Impact of Obesity on Postoperative Outcomes following cardiac Surgery (The OPOS study): rationale and design of an investigator-initiated prospective study

Abstract

Introduction: Increasing levels of obesity worldwide have led to a rise in the prevalence of obesity-related complications including cardiovascular risk factors such as diabetes, hypertension and dyslipidaemia. Healthcare providers believe that overweight and obese cardiac surgery patients are more likely to experience adverse postoperative outcomes. The body mass index (BMI) is the primary measure of obesity in clinical practice, without accounting for a patient's level of cardiopulmonary fitness or muscle mass. The objective of this study is to determine whether fitness capacity of obese cardiac surgical patients and biomarkers, alone or in combination, will help identify patients at risk for adverse outcomes when undergoing cardiac surgery.

Methods and analysis: Patients between the ages of 18 and 75 years undergoing elective cardiac surgery are consented to participate in this prospective observational study. Patients will be invited to participate in measures of obesity, functional capacity and exercise capacity assessments, quality of life questionnaires, and blood and tissue sampling for biomarker analysis. The endpoints evaluated are measures other than BMI that could be predictive of short-term and long-term postoperative outcomes. Clinical outcomes of interest are prolonged ventilation, hospital length of stay, renal failure and all-cause mortality. Biomarkers of interest will largely focus on metabolism (lipids, amino acids) and inflammation (adipokines, cytokines and chemokines).

Ethics and dissemination: This study has been approved by the institutional review board at the Horizon Health Network. On completion of the study, the results shall be disseminated through conference presentations and publications in peer-reviewed journals. Additionally, the report shall also be diffused more broadly to the general public and the cardiovascular community.

Trial registration number: NCT03248921.

Keywords: adipose tissue; atrial appendage; coronary artery bypass grafting; globesity; inflammation; morbidity.

Conflict of interest statement

Competing interests: None declared.

© Author(s) (or their employer(s)) 2019. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.

Figures

Figure 1

Study design flow chart: From left to right: Patients are admitted for surgical consultation and cardiac catheterisation. Consent may be obtained at this time as well as a venous blood sample of 8–10 mL collected. Consent could also be obtained at preoperative admission for cardiac surgery, as well as a venous blood sample of 8–10 mL. (Surgery is elective and typically is scheduled between 2 months and 1 year after surgical consult but not time restrictive to participation.) Patients are admitted 24 hours prior to surgery, and a 30-min preoperative arterial blood sample is collected. Tissue sampling is carried out intraoperatively. At the early postoperative follow-up appointment (occurring between 6 weeks and 3 months), a nonfasting venous blood sample may be collected. At the late postoperative follow-up appointment (approximately 1 year postoperatively), telephone follow-up by questionnaire is conducted. Pre-op, preoperative.

Figure 2

Flow chart showing protocol for the OPOS study. 6MWT, six-minute walk test; CV, cardiovascular; DASI, Duke activity Status Index; ICU: intensive care unit; OPOS, Obesity on Postoperative Outcomes following cardiac Surgery; Pre-op, preoperative; PSMS, Physical Self-maintenance Scale; QOL, quality of life; SF-12, short form-12.