All open-heart procedures carry risks related to the use of cardiopulmonary bypass. The safety of cardiopulmonary bypass has improved significantly over the years. Major complications are now exceedingly rare. Bypass times up to four to eight hours are well tolerated.
The risks of bypass itself include inadequate perfusion of organs or tissues, activation of a systemic inflammatory response, and embolization of air or particles. Especially concerning is the potential of embolization to the brain, but this risk should be quite low – less than 1 percent in most cases.
“Inadequate perfusion of organs and tissues” means that the bypass machine is not as efficient of a pump as your own heart, so some organs and tissues get a little less blood flow during surgery than they would normally. These organs protect themselves by slowing down. However, this is rare during modern cardiopulmonary bypass.
“Activation of a systemic inflammatory response” means that the heart-lung machine activates the body to release chemicals and cells that cause inflammation. This is why children after cardiopulmonary bypass can be somewhat swollen and their lungs can become “wet.” Lasix (a medicine that helps your child get rid of fluid by urinating) is usually given after surgery. “Embolization” occurs when a particle breaks loose and travels from one location in the body to another. Both air and clots can break lose and embolize, and can cause a potentially dangerous event (such as stroke). A potentially significant, yet rare, complication of cardiopulmonary bypass is neurologic injury resulting in stroke or seizures.
Bleeding is also a risk after open heart surgery. Due to the use of Heparin (a blood thinner) during bypass, bleeding sometimes occurs where we have placed sutures. Usually the bleeding is minimal and easily controlled with medications and bandages. The need for re-operation for bleeding following open-heart operations is low, about 2 percent.
In addition to the risks of bypass, the heart itself can be affected. First, the heart undergoes a period of cold ischemia (no blood flow) during most open-heart operations. Myocardial function may be compromised by this period of ischemia despite efforts to protect the heart muscle using cardioplegia and cooling. Second, the heart’s function may be decreased or “depressed” after surgery. The heart needs time to adapt to new anatomy and physiology after repair. Last, the heart rhythm may also be affected by open-heart procedures. Some patients require temporary or even permanent pacing (stimulation of the heart to assure a normal rhythm).