What is a Cardiopulmonary Bypass? | How Does it Work?

What is a Cardiopulmonary Bypass

A Cardiopulmonary Bypass (CPB) is the process of artificially bypassing the heart and the lungs with a heart-lung machine in cardiac surgery. It is used to introduce oxygen into the blood, pump the blood through the cardiopulmonary bypass circuit for the patient, and remove excess carbon dioxide from the blood to provide patients with cardiac and pulmonary support during surgery.

What is it used for?

Cardiopulmonary Bypass is a technique used to temporarily take over the function of the patient’s heart and lungs during surgery. It is performed by a machine often referred to as a ‘heart-lung machine’ or, simply, as ‘the pump.’

This technique makes an appearance in many operations involving the heart, as it keeps the patient’s body well oxygenated and circulated while the surgeon operates. We’ve provided a more comprehensive list below of the most common surgical procedures where a CPB might be used:

  • Coronary Artery Bypass Surgery
  • Cardiac Valve Repair
  • Transplantation
  • Pulmonary Thrombectomy
  • Isolated Limb Perfusion
  • Large Septal Defect Repairs
  • Congenital Heart Defects Repairs or Palliation
  • Large Aneurysms Repairs 

Note, there is some variation to how a CPB is used in certain operations.

Like, for example, during a Coronary Artery Bypass Graft (CABG) operation, it is common that the heart is arrested—stopped—so that surgeons can operate more efficiently without having to deal with a beating heart. In that case, a CPB is used simply to make sure that the patient’s blood is well oxygenated and circulated.

A CPB can also be used to pump the patient’s blood for operations that require that the chambers of the heart remain open, like for mitral valve repairs or replacements. And, it can also be used to induce total body hypothermia to keep the body in a state without perfusion (blood flow.)

How is a Cardiopulmonary Bypass Performed?

A Cardiopulmonary Bypass Pump is operated by a medical ‘perfusionist.’ However, they usually work in tandem with other medical professionals, specifically a surgeon and an anesthesiologist, to make sure that the process goes smoothly.

To illustrate the process, we’ve broken down the setup and the operation of the CPB pump in three basic steps below:

  1. The process is initiated by the surgeon, who places a cannula (a piece of tubing inserted into the body to either deliver or remove fluids), into the patient’s right atrium, femoral vein, or vena cava so that blood can be drawn (taken) from the body.
  2. The patient’s blood is then drawn into a reservoir, where it is filtered, cooled, or warmed, through a pump that delivers the blood into an oxygenator (an artificial lung) that will remove carbon dioxide and introduce oxygen.
  3. From this point on, the oxygenated blood is transferred to another tube that will return the blood to the body through another cannula inserted into an artery (usually the ascending aorta, but it can also be inserted in the femoral artery, the brachiocephalic artery, the axillary artery, and so on.)

This process is repeated over and over until the time comes for the patient to be removed from the machine. Note, the patient is usually administered some heparin before the process is initiated to prevent clotting, and, after, are given protamine sulfate to reverse its effects.

What are the Risks Involved?

Unfortunately, CPB is not a fail-proof technique, it’s been associated with plenty of complications. And, as such, is often used only in moderation or under very critical conditions.

The longest that a patient is usually made to go under ‘The Pump’ is often limited to a maximum of 6 hours. Although, there are some rare occasions where it is used for up to ten hours or more. For any occasion where a longer session might be required, an ECMO (a simplified version of the CPB) is used to accommodate situations where the patient needs to spend more than several days under the pump.

Final Thoughts: What is a Cardiopulmonary Bypass?

Should you have any specific concerns for this particular subject, we recommend that you approach your doctor directly for a more personalized view of what you should or should not expect if a CPB is performed on you.

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