A new CHEO-led study has found that some cardiac patients who flatline after being removed from life support will experience a brief recurrence of heart activity before dying.
Published Wednesday in The New England Journal of Medicine, the international study was designed to inform organ donation decisions by providing evidence to back the current method used to declare someone dead in an intensive care unit.
“We wanted to study the dying process scientifically,” said study lead Dr. Sonny Dhanani, CHEO’s chief of critical care.
Six years in the making, the study on the physiology of dying largely supports the standard practice of declaring a flatlined patient dead after five minutes without a pulse.
It’s a necessary and critical step in the organ donation process.
“We’re very confident when we look at the findings of this study, we’ve got the scientific evidence to reaffirm our current standards in organ donation,” Dhanani said.
Researchers studied the deaths of 480 adults at 20 intensive care units in Canada, the Czech Republic and the Netherlands. Patients were only eligible if their surrogate decision makers had opted to withdraw life support measures and if “imminent death” was anticipated.
Researchers later examined the electrocardiogram and blood pressure records of the patients, along with all bedside clinical observations.
The study found that circulatory death is not always straightforward: 14 per cent of dying patients experienced a “transient” resumption of heart activity after flatlining.
In most cases, the duration of that heart activity was brief with a median average of 3.9 seconds. In one case, it lasted 13 minutes.
The physiology of that on-again-off-again heart activity needs to be further explored, Dhanani said, but makes sense given that the heart is such a “strong and robust organ.”
None of the 67 patients who experienced a resumption of heart activity regained consciousness or survived.
In all cases, the heart activity occurred within five minutes of a patient flatlining. In one case, a patient’s heart began to pump blood again, briefly, after four minutes and 20 seconds without a pulse.
The research supports the standard protocol for organ donation, which requires that patients be declared dead only after they’ve been without a pulse for five minutes.
Dhanani said the findings also reinforce the need to “reset” the five-minute clock if a patient experiences a resumption of heart activity after flatlining. “I think that would be a very safe way to move forward,” said Dhanani.
Early in their work, researchers turned to a Toronto woman, Heather Talbot, the mother of an organ donor, for help in understanding how to approach families in ICUs about taking part in the unusual study. Her advice helped to secure a 93 per cent consent rate among the families of dying patients.
Talbot’s son, Jonathon, 22, was declared brain dead in March 2009 following a car accident; his donated kidneys, liver and lungs helped save the lives of four people. “It turns something terrible into something good,” Talbot said of organ donation.
More than 4,000 Canadians are now on waiting lists for an organ transplant.
Dhanani said the study was motivated by the desire to use science to dispel some of the popular myths about patients “coming back to life” after being removed from life support and flatlining. “We think some of the stories were impacting people’s comfort level with the donation process,” he said.
Time is a critical element in the organ donation process. Once a heart stops beating, the body’s organs are no longer being perfused with blood, and any organ that goes without that supply for more than 10 minutes is usually unsuitable for transplant, Dhanani said.
In Ontario, there is no law that establishes how to determine circulatory or neurological death. In 2019, the Court of Appeal for Ontario ruled that while death is not defined in law, common law considers someone dead when there is the irreversible cessation of either cardiorespiratory or brain function.
Organ donation is governed by the “dead donor rule,” an ethical and legal requirement that says organ removal cannot be the cause of a donor’s death.
Copyright Postmedia Network Inc., 2021
