ARDS Predicted Mortality in Nontrauma Patients

COLORADO SPRINGS — Nontrauma surgical ICU patients who develop acute respiratory distress syndrome have a 10-fold greater 30-day mortality than those without this complication, Dr. Shirin Towfigh reported at the annual meeting of the Western Surgical Association.

This observation, derived from analysis of a large, prospective, single-center acute respiratory distress syndrome (ARDS) registry, stands in marked contrast to the situation prevailing among trauma surgical ICU patients. Multiple centers have reported that in contemporary practice, ARDS in trauma surgery patients in the ICU isn't an independent predictor of increased mortality, said Dr. Towfigh of the University of Southern California, Los Angeles.

Although ARDS has historically been a major cause of mortality among the critically ill, the incidence of ARDS among surgical ICU patients has declined sharply during the past decade. However, nearly all prior studies of ARDS in surgical patients have been restricted to trauma patients. To round out the picture, Dr. Towfigh reported on 2,046 consecutive nontrauma surgical patients admitted to the ICU at USC during 2000–2005. All were evaluated daily for ARDS, as has been routine practice there since 2000.

The overall incidence of ARDS in the study population was 6.1%. But as has previously been reported, the rate among these nontrauma surgical ICU patients declined sharply over time, from 12.2% in 2000 to 2.1% in 2005, an 83% drop in 5 years.

“The cause of this is unknown, but we do know that over the past decade or so in our ICU we have managed our patients differently, using lung-protective ventilation strategies, infection control measures, early extubation protocols, and judicious use of IV fluids, which may have improved the incidence of ARDS,” Dr. Towfigh said.

Patients who developed ARDS were an average of 3.6 years older than those who didn't. They were also sicker upon ICU admission, as reflected in a mean APACHE-2 score of 23.8, compared with just 5.3 in nontrauma surgical patients without ARDS, and they had roughly a 50% greater prevalence of obesity. In a multivariate logistic regression analysis, risk factors for ARDS were obesity and evidence of sepsis, including tachycardia and use of pressors on admission.

Development of ARDS was associated with a 6.9-fold increased rate of mortality in the ICU, as well as with other major adverse outcomes. Other independent predictors of ICU mortality included the use of pressors, which conferred a 2.9-fold increased risk, and a positive fluid balance, with a 2.3-fold greater risk.

Nontrauma patients were admitted to the ICU from virtually all general surgery divisions. Patients from two divisions had a disproportionate incidence of ARDS: those admitted from acute care surgery represented 23% of all nontrauma surgical ICU patients but accounted for 46% of those who developed ARDS; and colorectal surgery patients made up 8% of the total ICU population but 11% of those with ARDS.

Discussant Dr. Christine S. Cocanour commented that the mortality associated with ARDS in nontrauma surgical ICU patients in this study is closer to the mortality seen with ARDS in the medical ICU.

“I would not be surprised if most of these nontrauma surgical patients with ARDS have underlying chronic medical comorbidities, like those patients in the medical ICU—but they have surgical disease as well,” said Dr. Cocanour of the University of California, Davis.

Dr. Towfigh replied that she and her coworkers plan to reanalyze their data to examine medical comorbidities as potential risk factors for ARDS among nontrauma surgical ICU patients.

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