Introduction: The Quest for the Optimal Perioperative Blood Pressure
For decades, anesthesiologists and surgeons have debated the optimal blood pressure threshold to maintain organ perfusion during major surgery. Intraoperative hypotension is a well-recognized risk factor for postoperative complications, particularly acute kidney injury (AKI) and myocardial injury. While a mean arterial pressure (MAP) of 65 mm Hg has long been the clinical standard, the concept of individualized blood pressure management—tailoring targets to a patient’s unique physiological baseline—has gained significant traction. The IMPROVE-multi randomized clinical trial sought to provide definitive evidence on whether this personalized approach truly improves clinical outcomes for high-risk patients undergoing major abdominal surgery.
Highlights
- Individualized MAP targets based on preoperative nighttime measurements did not reduce the incidence of postoperative complications compared to a routine 65 mm Hg target.
- The primary composite outcome (AKI, myocardial injury, cardiac arrest, or death) occurred in 33.5% of the individualized group versus 30.5% in the routine group.
- None of the 22 secondary outcomes, including 90-day survival and infectious complications, showed a significant difference between the two strategies.
- The results reinforce the validity of a 65 mm Hg MAP threshold as a robust and safe standard of care in the perioperative setting.
Background: The Rationale for Individualization
The physiological rationale for individualized blood pressure management stems from the theory of autoregulation. Every individual has a unique “lower limit” of autoregulation, below which organ perfusion becomes pressure-dependent. Patients with chronic hypertension often have shifted autoregulation curves, potentially requiring higher intraoperative pressures to prevent ischemia. Previous studies, such as the INPRESS trial, suggested that maintaining MAP within 10% of a patient’s resting baseline could reduce postoperative organ dysfunction. However, defining the true “resting” baseline is challenging, as clinic or preoperative measurements are often confounded by anxiety (white-coat effect). The IMPROVE-multi investigators utilized automated nighttime blood pressure monitoring to establish a stable, physiological baseline, hypothesized to be a more accurate target for individualization.
Study Design and Methodology
The IMPROVE-multi trial was a randomized, single-blind clinical trial conducted across 15 German university hospitals between February 2023 and April 2024. The study enrolled 1272 patients aged 45 years or older undergoing elective major abdominal surgery under general anesthesia expected to last at least 90 minutes. Participants were required to have at least one additional high-risk criterion, such as advanced age, American Society of Anesthesiologists (ASA) physical status III or IV, or pre-existing cardiovascular or renal disease.
Interventions
Patients were randomized 1:1 into two groups:
- Individualized Management Group: MAP targets were set based on the patient’s preoperative mean nighttime MAP, assessed using 24-hour ambulatory blood pressure monitoring.
- Routine Management Group: A standard MAP target of 65 mm Hg or higher was maintained throughout the procedure.
Endpoints
The primary outcome was a composite of acute kidney injury (defined by KDIGO criteria), acute myocardial injury (defined by elevated troponin levels), nonfatal cardiac arrest, or death within the first seven postoperative days. Secondary outcomes included infectious complications, the need for kidney replacement therapy, and 90-day mortality.
Key Findings and Results
Of the 1142 patients included in the final analysis (median age 66 years; 34.1% female), the results were strikingly consistent across both groups. The primary composite outcome occurred in 190 of 567 patients (33.5%) in the individualized group and 173 of 567 patients (30.5%) in the routine group. This resulted in a relative risk (RR) of 1.10 (95% CI, 0.93-1.30; P = .31), indicating no statistical difference.
Detailed Outcome Analysis
When breaking down the components of the primary and secondary endpoints, the lack of benefit for individualization remained clear:
- Acute Kidney Injury: No significant difference was noted in the incidence of AKI within seven days.
- Myocardial Injury: Rates of postoperative troponin elevation were similar between groups.
- Infectious Complications: Occurred in 15.9% of the individualized group vs. 17.1% in the routine group (P = .63).
- 90-Day Outcomes: A composite of kidney replacement therapy, MI, cardiac arrest, or death within 90 days showed no significant variance (5.7% vs. 3.5%; P = .12).
Interestingly, the individualized group often required more aggressive vasopressor support to meet higher MAP targets, yet this did not translate into better organ protection. The median MAP maintained in the individualized group was significantly higher than in the routine group, confirming that the intervention was successfully delivered but simply ineffective in changing the clinical trajectory.
Expert Commentary and Clinical Implications
The IMPROVE-multi trial provides a sobering contrast to earlier studies that favored individualized targets. Several factors may explain these results. First, the use of nighttime MAP as a baseline may have resulted in targets that were too low for some and unnecessarily high for others. While nighttime MAP avoids the white-coat effect, it may not represent the physiological requirements of a patient under the stress of major surgery.
Furthermore, the “65 mm Hg” standard used in the control group is a relatively proactive threshold compared to historical practices where lower pressures were often tolerated. It is possible that as long as MAP is kept above 65 mm Hg, further increases in pressure do not provide incremental benefits for the kidneys or heart, and may even introduce risks associated with excessive vasopressor use, such as increased myocardial oxygen demand or mesenteric ischemia.
From a health policy and resource perspective, these findings are significant. Setting individualized targets based on 24-hour monitoring requires additional equipment, time, and clinical oversight. If a standard MAP target of 65 mm Hg—which is easily monitored and achieved—provides equivalent outcomes, the routine adoption of personalized targets may not be justified in the broader surgical population.
Conclusion
The IMPROVE-multi trial concludes that for high-risk patients undergoing major abdominal surgery, individualized perioperative blood pressure management based on preoperative nighttime MAP does not reduce major postoperative complications compared to standard care. While the search for the “perfect” blood pressure continues, this study reinforces that maintaining a MAP of at least 65 mm Hg remains a reliable and evidence-based benchmark for perioperative safety. Future research may need to focus on other markers of perfusion beyond macro-hemodynamic parameters like MAP, such as microcirculatory flow or oxygen delivery metrics.
Funding and Clinical Trial Information
The IMPROVE-multi trial was funded by various institutional grants and supported by 15 German university hospitals. ClinicalTrials.gov Identifier: NCT05416944.
References
- Saugel B, Meidert AS, Brunkhorst FM, et al. Individualized Perioperative Blood Pressure Management in Patients Undergoing Major Abdominal Surgery: The IMPROVE-multi Randomized Clinical Trial. JAMA. 2025;334(21):1893-1904. doi:10.1001/jama.2025.17235.
- Futier E, Lefrant JY, Guinot PG, et al. Effect of Individualized vs Standard Blood Pressure Management Strategies on Postoperative Organ Dysfunction Among High-Risk Patients Undergoing Major Surgery: A Randomized Clinical Trial. JAMA. 2017;318(14):1346-1357.
- Salmasi V, Maheshwari K, Yang D, et al. Relationship between Intraoperative Hypotension, Defined by Either Reduction from Baseline or Absolute Thresholds, and Acute Kidney and Myocardial Injury after Noncardiac Surgery. Anesthesiology. 2017;126(1):47-65.
