Heart-lung machine
Encyclopedia
Cardiopulmonary bypass is a technique that temporarily takes over the function of the heart
and lung
s during surgery
, maintaining the circulation of blood and the oxygen content of the body. The CPB pump itself is often referred to as a heart–lung machine or "the pump". Cardiopulmonary bypass pumps are operated by perfusionist
s in association with surgeons who connect the pump to the patient's body. CPB is a form of extracorporeal
circulation.
during that period.
CPB can be used for the induction of total body hypothermia
, a state in which the body can be maintained for up to 45 minutes without perfusion
(blood flow). If blood flow is stopped at normal body temperature, permanent brain damage
normally occurs in three to four minutes — death may follow shortly afterward. Similarly, CPB can be used to rewarm individuals suffering from hypothermia
.
Extracorporeal membrane oxygenation (ECMO) is a simplified form of CPB sometimes used as life-support for newborns with serious birth defects, or to oxygenate
and maintain recipients for organ transplantation until new organs can be found.
CPB mechanically circulates and oxygenates blood for the body while bypassing the heart and lungs. It uses a heart–lung machine to maintain perfusion to other body organs and tissues while the surgeon works in a bloodless surgical field. The surgeon places a cannula
in right atrium, vena cava, or femoral vein to withdraw blood from the body. The cannula is connected to tubing filled with isotonic crystalloid solution. Venous blood that is removed from the body by the cannula is filtered, cooled or warmed, oxygenated, and then returned to the body. The cannula used to return oxygenated blood is usually inserted in the ascending aorta, but it may be inserted in the femoral artery. The patient is administered heparin
to prevent clotting, and protamine sulfate
is given after to reverse effects of heparin. During the procedure, hypothermia is maintained; body temperature is usually kept at 28ºC to 32ºC (82.4–89.6ºF). The blood is cooled during CPB and returned to the body. The cooled blood slows the body’s basal metabolic rate, decreasing its demand for oxygen. Cooled blood usually has a higher viscosity, but the crystalloid solution used to prime the bypass tubing dilutes the blood.
Dr. Clarence Dennis led the team that conducted the first known operation involving open cardiotomy with temporary mechanical takeover of both heart and lung functions on April 5, 1951 at the University of Minnesota Hospital. The patient did not survive due to an unexpected complex congenital heart defect. This followed four years of laboratory experimentation with dogs with a unit called the Iron Heart. A team of scientists at Birmingham University (including Eric Charles a Chemical Engineer) were among the pioneers of this technology. Another member of the team was Dr. Russell M. Nelson
, who performed the first open heart surgery in Utah
, he currently is a LDS Church Apostle.
The first successful mechanical support of left ventricular function was performed in July 3, 1952 by Forest Dewey Dodrill
using a machine, the Dodrill-GMR
co-developed with General Motors. The machine was later used to support right ventricular function.
The first successful open heart procedure on a human utilizing the heart lung machine was performed by John Gibbon
on May 6, 1953 at Thomas Jefferson University
Hospital in Philadelphia. He repaired an atrial septal defect
in an 18-year-old woman.
The oxygenator was first conceptualized in the 17th century by Robert Hooke
and developed into practical extracorporeal oxygenators by French and German experimental physiologists in the 19th century. Bubble oxygenators have no intervening barrier between blood and oxygen, these are called 'direct contact' oxygenators. Membrane oxygenators introduce a gas-permeable membrane between blood and oxygen that decreases the blood trauma of direct-contact oxygenators. Much work since the 1960s focused on overcoming the gas exchange handicap of the membrane barrier, leading to the development of high-performance microporous hollow-fibre oxygenators that eventually replaced direct-contact oxygenators in cardiac theatres.
and the oxygenator
which remove oxygen-deprived blood from a patient's body and replace it with oxygen-rich blood through a series of tubes (hoses).
or PVC
.
