Conditional Vasospasm-Free Survival Following Aneurysmal Subarachnoid Hemorrhage

Abstract

Background: Following aneurysmal subarachnoid hemorrhage (SAH), patients are monitored closely for vasospasm in the intensive care unit. Conditional vasospasm-free survival describes the risk of future vasospasm as a function of time elapsed without vasospasm. Conditional survival has not been applied to this clinical scenario but could improve patient counseling and intensive care unit use. The objective of this study was to characterize conditional vasospasm-free survival following SAH.

Methods: This was a single institution, retrospective cohort study of patients treated for aneurysmal SAH between 1/1/2000-6/1/2020. The primary outcome was the development of vasospasm defined by the first instance of either radiographic vasospasm on computed tomography angiography, Lindegaard Index > 3.0 by transcranial doppler ultrasonography, or vasospasm-specific intraarterial therapy. Multivariable Cox regression was performed, and conditional vasospasm-free survival curves were constructed.

Results: A total of 528 patients were treated for aneurysmal SAH and 309 (58.5%) developed vasospasm. Conditional survival curves suggest patients who survive to postbleed day 10 without vasospasm have a nearly 90% chance of being discharged without vasospasm. The median onset of vasospasm was postbleed day 6. Age more than 50 years was associated with a lower risk (hazard ratio [HR] = .76; 95% confidence interval [CI] 0.64-0.91; p < 0.001). Higher initial systolic blood pressure (HR = 1.18; 95% CI 1.046-1.350; p = .008), Hunt-Hess grades 4 or 5 (HR = 1.304; 95% CI 1.014-1.676), and modified Fisher scale score of 4 (HR = 1.808; 95% CI 1.198-2.728) were associated with higher vasospasm than the respective lower grades.

Conclusion: Conditional survival provides a useful framework for counseling patients and making decisions around vasospasm risk for patients with aneurysmal SAH, while risk factor-stratified plots facilitate a patient-centric, evidence-based approach to these conversations and decisions.

Keywords: Intensive care units; Intracranial vasospasm; Subarachnoid hemorrhage; Survival analysis.

FIGURE 1:

Vasospasm risk profile. (A) Estimated hazard function for the development of vasospasm, (B) Kaplan-Meier plot of vasospasm-free survival.

FIGURE 2:

Conditional vasospasm-free survival curve. The Y-axis represents the estimated probability of survival to hospital discharge without developing vasospasm; the X-axis represents the time already elapsed without vasospasm.

FIGURE 3:

Stratified conditional vasospasm-free survival curves for age (A), sex (B), tobacco use (C), and modified Fisher grade (D).