Hello everyone,
I am an anesthesiologist with significant cardiac anesthesia experience...I am also working towards CPC and own a medical billing company. I learn so much here and humbly offer my clinical experience.
All patients who are put on bypass (heart-lung machine) are cooled, usually to around 34 degrees. this is to decrease the metabolism of the major organs, esp the brain, to tolerate the possibility of decreased delivery of oxygen to the organs. Bypass, of course, is a circuit of tubing and a heart-lung machine that provides circulation of the patient's blood while the heart is stopped, making it much easier to work on.
However, on rare occasions, it is necessary to additionally place a patient in deep hypothermic circulatory arrest (DHCA), often for surgery on the major blood vessels entering and exiting the heart: aorta, superior venae cava, etc The patients are heparinzed, put on bypass and cooled to 34. Then, they are cooled down even more dramatically down to about 18 degrees, and then the bypass machine is completely STOPPED. IOW, there is NO CIRCULATION AT ALL to the body since neither the heart nor the heart-lung machine are causing flow of the blood. This is called "circulatory arrest." The patients, are so cold that they can survive without blood supply, usually with the goal of 30 minutes or less before restarting blood flow via the bypass machine, then weaning off bypass to complete the surgery.
So, as you can see, DHCA is a big deal. Standard documentation on our records would note the start and stop time for Cardiopulmonary bypass, start and stop times for aortic cross-clamping, if appled, AND start and stop times for DHCA.
I hope that is helpful.
https://en.wikipedia.org/wiki/Deep_hypothermic_circulatory_arrest