HPI Index With GDHT in Predicting Hypotension In General Anesthesia Patients

The perioperative period is characterized by hemodynamic instability. Intraoperative hypotension (IOH) can be caused by anesthesia drugs, surgical manipulations, hypovolemia or inhibition of the sympathetic nervous system and impairment of baroreflex regulatory mechanisms. In a retrospective analysis performed at the Cleveland Clinic, the risk for acute kidney injury (AKI) and myocardial injury (MI) increased when mean arterial pressure (MAP) was less than 55 mmHg. Further, even short durations of intraoperative hypotension were associated with AKI and MI. Salmasi and coll analyzed whether associations based on relative thresholds were stronger than those based on absolute thresholds regarding blood pressure. They found that there were no clinically important interactions between preoperative blood pressures and the relationship between hypotension and ΜΙ or ΑΚΙ at intraoperative mean arterial blood pressures less than 65 mmHg. Absolute and relative thresholds had comparable ability to discriminate patients with ΜΙ or ΑΚΙ from those without it. The authors concluded that anesthetic management can thus be based on intraoperative pressures without regard to preoperative pressure. In a retrospective cohort study Sun and coll conclude that an increased risk of postoperative stage I AKI occurs when intraoperative MAP was less than 60 mmHg for more than 20 min and less than 55 mmHg for more than 10 min.

Hence it is fundamental for the management of any hemodynamically unstable patient the rapid assessment of the factors that determine the cardiovascular collapse, followed by prompt treatment and, ultimately, reversal of the responsible process. Recently a Hypotension Probability Indicator (HPI) algorithm has been developed from Edwards Lifesciences using continuous invasively-measured arterial waveforms to predict hypotension with high accuracy minutes before blood pressure actually decreases. The HPI algorithm can be integrated with a goal-directed hemodynamic treatment (GDHT) to achieve hemodynamic optimization by increasing global blood flow and prevent organ failure. We developed a treatment protocol implementing HPI with GDHT that can be used in general anesthesia patients to guide clinical practice.

Inclusion criteria

• Aged 18 years or older
• Planned to receive general anaesthesia > 2h
• Planned to receive an arterial line during surgery
• Aim for MAP of ≥ 65 mmHg during surgery
• Being able to give written informed consent prior to surgery

Exclusion criteria

• Aim for MAP other than 65 mmHg at discretion treating physician
• Significant hypotension before surgery defined as a MAP <65
• Right- or left sided cardiac failure (e.g. LVEF<35%)
• Known cardiac shunts (significant)
• Known aortic stenosis (severe)
• Severe cardiac arrhythmias including atrial fibrillation
• Requiring dialysis
• Liver surgery with Pringle maneuver
• Vascular surgery with clamping of the aorta