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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_3869_Библиотеки_им_академика_М_И_Перельмана.pdf
4 Temporary Embolic Agents 47
• Not a good agent for GI bleeding, because of the real risk of non-target bowel
necrosis. Rarely, situations can arise where a major coagulopathy or uremia may
make proximal control of bleeding unsuccessful, necessitating more distal, highorder embolization in massive GI hemorrhage, etc.
• Should NOT be used in individuals with high arteriovenous fistula
potential.
Detecting Problems
• Of all the three gelatin agents, powder results in the most distal level of embolization, beyond most collateral vessels and therefore may result in more severe
ischemia.
• As with all gelatin sponge products, an idiopathic, temporary rise in temperature
can sometimes be seen (as high as 39
This post-embolization fever will often resolve spontaneously with blood cultures
and WBC count remaining unremarkable.
◦
C) and may persist as long as 1–2 days.
Pledgets
Physical Description and Properties
• Purified pork skin, packaged into sterile sheets.
• Sizes can be tailored. Typical sizes for Gelfoam cubes range in size from 0.5 to
2.0 mm. Typical pledget sizes are 1 × 2 × 5 mm rectangles. Torpedos can be
formed for tailored proximal occlusion, but typically are 3–4 mm in size.
Mode of Action
• Off-label use, but considered standard of care.
• Mechanical, temporary occlusion that can be tailored to occlude medium and
larger sized vessels or tissue tracts.
• Inflammation of vessel wall and superimposed thrombosis are also likely contributors.
• As with all gelatin sponge products, recanalization can occur in a matter of days
and take as long as 4–6 weeks.
How to Prepare and Use It
• Cubes, pledgets, and torpedoes are cut from the gelatin sponge and may be soaked
in contrast to improve fluoroscopic visibility. Remove the plunger from the tube
of the syringe, load the cube, pledget, or torpedo as desired. Replace the plunger.
• Deliver with contrast to facilitate transfer through the catheter and visibility.
48 M. Brinckman
• Delivery syringe sizes of 1–3 ml are typical with a Luerlock tip that keeps the
syringe from dislodging from the catheter during injection.
• Following syringe preparation, the tip should be kept up to keep the agent in the
leading part of the delivery and prevent aggregation if suspended cubes are used.
• If a slightly longer lasting occlusion is desired, then the contrast/saline/Gelfoam
mixture can be mixed with -aminocaproic acid.
• Agent should be delivered until antegrade flow ceases. Further injection risks
reflux and/or non-target embolization.
• Larger pledgets and torpedoes can be delivered and placed with lodging in the
natural taper of the vessel and therefore must be appropriately sized.
• Smaller cube/contrast solutions are often best delivered in a pulsatile fashion.
• When large vessel occlusion is beyond the upper limit of tailored torpedo capa-
bility alone (e.g., transected vessel from trauma), a coil may be used as a scaffold
or backstop on which Gelfoam can be packed (“coil-Gelfoam sandwich”).
When and When Not to Use It
• As with all temporary agents, other agents should be considered if long-term
occlusion is required.
• Widely used in gastrointestinal bleeding, early post-partum hemorrhage, and
trauma, particularly pelvic trauma.
• Good agent for use to occlude percutaneous biopsy tracks.
Detecting Problems
• Reflux or non-target embolization can generally be precluded with direct angiographic visualization during delivery.
• If reflux or non-target embolization does occur, then suction embolectomy can be
considered.
• Gelfoam embolization may result in a temporary, idiopathic fever. This should
only last 1–2 days and culture/white count are usually unremarkable.
• Detection of air in the biopsy track following Gelfoam placement is usually airtrapped in the pledgets and not of significant concern.
Microfibrillar Collagen
Commercially sold as Avitene.
Physical Description and Properties
• Derived from bovine hide collagen.
• Dry, thinly shredded flakes packaged in 1–5 g containers.
• Fiber size: 5 × 70–200 μm.
4 Temporary Embolic Agents 49
Mode of Action
• Avitene is a potent thrombogenic agent that causes occlusion by mechanical
means, but unlike gelatin sponge, has been demonstrated to cause a granulomatous arteritis.
• The granulomatous reaction is followed by fibrosis as the inflammation subsides
at 3 months.
• Recanalization begins in roughly a week and may take up to 8 weeks.
How to Prepare and Use It
• Roughly 0.5 g of microfibrillar collagen is mixed with 10 ml of contrast to form
a semi-liquid suspension (applesauce consistency).
• 0.1–1.0 ml can be injected through a microcatheter or catheter delivery system
followed by ~5 ml; a saline bolus chaser to flush the catheter, advance embolus,
and prevent catheter occlusion.
When and When Not to Use It
• Avitene is suitable for tumor embolization, where a high order of occlusion for
hemostasis during surgery is desired.
• Not suitable for GI embolization, for reasons similar to Gelfoam powder. The
distal third- or fourth-order vessel occlusion increases risks for inadvertent
gastrointestinal ischemia.
