A Method for Detecting Life-Threatening Signals in Serum Potassium Level   after Myocardial Infarction
  Clinical guidelines recommend maintaining serum potassium levels between 4.0 and 5.0 mEq/L in patients with acute myocardial infarction (MI). These guidelines are based on recent studies that found significant associations between crossing of absolute potassium limits (by in-hospital mean or by min/max values) and mortality. This paper investigates a different approach: we hypothesized that a change in the potassium level may be a harbinger of short survivability, rather than crossing of absolute boundaries. Our objectives were: (1) to examine if a "change in mean" indicator has the ability to distinguish between survivors and non-survivors of MI hospitalization, and if so, (2) to formulate a framework for detecting life-threatening changes in potassium level of patients hospitalized with MI. The study included 195 patients who were hospitalized for MI from 2002 to 2014, with at least 40 potassium measurements (i.e., severely ill). In a retrospective analysis we found evidence that the "change in mean" criterion significantly discriminated between survivors and non-survivors. A threshold for raising an alarm was specified by plotting an ROC curve and choosing the value that yields the best combination of sensitivity and specificity. In this case, the method detected ~80% of the patients that eventually died, while wrongly alerting for only ~40% of the survivors. The proposed approach is not intended for replacing the absolute-level protocols but to add valuable knowledge to cardiologists. 
Michal Shauly-Aharonov, Moshe Pollak, Ygal Plakht
stat.AP