(666) Serial CBF Analysis by O15-Water Dynamic PET During Hyperdynamic Therapy for Vasospasm After SAH

Introduction: For patients suffering from subarachnoid hemorrhage (SAH), symptomatic vasospasm and related delayed cerebral ischemia (DCI) remains a major cause of death and disability of hemorrhagic stroke. Although some prophylactics such as nimodipine and clazosentan have been approved for preventing vasospasm, DCI still unsatisfactorily solved. We hypothesized that the key for successful reversal of focal ischemia is to accomplish acute hemodynamic acceleration enough to improve cerebral microcirculation. We aimed to clarify improved regional cerebral blood flow (rCBF) during the initial phase of inotropic hemodynamic augmentation induced by low-dose dobutamine (DOB) in postoperative patients diagnosed with radiological vasospasm and DCI.

Methods: Quantitative CBF were measured serially by 15O-labelled water PET imaging every 30-min until 90 min after starting DOB at a rate of 3 µg/kg/min. Continuous cardiac output was monitored simultaneously. Regional CBF values were analyzed automatically by setting the region of interest using a commercially available reconstruction software.

Results: In subjects with localized vasospasm, initial uptake of rCBF was detected in focal brain areas affected by vasospasm, while no CBF changes were found in subjects with diffuse vasospasm involved in distal multiple vessels. In both cases, CO elevated rapidly above normal values, which can be suggestive of hyperdynamic state. The increased CBF kept above the normal range without neurological deterioration thereafter. In territories with diffuse vasospasm, DOB was ineffective to rCBF uptake and resulted in severe cerebral infarction and related functional impairments.

Conclusions: Low-dose DOB is a valuable initial rescue therapy for post-SAH symptomatic vasospasm to augment rCBF immediately after administration in vascular territories without diffuse vasospasm. This is the first qualitative CBF study to validate a mechanism of hyperdynamic therapy.