Detecting Problems
• Catheter occlusion—the potent thrombogenic nature and consistency of the
suspension may lend itself to occlusion. This can be avoided by a saline
bolus and exchanging the delivery catheter using a guide catheter or sheath
system.
• Reflux/non-target embolization –
◦ Stop short of complete embolization of target and/or if any reflux is
noted.
◦ Consider a balloon occlusion catheter delivery system to prevent significant
reflux.
◦ Consider other agents if the risk of ischemia beyond collateralization out-
weighs any benefit of using microfibrillar collagen (e.g., GI embolization).
50 M. Brinckman
Keypoints
1. Temporary embolization agents are most beneficial when a vessel can
safely be sacrificed but permanent occlusion is not necessary (e.g.,
trauma).
2. Temporary agents may result in permanent vascular damage even though
they are resorbed.
3. All temporary agents are non-radioopaque, and as such should be mixed
with contrast material for injection.
4. When used correctly and in the right clinical circumstances, temporary
agents are easy, quick, and cheap to use.
Chapter 5
Liquid Embolic Agents
Kimi Kondo
It is easy to understand how particles, coils, and other solid agents can lead to vascular occlusion. Liquid embolic agents can also be very effective at occluding vessels
and act by a variety of mechanisms.
• Sclerosant agents: e.g., absolute alcohol, sodium tetradecyl sulphate (STD)
• Glues: N-butyl cyanoacrylate (NBCA)
R
• Elastic polymers: ethylene vinyl alcohol/dimethyl sulfoxide (Onyx
• Iodized poppy seed oil droplets: lipiodol
Liquid agents pose particular challenges and are perhaps the hardest embolic
agents to use. They can be very unforgiving as there is little to no control once they
start to flow away from the delivery catheter.
)
Sclerosing Agents
• They include the following:
◦ Detergent agents
◦ Hyperosmolar agents
◦ Chemical irritants
• Sclerosants act by damaging endothelial cells.
• Many chemicals can achieve this; to realize how effective this can be, one only
has to think about the obliteration of veins in an intravenous drug abuser or patient
receiving chemotherapy.
• When using sclerosants, the intention is to destroy the endothelium to expose
subendothelial tissues which in turn will lead to irreversible vascular fibrosis.
• The sclerosant effect will depend on the following:
◦ The strength of the agent
◦ The time it is in contact with the endothelium
• The volume and rate of injection will influence outcome and also the propensity
to damage adjacent non-target vessels.
Transcatheter Embolization and Therapy,
Techniques in Interventional Radiology, DOI 10.1007/978-1-84800-897-7_5,
C
Springer-Verlag London Limited 2010
51
52 K. Kondo
Absolute Alcohol (Dehyrated Alcohol)
Physical Description and Properties
• C2H5OH—anhydrous ethanol
• Clear colorless liquid
• Completely miscible with water and organic solvents
Mode of Action
• Causes vasospasm
• Causes cell death by dehydration, denaturing proteins, and precipitation of
protoplasm.
• Cytotoxic—damages any tissue it contacts.
• Injection into a vessel denudes the endothelium, which leads to thrombosis and
eventual fibrosis.
• Toxic effect can extend beyond the blood vessels into the perivascular spaces.
• When injected in close proximity to nerve tissues, it can produce neuritis and
nerve degeneration (neurolysis).
How to Prepare and Use Alcohol
• Usually supplied in glass ampoules (1 and 5 ml); can draw up into a syringe.
A filter needle should be used to filter any glass shards from the ampoule.
• Can be diluted and opacificed with contrast up to 1:1 ratio.
• Normally administered by direct intralesional injection.
• Canbeusedwith
◦ Balloon occlusion catheter to prevent reflux and non-target embolization
◦ Tourniquet to prolong dwell time
Dosage and Side Effects
• Use with caution at high doses (0.5–1 ml/kg body weight) as alcohol is absorbed
systemically.
• Alcohol intoxication.
• Hemolysis.
• Systemic and pulmonary hypertension.
• Hyperthermia.
5 Liquid Embolic Agents 53
When to Use Absolute Alcohol
• Embolization:
◦ Renal cell carcinoma
◦ Aldosterone-producing adrenal adenomas
◦ Vascular malformations
Absolute alcohol can also be used for the following:
• Nerve blocks (e.g., celiac plexus block, trigeminal nerve block).
• Sclerosis of hepatic or renal cysts, seromas.
• Percutaneous ethanol injection (PEI):
◦ Hepatocellular carcinoma (HCC)
◦ Recurrent cervical lymph node disease for thyroid cancer
◦ Cystic thyroid nodules
◦ Parathyroid adenomas
When Not to Use It
• When optimal catheter or needle placement is not possible.
• High risk of non-target embolization.
Sodium Tetradecyl Sulfate
• Brand names: Sotradecol (Angiodynamics, Queesnbury, NY, USA), FibroVein
(STD Limited, Hereford, UK), Trombovar (Aventis Pharma, Le Trait, France),
Thromboject (Omega, Montreal, QC, Canada).
Physical Description and Properties
• Anionic surfactant; detergent.
