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There once was a king who offered a prize to the artist who would paint the best picture of peace. Many artists tried. The king looked at all the pictures. But there were only two he really liked, and he had to choose between them.

One picture was of a calm lake. The lake was a perfect mirror for peaceful towering mountains all around it. Overhead was a blue sky with fluffy white clouds. All who saw this picture thought that it was a perfect picture of peace. The other picture had mountains, too. But these were rugged and bare. Above was an angry sky, from which rain fell and in which lightning played. Down the side of the mountain tumbled a foaming waterfall. This did not look peaceful at all.

But when the king looked closely, he saw behind the waterfall a tiny bush growing in a crack in the rock. In the bush a mother bird had built her nest. There, in the midst of the rush of angry water, sat the mother bird on her nest - in perfect peace.

Which picture do you think won the prize? The king chose the second picture. Do you know why?

“Because,” explained the king, “peace does not mean to be in a place where there is no noise, trouble, or hard work. Peace means to be in the midst of all those things and still be calm in your heart. That is the real meaning of peace.”

Cardiopulmonary bypass (CPB) is a technique that temporarily takes over the function of the heart and lungs 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 Pumper. Cardiopulmonary bypass pumps are operated by allied health professionals known as Perfusionists in association with surgeons who connect the pump to the patient's body. CPB is a form of extracorporeal circulation.

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 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 an hour or more 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.

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.

Surgical procedures in which cardiopulmonary bypass is used

• Coronary artery bypass surgery
• Cardiac valve repair and/or replacement (aortic valve, mitral valve, tricuspid valve, pulmonic valve)
• Repair of large septal defects (atrial septal defect, ventricular septal defect, atrioventricular septal defect)
• Repair and/or palliation of congenital heart defects (Tetralogy of Fallot, transposition of the great vessels)
• Transplantation (heart transplantation, lung transplantation, heart-lung transplantation)
• Repair of some large aneurysms (aortic aneurysms, cerebral aneurysms)
• Pulmonary thromboendarterectomy
• Pulmonary thrombectomy

History

Dr. Clarence Dennis led the team that conducted the first known operation involving open cardiotomy with temporarary 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.^[1]

John Gibbon is credited with developing the first truly practical heart-lung bypass machine; he performed the first successful surgery with it on May 6, 1953 in Philadelphia, an atrial septal defect repair. But although he is accredited with the invention, many suspect that he was not awarded the Nobel Prize for it because of his failure to mention the other members of the team working with him. Other surgeons such as Bernard J. Miller, a young doctor at the time, created many of the pieces that make the machine function.

Components of cardiopulmonary bypass

Cardiopulmonary bypass consists of two main functional units, the pump and the oxygenator which remove oxygen deprived blood from a patients body and replace it with oxygen-rich blood through a series of hoses.

Tubing

The components of the CPB circuit are interconnected by a series of tubes made of silicone rubber, or PVC. The tubing in the CPB circuit is similar to transparent garden hose.

Pumps

Roller pump

The pump console usually comprises several rotating motor-driven pumps that peristaltically "massage" tubing . This action gently propels the blood through the tubing. This is commonly referred to as a roller pump, or peristaltic pump.

Centrifugal pump

Many CPB circuits now employ a centrifugal 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.).

Oxygenator

The oxygenator 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 oxygenators have supplanted bubble oxygenators since the 1980s.

The oxygenator was first conceptualised 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.^[2]

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 cannulae 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 patients 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.

Cardioplegia

Main article: 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 cardioplegia (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 crystalloid 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.

Complications

CPB is not benign and there are a number of associated problems:

• Postperfusion syndrome (also known as Pumphead)
• Hemolysis
• Capillary Leak Syndrome
• Clotting of blood in the circuit - can block the circuit (particularly the oxygenator) or send a clot into the patient.
• Air embolism
• Leakage - a patient can rapidly exsanguinate (lose blood perfusion of tissues) if a line becomes disconnected.

 References

http://en.wikipedia.org/wiki/Heart-lung_machine

Cardiac surgery is surgery on the heart and/or great vessels performed by a cardiac surgeon. Frequently, it is done to treat complications of ischemic heart disease (for example, coronary artery bypass grafting), correct congenital heart disease, or treat valvular heart disease created by various causes including endocarditis. It also includes heart transplantation.

The earliest operations on the pericardium (the sac that surrounds the heart) took place in the 19th century and were performed by, among others, Francisco Romero,^[1] Dominique Jean Larrey, Henry Dalton, and Daniel Hale Williams. The first successful surgery on the heart itself, performed without any complications, was by Dr. Ludwig Rehn of Frankfurt, Germany, who repaired a stab wound to the right ventricle on September 7, 1896.

