Monitoring: Equipment and Computers
Background and Goal of Study: Cerebral dysfunction following cardiopulmonary bypass (CPB) remains a major source of morbidity and mortality in cardiac surgery, with early diagnosis required for the prevention of neurological complications. Orbital ultrasound (OUS) monitoring can provide useful information regarding intracranial blood flow during a CPB procedure (1). The objective of the present study was to evaluate the clinical significance of quantitative OUS findings during cardiac surgery in terms of their relevance to postoperative neurological events.
Materials and Methods: We studied 30 adult patients scheduled for coronary artery bypass grafting or valve replacement surgery. A mini-mental state examination (MMSE) was performed 2 days before, and 7 and 14 days after the operation. OUS observations were made before, 20, 40, and 60 minutes after the start, and after the end of CPB. Maximal flow velocity (Vmax) in the central retinal artery (CRA) and MMSE scores after the operation were compared using regression analysis. Further, Vmax and the occurrence of postoperative neurological events were compared using a chi-square test.
Results and Discussions: MMSE scores were significantly decreased 7 days after the operation and then returned to preoperative levels by 14 days. No significant correlations were seen between Vmax at any time point during CPB and postoperative MMSE scores. Delirium occurred in 5 cases (17%), whereas no major complication, such as stroke, occurred. Each of those patients showed significantly lower MMSE scores after the operation as compared to the other patients, and OUS monitoring detected CRA blood flow during CPB. We considered that the absence of significant correlations between Vmax and postoperative neurological events may be due in part to the absence of major neurological complications in the present cases.
Conclusion(s): The Vmax of CRA blood flow obtained by OUS monitoring could not predict postoperative neurological events. Additional studies for quantitative evaluation of OUS monitoring during CPB when used as an indicator of postoperative minor neurological dysfunction are needed.
1 Orihashi K, Matsuura Y, Sueda T, et al. Ann Thorac Surg
2001; 71: 673-677.