Validation and clinical applicability of the Hypotension Prediction Index in a general ICU population: a prospective observational cohort study Study acronym Prediction of Hemodynamic Instability in Patients Admitted to the ICU; the PHYSIC study

Abstract Background: Hypotension is associated with adverse outcomes in patients admitted to the intensive care unit (ICU). The application of an arterial blood pressure derived algorithm predicting hypotension significantly reduced hypotension during surgery. This Hypotension Prediction Index (HPI), calculates the likelihood (range 0-100) of hypotension occurring within minutes. In this study, the performance and clinical applicability of HPI is assessed in ICU patients. Objectives: The primary objective was to assess overall performance of the HPI in ICU patients. Secondary objectives were to assess; the time to hypotensive events, change in the average sensitivity of HPI-85 preceding a hypotensive event, performance of HPI at clinical relevant threshold (HPI ≥ 85), and differences in patient subgroups. Methods: We performed a prospective cohort study in an adult general ICU population of a tertiary academic medical centre using continuous arterial pressure waveform data. Hypotension was defined as mean arterial pressure below 65 mmHg for at least one minute. The predictive ability of HPI was evaluated using a forward analysis, calculating sensitivity, specificity, positive predictive value (PPV), time to event, receiver operating characteristic (ROC) curve and precision recall (PR) curve. Results: In 499 included and analysed patients, HPI showed an excellent predictive performance (area under ROC curve 0.97, PR curve 0.95), with a statistical optimum calculated at HPI 95 (Youden Index 0.87). Employing HPI ≥ 85 as an alarm resulted in a sensitivity of 99.7%, specificity of 76.3%, PPV of 83% and a median time to hypotensive event of 160 sec [IQR 60–380]. There was no difference in HPI performance between different patient subgroups. Conclusions: HPI showed excellent performance in the prediction of hypotension in a general ICU population, without differences between subgroups. However, the average time between alarm (HPI ≥ 85) and the onset of hypotension is relatively short, which might affect the applicability and added value in an ICU setting. Trial registration This study was registered with the Netherlands Trial Register (NTR7349). The study was submitted and accepted for registration 2018-07-04, before the first patient was included. (https://www.trialregister.nl/trial/7150). Source ID: W18_142#18.176