Effect of body positioning during transcranial Doppler detection of right-to-left shunts

We adopted an expanded transcranial Doppler (TCD) protocol to evaluate if additional injections of agitated saline in different positions would improve shunt detection or grading. We report the safety and feasibility of this expanded contrast TCD protocol. Patients with ischemic stroke were evaluated. The standard protocol for RLS detection was followed and expanded after the initial injection in the supine position to the right lateral decubitus, upright sitting, and sitting with right lateral leaning. Changes in blood pressure, heart rate, and any subjective complaints were noted. Changes in body position and additional agitated saline injections were tolerated. Right-to-left shunt (RLS) was detected in 35% of patients ( n  = 55). If the initial supine testing was negative, all subsequent positions/injections were also negative for RLS. However, if the supine injection was positive for RLS, the change in body positions increased the microbubble ( μ B) count in eight of 19 (42%) RLS-positive patients. The mean μ B count in RLS-positive patients was 20 (95% CI: 9–32). The use of three additional body positions increased the μ B count to 73 (95% CI: 13–132). The highest μ B yield was achieved in the upright sitting position. Our findings support the safety and feasibility of the expanded TCD protocol. If the initial supine Valsalva-aided contrast TCD test is negative, there may be no need to study the patient in additional positions. However, if μ B are detected in the supine position, additional testing for RLS in alternative positions may be found to be worthwhile.