In medicine, a vascular bypass generally means an alternate or additional route for blood flow, which is created in bypass surgery, e.g. coronary artery bypass surgery by moving blood vessels or implanting synthetic tubing. Vessels frequently used for the bypass are large veins taken from the patient's leg. When and where possible, however, an artery is cut from one place and reconnected to another artery, which supplies a region that needs the blood supply more than the original site. Generally the blood flow in the receiving vessel is temporarily interrupted or reduced while the bypass is connected. To create a bypass to a critical artery, the connection can be made while blood is flowing through the receiving vessel with the ELANA operating technique.
Types of bypass surgeries 
There are several different types of bypass surgeries:
- Heart bypass surgery is performed when the arteries that bring blood to the heart muscle (coronary arteries) become clogged by plaque. Such condition may lead to chest pain or heart attack.
- A bypass may be performed on peripheral arteries with occlusive disease. For example, a femoral-popliteal bypass might be used if the femoral artery was occluded.
- The cerebral artery bypass surgery is performed to reroute blood flow around a blocked or damaged artery to improve or restore blood flow to an oxygen-deprived (ischemic) area of the brain.
When several arteries are blocked and thus several bypasses are needed the procedure is called multiple bypass. The number of bypasses needed does not increase the surgery's risks which depend on the patient's overall health. Weight and diabetes are examples of possible risks.
Care after bypass surgery 
Part of the recovery after any bypass surgery includes regular visits to a physician to monitor the patient's recovery. These visits gradually decrease as the patient's health improves.
Coronary artery bypass 
In the case of coronary artery bypass, patients stay in the hospital for four to six days and sometimes longer. Once the patient leaves the hospital the recovery time can vary greatly. Some patients start feeling normal after one month, while others may still experience problems up to six months after the procedure.
Since the coronary artery bypass does not represent a cure for coronary artery diseases, doctors recommend lifestyle changes that include quitting smoking, making diet changes, getting regular exercise, and lowering stress.
Cerebral artery bypass 
After cerebral artery bypass, patients can return to normal activities after two to four weeks. Patients are encouraged to take short walks and gradually increase them. However, lifting weight, house work and yard work should be avoided. Also, patients are prescribed narcotic pain killers for a period of two to four weeks.
Normally a follow up visit with the neurosurgeon is scheduled for two to four weeks after surgery.
Excimer laser assisted nonocclusive anastomosis (ELANA) is a technique in vascular surgery and neurosurgery to create a bypass without interrupting blood supply in the recipient blood vessels. This is a significant advance because the interruption of blood supply to those blood vessels (i.e., in the brain or heart) could cause a stroke or a rupture of the aneurysm.
The ELANA technique is a subtle modification of existing methods to establish a connection between blood vessels (anastomosis) to create a bypass in or to the brain. The only real differences involve how the recipient artery is opened. In conventional techniques the recipient artery is temporarily interrupted (occluded with clips) and opened using microscissors or scalpel while in the ELANA technique blood flow is not interrupted and the opening (arteriotomy) is created with radiation from a 308nm Excimer Laser delivered through a catheter inserted in the vessel that will become the bypass while blood continues to flow through the artery that receives the bypass. This subtle difference, however, is very important for the safety of the procedure and eliminates the risk of ischemia to the regions supplied by the artery receiving the bypass. The technique is most valuable in neurosurgery, as brain cells are particularly sensitive to the lack of blood supply (ischemia) that would be caused by traditional methods of bypass creation. The bypasses created with the help of the ELANA can be to one of the major arteries in the brain (extracranial to intracranial EC-IC bypass) or between two arteries in the brain (intracranial to intracranial).
Surgeons are creating such a bypass mainly as a step in the treatment of patients with unclippable and uncoilable giant aneurysms or tumors at the skull base or to treat patients at risk of stroke who can not be treated otherwise.
The ELANA technique has been extensively described in medical literature. It was developed in 1993 by Cornelis A.F. Tulleken, professor of neurosurgery at the University Medical Center Utrecht, the Netherlands, to find a way to treat patients with a bypass to a major cerebral artery without the risk of cerebral ischemia during the procedure. The surgery of some patients has been reported upon in the media e.g., in The New York Times in December 2006.
- "Bypass Surgery, Coronary Artery". Retrieved 2010-04-08.
- "What is cerebral bypass surgery?". Retrieved 2010-04-08.
- "After Bypass Surgery Care and Results". Retrieved 2010-04-08.
- "Life After Bypass Surgery". Retrieved 2010-04-08.
- "Heart Bypass Surgery". Retrieved 2010-04-08.
- "What happens after surgery?". Retrieved 2010-04-08.
- Tulleken CA, Verdaasdonk RM, Mansvelt Beck HJ, et al. "The modified excimer laser-assisted high-flow bypass operation". Surg. Neurol. 46:424––429, 1996
- Denise Grady: "With Lasers and Daring, Doctors Race to Save a Young Man's Brain." The New York Times December 19, 2006