A new probe holding device for continuous bilateral measurements of blood flow velocity in basal brain vessels

The clinical relevance of transcranial Doppler sonography for the evaluation of cerebral perfusion and cerebrovascular regulatory mechanisms, as well as for the registration of embolic events, has increased considerably as a technique of non-invasive monitoring. The continuous measurement of blood flow velocities in two different vessel segments, either ipsilateral or contralateral, is limited by intricate probe fixation and positioning for optimal insonation of the vessel on the one hand. On the other hand probes are displaced frequently during anaesthesiological measures, so that continuous registration during induction of anaesthesia is not always guaranteed. In view of these limitations, a new probe-positioning and holding device has been developed and tested in a clinical study of patients undergoing cardiac surgery (n = 22). The newly designed probe-positioning and holding device allowed the unilateral adjustment and continuous measurement of the blood flow velocity in the middle cerebral artery (Vmca) from anaesthesia induction to endotracheal intubation in all patients (n = 9). This was possible in only 61.5% (n = 8) of the patients who were monitored via conventional mode of probe fixation (n = 13). The new method rendered possible the positioning, insonation and measurement in two vessel segments in 77.8% of the patients, in contrast to 53.8% of the patients where the conventional technique was used. The newly designed probe holding device meets all standard requirements from the anaesthesiological viewpoint, and facilitates the perioperative application of transcranial Doppler sonography for non-invasive monitoring.