Intraventricular milrinone improves vasospasm in patients with subarachnoid hemorrhage

Background Cerebral vasospasm after aneurysmal subarachnoid hemorrhage (SAH) remains a leading cause of delayed cerebral ischemia (DCI). Standard therapies are often insufficient in refractory cases. Milrinone, a phosphodiesterase‐3 inhibitor with vasodilatory and anti‐inflammatory properties, has emerged as a potential treatment via intra‐arterial, intravenous, or intrathecal routes. However, intraventricular (IVT) administration remains scarcely reported. Case Report A 70‐year‐old man with atrial fibrillation on apixaban presented with seizure and was found to have diffuse SAH (modified Fisher grade 4) from a ruptured left internal carotid aneurysm. He underwent coil embolization and placement of an external ventricular drain (EVD). Despite nimodipine, hemodynamic augmentation, and intravenous milrinone (Montreal protocol), he developed diffuse vasospasm. Digital subtraction angiography confirmed moderate‐to‐severe narrowing, and intra‐arterial verapamil produced only transient benefit. IVT milrinone (870 mcg) was then administered via the EVD. Repeat angiography at 10 and 20 minutes demonstrated progressive arterial dilation (≈40% in MCA and ACA segments) and improved perfusion. The patient remained hemodynamically stable, including an intracranial pressure below 20 mmHg. IVT dosing was continued every eight hours. Although his hospital course was later complicated by acute respiratory distress syndrome unrelated to therapy, IVT milrinone was consistently associated with angiographic improvement. Conclusion This case demonstrates rapid, real‐time angiographic reversal of refractory vasospasm with intraventricular milrinone. By delivering high local concentrations directly into cerebrospinal fluid, IVT administration may overcome the limitations of systemic or intra‐arterial therapy. It may represent a practical bedside alternative that combines local efficacy with reduced repeated angiography procedural risk exposure. Larger prospective studies are needed to establish dosing, safety, and its role in improving long‐term outcomes in SAH.