Cerebral microembolism diagnosed by transcranial Doppler during total kneearthroplasty - Correlation with transesophageal echocardiography

Background: Tourniquet deflation following total knee arthroplasty (TKA) fr equently results in release of emboli into the pulmonary circulation. Small emboli may gain access to the systemic circulation via a transpulmonary ro ute or through a patent foramen ovale. This study examined the incidence of cerebral microembolism after tourniquet release by transcranial Doppler (T CD) ultrasonography and its correlation with echogenic material detected in the left atrium. Methods: Twenty-two adult patients (9 men, 13 women) undergoing TKA were st udied with simultaneous TCD ultrasonography and transesophageal echocardiog raphy. Data were recorded after anesthesia induction and tourniquet inflati on and during tourniquet deflation. Emboli counts mere performed manually o ff-line. Echogenic material in the left atrium was qualitatively assessed a nd correlated with TCD data. Patients were examined postoperatively for foc al neurologic deficits. Results: Fifteen patients had unilateral TKA (six left, nine right) and sev en had bilateral TKA. Cerebral emboli were detected in 9 of 15 patients (60 %) with unilateral TKA and in 4 of 7 patients (57%) with bilateral TKA. Ech ogenic material was identified in the left atrium in eight patients (two th rough a patent foramen ovale and six from the pulmonary veins). Emboli coun ts were significantly higher in patients with bilateral TKA compared with t hose with unilateral TKA (P < 0.05). Duration of tourniquet time in patient s with emboli was longer only during bilateral TKA (P < 0.05), All patients with echogenic material in the left atrium detected by transesophageal ech ocardiography had emboli as assessed by TCD ultrasonography, No focal neuro logic deficits were identified. Conclusions: Cerebral microembolism occurs frequently during tourniquet rel ease, even in the absence of a patient foramen ovale. This passage most lik ely occurs through the pulmonary capillaries or the opening of recruitable pulmonary vessels.