Nancy A. Melville

May 17, 2011

May 17, 2011 (Denver, Colorado) — Patients with pneumonia who go into cardiac arrest in the hospital often do so abruptly and away from the intensive care unit (ICU) or other critical care interventions that can keep them alive, according to research presented here at the American Thoracic Society 2011 International Conference.

Patients with pneumonia are known to be at increased risk for cardiac arrest while in the hospital; however, most are believed to do so only after a progressive slide that is marked by plenty of warning signs, according to lead author Gordon E. Carr, MD, pulmonary and critical care fellow at the University of Chicago Medical Center in Illinois.

"The patient in the classic [progressive slide] begins as a healthy individual, develops pneumonia or another life-threatening infection, and then passes through a series of syndromes that we think we can recognize," he explained.

Those syndromes include systemic inflammatory response syndrome, followed by organ failure, hemodynamic failure, and multiple organ failure; classically, the cardiac arrest results from a milieu of events such as hemodynamic failure, renal insufficiency, and severe metabolic problems.

But Dr. Carr said there is increasing concern that some patients bypass that process and rapidly deteriorate.

"We're concerned that not all patients follow this pathway. We wonder, along with other investigators, whether some patients with pneumonia develop a compensative severe infection and not other severe syndromes, and whether the state of compensative severe infection yields abruptly to cardiopulmonary collapse."

"Anecdotally, I'm sure many practicing pulmonologists have experienced this, but we don't have a lot of data to show it actually happens."

In the first large study documenting the characteristics of in-hospital cardiac arrest among such patients, the researchers worked with the American Heart Association, tapping into the organization's Get With the Guidelines – Resuscitation database, a large multicenter registry of adult in-hospital cardiac arrest events that includes data from more than 500 hospitals (formerly the National Registry of Cardiopulmonary Resuscitation).

They found that of the 44,416 cardiopulmonary arrest events that occurred within 72 hours of hospital admission, pneumonia was a preexisting condition in 5,367 cases (12.1%).

Nearly 40% of those patients had cardiac arrests that occurred outside of an ICU. In addition, only 40% of pneumonia patients were receiving mechanical ventilation at the time of the cardiac event, 12.2% had a central venous catheter in place, and 36.3% were receiving continuous infusions of vasoactive medications, according to the study.

The most common immediate causes of in-hospital cardiac arrest among the patients with pneumonia include arrhythmia (65.0%), respiratory insufficiency (53.9%), and hypotension/hypoperfusion (49.8%).

"The striking result was that of all patients with pneumonia, overt hypotension was the presumed immediate cause only 44% of the time; actually, arrhythmia was present most frequently," Dr. Carr said.

Among patients with pneumonia, the study highlights a pattern of a rapid descent into cardiac arrest. We need to reconsider how such patients are monitored, he added.

"Our study found a compelling signal that a significant portion of pneumonia patients who suffer a cardiac arrest in the hospital do so abruptly," he said. "We found that 56% of cases of cardiac arrest among these patients were not caused or preceded by hypotension, and almost 40% happened outside of the ICU."

"This really points to the need for further research to improve risk assessment in monitoring practice in the real world of pneumonia patients. I hope this will spur more research so we learn more about the incidence and etiology of this syndrome."

"We need to rethink how we are assessing risk and timing our interventions with these patients," Dr. Carr observed.

The study highlights important issues regarding the monitoring of pneumonia patients at risk for cardiac arrest, but it also raises some questions, said Brett Fenster, MD, a cardiologist with the National Jewish Hospital in Denver, Colorado.

"As a cardiologist, my first question is how many of these patients had some form of heart problem that was either undiagnosed or diagnosed but underappreciated? The abstract doesn't address cardiac comorbidities — the presence of coronary artery disease, heart failure, hypertension, diabetes, et cetera. I'm sure this will be a common question of the authors," Dr. Fenster said.

"What is surprising is that 20% were on a general medical unit where nursing ratios and monitoring is less intense," he added.

"This does raise the possibility that we are not triaging patients appropriately at the time of admission. It also raises the possibility that there is a confounding issue or set of issues. For example, is there a significant rate of previously undetected heart disease in this group? Is this the result of certain antibiotics causing heart rhythm issues? Were low oxygen levels not treated aggressively enough on a general medical unit? Hopefully, this large dataset will allow for future retrospective analyses of these issues," Dr. Fenster said.

The fact that arrhythmia was the leading cause of cardiac arrest among the patients is also notable, he said.

"If arrhythmia is indeed the most common cause of arrest, perhaps there is a role for more aggressive oxygen supplementation, electrolyte repletion, and avoidance of proarrhythmic drugs in an at-risk population."

Drs. Carr and Fenster have disclosed no relevant financial relationships.

American Thoracic Society (ATS) 2011 International Conference: Abstract 22539. Presented May 15, 2011.

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