Early blood pressure control in ambulances shows no clear benefit for stroke patients, study finds

By Dr. Priyom Bose, Ph.D.Reviewed by Benedette Cuffari, M.Sc.May 20 2024

A recent New England Journal of Medicine study assesses whether early blood-pressure control within ambulances leads to favorable clinical outcomes among patients with undifferentiated acute stroke.

Study: Intensive Ambulance-Delivered Blood-Pressure Reduction in Hyperacute Stroke. Image Credit: Jaromir Chalabala / Shutterstock.com

Treating stroke

Intensive treatment to lower blood pressure levels is often clinically beneficial in patients with acute intracerebral hemorrhage. However, trials on reducing blood pressure alone have yielded inconclusive results, which could be due to variations in trial designs, populations, or interventions. Clinical outcomes may be better if blood pressure reduction interventions are started as early as possible; however, this can be complicated in patients with acute ischemic stroke.

Previously, two trials reported similar results on the efficacy and safety of administering pre-hospital blood pressure reduction interventions within hours of an acute stroke. In patients with intracerebral hemorrhage, worse outcomes were noted in those who received the glyceryl trinitrate patch relative to those who received a sham patch. 

About this study

The current study reports on the Intensive Ambulance-Delivered Blood Pressure Reduction in Hyper-Acute Stroke Trial (INTERACT) 4 results. The aim of INTERACT 4 was to evaluate the efficacy and safety of ambulance initiation of intravenous antihypertensive treatment within two hours of an acute stroke.

The starting group comprised ambulance-treated patients within two hours of the onset of symptoms suspected to have had an acute stroke causing a motor deficit and had an elevated systolic blood pressure of 150 mm Hg or more. Study participants were randomly assigned to receive usual blood pressure management or immediate intervention to lower systolic blood pressure to a target range of 130-140 mm Hg.

The primary safety outcome was the occurrence of any serious adverse event. The primary efficacy outcome was assessed by reading the score on the modified Rankin scale, in which a score of zero represented no symptoms and a score of six represented death. The scores were noted 90 days after randomization.

Study findings

The sample comprised 2,404 patients in China, with a mean age of 70. The intervention group comprised 1,205 participants, and the median time interval between the onset of symptoms and randomization was 61 minutes.

The average blood pressure at the time of randomization was 178/98 mm Hg. Imaging was obtained for 2,204 patients to confirm the stroke, with 46.5% of patients confirmed to have had a hemorrhagic stroke.

When the patients arrived at the hospital, the average systolic blood pressure measurements in the intervention and usual care groups were 158 and 170 mm Hg, respectively. No difference in functional outcomes was observed across the intervention and usual care groups. Furthermore, the incidence of serious adverse events was similar across the two studied groups.

Among hemorrhagic stroke patients, pre-hospital reduction of blood pressure was associated with a reduced likelihood of a poor functional outcome. This relationship was reversed among patients with cerebral ischemia, in which an increased risk of a poor functional outcome was observed.

Strengths and limitations

The main strength of IMPACT 4 involves treatment provision by doctors in emergency services. Additional strengths include the use of a simple consent process, the ability to reduce blood pressure with a simple intravenous treatment regimen, and high rates of adherence to the protocol.

One limitation included the involvement of doctors in emergency services, which reduces the generalizability of the findings. Additionally, the current study was conducted in China, where the nature of stroke is different from that in North America and Europe.

For example, in North America, the proportion of ischemic stroke is higher, whereas the incidence of intracerebral hemorrhage is high in Europe. Moreover, outside China, intravenous urapidil is not widely available.

Due to the lack of generalizability, the study approach may be less appropriate for paramedic-run ambulance services and when strokes are caused by a minor neurologic deficit. The data quality could also have been compromised due to several factors, such as quarantine restrictions during the coronavirus disease 2019 (COVID-19) pandemic, open-label design, variability of other medical care, and broad inclusion criteria. 

Conclusions

The current study demonstrated that quick initiation within two hours of intensive blood pressure reduction in patients with acute stroke did not lead to a significant benefit in functional outcomes as compared to standard care, during which blood pressure management is initiated after arrival at the hospital. In patients with cerebral ischemia and hemorrhagic stroke, the intervention could have had divergent effects.