番茄社区

While organ donations have traditionally come from dying patients who have a heartbeat but are considered brain dead, organs can also be harvested after circulatory death, when the heart and circulation reach a full stop.

Donation after circulatory death (DCD) "continues to be an opportunity to increase the pool of organs in our hospitals," said Marie-Carmelle Elie, MD, of the University of Alabama at Birmingham, during a presentation at the Society of Critical Care Medicine's virtual Critical Care Congress.

DCD has been done since the 1960s, "before the establishment of the brain death guidelines," Elie noted. "In fact, now there are programs for DCD heart transplants in several countries, including the U.K., Belgium, and Australia."

Research suggests that boosting the number of transplanted hearts from DCD candidates could increase the heart donor pool by 20%, she added.

In addition, a study published in December 2021 found that transplanted adult hearts harvested after circulatory death fared similarly as those harvested following brain death, with overall 30-day and 6-month survival rates of 96.8% and 92.5%.

DCD candidates often "have devastating neurologic injuries or other organ failures that require mechanical ventilator or circulatory support," such as left ventricular assist device, ventricular assist device, or venoarterial extracorporeal membrane oxygenation (ECMO), said Elie.

After consent is obtained, support is typically withdrawn in an operating room, and the patient is monitored to see if cardiac death occurs. "If the clinical team makes an assessment of cardiac death in the operating room, there is a period of 'standoff,'" she explained.

The term "standoff" (or "hands-off") refers to a waiting period in which clinicians monitor the patient for revival. "This could be 5 to 10 minutes based on your local law or [policy], at which point the death could be officially declared and the procurement could begin," Elie continued.

Complications can arise, such as the patient remaining alive for an extended period of time. "The progression could actually be prolonged for up to 2 hours. Now, most institutions don't typically wait for 2 hours. Some institutions wait as long as 30 minutes, and then will discontinue the procedure," she noted.

Organs may deteriorate over this kind of extended period, making it important to carefully match them to appropriate recipients. For example, "an organ from a young patient who had a progressed time to death would be most appropriately placed in a young patient who may have much more reserve and could accept that organ," she said.

Of note, a more controversial strategy is also being researched, in which hearts are resuscitated after circulatory death in order to allow them to be harvested.

, the , and the are experimenting with resuscitating the heart via normothermic regional perfusion after circulatory death. "In essence, following circulatory arrest, there will be a ligation of bilateral vertebral and carotid arteries, allowing a natural cessation of brain function," Elie explained. "Subsequent to the ligation, patients would be immediately placed on ECMO, and this would allow prolongation of warm ischemia time, extended assessment time, and increased organ procurement."

However, these procedures raise ethical questions, she noted. In 2021, the American College of Physicians said that heart donations following this procedure appear to violate the tenets that patients cannot be killed in order to obtain their organs, and organ retrieval cannot cause death.

Comment