Particulate embolization

Bioactive sorbents represent the simplest form of artificial cells already used in routine clinical applications for humans. Sorbents such as activated charcoal, resins, and immunosorbents could not be used in direct blood perfusion because particulate embolism and blood cells were removed. However, sorbents such as activated charcoal inside artificial cells no longer cause particulate embolism and blood cells removal. This application was developed and used successfully in patients. For example, the hemoperfusion device now used in patients contains 70 g of artificial cells. Each artificial cell is formed by applying an ultrathin coating of collodion membrane or other polymer membranes on each of the 100-p-diameter activated-charcoal microspheres. The mass transfer for this small device is many times higher than that for a standard dialysis machine. 

Particulate embolic agents are typically used for the embolization of tumor and tumor-related symptoms in addition to the treatment of certain hemorrhagic conditions. In general, these agents are administered from a selective position within the arterial vasculature of the target organ and are subsequently... 

Coils are available in a wide variety of sizes from 2 mm to 15 mm in size and are made from either stainless steel or platinum and may have Dacron fibers placed at right angles to the long axis of the coil to increase the surface area and thereby to increase the speed and permanence of thrombosis. In practice, most coils utilized in microcatheters are platinum and those in 4- to 5-F catheters, stainless steel. It should be noted that all coils are permanent devices and should be utilized when the desired occlusion is permanent. Coils should not be used in combination with particulate embolization for the treatment of tumors, as they will occlude the access for further treatment. Coils may, on the other hand, be utilized with Gelfoam embolization in the treatment of pelvic bleedings allowing the hemorrhage to be halted quickly and permanently. 

Choe DH, Moon HH, Gyeong HK, et al. (1997) An experimental study of embolic effect according to infusion rate and concentration of suspension in transarterial particulate embolization. Invest Radiol 32 260-267... 

Particulate embolization is an option when contrast extravasates and the bleeding branch is beyond the reach of superselective catheterization (Fig. 5.7). Non-calibrated polyvinyl alcohol particles (PVA) in sizes of 150-250 [i to 250-350 p or even larger should be used. The amount of particles should be kept as low as possible to avoid diffuse distal embolization. After each injection of 0.1-0.2 ml (up to a maximum of 1 ml) of a dilution of PVA, control arteriography should verify that the bleeding point has been... 

Bleeding from hypervascular tumors, such as duodenal metastasis of renal cell carcinoma, can be stopped by palliative particulate embolization (Fig. 5.8), although other authors preferred Gelfoam [88,89). 

Particulate embolization can also be applied pre-operatively for lesions requiring extensive surgery. As fast recanalization is expected, surgery should follow embolization with little delay. 

In case of high-risk (Borden II-III) DAVMs, particulate embolization as a sole treatment does not provide safe and permanent prevention from subsequent bleeding. If transarterial embolization is considered in such cases because neither surgery nor transvenous embolization is feasible or recommended, liquid embolics should be chosen (Fig. 4.21). Cyanoacrylate glue mixed with Lipiodol... 

Pierot L, Chiras J, Duyckaerts C et al (1993) Intracranial dural arteriovenous fistulas and sinus thrombosis. Report of five cases. J Neuroradiol 20 9-18 Pollock BE, Nichols DA, Garrity JA et al (1999) Stereotactic radiosurgery and particulate embolization for cavernous sinus dural arteriovenous fistulae. Neurosurgery 45 459-466 discussion 466-457... 

Chemoembolization has also been performed in an attempt to improve upon the results obtained with particulate embolization alone. Microencapsulated cisplatin particles (100 pm in diameter) were prepared at MDACC by a solvent evaporation technique and contained 46% by weight of cisplatin and poly(D,L)-lactide. In a 1 1 ratio of chemotherapeutic agent to capsular material, approximately 40% of the cisplatin was released within the first 4 h after delivery, as determined by in vitro studies. A Phase I/II Clinical study was performed at MDACC in 20 patients utilizing microcapsules containing cisplatin 100 mg/m as the maximum tolerated dose (MTD), delivered every 4-6 weeks. The median number of vascular occlusion procedures per patient was three. Of the 18 evaluable patients, 12 (67%) had a PR in their symptoms. Of the 15 patients with elevated 5-hydroxyindoleacetic acid, 11 (73%) had a median reduction of 64%. In 14 of 18 patients there was an objective decrease in the tumor, of which six (33%) were PR and eight (44%) were MR. One treatment-related death occurred from hepatorenal syndrome and five (25%) of the 20 patients died of the disease during the study (Diamandidou et al. 1998). 

One of the feared complications of deploying coils, injecting thrombin or glue, or infusing particulate embolics is nontarget embolization. Stringent technique to ensure satisfactory positioning... 

Spigos et al. [112] adopted a strict protocol that resulted in a remarkably low number of complications. The protocol included broad-spectrum antibiotics started 8-12 hours before the procedure and continued for 1-2 weeks, local antibiotics (such as gentamicin) suspended in the solution used to deliver the particulate embolic agents and administered through the angiographic catheter, strict attention to sterility (whole-body povidone-iodine bath or wide surgical scrub at the site of catheter insertion), selective catheterization with the catheter tip beyond pancreatic branches, effective pain control with narcotics or epidural anesthesia for 48 hours (which prevents the splinting that may... 

The stomach and duodenum have a rich collateral blood supply and hence embolization of branches of the coeliac axis can be performed with a low risk of infarction of the viscera. Conversely, the extensive vascular supply may make embolization more difficult to achieve. Thus, in addition to coils, a small particulate embolic agent is often required for a more distal block. A co-axial catheter system is likely to be necessary for this. The method of embolization depends on the angiographic findings but occlusion of the artery needs to be performed on either side of the abnormality (eroded artery or aneurysm) to achieve haemostasis. Ischaemia may be provoked... 

WEAR AND PARTICULATE EMBOLIZATION OF PROSTHETIC HEART VALVES... 

---