Improving value through cerebral oximetry monitoring: Mitigating surgical complications in the cardiac operating room

David Theodoro & Robert Palmer

Abstract

Hospitals operate in an increasingly complex financial and regulatory environment, and demonstrating value in medical care has become a critical element of healthcare reform. In this retrospective analysis of cardiac surgical cases, participating hospitals were categorized as either Users or Non-Users of cerebral regional oximetry (rSO2) monitoring. Outcomes of interest included the rates of selected surgical complications (permanent stroke, renal failure, and prolonged mechanical ventilation) and 30-day readmission rates. Analysis of Expected vs. Observed complication rates indicated that users of rSO2 monitoring had fewer events than expected (or as expected for prolonged ventilation), and that non-users had higher than expected events. The use of rSO2 monitoring was also associated with a favorable difference in 30-day readmission rates between the User and Non-User groups. The results of this analysis indicate that rSO2 monitoring during cardiac surgery can favorably impact patient outcomes and quality of life while leading to substantial cost savings.

Introduction

Value in healthcare can be defined as health outcomes that matter to patients divided by the total costs of care for a patient’s condition over the care cycle of delivering these outcomes¹. The delivery and demonstration of “value” is a fundamental element of reform, yet for many reasons, the clinical and economic outcomes for treatment options have been historically hard to measure in a consistent, systematic way. Understanding cost, quality, and cost-effectiveness in provided care is central to developing value-based healthcare (VBHC) business models. Cardiac surgery is an important clinical service and profit center to hospitals and the impact of new technology and healthcare reform is of great interest to providers, medical-technology companies, and payors². Cerebral ischemic events (events of reduced brain oxygen levels) during cardiac surgery are relatively common and are associated with significant postoperative complications^3-9. More specifically, up to 37% of cardiac surgery patients exhibit some degree of cerebral ischemia⁷ and during high-risk surgery, up to 76% of patients experience abnormally low oxygen levels (cerebral desaturation)⁸. Clinical trials have shown that cerebral oxygen desaturation during cardiac surgery is associated with significant postoperative major complications including neurological injury^3,6,9, increased time on mechanical ventilation⁵, and prolonged hospital stay ^4,6. Regional oximetry (rSO2) is a noninvasive technology for monitoring cerebral oxygen saturation that can alert the clinician to potentially dangerous cerebral oxygen desaturation events and help avoid associated complications. Cerebral oximetry monitoring during cardiac surgery may help to: expedite corrective interventions^10,11, reduce postoperative complications ^4,9,12, reduce the length of ICU and overall hospital stay ^4,13, and contribute to a lower total cost of care ^4,12,13. Given the potential benefits of rSO2 monitoring within the context of a changing and more demanding healthcare landscape and an increased focus on value-based healthcare, the objective of this analysis was to describe the clinical and economic value of using one such cerebral oximetry monitoring system, specifically the INVOS™ cerebral/somatic oximetry system (“INVOS™ system” hereafter), using a retrospective review of cardiac surgical cases.

Methods

This retrospective, observational analysis encompassed 10,778 surgical cases. The participants included 7 cardiac centers located in Western, Midwestern, and Eastern regions of the United States over a 5-year time period (2010-2014). Participating hospitals were placed into one of two cohorts based on whether they were Users or Non-Users of rSO2 monitoring. Primary procedure type (coronary artery bypass grafting [CABG], valve surgery, and other) was also well balanced across Users and Non-Users (Figure 1). As described below, the analysis explored differences between the two cohorts in clinical and economic outcomes of adult patients undergoing cardiac surgery.

The clinical outcomes of interest included post-operative neurological injury defined by permanent stroke, renal failure (RF) defined as patients starting dialysis following surgery, and prolonged mechanical ventilation (PMV) defined as mechanical ventilation greater than 24-hours in the postoperative period. Clinical outcomes were risk-adjusted using risk scores as provided by the Society of Thoracic Surgeons (STS) predicted risk score^14-17. Thirty-day readmission rate was also included as an outcome of interest. The analysis compared the expected (or predicted) rate of a complication based on the risk score as described above with the observed (or actual) number of patients that died or suffered a complication.

