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

The use of intraoperative monitoring and treatment of symptomatic microemboli in carotid artery stenting: case report and discussion

Carotid artery stenting is a recently introduced treatment in symptomatic atherosclerotic carotid artery disease with acceptable complication rates. The major risk is perioperative embolic stroke. Transcranial Doppler ultrasonography (TCD) can be used to identify embolic signals and guide therapy. We present a case of symptomatic embolization in a 72-year-old female following carotid stent deployment complicated by haemodynamic changes. Despite concurrent dual antiplatelet medication significant symptomatic embolization occurred even after restoration of the blood pressure, and modulation of the rate of embolization was achieved using dextran-40 guided by TCD monitoring. The patient recovered from an initially profound hemiparesis and dysphasia to minor sensory changes. Microemboli are common following carotid artery stenting and there appears to be a threshold phenomenon associated with prolonged embolization and progression to cerebral infarction. TCD can be used to detect particulate microemboli and therefore may be useful in guiding antithrombotic therapy in this setting. Dextran-40 has been shown to reduce the embolic load following carotid endarterectomy and was used to good effect in this patient in terms of both embolic load and clinical outcome. This is the first case of embolization following carotid stenting successfully treated with dextran-40, and offers a further option for therapeutic intervention in microembolism detected by TCD and stresses the importance of perioperative monitoring of embolic load for postoperative stroke risk.

Dextran reduces embolic signals after carotid endarterectomy

One hundred fifty patients undergoing carotid endarterectomy were randomly assigned to receive intravenous 10% dextran 40 or placebo. Transcranial Doppler monitoring of the ipsilateral middle cerebral artery 0 to 1 hour postoperatively detected embolic signals in 57% of placebo and 42% of dextran patients, with overall embolic signal counts 46% less for dextran (p = 0.052). Two to 3 hours postoperatively, embolic signals were present in 45% of placebo and 27% of dextran patients, with embolic signal counts 64% less for dextran (p = 0.040). We conclude that dextran reduces embolic signals within 3 hours of CEA.

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.