"massage" tubing. This action gently propels the blood through the tubing. This is commonly referred to as a roller pump, or peristaltic pump
.
for the maintenance and control of blood flow during CPB. By altering the speed of revolution (RPM) of the pump head, blood flow is produced by centrifugal force. This type of pumping action is considered to be superior to the action of the roller pump by many because it is thought to produce less blood damage (Hemolysis
, etc.).
is designed to transfer oxygen
to infused blood
and remove carbon dioxide
from the venous blood
. Cardiac surgery was made possible by CPB using bubble oxygenators, but membrane oxygenator
s have supplanted bubble oxygenators since the 1980s.
Another type of oxygenator gaining favour recently is the heparin-coated blood oxygenator which is believed to produce less systemic inflammation and decrease the propensity for blood to clot in the CPB circuit.
are sewn into the patient's body in a variety of locations, depending on the type of surgery. A venous cannula removes oxygen deprived blood from a patient's body. An arterial cannula is sewn into a patient's body and is used to infuse oxygen-rich blood. A cardioplegia
cannula is sewn into the heart to deliver a cardioplegia solution to cause the heart to stop beating.
(i.e. to stop the heart from beating), and to provide myocardial protection (i.e. to prevent death of heart tissue).
solution and sometimes blood products are also added. The patient must be fully anticoagulated with an anticoagulant
such as heparin
to prevent massive clotting of blood in the circuit.
As a consequence, CPB is only used during the several hours a cardiac surgery may take. Most oxygenators come with a manufacturer's recommendation that they are only used for a maximum of 6 hours, although they are sometimes used for up to 10 hours, with care being taken to ensure they do not clot off and stop working. For longer periods than this, an ECMO (extra-corporeal membrane oxygenation) or VAD (ventricular assist device) circuit is used, which can be in operation for up to 31 days – such as in this Taiwanese case, for 16 days, after which the patient received a heart transplant.
CPB may contribute to immediate cognitive decline. The heart-lung blood circulation system and the connection surgery itself release a variety of debris into the bloodstream, including bits of blood cells, tubing, and plaque. For example, when surgeons clamp and connect the aorta to tubing, resulting emboli may block blood flow and cause mini strokes. Other heart surgery factors related to mental damage may be events of hypoxia, high or low body temperature, abnormal blood pressure, irregular heart rhythms, and fever after surgery.
Heart
The heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...
and lung
Lung
The lung is the essential respiration organ in many air-breathing animals, including most tetrapods, a few fish and a few snails. In mammals and the more complex life forms, the two lungs are located near the backbone on either side of the heart...
s during surgery
Surgery
Surgery is an ancient medical specialty that uses operative manual and instrumental techniques on a patient to investigate and/or treat a pathological condition such as disease or injury, or to help improve bodily function or appearance.An act of performing surgery may be called a surgical...
, maintaining the circulation of blood and the oxygen content of the body. The CPB pump itself is often referred to as a heart–lung machine or "the pump". Cardiopulmonary bypass pumps are operated by perfusionist
Perfusionist
A perfusionist, also known as a clinical perfusionist or a cardiovascular perfusionist, is a specialized health professional who operates the heart-lung machine during cardiac surgery and other surgeries that require cardiopulmonary bypass....
s in association with surgeons who connect the pump to the patient's body. CPB is a form of extracorporeal
Extracorporeal
An extracorporeal medical procedure is a medical procedure which is performed outside the body.-Circulatory procedures:A procedure in which blood is taken from a patient's circulation to have a process applied to it before it is returned to the circulation...
circulation.
Uses of cardiopulmonary bypass
Cardiopulmonary bypass is commonly used in heart surgery because of the difficulty of operating on the beating heart. Operations requiring the opening of the chambers of the heart require the use of CPB to support the circulationCirculatory system
The circulatory system is an organ system that passes nutrients , gases, hormones, blood cells, etc...
during that period.
CPB can be used for the induction of total body hypothermia
Therapeutic hypothermia
Therapeutic hypothermia, also known as protective hypothermia, is a medical treatment that lowers a patient's body temperature in order to help reduce the risk of the ischemic injury to tissue following a period of insufficient blood flow. Periods of insufficient blood flow may be due to cardiac...
, a state in which the body can be maintained for up to 45 minutes without perfusion
Perfusion
In physiology, perfusion is the process of nutritive delivery of arterial blood to a capillary bed in the biological tissue. The word is derived from the French verb "perfuser" meaning to "pour over or through."...
