Jan T. Christenson

Surgical removal of an inferior vena cava thrombus

Studies on the management of inferior vena cava (IVC) thrombosis have rarely focused upon the risk of later development of post-thrombotic syndrome of the lower limbs. From 1983-1989, 52 patients with ilio-femoral thrombosis with an extension of thrombus into the IVC were treated. In addition to lower limb pain and swelling, 12 (23%) patients had symptomatic pulmonary embolism on admission. Perfusion/ventilation pulmonary scans were positive in 63%. Twelve patients received only anti-coagulant treatment. Thrombectomy was attempted in 40 patients, but failed in 13 patients due to old thrombi. Twenty-seven patients had surgical removal of thrombus combined with anti-coagulation [temporary arterio-venous fistula (AVF) and IVC interruption (n = 15); AVF alone (n = 9); and without fistula n = 3)]. The mortality and morbidity were low and hospital stay was not prolonged. Thirty-eight legs were examined at 7-66 months (mean: 23 +/- 3) after initial treatment. The limbs in which the IVC thrombus could not be removed (n = 20) were symptomatic in 25% of patients, venous ulcer developed in 4 of 20 limbs. The ilio-femoral segment was patent in only 35%. The thrombectomised limbs (n = 18) were asymptomatic in 56%; none had developed ulcer and iliac patency was 72%. Doppler investigations and refilling times were normal in 39% of the thrombectomised limbs. All patients without surgical IVC thrombus removal developed contralateral deep venous thrombosis during the follow-up period. This study shows that femoro-ilio-caval thrombectomy is successful only in patients with a short history and fresh clot, and can be safely performed with low morbidity and mortality.(ABSTRACT TRUNCATED AT 250 WORDS)

Compartment pressure following leg injury: the effect of diuretic treatment.

Acute ischaemia in the tibial compartments is a recognized complication of fractures, vascular injury, vascular surgery, crush injuries and burns. The tissue pressure was measured in the first week after injury and the effect of diuretics has been evaluated in a double-blind randomized manner. The pressure in the anterior tibial compartment was measured in the first week after injury in a double-blind randomized manner in 40 patients who had sustained either accidental or surgical injury of the leg. The pressure in the group treated with placebos increased by 20 per cent in the first 24 hours, whereas the pressure fell by 25 per cent in those treated with diuretics. Diuretic treatment is recommended for patients with injury of the lower limbs.

Direct platelet effect of low molecular weight dextran in small calibre PTFE grafts.

The thrombogenicity of synthetic vascular grafts is a major factor in occlusion of grafts when they are used to bypass small calibre arteries. In this paper, the effect of low molecular weight dextran (LMWD, Dextran-40) on graft surface-platelet interaction was studied using Indium-III-oxine labelled platelets. It was found that LMWD significantly reduced platelet deposition onto graft surfaces (P less than 0.001). Dextran had a direct antiplatelet effect independent of plasma volume expansion as dextran-soaked grafts significantly reduced platelet deposition when compared to systemic dextran administration (P less than 0.001). We therefore conclude that LMWD has a direct antiplatelet effect which is beneficial in reducing platelet deposition on synthetic PTFE grafts which may improve the early patency of such grafts.

Forskolin Impregnation of Small Calibre PTFE Grafts Lowers Early Platelet Graft Sequestration and Improves Patency in a Sheep Model

Synthetic vascular grafts have a thrombogenic surface which plays a role in graft failure. Systemic pharmacologic interventions have been used to lower platelet sequestration onto the graft surface but are associated with side effects. In this communication we describe the results of a new therapeutic principle of applying forskolin, a powerful cyclic adenosine monophosphate stimulator (cAMP) to the inner surface of PTFE vascular grafts. The grafts were evaluated with Indium-III-oxine labelled platelets and by graft patency on 3 consecutive days after implantation at 1 month and 3 months. Forskolin significantly lowered early platelet sequestration onto the treated graft surface when compared with controls. Graft potency at 1 and 3 months was also significantly higher in the forskolin treated grafts.

Hyperpressure in the trapezius muscle associated with fibrosis

The intramuscular pressure at rest and during load in 25 symptomatic trapezius muscles was found to be higher than in 32 asymptomatic muscles. Operative findings in 4 patients revealed dense fibrosis around the muscle, including the accessory nerve, which might explain the increased intramuscular pressure. Fibrotic tissue release resulted in the relief of symptoms and normalized pressure both at rest and during load. We believe trapezius fibrosis may be a new entity to include in the neck-shoulder syndrome.

