(154) Transcranial Doppler-Based Circulatory Parameters in Mechanical Circulatory Support (CIRCULATE-MCS)

Introduction: There is a paucity of data on normative values for transcranial Doppler (TCD) in adult patients who receive mechanical circulatory support (MCS). We undertook a prospective observational study to gather normative data on patients with various forms of MCS, adjusted to patient factors like demographics and contribution of left ventricular output, as well as MCS related factors like flow.

Methods: After obtaining Institutional Review Board (IRB) approval, we started a pilot study at three sites endorsed by the Society of Critical Care Medicine Discovery Research Network. All patients on MCS were screened based on eligibility criteria. Patients who consented underwent daily TCD monitoring using bilateral robotic image acquisition TCD probes [Viasonics, Inc. Image Monitoring]. We gathered normative values on TCD: mean flow velocity (MFV), peak flow velocity (PFV), end-diastolic velocity (EDV), and pulsatility index (PI). Patient-related factors, demographics, and MCS device settings were obtained from the electronic medical record.

Results: Seven patients enrolled at site one with a median age of 62 years (34-77, 6 males, 1 female), body mass index of 27.73 kg/m2 (24.82-46.04), and Glasgow Coma Scale of 15 with sedation on four patients. Patients were on MCS for a median of 16.5 days (3-54) with 2 scans on VA-ECMO, 23 on Impella 5.5, and 1 on VV-ECMO. Across all scans, there was a median mean arterial pressure (MAP) of 81 mmHg, median middle cerebral artery (MCA) MFV of 36 cm/s and 36.5 cm/s for the right and left, and PI 0.74 and 0.91 for the right and left, respectively. The correlations between systemic MAPs, cardiac output, and either MCA mean flow velocity or PIs were low (0.004-0.346).

Conclusions: With the limitations of a small sample size, there is significant variability in TCD metrics in MCS patients, with poor correlation between systemic and cerebral hemodynamics suggesting a lack of autoregulation. The CIRCULATE-MCS global registry will perform large-scale validation of these results to establish normative values of TCD parameters for patients with MCS. As a result, future studies can evaluate the use of TCD metrics as a target for hemodynamic resuscitation, with the goal to reduce neurological complications in this high-risk population.