Mode of Action
• Intravascular injection causes intimal inflammation and superimposed thrombus
formation.
• Dissolution of endothelial cell membrane.
• Subsequent formation of fibrous tissue results in partial or complete vessel
obliteration that may or may not be permanent.
54 K. Kondo
• Foam preparation also displaces blood in the vessel that enhances sclerosing
power.
• May have effect up to 20 cm from injection site.
How to Prepare and Use It
• Commercially available in concentrations between 0.2% (2 mg/ml) and 3%
(30 mg/ml) depending on manufacturer.
◦ Maximum single treatment should not exceed 300 mg (10 ml of 3% solution)
(American manufacturer recommendations), 120 mg (British manufacturer
recommendations).
• Dissolves rubber stoppers; therefore, use latex-free syringes.
• Foam: one part sclerosant: four parts air mixed through 20 passages in two
syringes (2–10 ml) connected by three-way stopcock (Tessari method).
• Injected directly into vessel.
When to Use
• Varicose veins and telangectasias: concentrations between 0.1% and 3.0% used
depending on the size of the vein to be treated; foam.
• Varicoceles and pelvic congestion syndrome: 2–3% concentration; foam.
• Peripheral venous vascular malformations: 2–3% concentration; foam.
When Not to Use It
• Previous hypersensitivity reaction to the drug
• Acute infection
• Asthma
• Large superficial veins with wide-open communication to deeper veins
N-Butyl Cyanoacrylate
Brand name: TRUFILL n-Butyl Cyanoacrylate (n-BCA) Liquid Embolic System
(Cordis Neurovascular, Inc., Miami Lakes, FL, USA).
Physical Description and Properties
• Free-flowing clear liquid adhesive similar to “superglue.”
5 Liquid Embolic Agents 55
Mode of Action
• Polymerizes into a solid material upon contact with any ionic media such as
contrast, body fluids or tissues.
• Adheres to most body tissues.
How to Prepare and Use It
• Do not use with any device containing polycarbonate, as it will cause polycar-
bonate to deteriorate. Use polyethylene or polypropylene syringes.
• Use a sterile 25–50 cc glass beaker or equivalent as a mixing container to prepare
the mixture.
• Radiopacification of n-BCA accomplished by adding lipiodol and if necessary
tantalum powder.
• Addition of lipiodol and/or tantalum powder extends the polymerization time of
n-BCA.
• Mix lipiodol and tantalum powder in the glass beaker by aspirating in and out of
a syringe until the mixture is homogenous.
• Add desired amount of n-BCA and mix by aspirating in and out with a syringe.
• Compare the mixture fluoroscopically to a similar syringe of contrast to deter-
mine adequate radiopacity.
• Flush catheter and rinse outside of the catheter hub with 5% dextrose.
• Aspirate n-BCA/lipiodol mixture into syringe using a 21- or 23-gauged needle
and verify that the mixture is well suspended and free of air bubbles.
• After injection under fluoroscopy, immediately aspirate with injection syringe
and rapidly withdraw the catheter.
• Discard used catheter; do not flush the catheter or perform check angiography
after use, in case residual glue remains in the lumen or hub and causes non-target
embolization.
When to Use
• FDA approved for embolization of cerebral arteriovenous malformations (AVMs)
when presurgical embolization is desired.
• Embolization:
◦ Vascular malformations
◦ Thoracic duct ablation for postoperative chylothorax
◦ Trauma
◦ Upper gastrointestinal bleeding
56 K. Kondo
When Not to Use It
• Previous history of reactions to cyanoacrylates.
• When vasospasm stops blood flow.
• When optimal catheter placement is not possible.
Ethylene Vinyl Alcohol/Dimethyl Sulfoxide (OnyxR)
• Brand name: Onyx Liquid Embolic System (Micro Therapeutics, Inc., Irvine,
CA, USA).
Physical Description and Properties
• Non-adhesive elastic polymer.
• Non-thrombogenic.
• Comprised of EVOH (ethylene vinyl alcohol) copolymer dissolved in DMSO
(dimethyl sulfoxide) and suspended micronized tantalum powder.
• Two product formulations
◦ Onyx 18 (6% EVOH) and Onyx 34 (8% EVOH).
◦ Onyx 18 is less viscous than Onyx 34 and will embolize more distally.
Mode of Action
• DMSO solvent dissipates into the blood causing the EVOH copolymer
and suspended tantalum to precipitate in situ into a spongy, coherent
embolus.
• The polymeric embolus solidifies from the outside to the inside, while traveling
distally.
• Final solidification occurs within 5 min.
• Unlike n-BCA, Onyx causes a mechanical occlusion without significant tissue
adherence.
How to Prepare and Use It
• Use DMSO compatible delivery microcatheter (Marathon, Rebar, or Ultraflow
HPC catheters [Microtherapeutics]) and syringes.
• Shake Onyx at least 20 mins on an Onyx mixer (at a setting of 8) and mix until
ready to inject.
• Flush contrast from microcatheter with 10 cc NS.
• Fill microcatheter deadspace volume with DMSO.