In a randomized controlled clinical trial, the efficacy and safety of two low molecular weight heparin ( LMWH ) fractions in the prophylaxis of deep vein thrombosis (DVT) were assessed. One hundred twenty-six patients undergoing major abdominal surgery received alternatively 2,500 APTT units b.i.d. of two LMWH fractions or 5,000 APTT units b.i.d. of an unfractionated sodium mucosal heparin ( UFH ). LMWH 2 differed from LMWH 1 by presenting a lower mean molecular weight and a higher anti-Xa/APTT ratio in vitro. Patients were randomly allocated to the three groups, and the development of DVT was studied with the 125I-fibrinogen uptake test ( RFUT ). The study was interrupted and the code broken prematurely because of otherwise unexplainable bleeding events. While no thrombosis and no severe bleeding were detected in the UFH group, three (7%) RFUT -positive DVT and two (5%) hemorrhagic complications occurred in the LMWH 1 group. No thrombosis and nine (22%) cases of severe bleeding were observed in the LMWH 2 group. Thus, the latter group differed significantly from the control group with regard to subjective and objective criteria for postoperative bleeding. Although these results do not allow general conclusions as to the value of LMWH fractions in the prevention of DVT, they indicate that these preparations just as ordinary heparin have a limited therapeutic range.
The purpose of this experimental study was to compare two methods of pulmonary blood flow manipulation during one-lung ventilation (OLV), either reducing pulmonary blood flow to the non-ventilated lung by inflation of a pulmonary artery catheter balloon (PAB) or by infusion of prostaglandin F2 alpha (PGF2 alpha). Seven anaesthetized dogs were intubated with a Kottmeier endobronchial tube and ventilated with 66% O2. Systemic and pulmonary pressures and blood gases, cardiac output and airway pressure were measured, and the venous admixture (QSP/QT) was calculated. During two-lung ventilation (TLV) Pao2 was 43.6 +/- 1.9 kPa (mean +/- s.d.) and (QSP/QT) was 11 +/- 3%. OLV reduced Pao2 to 12.1 +/- 1.6 kPa (P less than or equal to 0.001) and increased QSP/QT to 40 +/- 4% (P less than or equal to 0.001). Mean pulmonary artery pressure and airway pressure increased. PAB inflation caused an increase in Pao2 to 19.9 +/- 2.9 kPa (P less than or equal to 0.02) and a decrease in QSP/QT to 27 +/- 6% (P less than or equal to 0.001). PGF2 alpha infusion (1.2 micrograms kg-1 min-1) into the pulmonary artery of the non-ventilated lung increased Pao2 to 22.4 +/- 3.3 kPa (P less than or equal to 0.001) and decreased QSP/QT to 25 +/- 4 (P less than or equal to 0.001). PGF2 alpha infusion resulted in a small increase in mean systemic and pulmonary artery pressures. During the infusion of 1.2 micrograms kg-1 min-1 of PGF2 alpha no signs of bronchoconstriction were observed. PAB inflation and PGF2 alpha infusion were equally effective in improving oxygenation and reducing venous admixture during OLV.(ABSTRACT TRUNCATED AT 250 WORDS)
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