Surgery on the great vessels (aortic coarctation repair, Blalock-Taussig shunt creation, closure of patent ductus arteriosus), became common after the turn of the century and falls in the domain of cardiac surgery, but technically cannot be considered heart surgery.

 Closed heart surgery

Surgery on the great vessels was followed by the development of closed heart surgery, where the surgeon blindly worked on the beating heart. It left a great deal to be desired, but had much to offer for great risk. Palliation of severe mitral valve stenosis, which was common in the past due to rheumatic fever, could be accomplished by poking a finger into the (mitral) valve through an incision in the left atrium.^[2] If a finger didn't do, a knife was passed through the incision to cut out tissue. Following successful treatment of mitral stenosis, a special cutter for aortic valve stenosis was developed, that maneuvered through an incision in the left atrium, accomplished much the same thing as the surgeon's finger in a stenosed mitral valve.

Operations under hypothermia

It was soon discovered that the repair of intracardiac pathologies required a bloodless and motionless environment, which means that the heart should be stopped and drained of blood. The first successful intracardiac correction of a congenital heart defect using hypothermia was performed by Dr. C. Walton Lillehei and Dr. F. John Lewis at the University of Minnesota on September 2, 1952. The following year, Soviet surgeon Aleksandr Aleksandrovich Vishnevskiy conducted the first cardiac surgery under local anesthesia.

 Operations on the open heart

Surgeons realized the limitations of hypothermia - complex intracardiac repairs take more time and the patient needs blood flow to the body (and particularly the brain); the patient needs the function of the heart and lungs provided by an artificial method, hence the term cardiopulmonary bypass. Dr. John Heysham Gibbon at Jefferson Medical School in Philadelphia reported in 1953 the first successful use of extracorporeal circulation by means of an oxygenator, but he abandoned the method, disappointed by subsequent failures. In 1954 Dr. Lillehei realized a successful series of operations with the controlled cross-circulation technique in which the patient's mother or father was used as a 'heart-lung machine'. Dr. John W. Kirklin at the Mayo Clinic in Rochester, Minnesota started using a Gibbon type pump-oxygenator in a series of successful operations, and was soon followed by surgeons in various parts of the world.

 Modern beating-heart surgery

Since the 1990s, surgeons have begun to perform "off-pump bypass surgery" - coronary artery bypass surgery without the aforementioned cardiopulmonary bypass. In these operations, the heart is beating during surgery, but is stabilized to provide a (almost) still work area. Some researchers believe this approach results in fewer post-operative complications (such as postperfusion syndrome) and better overall results (studies results are controversial as of 2007, surgeon's preference and hospital results still play a major role).

Minimally invasive surgery

A new form of heart surgery that has grown in popularity is robotic heart surgery. This is where a machine (today by far and away the most popular is the da Vinci surgical system by Intuitive Surgical) is used to perform surgery while being controlled by the heart surgeon. The main advantage to this is the size of the incision made in the patient. Instead of a incision being at least big enough for the doctor to put his hands inside, it does not have to be bigger than 3 small holes for the robot's much smaller hands to get through. Also, a major advantage to the robot is the recovery time of a patient, instead of 6 months of recovery time, some patients have recovered and resumed playing athletics in a matter of weeks.^{[citation needed]}

 Risks

The development of cardiac surgery and cardiopulmonary bypass techniques has reduced the mortality rates of these surgeries to relatively low levels. For instance, repairs of congenital heart defects are currently estimated to have 4-6% mortality rates.^[3][4]

A major concern with cardiac surgery is the incidence of neurological damage. Stroke occurs in 2-3% of all people undergoing cardiac surgery, and is higher in patients at risk for stroke. ^{[citation needed]} A more subtle constellation of neurocognitive deficits attributed to cardiopulmonary bypass is known as postperfusion syndrome (sometimes called 'pumphead'). The symptoms of postperfusion syndrome were initially felt to be permanent,^[5] but were shown to be transient with no permanent neurological impairment.^[6]

 See also

• Cardiac surgeon
• Cardiothoracic surgery
• Vascular surgery

 References

 Further reading

• [edited by] Lawrence H. Cohn, L. Henry Edmunds, Jr (2003). Cardiac surgery in the adult. New York: McGraw-Hill, Medical Pub. Division. ISBN 0-07-139129-0.  Full text online