Distal embolisation from the surface of PTFE grafts in vivo and the effect of low molecular weight dextran

Platelet deposition onto the surface of biomaterial is an important component of the interaction between blood and a synthetic arterial graft. Once platelet deposition has occurred, the possibility of distal embolisation exists. Using PTFE interposition femoral grafts and Indium-III-levelled autologous platelets in 16 adult sheep we have studied platelet uptake onto the graft surface using a gamma camera. Radioactivity in the legs was measured by a miniature cadmium-Telluride counter and blood flow was simultaneously recorded. In 8 animals low molecular weight dextran (LMWD) was infused intravenously. It was found that platelet deposition onto PTFE grafts was significantly lower in the LMWD treated group than in controls (P less than 0.001). These differences were confirmed by histological examination and in vitro measurement of graft activity. Furthermore, distal embolisation was frequently seen in both groups with a simultaneous drop in graft activity seen in both groups with a simultaneous drop in graft activity with an increased activity in the peripheral circulation. This distal embolisation was less pronounced in the LMWD treated group.

Subcutaneous and intramuscular pressures in the post-phlebitic limb

The mechanisms of pain in patients with chronic iliac vein obstruction and venous claudication is not fully understood. Ten patients with severe to moderate unilateral post-thrombotic syndrome with chronic iliac vein obstruction were studied. Subcutaneous tissue pressures and intramuscular pressures were measured using the slit-catheter technique in both legs, at rest and during exercise. The subcutaneous tissue pressure was higher, but not significantly higher, in the leg with iliac vein obstruction, +2 (-2 to +10) mmHg, than in the contralateral healthy legs, 0 (-4 to +4) mmHg in supine position at rest. During exercise in the standing position the subcutaneous tissue pressure rose significantly (p less than 0.01) in the diseased leg to 9 (+4 to +15) mmHg, while no such increase was seen in the control limb, 0 (-4 to +4) versus -1 (-5 to +4) mmHg. The intramuscular pressures were significantly higher (p less than 0.01) in the leg with iliac vein obstruction 26 (15 to 42) mmHg, than in the control leg, 11 (1 to 15) mmHg at rest in supine position as well as during exercise in standing position, 64 (35 to 82) mmHg and 26 (10 to 36) mmHg, respectively.

Leucocyte sequestration in endotoxemia and the effect of low-molecular-weight dextran

Leucocyte sequestration in various organs during endotoxin-induced shock in sheep was studied using leucocytes labelled with indium 111 oxine. A moderate dose ofEscherichia coli endotoxin (10 μg/kg body weight) was slowly infused intravenously in 16 sheep, 9 of which subsequently received a continuous i.v. infusion of low-molecular-weight dextran (LMWD) given at an infusion rate of 15 ml/h over 4 h, starting 30 min after administration of the endotoxin. By that time, signs of acute lung injury had developed, thus mimicking a clinical situation. The remaining animals were untreated and served as controls. A marked increase in lung, liver and kidney leucocyte sequestration, together with a sharp, corresponding drop in splenic activity and leucocyte count in peripheral blood, occurred shortly after the endotoxin infusion in both groups. However, after 90 min there was a significantly lower leucocyte activity in the lungs, liver and kidneys of LMWD-treated animals as compared with controls. Less marked hemodynamic and respiratory alterations were also observed in animals treated with LMWD. The present study confirms previous reports that significant leucocyte sequestration in the lungs occurs early during endotoxemia. Furthermore, we found that leucocyte sequestration also occurs in the liver and kidneys, which could explain the development of multi-organ failure, frequently described in clinical sepsis. Even after injury to organs, LMWD infusion seems to be beneficial by significantly lowering leucocyte sequestration and could therefore be justified as an addition to the arsenal of interventions used in the treatment of endotoxemia.

Microcalorimetric Measurements of Platelet Metabolism After Synthetic Arterial Bypass Procedures in Sheep and the Effect of Low Molecular Weight Dextran

The overall metabolic activity in platelets after vascular grafting procedure with polytetrafluoroethylene arterial grafts was studied in 18 sheep by use of microcalorimetric measurements. It was found that the heat production (P) from platelets was abnormally low in grafted animals, P=51±8 fW/cell com pared with nongrafted controls, P=60±11 fW/cell, p < 0.001 (fW = 10-15 W). When low molecular weight dextran (LMWD) was given, a significantly higher heat production was observed, P =132 ± 6 fW/cell, thus suggesting a direct platelet effect by the dextran. Platelet aggregation response was decreased after grafting without statistically significant differences between grafted control ani mals and LMWD-treated animals. After the grafting procedure, a drop in platelet count was noted, but it was less pronounced in the LMWD-treated group.