Open heart surgery is performed after putting the patient to sleep under a general anesthetic. The chest is then opened by the surgeon, and the heart is temporarily bypassed or deactivated for the duration of surgery (although in some new techniques like beating heart surgery or minimal invasion heart surgery, the operation is possible without deactivation of the heart) During this period the functions of the heart are performed by an artificial lung mechanism called the heart-lung machine (cardiopulmonary bypass machine). Performing surgery on a working heart cases where there is no facility for beating heart surgery would be like trying to repair the engine of a car while it is in motion. This is why it is necessary to temporarily prevent the functions of the heart during the operation, which requires great care and accuracy.
Stopping the heart
During this procedure the patient is connected to the machine, thin pipes called cannulae are inserted into the main veins which lead to the heart, and thus the blood which goes to the heart is directed into the heart-lung pump, fed with oxygen, and then redirected into the body. Preventing the function of the heart is not a very difficult process. When the heart-lung machine is activated and the blood is cooled and redirected into the blood vessels, the body temperature is reduced to below 30°C, and this lowers the heart rate and assists the heart to stop functioning. The actual stopping of the heart is performed by feeding a serum containing a concentrated solution of potassium ions into the coronary artery, which feeds the heart muscle. Potassium ions are normally found in the human body but in a fixed proportion; potassium is an electrolyte which, if increased, causes a defect in the heart’s rhythm and can lead to ceasing of the heart function. Feeding the coronary artery rapidly with a rich potassium solution causes the heart to stop within a few seconds and allows the surgeon to perform the operation on a non-functioning, motionless heart.
The heart should not be stopped from functioning for a long period, even if the heart-lung pump is performing the function of the heart successfully. Under normal conditions the pump cannot perform the whole duty of the actual heart and lungs. When the body temperature is reduced, there is a reduction of functioning in many organs of the body to such an extent that they almost stop working, especially the brain. This means that every organ freezes and if the patient’s pulse were taken within this period, they would be assessed as dead.
Restarting the heart
To restart the heart following the operation a reversal of the procedure performed at the beginning of surgery is necessary; the temperature of the body is increased to 36.5–37°C again with the help of the heart-lung pump, and at the same time the amount of potassium in the blood is reduced to a normal level. This is usually executed by ensuring the normal function of the kidneys which discard the potassium from the body. This is when the function of the heart is monitored closely because there is a reversal in the process of inducing low body temperature and the excess of potassium which caused the heart to stop. In other words, the barrier which stopped the flowing river is removed; therefore, according to the laws of physics, the trapped fluid should flow again at great speed, and although following surgery the majority of hearts do begin to function again when these procedures are performed, there is unfortunately no actual guarantee. There may be certain complications or even causes which we have not yet discovered, in which case an electric shock of 10–20 joules is delivered directly to the heart muscle to encourage it to function normally. If this is unsuccessful, medication such as adrenalin, which induces the functioning of the heart, is given to the patient. If, following these repeated procedures, there is no effect, and, regardless of all the effort, the heart does not function, then everything is performed again from the beginning, including the operation. But there is always the possibility that the desired result may not be achieved. Human beings always face the prospect of death in daily life, and although there is a very slim chance of death, with such a big operation there is always the possibility.
We are normally totally unaware of the rhythmic incidents, a combination of great harmony, occurring within our bodies. Even breathing, a necessity for every living creature to stay alive, is not an action which we activate and continue of our own will. Sight, hearing, hunger and senses are acts of nature over which we have little direct will or power. Nevertheless, they are all events which we can only describe as divine miracles and what a great blessing it is that none of these complex functions of our bodies have been left to us humans.