Does prophylactic postoperative hypervolemic therapy prevent cerebral vasospasm and improve clinical outcome after aneurysmal subarachnoid hemorrhage?

Background: Delayed cerebral vasospasm is a common cause of morbidity and mortality after acute aneurysmal subarachnoid hemorrhage. Hypovolemia and fluid restriction are risk factors for delayed vasospasm; hypervolemic therapeutic approaches are commonly used in patients with subarachnoid hemorrhage to prevent and to treat cerebral vasospasm. Objective: To determine if postoperative prophylactic hypervolemic therapy prevents cerebral vasospasm and improves clinical outcome in patients with aneurysmal subarachnoid hemorrhage. Methods: The objective was addressed through the development of a structured critically appraised topic. This included a clinical scenario, structured question, search strategy, critical appraisal, results, evidence summary, commentary, and bottom line conclusions. Participants included consultant and resident neurologists, a medical librarian, clinical epidemiologists, and content experts in the field of vascular neurology. Results: One randomized controlled trial addressed the questions. There was no difference in the incidence of symptomatic cerebral vasospasm (20% each) or clinical outcome at 14 days and 3 months between the hypervolemic and normovolemic groups. Hypervolemic therapy also had no effect on measures of cerebral blood flow. A second quasi-randomized trial reached the same conclusions. Conclusion: Available evidence is insufficient to support use of prophylactic hypervolemic therapy after surgery in patients with aneurysmal subaraclmoid hemorrhage. Although completed studies may be insufficiently sensitive (underpowered) to detect a treatment effect, the magnitude of any as yet undetected benefit of prophylactic hypervolemic therapy is likely modest and its risks have not been systematically evaluated.