(blood flow). If blood flow is stopped at normal body temperature, permanent brain damage
Brain damage
"Brain damage" or "brain injury" is the destruction or degeneration of brain cells. Brain injuries occur due to a wide range of internal and external factors...
normally occurs in three to four minutes — death may follow shortly afterward. Similarly, CPB can be used to rewarm individuals suffering from hypothermia
Hypothermia
Hypothermia is a condition in which core temperature drops below the required temperature for normal metabolism and body functions which is defined as . Body temperature is usually maintained near a constant level of through biologic homeostasis or thermoregulation...
.
Extracorporeal membrane oxygenation (ECMO) is a simplified form of CPB sometimes used as life-support for newborns with serious birth defects, or to oxygenate
Oxygenate
Oxygenated chemical compounds contain oxygen as a part of their chemical structure. The term usually refers to oxygenated fuels. Oxygenates are usually employed as gasoline additives to reduce carbon monoxide that is created during the burning of the fuel....
and maintain recipients for organ transplantation until new organs can be found.
CPB mechanically circulates and oxygenates blood for the body while bypassing the heart and lungs. It uses a heart–lung machine to maintain perfusion to other body organs and tissues while the surgeon works in a bloodless surgical field. The surgeon places a cannula
Cannula
A cannula or canula is a tube that can be inserted into the body, often for the delivery or removal of fluid or for the gathering of data...
in right atrium, vena cava, or femoral vein to withdraw blood from the body. The cannula is connected to tubing filled with isotonic crystalloid solution. Venous blood that is removed from the body by the cannula is filtered, cooled or warmed, oxygenated, and then returned to the body. The cannula used to return oxygenated blood is usually inserted in the ascending aorta, but it may be inserted in the femoral artery. The patient is administered heparin
Heparin
Heparin , also known as unfractionated heparin, a highly sulfated glycosaminoglycan, is widely used as an injectable anticoagulant, and has the highest negative charge density of any known biological molecule...
to prevent clotting, and protamine sulfate
Protamine sulfate
Protamine sulfate is a drug that reverses the anticoagulant effects of heparin by binding to it.Protamine was originally isolated from the sperm of salmon and other species of fish but is now produced primarily through recombinant biotechnology. It is a highly cationic peptide...
is given after to reverse effects of heparin. During the procedure, hypothermia is maintained; body temperature is usually kept at 28ºC to 32ºC (82.4–89.6ºF). The blood is cooled during CPB and returned to the body. The cooled blood slows the body’s basal metabolic rate, decreasing its demand for oxygen. Cooled blood usually has a higher viscosity, but the crystalloid solution used to prime the bypass tubing dilutes the blood.
Surgical procedures in which cardiopulmonary bypass is used
- Coronary artery bypass surgeryCoronary artery bypass surgeryCoronary artery bypass surgery, also coronary artery bypass graft surgery, and colloquially heart bypass or bypass surgery is a surgical procedure performed to relieve angina and reduce the risk of death from coronary artery disease...
- Cardiac valve repair and/or replacement (aortic valveAortic valveThe aortic valve is one of the valves of the heart. It is normally tricuspid , although in 1% of the population it is found to be congenitally bicuspid . It lies between the left ventricle and the aorta....
, mitral valveMitral valveThe mitral valve is a dual-flap valve in the heart that lies between the left atrium and the left ventricle...
, tricuspid valveTricuspid valveThe tricuspid valve, or right atrioventricular valve, is on the right dorsal side of the mammalian heart, between the right atrium and the right ventricle. The normal tricuspid valve usually has three leaflets and three papillary muscles. They are connected to the papillary muscles by the chordae...
, pulmonic valve) - Repair of large septalSeptumIn anatomy, a septum is a wall, dividing a cavity or structure into smaller ones.-In human anatomy:...
defects (atrial septal defectAtrial septal defectAtrial septal defect is a form of congenital heart defect that enables blood flow between the left and right atria via the interatrial septum. The interatrial septum is the tissue that divides the right and left atria...
