Foam Sclerotherapy
The Tessari method is the one most often used to foam detergent sclerosants. [24] A syringe of liquid sclerosant is connected to a syringe of air by a three-way stopcock valve. The stopcock valve is turned 30-45º from its flat position to make the foamed bubbles as small as possible while still allowing the two syringes to mix. The syringes are mixed vigorously back and forth at least 20 times.
The ratio of gas volume to liquid sclerosant volume is a significant variable. Dry foams (eg, 6 mL gas to 1 mL liquid) increase blood displacement distance and can decrease bubble size in comparison with wet foams (eg, 3 mL gas to 1 mL liquid). A 4:1 gas-to-liquid ratio is the consensus recommendation. The size of the sclerofoam bubbles and their stability (ie, how long they remain small) may be key variables in decreasing systemic symptoms.
With the above technique (ie, 4:1 gas-to-liquid ratio), the foam should be used within 60-90 seconds. Other techniques that are believed to reduce bubble size, enhance bubble stability, or both include using a mixture of carbon dioxide and oxygen (instead of the primarily nitrogen-oxygen mixture characteristic of air), using low-silicone-content syringes, using larger-bore needles, and using bubble-size filters. [25]
A 27-gauge butterfly needle can be used with a syringe for treatment of localized varicosities. The appearance of blood in the butterfly tubing indicates successful cannulation. The sclerosant is then injected into the target vein, and the vessel blanches, indicating the replacement of blood with sclerosant. The injection is halted immediately when the target vein is filled, with injection volume per site usually less than 0.5 mL. The injection is halted if any bleb appears. Magnification is useful in treating smaller varicosities. Keeping the needle flat to the skin surface and aiming very superficially also helps.
For larger veins or veins near deep junctions, ultrasonographic (US) guidance is commonly used to guide needle and catheter placement into the target vein and to monitor for foam migration into deep veins. In general, the catheter should be placed more than 10 cm from any major deep-superficial junctions (eg, the saphenofemoral junction).
After US-guided venous access, the patient can be placed in the Trendelenburg position. The sclerofoam is mixed, then injected into the target vein under US guidance; it will be easily visible on US as hyperdense bubbles displacing hypodense blood. To prevent foam passage into the deep system, foam placement should be stopped well short of (ie, at least 5 cm from) any deep saphenous junctions. The current consensus recommendation is to limit the total volume of foam injected to 2-4 mL per site and 10 mL per session.
In a randomized controlled trial assessing endovenous laser ablation (EVLA) combined with either direct-puncture US-guided foam sclerotherapy (UGFS) or transluminal (ie, through the access sheath) foam sclerotherapy (TLFS) in chronic venous disease patients with GSV reflux, Watanabe et al found that TLFS plus EVLA, as compared with UGFS plus EVLA, was safe and feasible, improved the 1-year venous clinical severity score (VCSS), and reduced the need for additional second-stage interventions. [26]
After sclerofoam injection, the extremity is kept with elevated for another 5-10 minutes to allow the foam to liquefy as much as possible, to dilute the sclerosant, and to prevent early proximal foam movement. If no symptoms develop, compression may then be applied, and the patient may be allowed to walk.
Clinical practice guidelines published in 2019 by the American Venous Forum, the Society for Vascular Surgery, the American College of Phlebology, the Society for Vascular Medicine, and the International Union of Phlebology suggested that compression therapy be initiated immediately after treatment of superficial veins with sclerotherapy in order to improve outcomes. [27] With respect to the duration of such therapy, in the absence of convincing evidence, the guidelines recommended that it be determined on the basis of best clinical judgment.
Complications
Thrombotic complications include deep venous thrombosis (DVT) and superficial thrombophlebitis. The risk of DVT is low, well under 1% for most veins, [28] but may be higher in large-diameter veins. One study showed an increased risk of DVT in veins greater than 5 mm diameter and for total sclerofoam volumes over 10 mL. [29] Postsclerotherapy US is usually unnecessary except in the case of a higher-risk patient (eg, a less mobile person) or a higher-risk vein (eg, a larger vein or one near a major junction).
Treatment of DVT includes anticoagulation, close US surveillance (eg, repeat US every 2-3 days) for clot improvement and resolution, and compression stockings. Superficial thrombophlebitis can usually be treated with microphlebectomy or compression.
Superficial phlebitis at the site of foam injection is also called trapped blood or intravascular hematoma. It presents as a hard, tender vein in a recently treated area. It should be drained at around 2-3 weeks with a large-caliber (18-gauge) needle and pressure to reduce pain and lower the risk of hyperpigmentation.
Hyperpigmentation occurs in about 20% of sessions. It is a brown discoloration that occurs at injected sites as a consequence of hemosiderin deposition. Most hyperpigmentation resolves spontaneously within 1 year. For patients whose hyperpigmentation does not resolve within a year, surface laser or intense pulsed-light therapy may be considered. Topical bleaching agents are sometimes used as well.
Matting is the development of tiny red vessels around the site of an injected vein. It is probably a neovascularization phenomenon. Matting occurs in around 15-20% of sessions and usually resolves within 1 year. Sclerotherapy or surface laser can be considered for persistent matting.
On rare occasions, systemic symptoms occur after foam sclerotherapy. Visual disturbances similar to a migraine aura and migraine headaches are sometimes noted. Chest tightness and dry cough have been described. Foam therapy has been associated with very rare episodes of cerebrovascular accident (CVA) and transient ischemic attack (TIA). These systemic symptoms may be caused by gas emboli, which have been seen on transthoracic echocardiography (TTE) and transcranial Doppler US after foam injection. [30]
If, as is believed to be the case, some of these symptoms (especially CVA and TIA) are caused by gas-bubble occlusion of small arterioles, injecting smaller bubbles and using carbon dioxide (which diffuses more rapidly than nitrogen) may reduce the risk.
Other technique modifications that have been suggested for reducing risk include limiting the total foam volume to under 10 mL, elevating the extremity around 45º, keeping the patient immobile for 5-10 minutes after injection to allow the foam to turn into liquid, and occluding the saphenofemoral junction with direct pressure. The sclerosant itself has probably been "scrubbed off" and replaced with serum by the time it reaches a distant systemic target. [31]
Allergic reactions and anaphylaxis are rare complications with current sclerosants. Treatment of these complications depends on their severity but may include oxygen, intravenous fluids, epinephrine, antihistamines, and corticosteroids.
Arterial or arteriolar occlusion is a very rare complication that results in tissue necrosis. US needle guidance for veins not visible on the skin surface should prevent this complication. High-risk areas include the groin, the popliteal fossa, and the ankle. Skin necrosis can result from extravasation of sclerosant at higher concentrations, causing direct injury or inadvertent injection into skin arterioles. Routine wound care produces acceptable results.
Abnormal veins may recur either at injected sites or at new sites. [32] No currently available treatments cure chronic venous disease. Recurrence rates can be reduced by employing excellent technique.
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Patient with large tortuous varicose veins, high-volume venous reflux, and early stasis changes of the medial ankle.
