Agitated saline with 10% blood increases number and stability of microbubbles in detection right-to-left shunt by contrast-enhanced transcranial Doppler: an in vitro and in vivo observational study

Background: Agitated saline (AS) with blood has been shown to have good tolerance and increased efficacy when used in contrast-enhanced transcranial Doppler (c-TCD) to detect right-to-left shunt (RLS). However, little is known about the effects of blood volume on c-TCD results. Our study investigated the characterization of AS with different blood volumes in vitro and compared the c-TCD results in vivo. Methods: In vitro, AS without blood, AS with 5% blood (5% BAS), and AS with 10% blood (10% BAS) were prepared based on previous studies and observed under microscopy. The numbers and sizes of the microbubbles from different contrast agents were compared immediately, 5 min, and 10 min post-agitation. In vivo, 74 patients were recruited. c-TCD was repeated 3 times using AS with different blood volumes in each patient. Signal detection times, positive rates, and classifications of RLS were compared among the 3 groups. Results: In vitro, the AS without blood produced 5.4±2.4/field microbubbles after agitation, the 5% BAS produced 30.4±4.2/field, and the 10% BAS produced 43.9±12.7/field. More microbubbles remained in the 10% BAS than the 5% BAS within 10 min (18.5±6.1 vs. 7.1±2.0/field, P<0.001). The size of the microbubbles from the 5% BAS increased from 9.2±8.2 to 22.1±10.6 µm within 10 min post-agitation (P=0.014), while the 10% BAS changed insignificantly. In vivo, the signal detection times of the 5% BAS (1.1±0.7 s) and 10% BAS (1.0±0.8 s) were significantly shorter than the AS without blood (4.0±1.5 s, P<0.0001). The RLS positive rates were 63.5%, 67.6% and 71.6% in AS without blood, 5% BAS and 10% BAS respectively; however, the differences were not statistically significant. The AS without blood reached 12.2% level III RLS, while the 5% BAS reached 25.7%, and the 10% BAS reached 35.1% (P=0.005). Conclusions: The 10% BAS would be suggested in c-TCD as it addressed larger RLS by increasing the number and stability of microbubbles, and it improves the diagnosis of patent foramen ovale (PFO).