, ventricular septal defectVentricular septal defectA ventricular septal defect is a defect in the ventricular septum, the wall dividing the left and right ventricles of the heart.The ventricular septum consists of an inferior muscular and superior membranous portion and is extensively innervated with conducting cardiomyocytes.The membranous...
, atrioventricular septal defectAtrioventricular septal defectAtrioventricular septal defect or atrioventricular canal defect , previously known as "common atrioventricular canal" or "endocardial cushion defect", is characterized by a deficiency of the atrioventricular septum of the heart...
) - Repair and/or palliation of congenital heart defectCongenital heart defectA congenital heart defect is a defect in the structure of the heart and great vessels which is present at birth. Many types of heart defects exist, most of which either obstruct blood flow in the heart or vessels near it, or cause blood to flow through the heart in an abnormal pattern. Other...
s (Tetralogy of FallotTetralogy of FallotTetralogy of Fallot is a congenital heart defect which is classically understood to involve four anatomical abnormalities...
, transposition of the great vesselsTransposition of the great vesselsTransposition of the great vessels is a group of congenital heart defects involving an abnormal spatial arrangement of any of the primary blood vessels: superior and/or inferior vena cavae , pulmonary artery, pulmonary veins, and aorta...
) - Transplantation (heart transplantationHeart transplantationA heart transplant, or a cardiac transplantation, is a surgical transplant procedure performed on patients with end-stage heart failure or severe coronary artery disease. As of 2007 the most common procedure was to take a working heart from a recently deceased organ donor and implant it into the...
, lung transplantationLung transplantationLung transplantation, or pulmonary transplantation is a surgical procedure in which a patient's diseased lungs are partially or totally replaced by lungs which come from a donor...
, heart–lung transplantation) - Repair of some large aneurysms (aortic aneurysmAortic aneurysmAn aortic aneurysm is a general term for any swelling of the aorta to greater than 1.5 times normal, usually representing an underlying weakness in the wall of the aorta at that location...
s, cerebral aneurysmCerebral aneurysmA cerebral or brain aneurysm is a cerebrovascular disorder in which weakness in the wall of a cerebral artery or vein causes a localized dilation or ballooning of the blood vessel.- Signs and symptoms :...
s) - Pulmonary thromboendarterectomyPulmonary thromboendarterectomyIn thoracic surgery, a pulmonary thromboendarterectomy, PTE, is an operation that removes organized clotted blood from the pulmonary arteries.-Indication:...
- Pulmonary thrombectomyPulmonary thrombectomyIn thoracic surgery, a pulmonary thrombectomy, is an emergency procedure that removes clotted blood from the pulmonary arteries.Mechanical thrombectomies can be surgical or percutaneous ....
History
Russell M. Nelson
Russell Marion Nelson is a member of the Quorum of the Twelve Apostles of the Church of Jesus Christ of Latter-day Saints and an internationally renowned cardiothoracic surgeon.-Medical career:...
, who performed the first open heart surgery in Utah
Utah
Utah is a state in the Western United States. It was the 45th state to join the Union, on January 4, 1896. Approximately 80% of Utah's 2,763,885 people live along the Wasatch Front, centering on Salt Lake City. This leaves vast expanses of the state nearly uninhabited, making the population the...
, he currently is a LDS Church Apostle.
The first successful mechanical support of left ventricular function was performed in July 3, 1952 by Forest Dewey Dodrill
Forest Dewey Dodrill
Forest Dewey Dodrill was a doctor at Harper University Hospital at Wayne State University in Michigan.Forest Dewey Dodrill was born on 26 January 1902, in Webster Spring. After receiving a bachelor's degree from West Virginia University in 1925, he attended Harvard Medical School, graduating in...
using a machine, the Dodrill-GMR
Dodrill-GMR
The Dodrill–GMR machine was the first operational mechanical heart successfully used while performing open heart surgery. It was developed by Dr. Forest Dewey Dodrill, a surgeon at Harper University Hospital in Detroit, and General Motors Research....
co-developed with General Motors. The machine was later used to support right ventricular function.
