate for prevention of deep vein thrombosis in hip fracture.

Dermatan sulphate (MF 701) is a natural glycosaminoglycan that catalyses thrombin inhibition by heparin cofactor II. The aim of the study was to evaluate the efficacy and safety of MF 701 for prevention of deep vein thrombosis (DVT) in patients with hip fracture. A randomised, double-blind, placebo-controlled design was used to assess two dose regimens of MF 701 in two consecutive study phases. Treatment was started within 48 h from the trauma and continued for 14 days for non-operated patients or until the 10th postoperative day. Bilateral mandatory venography was used to assess the end-point. Eighty patients were included in the first phase (40 MF 701, 40 placebo). MF 701, 100 mg IM b.i.d., did not reduce incidence of DVT from that on placebo and did not induce any bleeding. In the second phase 126 patients were included, with a randomisation ratio of 2:1 (84 MF 701, 300 mg IM b.i.d., 42 placebo). Bilateral venography was obtained for 110 patients. The incidence of DVT was 64% (23/36) in the placebo group and 38% (28/74) in the MF 701 group (p = 0.01; odds ratio [OR] = 0.34, 95% confidence limits [CL] = 0.15-0.80p; proximal DVTs were 42% (15/36) and 20% (15/74), respectively (p = 0.02; OR = 0.36, CL = 0.15-0.89). No significant differences were found in haemorrhagic complications (2.4% in each group), blood loss from drains, blood transfusions, haemoglobin and haematocrit values. This study is the first demonstration that dermatan sulphate is a clinically effective antithrombotic agent without bleeding effects. It also provides evidence of the biological role of heparin cofactor II.