CMAJ: Improved outcomes possible for cardiac arrests in the ICU
Patients who experience cardiac or respiratory arrest while in an intensive care unit (ICU) are at a higher risk of death if the cardiac arrest was due to pulseless electrical activity or asystole or if they were on CPR for a prolonged period, according to a study in the Aug. 15 issue of the Canadian Medical Association Journal that tracked outcomes over five years. But ICU patients have better chances of surviving cardiac arrest than patients in non-ICU wards, researchers found. An accompanying editorial argued that the results identified survival to hospital discharge as a potential sweet spot for improving patient outcomes.

In a previous study, Demetrios J. Kutsogiannis, MD, MHS, and Peter G. Brindley, MD, both of the division of critical care medicine at the University of Alberta in Edmonton, Canada, determined survival outcomes after cardiac arrest in non-ICU hospital wards. In the present study, they asked whether cardiac arrests in ICUs might have increased survival because the setting offered 24-hour cardiac monitoring and a high patient-to-nurse ratio, or decreased survival because patients in ICUs already had a high disease burden. They chose a five-year follow-up period to assess both short- and long-term outcomes and identify risk factors within 24 hours of arrest and later.

“We hypothesized that patients theoretically should do slightly better in the ICUs because conditions are monitored more carefully, and in fact, that is what we found,” Kutsogiannis said in an interview with Cardiovascular Business. “Although the patients overall are sicker in coronary care units, cardiovascular units and general ICUs than on the ward, the ICU patients did better; in fact, they did twice as well for survival at one year.”

The researchers reviewed records of adults who had experienced cardiac or respiratory arrest while in an ICU at any of four hospitals in Edmonton in order to evaluate patient and clinical characteristics as well as outcomes. The ICUs were one of three types—general, coronary care and cardiovascular surgery—and the study period spanned from Jan. 1, 2000, to April 30, 2005. The study included 517 patients, 62.3 percent male, with a mean age of 66.5 years. To determine risk, the team looked at patient data, including Acute Physiology and Chronic Health Evaluation (APACHE II) scores that were obtained on admission, and calculated CPR duration as arrival of the code team leader to return of spontaneous circulation.

Of the 517 patients, 307 (59.6 percent) were resuscitated; 156 (30.4 percent) survived to discharge from the ICU; 138 (26.9 percent) survived to discharge from the hospital; 126 (24.3 percent) survived to one year; and 83 (15.9 percent) survived to five years.

The researchers found that type of cardiac arrest affected outcomes. Pulseless electrical activity or asystole were associated with high mortality risk, with only 10.6 percent of patients with those rhythms surviving to one year compared to 36.3 percent of patients with other rhythms. Longer duration of CPR was an independent predictor of death within 24 hours of arrest and later, and age a predictor of death after eight months and later.

Kutsogiannis said that the research team was motivated in part from experience counseling patients and their families about in-hospital cardiac arrest outcomes. The study’s findings may provide physicians with evidence to help patients and their families make end-of-life decisions before being admitted to an ICU. “These results help inform physicians about what the actual outcomes may be, particularly for those who are very ill in the ICU,” he said in the interview. “It should be made clear that their outcomes are poor.”

The authors wrote that on average, survival to discharge from ICU for all patients exceeds 80 percent. But over the past two decades, survival rates from ICU cardiac arrest have not improved. “In our study, only about 30 percent of patients survived to ICU discharge after their arrest,” they wrote.

The authors noted that results from their study of non-ICU hospital wards showed comparatively worse survival for non-ICU patients, though: only about 30 percent of those patients regained a pulse and only 13 percent survived to hospital discharge. Kutsogiannis attributed the 13 percent survival rate in part to less monitoring in the ward setting. “Collectively, the results of our two studies highlight the primacy of whether an arrest is witnessed over where the arrest occurs in a hospital,” the authors wrote.

The researchers noted some limitations, including being underpowered, vulnerable to record-keeping inaccuracies and restricted to data up to 2005. In an accompanying editorial, Benjamin S. Abella, MD, from the Center for Resuscitation Science at the University of Pennsylvania, agreed that the 2005 cutoff did not reflect current practice. In particular, he cited the use of therapeutic hypothermia as a newer treatment that could affect outcomes.

Abella noted that “not all cardiac arrests are the same” and recommended future studies that were more patient-centered and focused on physiology. He also provided an alternate interpretation of some data.

“Changing the denominator from the total number of patients who had an arrest to the number who survived to hospital discharge gives a survival rate of 91 percent at one year and 60 percent at five years,” Abella wrote. “This suggests that, contrary to conventional wisdom, patients who experience in-hospital cardiac arrest have a real opportunity for long-term survival, if we can improve that key initial step: survival to hospital discharge.”

Kutsogiannis said he hadn’t considered Abella’s interpretation but he agreed with it. As the study showed, early intervention and reversing the arrest are key to improving outcomes, he emphasized. “There is opportunity there and reason for optimism,” he said. “We can tell families now that just because an ICU patient had cardiac arrest, it does not mean they are going to die or have a bad prognosis, if we get them through the process.”