Defining the Intrinsic Cardiac Risks of Operations to Improve Preoperative Cardiac Risk Assessments

Jason B. Liu, M.D., M.S.; Yaoming Liu, Ph.D.; Mark E. Cohen, Ph.D.; Clifford Y. Ko, M.D., M.S., M.S.H.S., F.A.C.S.; Bobbie J. Sweitzer, M.D., F.A.C.P.

Disclosures

Anesthesiology. 2018;128(2):283-292. 

In This Article

Abstract and Introduction

Abstract

Background: Current preoperative cardiac risk stratification practices group operations into broad categories, which might inadequately consider the intrinsic cardiac risks of individual operations. We sought to define the intrinsic cardiac risks of individual operations and to demonstrate how grouping operations might lead to imprecise estimates of perioperative cardiac risk.

Methods: Elective operations (based on Common Procedural Terminology codes) performed from January 1, 2010 to December 31, 2015 at hospitals participating in the American College of Surgeons National Surgical Quality Improvement Program were studied. A composite measure of perioperative adverse cardiac events was defined as either cardiac arrest requiring cardiopulmonary resuscitation or acute myocardial infarction. Operations' intrinsic cardiac risks were derived from mixed-effects models while controlling for patient mix. Resultant risks were sorted into low-, intermediate-, and high-risk categories, and the most commonly performed operations within each category were identified. Intrinsic operative risks were also examined using a representative grouping of operations to portray within-group variation.

Results: Sixty-six low, 30 intermediate, and 106 high intrinsic cardiac risk operations were identified. Excisional breast biopsy had the lowest intrinsic cardiac risk (overall rate, 0.01%; odds ratio, 0.11; 95% CI, 0.02 to 0.25) relative to the average, whereas aorto-bifemoral bypass grafting had the highest (overall rate, 4.1%; odds ratio, 6.61; 95% CI, 5.54 to 7.90). There was wide variation in the intrinsic cardiac risks of operations within the representative grouping (median odds ratio, 1.40; interquartile range, 0.88 to 2.17).

Conclusions: A continuum of intrinsic cardiac risk exists among operations. Grouping operations into broad categories inadequately accounts for the intrinsic cardiac risk of individual operations.

Introduction

MORE than 26.8 million operations are performed annually in the United States.[1] Of these, approximately 1.5% of patients will die during the subsequent 30 days, most often due to perioperative cardiac complications.[2] Accurate preoperative risk stratification is paramount to mitigate the risk of perioperative cardiac complications.[3–5] It allows for appropriate preoperative medical optimization, timely cardiac-specific interventions, and guidance regarding perioperative management. Most important, it provides patients the opportunity to make a truly informed decision regarding surgical treatment.[6,7]

Primary care physicians, internists, hospitalists, cardiologists, and anesthesiologists play an integral role in preoperative cardiac risk assessments.[5] Currently, these assessments rely on clinical risk indices, such as the Revised Cardiac Risk Index (RCRI), and clinical practice guidelines to inform decision-making.[7–10] These strategies typically group procedures into broadly defined anatomical categories for the sake of simplicity and to facilitate ease of use. However, these broad categories can potentially underestimate the true risk contributed by any one operation. Additionally, risk assessments such as the RCRI consider patient factors more than the risk of the operation itself. This approach may overestimate risk and result in unnecessary consultations, unnecessary costs, delays in surgery, and even harm from further interventions.[5,11,12]

Operations themselves carry risks for adverse outcomes beyond the influence of patient comorbidities for myriad reasons, such as amount of blood loss, fluid shifts, cytokine release from tissue injury, inflammation, and other acute pathophysiologic changes. Accordingly, surgeons and anesthesiologists recognize that different operations carry intrinsically different risks of complication, but this gestalt can be difficult to formally share with those performing preoperative cardiac risk assessments.[13] For instance, the RCRI labels all intraperitoneal, intrathoracic, and suprainguinal vascular operations as high-risk.[9] However, a laparoscopic cholecystectomy, gastric bypass for morbid obesity, and pancreatoduodenectomy (all intraperitoneal) appear to have different intrinsic risks for perioperative adverse cardiac events. Classifying the risk of operations based on anatomic location or clinical impression may inadequately inform risk assessment for an individual procedure. Lack of granularity may therefore result in misleading predictions of risk and affect clinical decision-making.

To improve upon current preoperative cardiac risk assessment strategies and to facilitate interdisciplinary communication, the objectives of this study were to define the intrinsic risks of operations for perioperative adverse cardiac events (PACEs), and to demonstrate how grouping operations into broad categories rather than considering operations individually might be insufficient for preoperative cardiac risk assessments.

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