Assessment of Microcirculatory Alteration by a Vascular Occlusion Test Using Near-infrared Spectroscopy in Pediatric Cardiac Surgery:Effect of Cardiopulmonary Bypass

Cardiac surgery and cardiopulmonary bypass (CPB) procedures cause microcirculatory alterations, and microvascular alterations and the impairment of tissue oxygen saturation (StO2) after cardiac surgery with CPB have been associated with adverse patient outcomes. It has been shown that contact with foreign surfaces causes transient microcirculatory dysfunction and activation of the inflammatory and hemostatic systems and that tissue trauma and anesthesia also affect microcirculation. Although microcirculation is affected by surgery with CPB, monitoring of the microcirculatory function is still not part of routine practice. Continuous real-time monitoring may aid in the early detection of tissue malperfusion.

StO2 measurement using NIRS and vascular occlusion testing (VOT) are novel techniques for assessing the microcirculatory function of peripheral tissue, specifically in patients undergoing cardiac surgery with CPB. The level of StO2 is determined by the amount of oxygen delivered and consumed. The deoxygenation rate, minimum rSO2, and reoxygenation rate measured using VOT may indicate tissue perfusion, the local metabolic rate, the oxygen reserve, and microvascular reactivity. It has been shown that prolonged exposure to CPB is associated with abnormal vasomotor responses and end-organ dysfunction. Although the INVOS system is not commonly used for VOT in children undergoing cardiac surgery with CPB, we hypothesized that using this noninvasive method to measure StO2 would allow detection of the local metabolic rate and local tissue perfusion adequacy change and that StO2 changes would reflect the preexisting cardiovascular reserve.