Duplex screening as a method of quality assurance of perioperative thromboembolism prophylaxis

Improvements in thrombosis prophylaxis in both the operative and non-operative fields aim to reduce further the not inconsiderable residual risk of suffering a deep vein thrombosis or embolism. The goal of the study was to establish the part played in a quality assurance strategy by early diagnosis of a thrombosis and by knowledge of the hospital's internal patient-risk profile in order to counter the unpredictability of thromboembolic complications and make rational decisions about thromboembolism prophylaxis.

Duplex ultrasonography has been used routinely in trauma surgical patients in Krefeld Hospital since September 1991 as a screening method for diagnosing deep leg and pelvic vein thrombosis prior to mobilisation of the patients. 778 patients were investigated up to March 1997. In the period from September 1991 to September 1994, patients received standardised low-dose prophylaxis with unfractionated heparin (UFH). In October 1994, the prophylaxis regimen was modified by changing the anti-embolism stockings from bidirectional elastic stockings to transverse elastic graduated compression stockings (TED) and by adapting the dosage of the heparin prophylaxis to patient risk, with the use of low molecular weight heparin (LMWH) Certoparin (Mono-Embolex NM) since April 1995. All patients with a deep vein thrombosis were treated immediately with APTT-monitored full heparinisation and immobilisation.

In the period from September 1991 to March 1997, an asymptomatic deep vein thrombosis of the lower limbs was diagnosed in 68 cases (8.7%) out of 778 trauma surgical patients by means of routine duplex ultrasound. Using a strategy of duplex screening and immediate anticoagulation/immobilisation, no clinically significant pulmonary emboli occurred in this period. At the same time, the antithrombotic efficacy of the prophylaxis could be improved and assessed objectively by means of duplex screening: with optimal compression stockings and consistent use of risk-adapted UFH prophylaxis, it was possible to reduce the residual thrombosis rate, which was 11.5% (95% CI 7.7-15.2%) with standard UFH prophylaxis, to 8.7 % (95% CI 4.5-12.9%) and ultimately, using the combination of optimal anti-embolism stockings and LMWH prophylaxis, to 6.0% (95% CI 3.0-8.9%) which was significant (p<0.05). The cost-effectiveness analysis resulted in a cost-relation per successfully treated patient of about 1:100 for the diagnosis of a deep vein thrombosis using duplex ultrasound and subsequent heparin treatment compared to the diagnosis and intensive care treatment of a massive pulmonary embolism.

Duplex ultrasound screening for asymptomatic deep vein thrombosis thus proves to be a suitable instrument for internal hospital quality control in thrombosis prophylaxis. Its routine use can be recommended at least in high-risk patients, not only from the medicolegal aspect but also from the purely economic aspect.