Cardiopulmonary Bypass: Procedure and Uses | GetWellGo

Cardiopulmonary Bypass

Cardiopulmonary bypass also known as heart lung machine is a mechanical apparatus utilized in some types of heart surgery where the work of the heart and lungs are assumed by a noisy apparatus. It enables the surgeon to work on a motionless and non-blood pumping heart or any other kind of heart as in:

• Coronary artery bypass grafting (CABG)
• Heart valve repair or replacement
• Congenital heart defect repair
• Heart transplants or major vascular surgeries

How Cardiopulmonary Bypass Works:

• During CPB patient is connected to a Heart-Lung machine also known as cardiopulmonary bypass machine which performs the pumping and oxygenation of the blood to both the heart and lungs.
• Deoxygenated blood, collected from different body parts is carried by the veins back to the heart usually from the right atrium or vena cava.
• It is in an oxygenator, which is part of the bypass machine, where the blood is oxygenated.
• The exchange of gases also takes place where carbon dioxide produced during the breakdown of food is transported and removed from the blood.
• The oxygenated blood is then pumped back into the body normally through the large blood vessel referred to as the aorta.

Components of a CPB System:

• Pump: Circulates blood (mimics heart)
• Oxygenator: This device adds the oxygen required into the system while it also removes the carbondioxide that may be present in the system.
• Heat exchanger: Controls blood temperature
• Reservoir: Collects and holds blood
• Filters: Remove debris and air bubbles

Steps in CPB:

• Heparin is given during bypass surgery to avoid the formation of blood clots.
• Cannulation – tubes placed in Veins and Arteries
• Starting blood process – blood supply is switched to the machine
• Cooling: body temperature may be decreased in order to deprive the organs of any excessive energy requirements
• Surgical procedure
• Rewarming and weaning – body regains its temperature, and heart and lungs resume their activity
• Decannulation and protamine administration: This was done through removal of the tubes and administration of protamine for heparin reversal

Cardiac Surgery Bypass

Cardiac Surgery Bypass also known as Coronary Artery Bypass Grafting (CABG) is a heart surgery meant to remedy circulation issues for patients with severely aggravated CAD. It is one of the frequent operations to be conducted all over the world.

What Is CABG?

CABG entails the removal of apparently healthy vessel (or graft) from other part of the body as leg, arm or chest, and then tends to replace the diseased or constricted coronary arteries. This results in increased oxygen supply to the heart muscles by increasing the flow of the oxygenated blood.

Why It’s Done:

• Severe blockages in one or more coronary arteries
• Unstable angina is when chest pain occurs and does not improve with taking Nitroglycerine/Heart rate increasing.
• Risk of heart attack due to poor blood supply
• This is especially common with the diabetes or high risk patients where other arteries are also blocked
• Left main coronary artery disease

Cardioplegia in Cardiac Surgery

Cardioplegia involves the use of an efficient myocardial protection method that stops the heart and renders it stable in order to enable surgeons operate on a heart muscle that is non-contractile and devoid of blood flow. It’s mostly employed in operations that demand the use of CPB, for instance, CABG or valve replacement operations.

Purpose of Cardioplegia

• To protect the myocardium, the muscular walls of the heart that is critical during surgery.
• To decrease the metabolic demand of the heart 
• Specifically, the ability to regulate the processes of blood circulation and oxygen supply in tissues helps to minimize the consequences of a lack of oxygen (ischemia)

How Cardioplegia Works

• A cold, potassium-rich solution is given to the heart in which it shocks and restores the regular rhythm, as in the third picture where the doctor is using a device to control the patient’s heartbeat.
• Halts the generation of electricity (used in stopping the heart during diastole)
• Reduces heart rate and contraction
• It saves on oxygen usage so that it does not be used wastefully.
• To carry these strategies to an extreme the solution is usually cooled to some extent 4-10°C to decrease metabolism even more.

