Milrinone's Effect on Transcranial Doppler Parameters in Aneurysmal Subarachnoid Hemorrhage

Introduction/Purpose Cerebral vasospasm following aneurysmal subarachnoid hemorrhage (aSAH) can lead to delayed cerebral ischemia and neurological decline. Transcranial Doppler (TCD) is a widely used, noninvasive modality for tracking vasospasm using mean flow velocity (MFV) and Lindegaard Ratio (LR). Intravenous milrinone, a phosphodiesterase‐3 inhibitor with vasodilatory and inotropic effects, is increasingly used for vasospasm treatment, though its real‐time impact on TCD‐based hemodynamic measures is not well characterized. We hypothesize that intravenous milrinone would induce a hemodynamic response as measured by MFV, LR, and PI. Methods This retrospective cohort study included adult patients with aSAH and confirmed sonographic vasospasm between January 2021 and May 2025, treated with IV milrinone, with at least three days of TCD data pre‐ and post‐treatment. A time series segmented linear regression was performed to analyze the slope and level changes in MFV, LR, and PI across pre and post milrinone initiation, with sensitivity analysis adjusting for MAP and hematocrit. Results Of a total of 300 patients, 36 met inclusion criteria. LR slope significantly decreased after milrinone (e.g., right LR from 0.21 to ‐0.07; p=0.0014), while MFV slope decreased non‐significantly (from 3.76 to 0.79; p=0.083). PI slope showed no significant change. No immediate jump in values was detected on milrinone start day. Conclusion Intravenous milrinone may affect transcranial doppler parameters used to monitor vasospasm. Further research is needed on improving vasospasm prediction and detection on patients receiving these medications.