Lying flat prior to thrombectomy good for LVO stroke

Positioning patients with large vessel occlusion (LVO) stroke flat on the bed prior to thrombectomy helps improve neurologic outcomes in the randomized controlled ZODIAC* trial.

As the standard of care prior to thrombectomy is to position patients’ heads at a 30-degree elevation, the finding suggests that changes to presurgical outcomes may be beneficial for patient outcomes.

“The number needed to harm if the head of the bed was elevated 30 degrees compared with the patient being laid flat at zero degrees was 1.88,” said study author Professor Anne Alexandrov from the University of Tennessee Health Science Center in Memphis, Tennessee at ISC 2024. “That means for every two patients that you sit up, one will deteriorate significantly compared to the baseline score, which will not happen if they are laid flat. So, this was a very robust finding.”

The trial was stopped at the interim analysis because of the early benefits of the zero-degree positioning.

Simple intervention with a huge benefit

Lying flat on a bed markedly reduced early neurological deterioration, defined as an increase of at least 2 points on the National Institutes of Health Stroke Scale (NIHSS) prior to thrombectomy (2.2 percent vs 55.3 percent; p<0.001).

The approach was safe, with no cases of symptomatic intracerebral haemorrhage or hospital-acquired pneumonia observed and a lower rate of all-cause death at 90 days compared with a 30-degree angle (4.4 percent vs 21.7 percent; p=0.03).

Looking at the rate of severe neurologic deterioration (≥4-point increase on the NIHSS), the result also favoured the zero-degree positioning (2.2 percent vs 42.6 percent; p<0.001).

“We were expecting a sizeable effect based on our preliminary work, but we were quite shocked in a good way at how large the benefit was in this study from such a simple intervention,” Alexandrov said.

Keeping patients stable important

Patients (n=92; mean age 66 years) included in the ZODIAC trial had a computed tomography (CT) angiography–confirmed LVO stroke viable parenchyma and a treatment plan that included mechanical thrombectomy. Baseline NIHSS scores were calculated while patients were lying flat on the CT scanning bed. Thrombolytic therapy was administered when suitable.

The patients were randomly assigned to remain in the zero-degree or a 30-degree position until taken in for thrombectomy. Repeat NIHSS scores were measured every 10 minutes until they were moved to the catheterization table.

“We wanted to see if these patients would be more stable or potentially improve if they were laid flat or their heads were elevated,” Alexandrov said. “What we found was that blood flow is increased by 20 percent if patients are placed at zero-degree vs 30 degrees. Hence, it is likely that this is having an important effect in keeping these patients stable until the clot is removed.”

Postprocedural outcomes

Further exploratory endpoints showed that patients who were kept at a zero-degree positioning were more likely than those on the 30-degree positioning to have an improvement in NIHSS score at 24 hours (86.7 percent vs 60.9 percent; p= 0.008) and 7 days or discharge (86.7 percent vs 67.4 percent; p=0.045).

“By 3 months, there was no difference in outcomes for patients in either group, especially as thrombectomy was expected to have a large beneficial effect in both groups. However, it’s exciting to see that we were able to discharge patients from the hospital with less disability requiring rehabilitation,” Alexandrov said.

Due to the overwhelming efficacy of the zero-degree positioning prior to thrombectomy in LVO stroke, the Data and Safety Monitoring Board stopped enrolment into the trial on November 1, 2023.

Head positioning matters

Alexandrov clarified that the zero-degree head positioning is not a treatment for stroke. Rather, it is “a rescue manoeuvre” that could help preserve brain function until a thrombectomy can be performed.

“Head positioning at zero degrees is a safe and effective strategy to optimize blood flow to the brain prior to thrombectomy … this minimizes the risk of neurological deterioration. It should be considered the standard of care for patients with stroke prior to thrombectomy.”

“Putting the head down flat to keep the brain optimally perfused is one of the most important things we can do first for a patient with an LVO stroke … it has critical significance in those who arrive at a hospital that cannot perform thrombectomy and have to be transferred,” she pointed out.

However, Alexandrov cautioned that the results do not apply to patients who have no definitive diagnosis of LVO stroke yet, or those with suspected stroke on their way to the hospital. “Some patients may have haemorrhagic stroke. If that is the case, there is a chance that lying the head flat may cause increased intracranial pressure,” she added.

Bridge to thrombectomy

Dr Louise McCullough from the McGovern Medical School and co-director of UT Health Neurosciences, in Houston, Texas, described the findings as “very interesting.” 

“Laying the head flat is such a simple strategy and a low-cost thing to do,” she commented. “The only thing I would worry about would be the risk of aspiration pneumonia in these patients, but that was not seen in the study.”

As there are often delays in performing thrombectomy following LVO stroke diagnosis, this simple positioning intervention may serve as a bridge to improve brain perfusion until the artery is opened and the clot is addressed, concluded McCullough.