Laying large vessel occlusion (LVO) ischaemic stroke patients flat with their heads at a zero-degree angle prior to a mechanical thrombectomy procedure has resulted in significant short-term improvements in neurological function, as compared to patients whose heads were elevated at a 30-degree angle, in the randomised ZODIAC trial. Researchers are keen to impress, however, that zero-degree head positioning is “a rescue manoeuvre, not a treatment” in stroke, serving as a way to preserve brain function by optimising blood flow until the thrombectomy can be performed.
“By three months following surgery, there was no difference in outcomes for patients in either group; however, it’s exciting to see that we were able to discharge patients from the hospital with less disability requiring rehabilitation,” said lead researcher Anne Alexandrov (University of Tennessee Health Science Center, Memphis, USA), who presented preliminary late-breaking data from the study at the recent International Stroke Conference (ISC; 7–9 February, Phoenix, USA). “Our findings suggest that gravitational force can play an important role in improving blood flow temporarily while patients are waiting for surgery. Zero-degree head positioning is a safe and effective strategy to optimise blood flow to the brain until the thrombectomy can be performed, and it should be considered the standard of care for stroke patients prior to thrombectomy.”
Currently, hospital beds for stroke patients awaiting thrombectomy are typically set with the head of the bed at a slight incline of 30 degrees, according to Alexandrov. However, pilot studies conducted previously by her and her team showed that, when the head of the bed is flat, thrombectomy patients benefit from increased gravitational blood flow through their stroke-causing occluded artery, as well as having more open collateral arteries for the procedure.
“Many thrombectomy patients have delays until the procedure can be started, whether due to slow internal hospital processes, multiple patients arriving at the same time, or if the patient needs to be transferred to another hospital,” Alexandrov noted. “Optimising blood flow to the brain while patients are waiting for surgery is essential to minimise the risk of neurological deficits and ultimately disability.”
In the prospective, randomised ZODIAC clinical trial, which included 92 patients with acute ischaemic strokes caused by an LVO from 12 US centres, researchers used the National Institutes of Health stroke scale (NIHSS) to evaluate patients’ consciousness, vision, speech, motor strength, and sensory loss. Their primary endpoint looked at whether patients’ conditions remained stable or worsened depending on if they were set with zero-degree or 30-degree head positioning before thrombectomy.
Stroke patients’ baseline NIHSS scores were measured at zero degrees immediately after neuroimaging, and they were then randomly assigned to head positioning at either zero or 30 degrees. Patients underwent repeated NIHSS scoring every 10 minutes until the thrombectomy was performed (or until more than two hours passed), with a final NIHSS score being assessed immediately before they were positioned on the surgical table.
An interim analysis of the trial found that—based on these repeated NIHSS scores—zero-degree head positioning before thrombectomy resulted in greater stability and/or clinical improvement prior to surgery compared with 30-degree head positioning. Due to this demonstration of the potential efficacy of zero-degree positioning in stroke patients awaiting thrombectomy, ZODIAC’s data and safety monitoring board (DSMB) stopped enrolment in the trial on 1 November 2023.
ZODIAC ultimately found a significant between-group difference favouring zero-degree positioning, as per its primary outcome measure of an NIHSS score worsening ≥2, with Alexandrov also reporting an estimated number needed to harm of 1.88 with an elevated pre-thrombectomy head position in the trial.
In addition to their preprocedural assessments, the investigators also explored whether there would be differences in NIHSS scores at 24 hours following surgery, and at seven days post-surgery or discharge—whichever came first. Alexandrov conceded that they did not expect to find a significant difference on this front due to the well-known and dramatic improvements in patient outcomes associated with thrombectomy. As such, it came as a “pleasant surprise” to find that, at both 24 hours and seven days/discharge, patients in the zero-degree head-position group had reduced disability and fewer neurological deficits—as per their NIHSS scores—compared to those in the 30-degree group.
Alexandrov concluded her presentation of these findings at ISC 2024 by stating that zero-degree head positioning “may be one of the most important first steps” in managing an LVO stroke patient who is a candidate for thrombectomy—also averring that this is “critically important” when immediate access to thrombectomy is unavailable, and particularly in LVO cases requiring hospital-to-hospital transfer for the procedure.