The first successful open heart procedure on a human utilizing the heart lung machine was performed by John Gibbon
John Heysham Gibbon
John Heysham Gibbon Jr., AB, MD, a surgeon best known for inventing the heart-lung machine and performing the first open heart surgery . He was the son of Dr...
on May 6, 1953 at Thomas Jefferson University
Thomas Jefferson University
Thomas Jefferson University is a private health sciences university in Center City, Philadelphia, Pennsylvania in the United States. The university consists of six constituent colleges and schools, Jefferson Medical College, Jefferson College of Graduate Studies, Jefferson School of Health...
Hospital in Philadelphia. He repaired an atrial septal defect
Atrial septal defect
Atrial septal defect is a form of congenital heart defect that enables blood flow between the left and right atria via the interatrial septum. The interatrial septum is the tissue that divides the right and left atria...
in an 18-year-old woman.
The oxygenator was first conceptualized in the 17th century by Robert Hooke
Robert Hooke
Robert Hooke FRS was an English natural philosopher, architect and polymath.His adult life comprised three distinct periods: as a scientific inquirer lacking money; achieving great wealth and standing through his reputation for hard work and scrupulous honesty following the great fire of 1666, but...
and developed into practical extracorporeal oxygenators by French and German experimental physiologists in the 19th century. Bubble oxygenators have no intervening barrier between blood and oxygen, these are called 'direct contact' oxygenators. Membrane oxygenators introduce a gas-permeable membrane between blood and oxygen that decreases the blood trauma of direct-contact oxygenators. Much work since the 1960s focused on overcoming the gas exchange handicap of the membrane barrier, leading to the development of high-performance microporous hollow-fibre oxygenators that eventually replaced direct-contact oxygenators in cardiac theatres.
Components of cardiopulmonary bypass
Cardiopulmonary bypass consists of two main functional units, the pumpPump
A pump is a device used to move fluids, such as liquids, gases or slurries.A pump displaces a volume by physical or mechanical action. Pumps fall into three major groups: direct lift, displacement, and gravity pumps...
and the oxygenator
Oxygenator
An oxygenator is a medical device that is capable of exchanging oxygen and carbon dioxide in the blood of human patient in surgical procedures that may necessitate the interruption or cessation of blood flow in the body, a critical organ or great blood vessel...
which remove oxygen-deprived blood from a patient's body and replace it with oxygen-rich blood through a series of tubes (hoses).
Tubing
The components of the CPB circuit are interconnected by a series of tubes made of silicone rubberSilicone rubber
Silicone rubber is an elastomer composed of silicone—itself a polymer—containing silicon together with carbon, hydrogen, and oxygen. Silicone rubbers are widely used in industry, and there are multiple formulations...
or PVC
PVC
Polyvinyl chloride is a plastic.PVC may also refer to:*Param Vir Chakra, India's highest military honor*Peripheral venous catheter, a small, flexible tube placed into a peripheral vein in order to administer medication or fluids...
.
Roller pump
The pump console usually comprises several rotating motor-driven pumps that peristalticallyPeristalsis
Peristalsis is a radially symmetrical contraction and relaxation of muscles which propagates in a wave down the muscular tube, in an anterograde fashion. In humans, peristalsis is found in the contraction of smooth muscles to propel contents through the digestive tract. Earthworms use a similar...
"massage" tubing. This action gently propels the blood through the tubing. This is commonly referred to as a roller pump, or peristaltic pump
Peristaltic pump
A peristaltic pump, or roller pump, is a type of positive displacement pump used for pumping a variety of fluids. The fluid is contained within a flexible tube fitted inside a circular pump casing . A rotor with a number of "rollers", "shoes" or "wipers" attached to the external circumference...
.
Centrifugal pump
Many CPB circuits now employ a centrifugal pumpCentrifugal pump
A centrifugal pump is a rotodynamic pump that uses a rotating impeller to create flow by the addition of energy to a fluid. Centrifugal pumps are commonly used to move liquids through piping...
for the maintenance and control of blood flow during CPB. By altering the speed of revolution (RPM) of the pump head, blood flow is produced by centrifugal force. This type of pumping action is considered to be superior to the action of the roller pump by many because it is thought to produce less blood damage (Hemolysis
Hemolysis
Hemolysis —from the Greek meaning "blood" and meaning a "loosing", "setting free" or "releasing"—is the rupturing of erythrocytes and the release of their contents into surrounding fluid...
