Editing Cardiopulmonary bypass (section)

==Uses==
{{Unreferenced section|date=June 2024}}
[[File:Blausen 0468 Heart-Lung Machine.png|thumb|300px|Illustration of one typical way that a heart-lung machine may be connected to the veins and arteries near the heart. The three implements on the left represent (''from top to bottom'') the pump, the oxygenator, and the reservoir.]]CPB is commonly used in operations or surgical procedures involving the heart. The technique allows the surgical team to oxygenate and circulate the patient's blood, thus allowing the surgeon to operate safely on the heart. In many operations, such as [[Coronary artery bypass surgery|coronary artery bypass grafting]] (CABG), the heart is [[Cardioplegia|arrested]], due to the degree of the difficulty of operating on a beating heart.

Operations requiring the opening of the chambers of the heart, for example [[mitral valve repair]] or [[Mitral valve replacement|replacement]], requires the use of CPB. This is to avoid engulfing air systemically, and to provide a bloodless field to increase visibility for the surgeon. The machine pumps the blood and, using an oxygenator, allows red blood cells to pick up oxygen, as well as allowing carbon dioxide levels to decrease. This mimics the function of the heart and the lungs, respectively.

=== Hypothermia ===
CPB can be used for the induction of total body [[Therapeutic hypothermia|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]] can occur in three to four minutes — death may follow. Similarly, CPB can be used to rewarm individuals who have [[hypothermia]]. This rewarming method of using CPB is successful if the core temperature of the patient is above 16&nbsp;°C.

=== Cooled blood ===
The blood is cooled during CPB and is 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 various crystalloid or colloidal solutions that are used to prime the bypass tubing serve to dilute the blood. Maintaining appropriate blood pressure for organs is a challenge, but it is monitored carefully during the procedure. Hypothermia is also maintained (if necessary), and the body temperature is usually kept at {{convert|28|to|32|C|F}}.

=== Extracorporeal membrane oxygenation ===
[[Extracorporeal membrane oxygenation]] (ECMO) is a simplified version of the [[heart lung machine]] that includes a [[centrifugal pump]] and an oxygenator to temporarily take over the function of heart and/or the lungs. ECMO is useful for post-cardiac surgery patients with cardiac or pulmonary dysfunction, patients with acute pulmonary failure, massive [[pulmonary embolisms]], lung trauma from infections, and a range of other problems that impair cardiac or pulmonary function.

ECMO gives the heart and/or lungs time to repair and recover, but is only a temporary solution. Patients with terminal conditions, cancer, severe nervous system damage, uncontrolled [[sepsis]], and other conditions may not be candidates for ECMO.