Intraoperative cerebral high-intensity transient signals and postoperative cognitive function: a systematic review

Background: Much attention in the literature has focused on the relationship between perioperative microemboli during cardiac and vascular surgery and postoperative cognitive decline. Transcranial Doppler ultrasonography (TCD) has been used to measure high-intensity transient signals (HITS), which represent microemboli during cardiac, vascular, and orthopedic surgery. The purpose of this study was to systematically examine the literature with respect to HITS and postoperative cognitive function. Methods: Systematic PubMed searches identified articles related to the use of TCD and cognitive function in the surgical setting. Results: The literature remains largely undecided on the role of HITS and cognitive impairment after surgery, with most studies being underpowered to show a relationship. Although the cognitive effects of HITS may be difficult to detect, subclinical microemboli present potential harm, which may be modifiable. Conclusions: TCD represents a tool for intraoperative cerebral monitoring to reduce the number of HITS during surgery.