Matthew Maximillian Padrick, MD, BA
Petersen NH, Ortega-Gutierrez S, Wang A, Lopez GV, Strander S, Kodali S, et al. Decreases in Blood Pressure During Thrombectomy Are Associated With Larger Infarct Volumes and Worse Functional Outcome. Stroke. 2019;50:1797–1804.
This study recapitulates what should be a well-known phenomenon in the vascular neurology community: Decreases in blood pressure (BP) in patients undergoing endovascular thrombectomy (EVT) tend to result in poorer outcomes compared to outcomes of patients with sustained, stable blood pressure throughout diagnosis and EVT.
In this retrospective, observational study, the authors identified consecutive acute ischemic stroke patients with large vessel occlusion undergoing EVT at Yale-New Haven Hospital and University of Iowas and Clinics between 2014 and 2018. BP data was collected on admission and throughout EVT via anesthesia records. Decreases in BP were calculated between admission mean arterial pressure (MAP) and the single lowest MAP before recanalization during EVT. Sustained relative hypotension was measured as the area between baseline admission MAP and continuous measurements of intraprocedural MAP from procedure start to vessel recanalization. Primary imaging outcome was infarct volume assessed via admission computed tomography and at 24 hours post EVT via magnetic resonance imaging. Primary functional outcome was assessed via patient’s modified Rankin scale (mRS) at discharge and at 90 days post discharge.
In alignment with the existing literature, factors that were associated with good functional outcome were age, fewer comorbidities, lower NIH stroke scale at presentation, less early ischemic changes seen on admission CT, degree of reperfusion, earlier treatment, etc.
What this paper adds, however, is that independent of these factors, ∆MAP was associated with higher (worse) mRS at discharge (adjusted odds ratio per 10 mm HG, 1.15; 95% CI, 1.04- 1.32; P=0.003) and at 90 days (adjusted odds ratio per 10 mm Hg, 1.22; 95% CI, 1.07-1.38; P=0.003). ∆MAP among patients with favorable outcomes was 20±21 mm Hg compared to 30±24mm HG among patients with unfavorable outcomes (P=0.002). For every 10 mm Hg reduction in MAP, there was a 22% increased likelihood of shifting towards worse functional outcome. Sustained relative sustained hypotension was also significantly associated with poor function at discharge (P=0.002) and at 90 days (P=0.001). Radiologically, infarct growth was significantly associated with both ∆MAP (P=0.003) and sustained relative hypotension (P=0.005).
Physiologically, this makes sense. Imagine the chaos produced by cytotoxic cascade downstream of an acutely occluded middle cerebral artery. Autoregulatory mechanisms are extremely stressed if not broken down entirely: CO2 levels rise and the smaller, still patent, caliber collaterals are maximally dilated and doing all they can to deliver oxygen to the penumbra. Those collaterals need a reasonable cerebral perfusion pressure, a concept that has been accepted in the form of permissive hypertension for decades in the stroke literature. Therefore, it makes sense to be mindful of supporting these collaterals as best possible in the moments leading to recanalization.
The language in the current AHA/ASA guidelines is lacking. Understandably, the fear of reperfusion hemorrhage is real, and thus the only stated recommendation is to maintain BP <180/105. Only in the fine print does it mention the idea of supporting collaterals with: “The ESCAPE protocol states that systolic BP >= 150 is probably useful in promoting and keeping collateral flow adequate while the artery remains occluded” (Powers, et al). As the authors of the present study state, “this recommendation is likely inadequate for the management of this highly complex and heterogenous patient population.”
This study adds to the growing literature that supports aggressively avoiding hypotension during EVT. Vascular neurologists need to be cognizant of the potential consequences of iatrogenic hypotension, and to also maintain a line of communication with the anesthesiologist and interventionalist to communicate awareness of this potential pitfall. Moving forward, a prospective randomized trial evaluating BP management in the acute phase of LVO care, aimed at establishing a lower BP threshold in relation to admission BP, is warranted.