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Life-saving predictions from the ICU

By Quinn Eastman | Woodruff Health Sciences Center | Feb. 26, 2018

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It's similar to the "precogs" who predict crime in the movie Minority Report. That's how Tim Buchman, director of the Emory Critical Care Center, describes an emerging effort to detect and ward off sepsis in ICU patients hours before it starts to make their vital signs go haywire.

As landmark clinical studies have documented, every hour of delay in giving someone with sepsis antibiotics increases their risk of mortality. So detecting sepsis as early as possible could save lives. Many hospitals have developed "sniffer" systems that monitor patients for sepsis risk. See a 2016 feature in Emory Medicine for more details.

What Shamim Nemati and his colleagues, including bioinformatics chair Gari Clifford, have been exploring is more sophisticated. A vastly simplified way to summarize it is: if someone has a disorderly heart rate and blood pressure, those changes can be an early indicator of sepsis. It requires continuous monitoring—not just once an hour. But in the ICU, this can be done. The algorithm uses 65 indicators, such as respiration, temperature, and oxygen levels—not only heart rate and blood pressure.

As recently published in Critical Care Medicine, Nemati’s algorithm can predict sepsis onset—with some false alarms—four, eight, even 12 hours ahead of time. No predictor is going to be perfect, Nemati says. The paper lays out specificity, sensitivity, and accuracy under various timelines. They get to an AUROC (area under receiving operating characteristic) performance of 0.83 to 0.85, which this explainer website rates as good (B), and is better than any other previous sepsis predictor.

"To our knowledge, this is the first study to demonstrate acceptable performance of a sepsis prediction algorithm over incrementally longer time windows," the authors write.

The algorithm was "trained" on three years of Emory data, including 31,000 ICU admissions, and then validated on a publicly available data set from Beth Israel Deaconess Medical Center. The algorithm is headed for prospective clinical testing. The question is how to handle "alert fatigue"; nurses and physicians working at the bedside get lots of beeps and warnings already. The answer, Buchman thinks, is to create an additional level of care, including a remote team of safety officers whose primary charge is to detect and evaluate evolving threats to each patient.