, etc.).
Oxygenator
The oxygenatorOxygenator
An oxygenator is a medical device that is capable of exchanging oxygen and carbon dioxide in the blood of human patient in surgical procedures that may necessitate the interruption or cessation of blood flow in the body, a critical organ or great blood vessel...
is designed to transfer oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
to infused blood
Blood
Blood is a specialized bodily fluid in animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells....
and remove carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
from the venous blood
Venous blood
Venous blood is deoxygenated blood in the circulatory system. It runs in the systemic veins from the organs to the heart. Deoxygenated blood is then pumped by the heart to lungs via the pulmonary arteries, one of the few arteries in the body that carries deoxygenated blood .Venous blood is...
. Cardiac surgery was made possible by CPB using bubble oxygenators, but membrane oxygenator
Membrane oxygenator
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 , and to oxygenate blood in longer term life support, termed extracorporeal membrane oxygenation,...
s have supplanted bubble oxygenators since the 1980s.
Another type of oxygenator gaining favour recently is the heparin-coated blood oxygenator which is believed to produce less systemic inflammation and decrease the propensity for blood to clot in the CPB circuit.
Cannulae
Multiple cannulaeCannula
A cannula or canula is a tube that can be inserted into the body, often for the delivery or removal of fluid or for the gathering of data...
are sewn into the patient's body in a variety of locations, depending on the type of surgery. A venous cannula removes oxygen deprived blood from a patient's body. An arterial cannula is sewn into a patient's body and is used to infuse oxygen-rich blood. A cardioplegia
Cardioplegia
Cardioplegia is intentional and temporary cessation of cardiac activity, primarily for cardiac surgery.- Overview :The word cardioplegia means cardio-the heart and plegia- paralysis. Technically this means arresting or stopping the heart so that surgical procedures can be done in a still and...
cannula is sewn into the heart to deliver a cardioplegia solution to cause the heart to stop beating.
| Venous | Arterial | Cardioplegia |
|---|---|---|
| Right atrium Right atrium The right atrium is one of four chambers in the hearts of mammals and archosaurs... |
Proximal aorta Aorta The aorta is the largest artery in the body, originating from the left ventricle of the heart and extending down to the abdomen, where it branches off into two smaller arteries... , distal to the cross-clamp Aortic cross-clamp An aortic cross-clamp is a surgical instrument used in cardiac surgery to clamp the aorta and separate the systemic circulation from the outflow of the heart.... |
Proximal aorta Aorta The aorta is the largest artery in the body, originating from the left ventricle of the heart and extending down to the abdomen, where it branches off into two smaller arteries... , proximal to the cross-clamp Aortic cross-clamp An aortic cross-clamp is a surgical instrument used in cardiac surgery to clamp the aorta and separate the systemic circulation from the outflow of the heart.... |
| Vena cavae | Femoral artery Femoral artery The femoral artery is a general term comprising a few large arteries in the thigh. They begin at the inguinal ligament and end just above the knee at adductor canal or Hunter's canal traversing the extent of the femur bone.... |
Coronary sinus Coronary sinus The coronary sinus is a collection of veins joined together to form a large vessel that collects blood from the myocardium of the heart. It is present in all mammals, including humans... (retrograde delivery) |
| Femoral vein Femoral vein In the human body, the femoral vein is a blood vessel that accompanies the femoral artery in the femoral sheath. It begins at the adductor canal and is a continuation of the popliteal vein... |
Axillary artery Axillary artery In human anatomy, the axillary artery is a large blood vessel that conveys oxygenated blood to the lateral aspect of the thorax, the axilla and the upper limb... |
Coronary ostia |
| Distal aorta Aorta The aorta is the largest artery in the body, originating from the left ventricle of the heart and extending down to the abdomen, where it branches off into two smaller arteries... |
Bypass grafts (during CABG) | |
| Apex of the heart Heart The heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions... |
||
Cardioplegia
A CPB circuit consists of a systemic circuit for oxygenating blood and reinfusing blood into a patient's body (bypassing the heart); and a separate circuit for infusing a solution into the heart itself to produce cardioplegiaCardioplegia
Cardioplegia is intentional and temporary cessation of cardiac activity, primarily for cardiac surgery.- Overview :The word cardioplegia means cardio-the heart and plegia- paralysis. Technically this means arresting or stopping the heart so that surgical procedures can be done in a still and...
