The HYPE-2 Randomized Clinical Trial

Hypotension during cardiac surgery and post-operative intensive care unit (ICU) admission is associated with adverse outcomes. Current management of hypotensive episodes is predominantly reactive and rather occurs with delay. Edwards Lifesciences (Irvine, CA) has developed an algorithm using continuous invasively-measured arterial waveforms to predict hypotension with high accuracy minutes before blood pressure actually decreases, the so called Hypotension Prediction Index (HPI). HPI has never been tested in cardiac surgery patients or patients admitted to the ICU. Elective coronary artery bypass graft (CABG) patients will be randomized in two groups, treatment and conventional. Treatment group: in addition to standard monitoring (continuous arterial blood pressure monitoring and pulse pressure variation), patients are connected to a HemoSphere monitor which provides additional advanced hemodynamic variables (e.g. cardiac output, systemic vascular resistance) and the HPI. The treating anesthesiologist, anesthesia nurse, intensivist and critical care nurse are trained to use these variables and are provided with a diagnostic flowchart to determine the cause (preload, contractility and afterload) of the upcoming hypotensive (mean arterial pressure (MAP) < 65 mmHg) event. Timing of treatment and choice of treatment is then left to the discretion of the attending anesthesiologist, anesthesia nurse, intensivist and critical care nurse. Conventional arm: institutional standard of care with an intention to keep MAP equal to or above (≥) 65 mmHg. The HemoSphere will be connected for data extraction but fully covered and silenced.

We hypothesize that the use of this algorithm will reduce hypotension as measured by the time weighted average (TWA) during both the off-pump phase of on-pump coronary artery bypass graft (CABG) surgery and the mechanically ventilated phase of post-operative ICU admission.

1. Pre-surgery: blood samples
2. During surgery and mechanically ventilated duration of ICU stay: blood samples and connecting arterial line to HemoSphere monitor
3. Post-ventilated ICU phase: blood samples and connecting arterial line to HemoSphere monitor (for 8 hours maximum)

Treatment group: in addition to standard monitoring (continuous arterial blood pressure monitoring and pulse pressure variation), patients are connected to a HemoSphere monitor which provides additional advanced hemodynamic variables (e.g. cardiac output, systemic vascular resistance) and the HPI. The treating anesthesiologist, anesthesia nurse, intensivist and critical care nurse are trained to use these variables and are provided with a diagnostic flowchart to determine the cause (preload, contractility and afterload) of the upcoming hypotensive (mean arterial pressure (MAP) < 65 mmHg) event. Timing of treatment and choice of treatment is then left to the discretion of the attending anesthesiologist, anesthesia nurse, intensivist and critical care nurse.