Carbon Dioxide Insufflation on the Number and Behavior of Air Microemboli in Open-Heart Surgery

To the Editor: Although useful neuropsychological (NP) benefits may result from the recent report by Svenarud et al1 of a reduction in air microemboli in a randomized controlled trial of CO2 insufflation during single-valve surgery, there are a number of issues relating to cerebral microemboli, valve versus coronary bypass surgery, and NP outcome that are not adequately addressed in this paper. A number of studies have linked cerebral microemboli to NP outcome, but the relationship between the two remains unclear. Other factors such as inflammatory response and altered cerebral blood flow must also be considered. Neville et al2 compared 193 patients having coronary artery bypass surgery with 73 patients having valve replacement surgery and confirmed previous findings that there were more microemboli detected during valve surgery but there was no difference found in NP outcome. Their result suggests that the number of microemboli may not always be the most significant determinant of NP outcome. Additionally, Svenarud et al1 only measured microemboli within the heart and ascending aorta, and these may not correlate with cerebral microemboli. I would be interested to know why …