(i.e. to stop the heart from beating), and to provide myocardial protection (i.e. to prevent death of heart tissue).
Operation
A CPB circuit must be primed with fluid and all air expunged before connection to the patient. The circuit is primed with a crystalloidIntravenous therapy
Intravenous therapy or IV therapy is the infusion of liquid substances directly into a vein. The word intravenous simply means "within a vein". Therapies administered intravenously are often called specialty pharmaceuticals...
solution and sometimes blood products are also added. The patient must be fully anticoagulated with an anticoagulant
Anticoagulant
An anticoagulant is a substance that prevents coagulation of blood. A group of pharmaceuticals called anticoagulants can be used in vivo as a medication for thrombotic disorders. Some anticoagulants are used in medical equipment, such as test tubes, blood transfusion bags, and renal dialysis...
such as heparin
Heparin
Heparin , also known as unfractionated heparin, a highly sulfated glycosaminoglycan, is widely used as an injectable anticoagulant, and has the highest negative charge density of any known biological molecule...
to prevent massive clotting of blood in the circuit.
Complications
CPB is not benign and there are a number of associated problems:- Postperfusion syndromePostperfusion syndromePostperfusion syndrome, also known as "pumphead" is a constellation of neurocognitive impairments attributed to cardiopulmonary bypass during cardiac surgery. Symptoms of postperfusion syndrome are subtle and include defects associated with attention, concentration, short term memory, fine motor...
(also known as Pumphead) - HemolysisHemolysisHemolysis —from the Greek meaning "blood" and meaning a "loosing", "setting free" or "releasing"—is the rupturing of erythrocytes and the release of their contents into surrounding fluid...
- Capillary leak syndromeCapillary leak syndromeCapillary leak syndrome is a rare medical conditioncharacterized by self-reversing episodes during which the endothelial cells which line the capillaries are thought to separate for a few days, allowing for a leakage of fluid from the circulatory system to the interstitial space, resulting in a...
- Clotting of blood in the circuit – can block the circuit (particularly the oxygenator) or send a clot into the patient.
- Air embolismAir embolismAn air embolism, or more generally gas embolism, is a pathological condition caused by gas bubbles in a vascular system. The most common context is a human body, in which case it refers to gas bubbles in the bloodstream...
- Leakage – a patient can rapidly exsanguinate (lose blood perfusion of tissues) if a line becomes disconnected.
- 1.5% of patients that undergo CPB are at risk of developing Acute Respiratory Distress Syndrome.
As a consequence, CPB is only used during the several hours a cardiac surgery may take. Most oxygenators come with a manufacturer's recommendation that they are only used for a maximum of 6 hours, although they are sometimes used for up to 10 hours, with care being taken to ensure they do not clot off and stop working. For longer periods than this, an ECMO (extra-corporeal membrane oxygenation) or VAD (ventricular assist device) circuit is used, which can be in operation for up to 31 days – such as in this Taiwanese case, for 16 days, after which the patient received a heart transplant.
CPB may contribute to immediate cognitive decline. The heart-lung blood circulation system and the connection surgery itself release a variety of debris into the bloodstream, including bits of blood cells, tubing, and plaque. For example, when surgeons clamp and connect the aorta to tubing, resulting emboli may block blood flow and cause mini strokes. Other heart surgery factors related to mental damage may be events of hypoxia, high or low body temperature, abnormal blood pressure, irregular heart rhythms, and fever after surgery.
External links
- International Consortium For Evidence-Based Perfusion
- CircuitSurfers: A Perfusion Blog about Cardiopulmonary Bypass
- Multimedia Manual of Cardiothoracic Surgery. Cardiopulmonary bypass collection.
- Perfusion Line
- The Virtual Textbook Of Extracorporeal Technology
- Video of early USSR heart–lung machine experiments