An oxygenator is a medical device that is capable of exchanging oxygen and carbon dioxide in the blood of human patient during surgical procedures that may necessitate the interruption or cessation of blood flow in the body, a critical organ or great blood vessel. These organs can be the heart, lungs or liver, while the great vessels can be the aorta, pulmonary artery, pulmonary veins or vena cava. [1]
An oxygenator is typically utilized by a perfusionist in cardiac surgery in conjunction with the heart-lung machine. However, oxygenators can also be utilized in extracorporeal membrane oxygenation in neonatal intensive care units by nurses. For most cardiac operations such as coronary artery bypass grafting, the cardiopulmonary bypass is performed using a heart-lung machine (or cardiopulmonary bypass machine). The heart-lung machine serves to replace the work of the heart during the open bypass surgery. The machine replaces both the heart's pumping action and the lungs' gas exchange function. Since the heart is stopped during the operation, this permits the surgeon to operate on a bloodless, stationary heart.
One component of the heart-lung machine is the oxygenator. The oxygenator component serves as the lung, and is designed to expose the blood to oxygen and remove carbon dioxide. It is disposable and contains about 2–4 m² of a membrane permeable to gas but impermeable to blood, in the form of hollow fibers. [2] Blood flows on the outside of the hollow fibers, while oxygen flows in the opposite direction on the inside of the fibers. As the blood passes through the oxygenator, the blood comes into intimate contact with the fine surfaces of the device itself. Gas containing oxygen and medical air is delivered to the interface between the blood and the device, permitting the blood cells to absorb oxygen molecules directly.
Operations which involve uncoated CPB circuits require a high dose of systemic heparin. Although the effects of heparin are reversible by administering protamine, there are a number of side effects associated with this. Side effects can include allergic reaction to heparin resulting in thrombocytopenia, various reactions to the administration of protamine and post-operative hemorrhage due to inadequate reversal of the anticoagulation. Systemic heparin does not completely prevent clotting or the activation of complement, neutrophils, and monocytes, which are the principal mediators of the inflammatory response. This response produces a wide range of cytotoxins, and cell-signaling proteins that circulate throughout the patient's body during surgery and disrupt homeostasis. The inflammatory responses can produce microembolic particles. A greater source of such microemboli are caused by the suction of surgical debris and lipids into the CPB circuit. [3]
Microparticles obstruct arterioles that supply small nests of cells throughout the body and, together with cytotoxins, damage organs and tissues and temporarily disturb organ function. All aspects of cardiopulmonary bypass, including manipulation of the aorta by the surgeon, may be associated with neurological symptoms following perfusion. Physicians refer to such temporary neurological deficits as “pumphead syndrome.” Heparin-coated blood oxygenators are one option available to a surgeon and a perfusionist to decrease morbidity associated with CPB to a limited degree.
Heparin-coated oxygenators are thought [ by whom? ][ citation needed ] to:
Heparin coating is reported to result in similar characteristics to the native endothelium. It has been shown to inhibit intrinsic coagulation, inhibit host responses to extracorporeal circulation, and lessen postperfusion, or “pumphead,” syndrome. Several studies have examined the clinical efficacy of these oxygenators.
Mirow et al. 2001[ full citation needed ] examined the effects of heparin-coated cardiopulmonary bypass systems combined with full and low dose systemic heparinization in coronary artery bypass patients. The researchers concluded that
Ovrum et al. 2001[ full citation needed ] compared the clinical outcomes of 1336 patients with the Carmeda Bioactive Surface and Duraflo II coatings. The researchers concluded that:
Statistics and conclusions from more studies are available here. Clearly, heparin-coated blood oxygenators exhibit some advantages over non-coated oxygenators. Some hospitals use heparin-coated oxygenators for the large majority of their cases requiring cardiopulmonary bypass. It is unclear whether most surgeons actually reduce the amount of systemic heparin used when their patients are being perfused with heparin-coated oxygenators. Ultimately, each surgeon makes this decision based upon the needs of individual patient.
