Fixed Compared to Autoregulation-Oriented Blood Pressure Thresholds after Mechanical Thrombectomy for Ischemic Stroke

Abstract

Background and Purpose:

Loss of cerebral autoregulation in the acute phase of ischemic stroke leaves patients vulnerable to blood pressure (BP) changes. Effective BP management after endovascular therapy (EVT) may protect the brain from hypo- or hyperperfusion. In this observational study, we compared personalized, autoregulation-based BP targets to static systolic blood pressure (SBP) thresholds.

Methods:

We prospectively enrolled 90 patients undergoing EVT for stroke. Autoregulatory function was continuously measured by interrogating changes in near-infrared spectroscopy-derived tissue oxygenation (a cerebral blood flow surrogate) in response to changes in mean arterial pressure (MAP). The resulting autoregulatory index was used to trend the BP range at which autoregulation was most preserved. Percent time that MAP exceeded the upper limit of autoregulation (ULA) or decreased below the lower limit of autoregulation (LLA) was calculated for each patient. Time above fixed SBP thresholds was computed in a similar fashion. Functional outcome was measured with the modified Rankin Scale (mRS) at 90 days.

Results:

Personalized limits of autoregulation (LA) were successfully computed in all 90 patients (age 71.6±16.2, 47% female, mean NIHSS 13.9±5.7, monitoring time 28.0±18.4 hours). Percent time with MAP above the ULA associated with worse 90-day outcomes (OR per 10% 1.84, 95% CI 1.3–2.7, P=0.002), and patients suffering from hemorrhagic transformation spent more time above the ULA (10.9% vs. 16.0%, P=0.042). While there appeared to be a non-significant trend towards worse outcome with increasing time above SBP thresholds of 140 mmHg and 160 mmHg, the effect sizes were smaller compared to the personalized approach.

Conclusions:

Non-invasive determination of personalized BP thresholds for stroke patients is feasible. Deviation from these limits may increase risk of further brain injury and poor functional outcome. This approach may present a better strategy compared to the classical approach of maintaining SBP below a pre-determined value, though a randomized trial is needed to determine the optimal approach for hemodynamic management.