Heart bypass surgery is a major procedure that is usually done when there is severe blockage in the arteries supplying the heart and dysfunction of the left ventricle (the part of the heart that pushes the blood into the body and itself). Usually a treatment known as angioplasty can be done, but when angioplasty has failed or is not an option, cardiac bypass is undertaken. It has the same risks as any surgical procedure, as well as many unique ones.
Infection
An infection of the chest wound made for surgical access is called mediastinitis. While it is quite rare, it is dangerous due to the location of the infection and the access that pathogens have to vital organs such as the heart and lungs. It can occur from three days post surgery up to six months later. Risk factors include a history of smoking, obesity, being male, obstructive lung disease and diabetes.
Kidney Failure
Kidney failure after cardiac bypass is rare, but the risk increases alongside the complexity of the procedure. Increased creatinine lab values before surgery is the major risk factor, and those with preexisting kidney disease are most likely to develop kidney failure. The kidney is very sensitive to a decrease in blood flow, which often occurs during heart surgery.
Stroke
Blood pressure is hard to control, and the brain can suffer damage similar to kidney damage during cardiac surgery. Most patients with atherosclerotic disease needing bypass also will have similar disease in the arteries that supply the brain. Any fluctuation in blood pressure or supply, and the already diseased vasculature will struggle to supply the brain with enough blood to prevent injury. The patients at highest risk include those with increased systolic blood pressure before surgery.
Bleeding
There is an increased risk of bleeding with cardiac bypass surgery. The complex procedure of cardiopulmonary bypass has the side effect of causing dysfunction in the blood clotting system, resulting in an increased tendency to bleed. Increased procedure length is also associated with an increase in bleeding complications for the patient. Increased bleeding and blood loss can also cause decreased blood delivery to tissues like the brain and kidneys, resulting in additional organ damage.
Neurologic Dysfunction
This is known as "pump head" and refers to memory loss or problems thinking clearly that can clear within 12 months. This is thought to be due to a variety of mechanisms. One is the loss of pulsatile blood flow to the head, as the heart is stopped and a machine is pumping constantly; another is the loss of brain regulation of blood flow as well due to the machine regulating it instead. One way to minimize neurologic problems is to maintain adequate blood pressure during bypass surgery, and the anesthesiologist can make considerable contributions to this goal.
References
- "Sabiston Textbook of Surgery, 18th Edition;" Townsend 2007
- Surgical Clinics of North America. Cardiopulmonary Bypass/Extracorporeal Membrane Oxygenation/Left Heart Bypass: Indications, Techniques, and Complications. Ailawadi G, Zacour R. Volume 89, Issue 4 (August 2009)
- Annals of Thoracic Surgery. "30-Day operative mortality and morbidity models." Shroyer ALW, Coombs LP, Peterson ED, et al. 2003; 75:1856-1864.
