Comparison Bewteen Intraoperative HPI vs. High Mean Arterial Pressure Threshold

Randomized Controlled Trial Comparing HPI and Elevated Threshold Monitor Alarms in Preventing Intraoperative Hypotension

Intraoperative hypotension (IOH) is a common and serious complication during surgery, closely associated with poor postoperative outcomes. Traditionally, anesthesiologists rely on real-time physiological parameters and alarms to monitor blood pressure, but the low alarm thresholds may lead to delayed interventions. The Hypotension Prediction Index (HPI) is a novel predictive tool that uses arterial waveform signals and advanced algorithms to forecast hypotensive events in advance. Recent observational studies have shown that HPI's accuracy in predicting hypotension is highly consistent with setting the physiological monitor's alarm threshold to 73 mmHg. This study will compare the effectiveness of HPI and a raised alarm threshold of 73 mmHg in preventing IOH. While HPI is promising with its AI-assisted approach to patient care, its high cost due to the advanced technology raises concerns. If its accuracy is comparable to simply raising the traditional monitor threshold, it may not lead to substantial changes in clinical practice.

Study Overview

• Status: Active, not recruiting
• Conditions: Hypotension During Surgery
• Intervention / Treatment: Device: Maintain HPI < 85; Drug: Maintain MAP>=73

Detailed Description

Intraoperative hypotension (IOH) is a significant complication that affects surgical patients, potentially leading to adverse outcomes postoperatively. Standard practices involve relying on monitoring devices with low alarm thresholds for blood pressure, which may result in delayed interventions. The Hypotension Prediction Index (HPI) offers a predictive approach by analyzing arterial waveform signals and using complex algorithms to detect potential hypotensive episodes early. Recent observational studies have suggested that HPI's accuracy in predicting hypotension aligns closely with raising the physiological monitor alarm threshold to 73 mmHg. To further investigate this, this study will compare the effects of setting a traditional monitor alarm threshold at 73 mmHg with using HPI to prevent IOH.

In this study, patients will be randomly assigned to two groups. In the HPI group, interventions will be initiated when the HPI value exceeds 85. These interventions will follow a protocol that includes fluid administration, norepinephrine, and dobutamine to prevent hypotension. The control group will have their alarm threshold set at 73 mmHg. For these patients, interventions will be based on stroke volume variation (SVV) and clinical judgment, utilizing fluid and norepinephrine as needed. HPI is an attractive AI-based tool for medical care, but its high cost due to advanced technology raises questions. If its accuracy proves to be similar to simply raising the alarm threshold to 73 mmHg, it may not lead to meaningful changes in clinical practice. The study aims to compare the efficacy of these two methods in reducing the incidence of IOH.

• Study Type: Interventional
• Enrollment (Estimated): 100
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Taiwan
  • Taipei, Taiwan, 100
    • National Taiwan University Hosipital
  • Taoyuan District, Taiwan, 302
    • National Taiwan University Hospital Hsin-Chu Branch

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• A: Patients undergoing surgeries requiring general anesthesia lasting more than two hours, and requiring continuous arterial blood pressure monitoring via arterial catheter according to standard medical practice. This includes:

ASA Class II or higher. Estimated surgery duration of three hours or more. High cardiovascular risk, such as poorly controlled hypertension, diabetes, coronary artery disease, chronic kidney disease, or chronic emphysema.

• B: Patients aged 18 years or older.

Exclusion Criteria:

• ASA Class I: Patients with mild systemic disease.
• Pregnancy: Pregnant women.
• End-stage renal disease: Patients with eGFR below 30 ml/min/1.73 m².
• Cardiac shunt: Presence of intracardiac shunt.
• Severe arrhythmias: Including supraventricular tachycardia (heart rate >100 bpm), ventricular tachycardia, or ventricular fibrillation.
• Factors affecting SVV accuracy: Conditions such as atrial fibrillation (A-Fib) or thoracic surgery that can invalidate stroke volume variation (SVV) measurements.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Triple

