Improving transfer times with innovative mobile transport models for stroke

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Speakers during “Planes, Teams and Automobiles: Going the Distance for the Acute Stroke Patient” on Thursday presented creative transport paradigms that are contributing to reduced treatment times for thrombolysis and thrombectomy and improving outcomes.

Enrique C. Leira, MD, MS, professor of neurology, neurosurgery and epidemiology at the University of Iowa in Iowa City, discussed the relevance of helicopter transport for stroke care, including facilitating the delivery of standard interventions and the potential of clinical trials based in the helicopter.

A few years ago, Leira’s team explored the possibility of using helicopters for dedicated clinical research during interhospital transport. “We noticed that the interhospital setting was quite different than the pre-hospital one. Patients already have a more accurate diagnosis in neuroimaging so there are less stroke mimics. Also, there is family nearby so we could acquire surrogate consent,” he said.

“Our hypothesis was that air medical crews could become co-investigators in clinical trials. That would allow testing of dedicated inflight interventions and expedite enrollment in the ongoing stroke trials.”

The randomized clinical trial in helicopter transport used a safe intervention of  intravenous ranitidine  for preventing aspiration pneumonitis as a vehicle to test the system, but the main intervention tested was a communication strategy combining faxing the consent form and speaking with the patient or surrogate about the Ranitidine trial during the outbound flight.

The interhospital approach moved the clock forward one hour rather than waiting for the patient to be enrolled once they arrived at the hospital.

The trial also demonstrated that it was possible to conduct trials while transporting patients, and that the air medical transport system has an opportunity to test different types of interventions in flight, including neuroprotective agents to protect the ischemic penumbra by slowing the neural loss.

The pros and cons of using the helicopter as a flying mobile stroke unit equipped with a CT scanner was also reviewed. A primary benefit is a patient in a remote area could be scanned on board the helicopter, the image could be interpreted by the provider in flight or through telemedicine and tPA could be initiated en route.

But Leira also pointed out limitations including weight and balance. “A helicopter fitted with a heavy CT scanner would have limited capabilities with regard to range, landing altitude and weight allowance of the patient,” he said.

Leira’s team also investigated the effect of unusual helicopter physical factors such as vibration on tPA infusion. These factors include low-frequency vibration, sudden hyperbaric changes, which could worsen the ischemic penumbra, and acceleration.

Johanna T. Fifi, MD, associate director of the cerebrovascular center of the Icahn School of Medicine at Mount Sinai in New York, compared the mobile interventional team model (MIST) model of transport to the mothership and drip-and-ship models.

“The challenge continues to be getting the right patient to the right place at the right time,” Fifi said. “If we look at traditional stroke service delivery models, we have had the mothership and drip-and ship models.” 

In the mothership model, patients are transported from their homes directly to comprehensive stroke centers where they can receive high level procedures such as thrombectomy. In the drip-and-ship model, patients first travel to the primary stroke center and then require transfer to a comprehensive stroke center where they will then receive higher level treatments such as thrombectomy.

“Time from brain imaging to reperfusion matters: The drip-and-ship model introduces some delay. The further from onset to the recanalization of blood vessels, the worse the outcomes,” she said. “We know that when you transfer patients, they do suffer significant delays when compared to the mothership model. According to the STRATIS Registry, the door-in, door-out of the primary stroke center plus the transfer resulted in a 2-hour and 18-minute delay and worse outcomes for the transfer patient. The transfer patients also missed treatment opportunities.”

She described the MIST model and showed that it is an opportunity to decrease delays in the drip-and-ship model. By making the primary stroke center thrombectomy capable, it changes the zone of endovascular therapy provision to involve other centers within a system or city.  The team that provides thrombectomy care travels to those centers or may be stationed there. This increases the zone of therapy and avoids transfers.

The MIST model also offers parallel processing. “While the patients are in the primary stroke center, they can be transferred to the thrombectomy suite to be prepped while the specialized team is in route. It also avoids the serial processing of drip-and-ship model,” she said.

She said the MIST model saved 68 minutes. Although the mothership model is faster, the MIST model can achieve quicker times compared to the drip-and-ship model.