Air embolism and veins is greater than atmospheric pressure, an air embolus does not often happen when a blood vessel is injured. In the veins above the heart, such as in the head and neck, the venous pressure may be less than atmospheric and an injury may let air in. This is one reason why surgeons must be particularly careful when operating on the brain, and why the head of the bed is tilted down when inserting or removing a central venous catheter from the jugular or subclavian veins. When air enters the veins, it travels to the right side of the
Varicose veins foams. Foams may allow more veins to be treated per session with comparable efficacy. Their use in contrast to liquid sclerosant is still somewhat controversial. Sclerotherapy has been used in the treatment of varicose veins for over 150 years. Sclerotherapy is often used for telangiectasias (spider veins) and varicose veins that persist or recur after vein stripping. Sclerotherapy can also be performed using foamed sclerosants under ultrasound guidance to treat larger varicose veins, including the great saphenous and small saphenous veins. A 1996 study reported a 76% success rate at 24 months in treating saphenofemoral junction and great saphenous vein