Kinetics of tissue oxygenation index during fast and slow cardiopulmonary bypass initiation

INTRODUCTION: Despite being a daily clinical application in cardiac operating theaters, an evidence-based approach on how to optimally initiate the heart–lung machine (HLM) to prevent critical phases of cerebral ischemia is still lacking. We therefore designed a study comparing two different initiation times for starting the cardiopulmonary bypass (CPB). METHODS: We conducted a monocentric, randomized, and prospective study comparing the impact of two initiation times, a rapid initiation of 15 s and a slow initiation of 180 s to reach the full target flow rate of 2.5 L/min/m(2) times the body surface area, on cerebral tissue oxygenation by near infrared spectroscopy measurements. RESULTS: The absolute values in tissue oxygenation index (TOI) showed no difference between the groups before and after the CPB with a 10% drop in oxygenation index in both groups due to the hemodilution through the HLM priming. Looking at the kinetics a rapid initiation of CPB produced a higher negative rate of change in TOI with a total of 21% in critical oxygenation readings compared to 6% in the slow initiation group. CONCLUSION: In order to avoid critical phases of cerebral ischemia during the initiation of CPB for cardiac procedures, we propose an initiation time of at least 90 s to reach the 100% of target flow rate of the HLM.