Validation of the Predictive Value of the FORE-SIGHT™ Monitor for Early Detection of Hemodynamic Deterioration After Pediatric Cardiac Surgery. A Data-mining Study.

1. Background

Accurate hemodynamic monitoring often requires the use of invasive tools or catheters. Many of these tools, available for adults, cannot be used for critically ill infants and children, because of their size, and because these invasive techniques carry a high risk of complications. Non-invasive monitoring techniques that allow for detecting critical hemodynamic states are of high interest in this population.

FORE-SIGHT™ is a non-invasive tool to measure cerebral tissue oxygen saturation. Cerebral tissue oxygen saturation (SctO2) values are important to clinicians because cerebral hypoxia (lack of oxygen supply to brain tissue) is one of the leading causes of brain injuries that occur in many surgical and clinical situations. The FORE-SIGHT™ Cerebral Oximeter utilizes optically-based Near Infra-Red Spectroscopy (NIRS) technology to monitor absolute SctO2. It works by projecting harmless near infra-red light through the scalp and skull and into the brain via a disposable sensor on the patient's forehead. The device measures the light that is returned to detectors on the sensor and analyzes this information utilizing patented algorithms to determine absolute cerebral tissue oxygen saturation levels. The FORE-SIGHT™ is designed to monitor SctO2 in a continuous way, and provides clinicians an opportunity to intervene before damage to the brain occurs. The monitor is currently part of the standard monitoring for children undergoing cardiopulmonary bypass, in the operating theatre, and is often continued in the postoperative phase in the pediatric intensive care unit (PICU) of the university hospitals Leuven.

Several studies have pointed to the potential advantages of SctO2 monitoring in the peri-operative phase after cardiac or abdominal surgery in adults [1,2,3,4], as well as in children undergoing surgical corrections of congenital cardiac defects [5,6,7]. Low SctO2 values are associated with worse outcome, and correspond with data from other monitors indicating that the oxygen content of the brain at that time is insufficient. In particular, the duration of SctO2 desaturations below 55%, 60%, and 65%, is predictive for postoperative complications [8]. These studies, however, have only analyzed the use of NIRS as a tool to monitor the brain at times when it is at the highest risk, during complex surgery with a compromised circulation. Although there is no evidence that has demonstrated that decision making based on NIRS data is favorable for patient outcome, many centers use NIRS as a monitoring tool outside of the surgical environment.

Because the brain is very sensitive to changes in oxygenation, monitoring of SctO2 might provide an indication of critical changes in the hemodynamic state of the patient, and thus serve as a monitor for the general hemodynamic status of the patient. The present study wishes to examine the added value of SctO2 monitoring over the routine monitoring of pediatric patients in PICU, in the postoperative phase after cardiac surgery. Ideally, in order to be of added value, SctO2 changes should precede an episode of hemodynamic deteriorations.