Economic outcomes were defined as the estimated reimbursement less the direct hospital costs of treating patients. Revenues were estimated using clinical factors to derive the expected MSDRG assignment and normalized using institution-specific CMS payment rates applied to each case. The direct cost related to pre-operative care, operative care, post-operative care, complications as well as discharge and transfer status were defined at the case level.

Results

Analysis of data from 10,778 cases showed that rSO2 monitoring was associated with fewer than expected cases of RF and stroke (Figure 2). For RF, the observed rate was 54% less than expected for Users and 2% more than expected for Non-Users. For stroke, the observed rate was 26% less than expected for Users, and 29% more than expected for Non-Users. Prolonged mechanical ventilation occurred at the expected rate for Users, while Non-Users had 7% more cases than expected. For each evaluated complication, comparative economic outcomes analysis indicated that rSO2 monitoring was associated with substantial implied cost savings when compared to no rSO2 monitoring, with calculated relative cost avoidances of $4,234,385, $1,533,902, and $2,090,056 for RF, stroke, and PMV, respectively.

Discussion

The healthcare economic landscape is changing, including new outcome-based payment models, increasing penalties, declining reimbursement, growing Medicaid and reduced private-pay populations. These economic dynamics, combined with an aging population, and with increasing comorbidities and chromic conditions, are pressuring hospitals to make well-informed purchasing decisions that consider a technology’s ability to bring value and/or reduce patient costs while delivering improved patient outcomes. In this analysis, we found differences between Users and Non-Users of rSO2 monitoring in the observed compared to the expected rate of clinically significant complications, including RF, stroke, and PMV. More specifically, rSO2 monitoring was associated with 54% fewer than expected events of RF and 26% fewer than expected events of stroke. For PMV, rSO2 non-users had 7% more events than expected. For these complications, rSO2 monitoring was associated with significant relative cost avoidance ranging from ~$1.5 million to ~$4.2 million. The use of rSO2 monitoring was also associated with a favorable difference in 30-day readmission rates across the User (5.2%) and Non-User (9.7%) groups, resulting in a relative cost avoidance of ~$210,000.

Together, these results indicate that using rSO2 monitoring to detect cerebral oxygen desaturation events during cardiac surgery can help to improve both patient outcomes and hospital financial performance through the avoidance of costly complications. The difference in patient quality of life, functional capacity and total cost of dealing with these complications over a lifetime is significant. While this report provides the largest analysis of regional/cerebral oximetry monitoring to date, this retrospective analysis is not without its limitations. Though prospective, randomized clinical studies are the standard for evaluating the effectiveness of any intervention, it is unlikely that a prospective study of this size would be performed given the potential costs and timeframe required. Furthermore, with the current evidence supporting the use of rSO2 monitoring during cardiac procedures, randomizing a large number of patients to “no rSO2” monitoring might likely raise ethical considerations.

Conclusions

In a complex healthcare environment, adopted technologies must deliver demonstrable value over the full cycle of care. This determination requires careful study of risk-adjusted outcomes and costs as compared to alternative approaches. In the current analysis, the use of cerebral oximetry monitoring was associated with fewer than expected cases of RF, stroke, and PMV, each of which are clinically significant complications with great human and economic implications. Together, these findings indicate that using cerebral oximetry monitoring during cardiac surgery can favorably impact patient outcomes and quality of life while leading to substantial cost savings. On a broader scale, increasing the use of cerebral oximetry monitoring during cardiac surgery procedures nationwide could have a significant impact on both clinical and economic outcomes for the overall U.S. healthcare system.

Acknowledgements

This analysis was supported by Medtronic.

About the authors

Dr. David Theodoro, MD is a practicing cardiac surgeon, chairman of the department of cardiovascular medicine and chairman of the 1,200 MD member clinically integrated network for SSM health.

Mr. Robert Palmer, MBA is President and CEO of PotentiaMetrics. He has over 20-years of industrial experience in developing analytic models for healthcare payers, providers, life and sciences.

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