Hypothermic Circulatory Arrest
During typical open-heart surgery, blood continues to circulate throughout the body although major blood vessels are clamped to prevent the flow of blood into the surgical area. In aortic surgery, it is necessary to perform procedures without clamping the aorta while keeping the surgical field free of blood. The dilemma facing aortic surgeons was how to temporarily stop blood circulation without causing neurological injury to the patient.
An effective solution to the dilemma of how to temporarily stop blood circulation without causing injury to the patient, resulted in the development of a technique in the 1970s known as hypothermic circulatory arrest (HCA). In the mid-1980s it was applied to surgery of the ascending aorta and Cedars-Sinai has been using it for descending and thoracoabdominal aortic surgery since 1994.
How does HC Work?
Hypothermic circulatory arrest temporarily suspends blood flow under very cold body temperatures. At cold temperatures, cellular activity levels slow significantly so blood circulation can be stopped for up to 40 minutes without harm to the patient. This allows surgery to safely be performed on the aorta when clamping to contain blood flow is either not possible or not desirable.
The open anastomosis technique for ascending aortic surgery, used in conjunction with HCA, clearly illustrates the significance of this approach. This technique has proven to be so important to the long-term results in surgery of the ascending aorta that it is now the standard of care for this surgery. With the open anastomosis technique, the ascending aorta is not clamped while the aneurysm is resected and the polyester graft sewn to the aortic arch, thus avoiding any damage a clamp might cause to the remaining aortic tissue. This same technique also applies when the surgery extends into the aortic arch. The ability to safely perform this procedure is due to the use of HCA during the time the aorta is open and unclamped.