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: HPI Group; Use the hypotension predictive index (HPI)-guided protocol to prevent intraoperative hypotension, initiating treatmentusing the fluid administration or intravenous norepinephrine infusion to keep intraoperative HPI below 85.	Device: Maintain HPI < 85; Protocolized treatment with fluid administration, norepinephrine, and dobutamine to prevent intraoperative hypotension. The two arms are triggered by different alarms: one from a traditional monitor with an elevated MAP threshold of 73 mmHg, and the other from an HPI threshold of 85.
Active Comparator: 73mmHg MAP Alarm Group; Intraoperative maintenance of the mean arterial pressure (MAP) at 73 mmHg or higher by using the fluid administration or intravenous norepinephrine infusion.	Drug: Maintain MAP>=73; Protocolized treatment with fluid administration, norepinephrine, and dobutamine to prevent intraoperative hypotension. The two arms are triggered by different alarms: one from a traditional monitor with an elevated MAP threshold of 73 mmHg, and the other from an HPI threshold of 85.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Comparison of Time-Weighted Average (TWA) for MAP below 65 mmHg During Surgery	The primary outcome will assess the time-weighted average (TWA) for both groups, comparing the duration and magnitude of mean arterial pressure (MAP) below 65 mmHg during surgery. This will help determine the effectiveness of the interventions in preventing intraoperative hypotension and hypertension.	From the start of surgery to the end of surgery, approximately up to 12 hours, depending on the duration of the operation.
Comparison of Time-Weighted Average (TWA) for MAP above 100 mmHg During Surgery	The primary outcome will assess the time-weighted average (TWA) for both groups, comparing the duration and magnitude of mean arterial pressure (MAP) above 100 mmHg during surgery. This will help determine the effectiveness of the interventions in preventing intraoperative hypotension and hypertension.	From the start of surgery to the end of surgery, approximately up to 12 hours, depending on the duration of the operation.

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
30-day mortality rate	30-day mortality rate from the day of the surgery.	From the day of surgery to 30 days postoperatively.
hospital stay	Total hospital stay duration in days.	Approximately 7 days from the date of enrollment
dosage of intraoperative interventions (such as vasopressors and fluids)	The type, and dosage of intraoperative interventions (such as vasopressors and fluids) administered during surgery.	During the surgery (from induction of anesthesia to the end of surgery, approximately up to 12 hours, depending on the duration of the surbery).

Collaborators and Investigators

• Sponsor: National Taiwan University Hospital
• Investigators: Principal Investigator: Tsung Ta Wu, MD., National Taiwan University Hospital HsinChu Branch

Publications and helpful links

General Publications

• Hatib F, Jian Z, Buddi S, Lee C, Settels J, Sibert K, Rinehart J, Cannesson M. Machine-learning Algorithm to Predict Hypotension Based on High-fidelity Arterial Pressure Waveform Analysis. Anesthesiology. 2018 Oct;129(4):663-674. doi: 10.1097/ALN.0000000000002300.
• Mulder MP, Harmannij-Markusse M, Fresiello L, Donker DW, Potters JW. Hypotension Prediction Index Is Equally Effective in Predicting Intraoperative Hypotension during Noncardiac Surgery Compared to a Mean Arterial Pressure Threshold: A Prospective Observational Study. Anesthesiology. 2024 Sep 1;141(3):453-462. doi: 10.1097/ALN.0000000000004990.

Study record dates

Study Major Dates

• Study Start (Actual): September 16, 2024
• Primary Completion (Actual): October 14, 2025
• Study Completion (Estimated): May 31, 2026

Study Registration Dates

• First Submitted: September 18, 2024
• First Submitted That Met QC Criteria: October 6, 2024
• First Posted (Actual): October 8, 2024

Study Record Updates

• Last Update Posted (Actual): December 17, 2025
• Last Update Submitted That Met QC Criteria: December 16, 2025
• Last Verified: November 1, 2025

More Information

Terms related to this study

• Keywords: overtreatment; HPI; intraopeartive hypotension
• Additional Relevant MeSH Terms: Cardiovascular Diseases; Vascular Diseases; Hypotension; Physiological Effects of Drugs; Central Nervous System Depressants; Peripheral Nervous System Agents; Sensory System Agents; Anesthetics; Anesthetics, Local; Benzocaine
• Other Study ID Numbers: 202406137RIND

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: Yes
• product manufactured in and exported from the U.S.: Yes