Although they offer advantages, these oxygenators are not widely regarded by surgeons as revolutionary breakthroughs in cardiopulmonary bypass. This is attributable to the fact that most of the morbidity associated with CPB is not caused by the contact between the blood with the oxygenator. The leading cause of hemolysis and microemboli is the return of blood suctioned from the surgical field to the CPB circuit. This blood has come into contact with air, lipids and debris that can significantly increase system inflammatory response. Surgeons are instead looking to off-pump cardiac procedures, wherein surgery is performed on beating hearts, as the next “big thing”[ by whom? ][ citation needed ] in open heart surgery.
Coated circuits have not been proven to alter surgical outcomes in any statistically significant manner. Furthermore, coated circuits are significantly more expensive than conventional circuits.
Veins are blood vessels in humans, and most other animals that carry blood towards the heart. Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are the pulmonary and umbilical veins, both of which carry oxygenated blood to the heart. In contrast to veins, arteries carry blood away from the heart.
Coronary artery bypass surgery, also known as coronary artery bypass graft is a surgical procedure for coronary artery disease (CAD) aiming to relieve angina, stall progression of ischemic heart disease and increase life expectancy. The goal is to bypass the stenotic lesions in native heart arteries using arterial or venous conduits, thus restoring adequate blood supply to the previously ischemic heart.
Cardiopulmonary bypass (CPB) is a technique in which a machine temporarily takes over the function of the heart and lungs during surgery, maintaining the circulation of blood and oxygen to the body. The CPB pump itself is often referred to as a heart–lung machine or "the pump". Cardiopulmonary bypass pumps are operated by perfusionists. CPB is a form of extracorporeal circulation. Extracorporeal membrane oxygenation is generally used for longer-term treatment.
Extracorporeal membrane oxygenation (ECMO), also known as extracorporeal life support (ECLS), is an extracorporeal technique of providing prolonged cardiac and respiratory support to persons whose heart and lungs are unable to provide an adequate amount of gas exchange or perfusion to sustain life. The technology for ECMO is largely derived from cardiopulmonary bypass, which provides shorter-term support with arrested native circulation. The device used is a membrane oxygenator, also known as an artificial lung.
Cardiothoracic surgery is the field of medicine involved in surgical treatment of organs inside the thoracic cavity — generally treatment of conditions of the heart, lungs, and other pleural or mediastinal structures.
dextro-Transposition of the great arteries is a potentially life-threatening birth defect in the large arteries of the heart. The primary arteries are transposed.
Cardiac surgery, or cardiovascular surgery, is surgery on the heart or great vessels performed by cardiac surgeons. It is often used to treat complications of ischemic heart disease ; to correct congenital heart disease; or to treat valvular heart disease from various causes, including endocarditis, rheumatic heart disease, and atherosclerosis. It also includes heart transplantation.
A cardiovascular perfusionist, clinical perfusionist or perfusiologist, and occasionally a cardiopulmonary bypass doctor or clinical perfusion scientist, is a healthcare professional who operates the cardiopulmonary bypass machine during cardiac surgery and other surgeries that require cardiopulmonary bypass to manage the patient's physiological status. As a member of the cardiovascular surgical team, the perfusionist also known as the clinical perfusionist helps maintain blood flow to the body's tissues as well as regulate levels of oxygen and carbon dioxide in the blood, using a heart–lung machine.
Arterial switch operation (ASO) or arterial switch, is an open heart surgical procedure used to correct dextro-transposition of the great arteries (d-TGA); its development was pioneered by Canadian cardiac surgeon William Mustard and it was named for Brazilian cardiac surgeon Adib Jatene, who was the first to use it successfully. It was the first method of d-TGA repair to be attempted, but the last to be put into regular use because of technological limitations at the time of its conception.
In thoracic surgery, a pulmonary thromboendarterectomy (PTE), also referred to as pulmonary endarterectomy (PEA), is an operation that removes organized clotted blood (thrombus) from the pulmonary arteries, which supply blood to the lungs.
Postperfusion syndrome, also known as "pumphead", is a constellation of neurocognitive impairments attributed to cardiopulmonary bypass (CPB) during cardiac surgery. Symptoms of postperfusion syndrome are subtle and include defects associated with attention, concentration, short-term memory, fine motor function, and speed of mental and motor responses. Studies have shown a high incidence of neurocognitive deficit soon after surgery, but the deficits are often transient with no permanent neurological impairment.
