Prolonged prophylaxis with dalteparin to prevent late thromboembolic complications in patients undergoing major abdominal surgery: a multicenter randomized open-label study.

BACKGROUND: Patients undergoing major abdominal surgery carry a high risk of venous thromboembolism (VTE), but the optimal duration of postoperative thromboprophylaxis is unknown. OBJECTIVES: To evaluate the efficacy and safety of thromboprophylaxis with the low molecular weight heparin (dalteparin), administered for 28 days after major abdominal surgery compared to 7 days' treatment. PATIENTS/METHODS: A multicenter, prospective, assessor-blinded, open-label, randomized trial was performed in order to evaluate prolonged thromboprophylaxis after major abdominal surgery. In total, 590 patients were recruited, of whom 427 were randomized and received at least 1 day of study medication, and 343 reached an evaluable endpoint. The primary efficacy endpoint was objectively verified VTE occurring between 7 and 28 days after surgery. All patients underwent bilateral venography at day 28. RESULTS: The cumulative incidence of VTE was reduced from 16.3% with short-term thromboprophylaxis (29/178 patients) to 7.3% after prolonged thromboprophylaxis (12/165) (relative risk reduction 55%; 95% confidence interval 15-76; P=0.012). The number that needed to be treated to prevent one case of VTE was 12 (95% confidence interval 7-44). Bleeding events were not increased with prolonged compared with short-term thromboprophylaxis. CONCLUSIONS: Four-week administration of dalteparin, 5000 IU once daily, after major abdominal surgery significantly reduces the rate of VTE, without increasing the risk of bleeding, compared with 1 week of thromboprophylaxis.

Three dimensional visualisation of velocity profiles in the normal porcine pulmonary trunk.

OBJECTIVE: The aim was to obtain detailed data of velocity profile development in the porcine pulmonary trunk. METHODS: Hot film anemometry was used for point blood velocity measurements in the entire cross sectional area one diameter downstream of the normal porcine pulmonary valve. Computerised three dimensional visualisations of the spatial and temporal development of blood velocity profiles were made. Measurement series were conducted under spontaneous and stressed haemodynamic conditions in 16 pigs with a body weight of approximately 90 kg. RESULTS: The velocity profiles revealed consistent temporal and spatial development characteristics. In the systolic acceleration phase the profile was flat, but during peak systole an initially counterclockwise rotation was seen; subsequently the profile turned clockwise and ultimately counterclockwise to become flat during early and late systolic deceleration phases. CONCLUSIONS: These skewed, rotating velocity profiles are in conflict with the generally accepted assumption that the velocity profile in the pulmonary trunk is flat. The rotating skewness of the velocity profile in the porcine pulmonary trunk has not been described before. The reason for the rotating velocity profile is obscure.

Studies by pulsed Doppler ultrasonography of velocity fields downstream of graded stenoses on the abdominal aorta in pigs.

PURPOSE: To investigate local hemodynamics downstream of arterial stenoses, a perivascular five-element Doppler ultrasound transducer was used for registration of one-dimensional velocity profiles and estimation of Reynolds (turbulent) normal stresses downstream of smooth, graded stenoses on the abdominal aorta in six 90 kg pigs. METHODS: Blood velocities were registered by a 10 MHz pulsed Doppler velocimeter that used a modified zero-crossing detector with an upper -3 dB cutoff frequency of 200 Hz. Signal analysis included ensemble averaging, turbulence analysis, and dimensional visualization of velocity profiles. RESULTS: Velocity profiles downstream of minor (< or = 40%) and moderate (40% to 65%) stenoses were skewed with the highest systolic velocities toward the anterior vessel wall and diastolic flow reversal occasionally present at the posterior vessel wall. Immediately downstream of severe (> or = 65%) stenoses a prominent poststenotic jet and systolic recirculation zones were present. Further downstream, vortices and eddies dominated the flow field. Reynolds normal stresses were highest at locations in the velocity field with high-velocity gradients corresponding to the parajet zone. CONCLUSIONS: The present study demonstrated that pulsed Doppler ultrasonography can provide detailed and quantitative information of flow phenomena such as jetlike flow, vortices, and recirculation zones in a poststenotic flow field in the abdominal aorta.