A case for evidence, patient selection, and urgency before prolonged partial aortic occlusion becomes a default transfer strategy.
In hemorrhage control, more time sounds like an obvious advantage.
That is part of the appeal of partial resuscitative endovascular balloon occlusion of the aorta, or partial REBOA. Instead of completely occluding the aorta, partial occlusion allows some blood to flow distally. The goal is compelling: preserve enough proximal pressure to support the heart and brain, allow enough distal perfusion to reduce ischemic injury, and potentially keep the patient alive longer while definitive hemorrhage control is arranged.
The physiology is attractive. The technology is advancing. And partial REBOA may ultimately prove extremely useful in selected patients.
But there is an important question we should be asking before prolonged partial REBOA, particularly during patient transfer, becomes accepted as the natural next step: Are we extending the patient’s opportunity to reach definitive care, or are we simply extending the amount of time we are comfortable delaying it? Those are not necessarily the same thing.
We are still defining where aortic occlusion itself adds the most value
Before adding greater complexity to REBOA, it is worth recognizing that trauma systems are still working through a more fundamental question: which patients benefit from aortic occlusion in the first place?
The evidence is not one-sided.
The UK-REBOA randomized clinical trial found that adding an emergency-department REBOA strategy to standard care did not reduce mortality and showed a concerning signal toward increased mortality. Ninety-day mortality was 54% in the REBOA strategy group versus 42% with standard care alone. Importantly, only a subset of patients randomized to the REBOA strategy ultimately had the balloon inflated, illustrating some of the challenges inherent in studying this intervention.
At the same time, newer comparative evidence suggests that REBOA can be very valuable in appropriately selected patients. A 2026 systematic review and meta-analysis involving more than 9,000 patients found substantially lower in-hospital mortality with REBOA compared with resuscitative thoracotomy, particularly among patients in hemorrhagic shock. But the authors also emphasized that the underlying evidence was observational, patient selection remained critical, and complications were more frequent with REBOA.
These findings do not have to be viewed as contradictory. They may instead be telling us something fundamental: REBOA is not universally good or universally bad. The comparator, patient, injury pattern, timing, team, and trauma system all matter.
If we have not completely resolved that first-order question, we should be cautious about assuming that changing from complete to prolonged partial occlusion automatically solves the remaining problems.
A bridge should not become the destination
REBOA is fundamentally a bridge to definitive hemorrhage control.
That distinction matters.
One of the more thought-provoking findings from the UK-REBOA trial was that the median time from randomization to definitive hemorrhage control was 19 minutes longer in the REBOA strategy group. The trial does not prove that REBOA itself caused that delay, but it provides a useful systems-level warning: a temporizing intervention can potentially compete with, or unintentionally distract from, the intervention that actually stops the bleeding.
Now consider what happens when the message around partial REBOA changes from “this may reduce distal ischemia” to “this means we can maintain aortic occlusion for hours.”
That change in language can change behavior.
A two-hour or four-hour window can begin to sound less like an outer boundary and more like permission. Transfer may feel more comfortable. Definitive intervention may seem less urgent. The clock can become psychologically quieter even though the source of hemorrhage has not changed.
Reducing ischemia during aortic occlusion would be an important advance. But reducing the consequences of a bridge does not make the bridge definitive treatment.
The most important clock in hemorrhagic shock remains the time to hemorrhage control.
Partial REBOA is not simply a lower setting on the same switch
Complete aortic occlusion is physiologically aggressive, but conceptually it is relatively binary: flow is stopped or it is not.
Partial occlusion introduces another variable that has to be managed.
How much distal flow is enough?
Enough to perfuse the kidneys and lower body; but not enough to accelerate hemorrhage?
Enough when the balloon is first adjusted; but what about after additional blood products, changing vascular tone, vasopressors, warming, correction of acidosis, or evolving shock?
Experimental work demonstrates that aortic diameter and the relationship between balloon inflation, distal pressure, and organ perfusion can change in hemorrhagic shock. In other words, “partial” is a dynamic physiologic state rather than a fixed balloon position.
There is also an unavoidable trade-off. By definition, partial REBOA restores some pressure and flow below the balloon. That is desirable for distal tissue. But when the uncontrolled bleeding source is also below the balloon, the same distal circulation that restores organ perfusion is potentially perfusing the injured vascular bed as well. Preclinical investigators have appropriately described this as a search for the right balance between hemorrhage control and distal perfusion.
That balance may change minute by minute.
Transport makes a dynamic intervention harder, not easier
This becomes particularly important when prolonged partial REBOA is proposed for interfacility or prehospital transport.
Successful transfers involving REBOA have been reported, demonstrating that the concept is feasible in selected circumstances. But a successful case report demonstrates feasibility; it cannot establish the comparative safety or effectiveness of routinely transporting patients with prolonged aortic occlusion.
A moving ambulance, aircraft, or austere transport platform is also very different from a resuscitation bay, operating room, or hybrid suite.
During transfer, a small team may simultaneously be responsible for blood administration, airway and ventilator management, temperature control, medications, vascular access, communication with the receiving center, documentation, and management of the underlying injuries.
Partial REBOA adds another dynamic variable to that workload.
The current Joint Trauma System clinical practice guideline recommends measurement of arterial pressure above and below the balloon for accurate partial-occlusion titration and emphasizes training, appropriate equipment, careful handoff, and consideration of evacuation timelines. It also states that partial Zone 1 occlusion should ideally be limited to two hours and Zone 3 to four hours, while explicitly describing prolonged partial occlusion as an active area of clinical and animal research.
Those numbers should not be mistaken for guarantees of safety.
A maximum recommended duration is very different from a demonstrated optimal duration.
Maybe the next big thing is not longer occlusion
There are other directions worth pursuing just as aggressively.
We can improve patient selection, identifying earlier which injury patterns and physiologic states are most likely to benefit from aortic occlusion.
We can improve vascular access, preserving the option for rapid intervention without necessarily beginning the occlusion clock.
We can improve trauma-system efficiency, shortening the interval from recognition of noncompressible hemorrhage to operative or endovascular control.
We can improve transport protocols, including explicit monitoring requirements, handoff standards, failure criteria, and contingency plans rather than treating partial occlusion itself as the transport solution.
We can continue advancing damage-control resuscitation, blood-product availability, hybrid operating capabilities, and forward surgical capability.
And if prolonged flow modulation is going to become an important part of REBOA, we should continue investigating ways to make it objective and reproducible; using meaningful physiologic endpoints rather than assuming that a particular balloon position will produce the same degree of partial flow throughout an evolving resuscitation.
Most importantly, we need prospective human evidence that measures outcomes patients care about: survival, organ function, limb outcomes, neurologic recovery, blood-product use, complications, and time to definitive hemorrhage control.
Keep partial REBOA in the toolbox without letting it reset the clock
Partial REBOA is an exciting concept. It may offer meaningful advantages over complete aortic occlusion in appropriately selected patients, and continued research is justified.
But we should resist turning promising physiology into a broad clinical assumption.
The fact that we may be able to maintain partial aortic occlusion longer does not necessarily mean that we should.
For prolonged transfer in particular, the question should not simply be, “How long can we leave the balloon partially inflated?”
It should be:
Does this strategy get the right patient to definitive hemorrhage control alive and does it do that better than the alternatives?
Until we can answer that question with stronger human evidence, prolonged partial REBOA deserves thoughtful investigation rather than automatic adoption.
The next major advance in hemorrhage control may not be finding a way to keep the balloon up longer. It may be building systems that allow us to take it down sooner.
