Edmonds et al. used a transcranial Doppler probe to record embolic signals (ESs) to determine whether microemboli to the brain occur during total hip arthroplasty. The authors first describe a case report of a preliminary study in one patient, a 43-yr-old woman admitted for revision of a right total hip arthroplasty. A shower of ESs was noted during insertion of a cemented femoral prosthesis, at a time when the patient’s mean pulmonary artery pressure increased from 13 to 20 mmHg.
The authors then prospectively studied 23 patients undergoing total hip arthroplasty. Patients were placed on the operating table in the lateral decubitus position, and the Doppler probe was secured over the middle cerebral artery. Throughout each surgery, a dedicated technician recorded ESs manually; these were verified by inspection of recorded tracings. ESs were defined as high-amplitude unidirectional transient signals lasting less than 0.1 s and associated with a characteristic chirping sound. Signal recordings were correlated with specific surgical events, such as reaming of the femoral canal and impaction of a cemented femoral component.
Three patients were excluded from final analysis; in the remaining 20 patients, in 8 patients ESs ranged in each patient from 1 to 200. In five of these patients, signals were noted during impaction of a cemented component, and in four patients, signals were noted after relocation of the hip joint. These two surgical maneuvers are also associated with intraoperative pulmonary emboli and with markers of thrombosis. One of two patients who had more than 150 ESs experienced mild chest pain and heaviness after surgery, but no further sequelae. None of the 20 patients exhibited signs of confusion or stroke after surgery; therefore, it is not clear whether these emboli are well-tolerated in the brain or whether the number of emboli is too few to result in cognitive deterioration. Further studies are needed to clarify the significance of these findings.
