Differential hypoxemia during peripheral cardiopulmonary bypass.

Introduction: Minimally invasive cardiac surgery (MICS) for mitral valve repair often uses cardiopulmonary bypass (CPB) through peripheral femoro-femoral cannulation. A rare complication of differential hypoxemia can cause upper body hypoxia.

Case Report: A 38-year-old man with Barlow Syndrome underwent MICS mitral valve repair with peripheral CPB. During the procedure, his right upper limb SpO2 dropped to 65% due to dislodgement of the venous cannula from the superior vena cava (SVC), causing inadequate right heart venous drainage, leading to differential hypoxemia. Repositioning the venous cannula to the SVC restored SpO2 to 100%, allowing the surgery to proceed without complications.

Discussion: Differential hypoxemia happens when deoxygenated blood from the left ventricle mixes with oxygenated CPB blood. A literature review found only one previous case of this complication on peripheral CPB for MICS. Unlike our case, Kanda et al. monitored cerebral hypoxia, underscoring the importance of cerebral oxygenation monitoring in future MICS procedures due to higher stroke risk compared to conventional sternotomy.

Conclusion: We recommend cerebral oxygenation monitoring in future MICS to prevent neurological complications, and highlight the need for effective team communication in the cardiac operating theatre.