CPB Complications

Neurological Complications

• Stroke: Resulting from air embolism or a plaque within the blood vessels. This was the most common disease on the list.
• Pump Head: Memory and concentration problems after the operation
• Delirium: Especially in older adults
• Seizures (rare)

Renal (Kidney) Dysfunction

• Acute kidney injury (AKI)
• Induced by pulsatility, mechanical trauma, constriction, hypoxia or hypotension

Pulmonary Complications

• Pulmonary edema
• Atelectasis (lung collapse)
• Postoperative pneumonia
• Acute respiratory distress syndrome (ARDS)

Cardiac Issues

• Arrhythmias (like atrial fibrillation)
• Low cardiac output syndrome
• Myocardial stunning (temporary heart dysfunction)

Coagulopathy and Bleeding

• CPB disturbs platelet and clotting factors
• It can also lead to bleeding with unexpected amounts or the need for transfusion.
• Heparin-induced thrombocytopenia (HIT)

Systemic Inflammatory Response Syndrome (SIRS)

• Arising from contact of patients’ blood with the non-endothelial surface of the CPB circuit
• May lead to inflammation, capillary leakage, and organ dysfunction of the entire body

Hemolysis

• Destruction of red blood cells due to mechanical forces
• Results in the release of free haemoglobin in the plasma which has deleterious effects on kidneys.

Electrolyte and Acid-Base Imbalances

• There are abnormalities in potassium, calcium, sodium and bicarbonate levels.
• Require tight monitoring and correction

Air Embolism

• Introduction of air into circulation
• May lead to a stroke, a heart attack, or death in the event of the consumption of a large amount

Infections

• Although there was no relation to CPB, prolonged surgical time and device utilization enhance the risk.
• Some are related to wound infection, sepsis, or mediastinitis

CPB Temperature Management

Maintenance of adequate temperature during Cardiopulmonary Bypass (CPB) is one of critical therapies that support the patient’s care during the surgery so as to protect the organs most notably the brain and the heart, based on their metabolic requirements. Process and phenomena associated with or are part of cardiopulmonary bypass includes deliberate cooling or hypothermia and deliberate rewarming or normothermia using the heat exchanger of the heart lung machine.

CPB Anticoagulation

The use of anticoagulation during Cardiopulmonary Bypass (CPB) is critical to avoid formation of clot in the CPB circuit and the patient’s circulation while circulation is in contact with non-physiological surfaces of the heart-lung machine. The initial anticoagulant used is heparin.

CPB Perfusionist Role

To perform its tasks, the perfusionist is a core member of the cardiac surgical team, and he or she operates the cardiopulmonary bypass (CPB) also referred to as the heart-lung machine. They are to ensure the circulation of blood and Oxygen supply to the patient during surgery when the heart and lungs have been shut down temporarily.

Key Responsibilities of the Perfusionist:

• Operate the Heart-Lung Machine
• Manage CPB Parameters
• Administer and Monitor Anticoagulation
• Thermal Regulation
• Blood Management
• Documentation
• Emergency Readiness

CPB Hemodynamics

Hemodynamics during Cardiopulmonary Bypass (CPB) refers to the circulation and pressure, as well as oxygen delivery to the critical organs when the heart and lungs are not fully functional. Since circulatory functions are replaced by the heart-lung machine, it is the perfusionist’s task to control the conditions during the procedure.

CPB Inflammatory Response

Cardiopulmonary bypass is known to be initiated when blood comes into contact with the surfaces of the non–endothelial CPB circuit as well as from the surgery procedure, ischemic reperfusion injury, dilutional coagulopathy, and hypothermia. This can cause Systemic Inflammatory Response Syndrome (SIRS) the effect of which adds to the possibilities of organ dysfunction postoperatively.

CPB vs Off-Pump Surgery

CPB is temporarily stopping the heart and substituting circulation and oxygenation with a heart-lung machine. CPB is usually the technique of choice for intricate operations, such as valve replacements or aortic procedures, since it provides a motionless and controlled field. CPB does come with an increased risk of complications such as neurological complications, renal failure, and a more intense inflammatory response from blood coming into contact with the artificial circuit.

Conversely, OPCAB is done with the heart beating, utilizing equipment to stabilize the heart and permit coronary artery bypass grafting without CPB. This method is usually used for patients with a greater risk of complications or those who need a less complex coronary bypass. It provides faster recovery, less inflammatory reaction, and reduced risks of neurological injury or renal failure than on-pump surgery, although it could be technically more demanding and less efficient for intricate procedures.

Best Hospitals for Cardiopulmonary Bypass

• Apollo Hospital, Delhi
• Fortis Escorts Heart Institute, Delhi
• Medanta-The Medicity, Gurgaon
• Max Hospital, Saket