Post-Operative Cerebral Oximetry for Detection of Low - Cardiac Output Syndrome after Coronary Artery Bypass Surgery in Patients with Low Pre-Operative Left Ventricular Ejection Fraction - A Protocol for an Observational Study on Simultaneous Monitoring of Cerebral Oximetry and Cardiac Index

Author(s): Miriam Silaschi, Markus Velten, Marc Rohner, Marcus Thudium, Jacqueline Kruse, Marwan Hamiko, David Rowlands, Stefan Kreyer, Christian Putensen, Nils Theuerkauf, Mark Coburn, Farhad Bakhtiary

Background: While cerebral near infrared spectroscopy (NIRS) is a valuable diagnostic tool to monitor brain oxygenation during cardiac surgery, its value in situations of low cardiac output in critical care patients has not been thoroughly evaluated. Thus, the aim of this study is to evaluate the correlation of NIRS with cardiac index in low cardiac output syndrome (LCOS). The hypothesis of this study is that NIRS shows significant decline during LCOS earlier than routine hemodynamic measurements.

Methods: This study is a monocentric, prospective, observational study. The reference diagnostic test for comparison is continuous cardiac index measurement through Swan-Ga\gnz ca\gtheter. Patients undergoing coronary artery bypass grafting and pre-operative reduced left ventricular ejection fraction (<35%) will be included. Patients will receive non-invasive cNIRS for up to 48 hours after surgery. Swan-Ganz catheter measurements will be performed simultaneously as per institutional standard. The primary endpoint is LCOS by a standard definition and its timepoint of onset. In addition to correlation of NIRS values with cardiac index, sensitivity and specificity analyses will be performed after adjustment for confounders (systemic vascular resistance, hemoglobin). Assuming a 20% LCOS rate in patients with baseline ejection fraction below 35%, at least 68 individuals need to be included in the study to gain enough data to reach statistical significance. In case at 68 individuals, the primary endpoint is not met in enough cases to perform robust statistical analysis, enrollment will be continued. Patients admitted to intensive-care unit (ICU) on mechanical circulatory support classify as screening failures.

Discussion: This study could improve understanding the value of NIRS in LCOS. Findings of this research potentially impact guideline recommendations on routine hemodynamic monitoring on cardiac ICU.

Trial registration: DRKS00017260 (German Registry of Clinical Studies)