Examining the Impact of Prehospital Blood Pressure Control on Stroke Outcomes

The recently conducted INTERACT 4 trial in China has sparked debates and discussions within the medical community regarding the efficacy of bringing blood pressure under control in the ambulance for stroke patients. The trial, led by Gang Li, MD, PhD, of Shanghai East Hospital at Tongji University, aimed to determine whether reducing systolic blood pressure to 130-140 mm Hg during transport to the hospital would improve functional outcomes for stroke patients. Surprisingly, the results showed no significant difference in functional outcome as measured by the modified Rankin Scale between the group with early blood pressure reduction and the group receiving usual care (common OR 1.00, 95% CI 0.87-1.15). These findings, published in the New England Journal of Medicine and presented at the European Stroke Organisation meeting in Switzerland, have raised questions about the impact of prehospital blood pressure control on stroke outcomes.

The Impact of Blood Pressure Control on Stroke Subtypes

An interesting observation from the INTERACT 4 trial was the differential effect of prehospital blood pressure control on stroke subtypes. For patients diagnosed with ischemic stroke upon hospital arrival, early blood pressure reduction was associated with an increased risk of poor functional outcome (common OR 1.30, 95% CI 1.06-1.60). In contrast, patients diagnosed with hemorrhagic stroke showed a significant relative reduction in the risk of poor functional outcome. These results, outlined by Jonathan A. Edlow, MD, of Beth Israel Deaconess Medical Center and Harvard Medical School, challenge the notion of a one-size-fits-all approach to prehospital blood pressure management in stroke patients.

Despite the intriguing findings of the INTERACT 4 trial, several limitations and considerations warrant further exploration. Edlow highlighted the use of urapidil, an α1 receptor blocker unavailable in the U.S., in the trial, as well as the unique patient population consisting of predominantly Han Chinese individuals. The balance between patients with intracerebral hemorrhage and acute ischemic stroke in the trial population is not reflective of typical North American or European settings, raising concerns about the generalizability of the results. Additionally, the unexpectedly high proportion of patients with visible signs of ischemia on initial CT scans within 3 hours of stroke onset poses questions about the trial cohort’s characteristics and the reliability of imaging techniques.

The findings of the INTERACT 4 trial underscore the complexity of managing blood pressure in the prehospital setting for stroke patients. While the trial did not demonstrate a clear benefit of early blood pressure reduction on functional outcomes, the differential effects on stroke subtypes highlight the need for individualized treatment approaches. Moving forward, researchers and clinicians should consider the nuances of stroke subtypes, patient demographics, and regional practices when developing protocols for prehospital stroke care. Validation of the trial results in diverse populations and settings is crucial to elucidating the optimal strategies for improving stroke outcomes through prehospital blood pressure control.