Our analytic methods mirror those of our original publication. [6 (link)] Doses of vasoactive medications were recorded hourly for the first 48 hours after post-operative admission to the CICU. The full list of medications can be viewed in Appendix 1. We calculated the Inotrope Score (IS) and the Vasoactive-Inotropic Score (VIS) as described previously [6 (link)] and as shown in Box 1.
We also assessed the sensitivity and specificity of a score including all inotropes, vasopressors, and vasodilators listed in Appendix 1. This formula was inferior to the IS and VIS, and was not further analyzed.
We calculated the maximum and mean IS and VIS in the first and second 24 hour periods after admission to the CICU. To account for vasoactive support over time, and for cases where a patient returned to the CICU on high support only to have it quickly weaned, we studied the mean IS/VIS. Mean IS/VIS was calculated by summing the hourly doses during the 24 hours period and dividing by 24. We also used the IS and VIS at hour 2 and compared this to the other measures. Patients were classified into one of the 5 mutually exclusive groups defined in our previous study [6 (link)] based on their scores at the different time points (Table 1), and assigned to the highest group achieved in either frame. For patients who reached a clinical endpoint (see next section below) in the first 48 hours, we did not use any IS or VIS scores after the event to calculate their maximum and mean scores or to classify them into the group framework. We chose to do this because we were interested in using VIS as a metric to predict eventual clinical outcome, and scores collected after an event (e.g. cardiac arrest or initiation of mechanical circulatory support) do not contribute meaningful data for that purpose.