A membrane oxygenator is a device used to add oxygen to, and remove carbon dioxide from the blood. It can be used in two principal modes: to imitate the function of the lungs in cardiopulmonary bypass (CPB), and to oxygenate blood in longer term life support, termed extracorporeal membrane oxygenation (ECMO). A membrane oxygenator consists of a thin gas-permeable membrane separating the blood and gas flows in the CPB circuit; oxygen diffuses from the gas side into the blood, and carbon dioxide diffuses from the blood into the gas for disposal.
Off-pump coronary artery bypass or "beating heart" surgery is a form of coronary artery bypass graft (CABG) surgery performed without cardiopulmonary bypass as a treatment for coronary heart disease. It was primarily developed in the early 1990s by Dr. Amano Atsushi. Historically, during bypass surgeries, the heart is stopped and a heart-lung machine takes over the work of the heart and lungs. When a cardiac surgeon chooses to perform the CABG procedure off-pump, also known as OPCAB, the heart is still beating while the graft attachments are made to bypass a blockage.
Atrial septostomy is a surgical procedure in which a small hole is created between the upper two chambers of the heart, the atria. This procedure is primarily used to palliate dextro-Transposition of the great arteries or d-TGA, a life-threatening cyanotic congenital heart defect seen in infants. It is performed prior to an arterial switch operation. Atrial septostomy has also seen limited use as a surgical treatment for pulmonary hypertension. The first atrial septostomy was developed by Vivien Thomas in a canine model and performed in humans by Alfred Blalock. The Rashkind balloon procedure, a common atrial septostomy technique, was developed in 1966 by American cardiologist William Rashkind at the Children's Hospital of Philadelphia.
The bidirectional Glenn (BDG) shunt, or bidirectional cavopulmonary anastomosis, is a surgical technique used in pediatric cardiac surgery procedure used to temporarily improve blood oxygenation for patients with a congenital cardiac defect resulting in a single functional ventricle. Creation of a bidirectional shunt reduces the amount of blood volume that the heart needs to pump at the time of surgical repair with the Fontan procedure.
Cardiothoracic anesthesiology is a subspeciality of the medical practice of anesthesiology, devoted to the preoperative, intraoperative, and postoperative care of adult and pediatric patients undergoing cardiothoracic surgery and related invasive procedures.
Minimized extracorporeal circulation (MECC) is a kind of cardiopulmonary bypass, a part of heart surgery. The introduction of extracorporeal circulation has facilitated open heart surgery. The development of modern techniques in extracorporeal circulation is the result of the combined efforts of physiologists, physicians, and engineers. During the first half of the 20th century scientists refined their methods in the development of extracorporeal circulation so that it could be used in humans.
The Senning procedure is an atrial switch heart operation performed to treat transposition of the great arteries. It is named after its inventor, the Swedish cardiac surgeon Åke Senning (1915–2000), also known for implanting the first permanent cardiac pacemaker in 1958.
Extracorporeal cardiopulmonary resuscitation is a method of cardiopulmonary resuscitation (CPR) that passes the patient's blood through a machine in a process to oxygenate the blood supply. A portable extracorporeal membrane oxygenation (ECMO) device is used as an adjunct to standard CPR. A patient who is deemed to be in cardiac arrest refractory to CPR has percutaneous catheters inserted into the femoral vein and artery. Theoretically, the application of ECPR allows for the return of cerebral perfusion in a more sustainable manner than with external compressions alone. By attaching an ECMO device to a person who has acutely undergone cardiovascular collapse, practitioners can maintain end-organ perfusion whilst assessing the potential reversal of causal pathology, with the goal of improving long-term survival and neurological outcomes.
Retrograde autologous priming (RAP) is a means to effectively and safely restrict the hemodilution caused by the direct homologous blood transfusion and reduce the blood transfusion requirements during cardiac surgery. It is also generally considered a blood conservation method used in most patients during the cardiopulmonary bypass (CPB). The processing of RAP includes three main steps, and the entire procedure of RAP could be completed within 5 to 8 minutes. This technique is proposed by Panico in 1960 for the first time and restated by Rosengart in 1998 to eliminate or reduce the risk of hemodilution during CPB. Moreover, to precisely determine the clinical efficacy of RAP, many related studies were conducted. Most results of researches indicate that RAP is available to provide some benefits to reducing the requirements for red blood cell transfusion. However, there are still some studies showing a failure of RAP to limit the hemodilution after the open heart operation.