When a patient is bleeding out, every second counts.
For the most critically injured trauma patients, rapid blood transfusion can be the difference between life and death, but what happens when standard IV and IO access fail?
In collaboration with London’s Air Ambulance and the Centre for Trauma Sciences, a new study led by Paolo Pallavicini has explored just that. The research, which analysed data from over 8,000 trauma patients, offers the most detailed insight yet into the effectiveness of central venous “trauma lines” in pre-hospital haemorrhagic shock.
On the World Extreme Medicine Podcast, host Eoin Walker sits down with Paolo to unpack the findings, the methodology, and the implications for the future of trauma care.
Understanding the Problem: When IO and IV Fall Short
Peripheral IV and intraosseous (IO) access are the gold standards for initial vascular access in trauma resuscitation. But in profoundly shocked patients, where veins have collapsed and circulation has slowed, both routes can quickly become unreliable.
As Paolo explains, IO access, while fast and technically straightforward, often fails to deliver the high flow rates needed for massive transfusion. Flow rates rarely exceed 50-70ml/min, and even under optimal conditions this is insufficient to replace the rapid blood loss seen in exsanguinating trauma.
“Even under ideal conditions, IO lines rarely exceed 50ml a minute,” Paolo notes. “That’s nowhere near what is needed for a patient who is bleeding out in profound shock.”
The Study: 8,000 Patients, 346 Trauma Lines
The observational study reviewed 8,000 trauma patients attended by London’s Air Ambulance between 2019 and 2023. Of these, 346 patients received pre-hospital trauma lines, short, large-calibre central venous catheters designed to enable rapid transfusion when conventional access fails.
The results were significant:
- 80% success rate for pre-hospital trauma line insertion
- Double the volume of blood products delivered compared to non-trauma-line cases
- Higher rates of return of spontaneous circulation (ROSC) in traumatic cardiac arrest
- Improved survival to hospital arrival
Complications were low, occurring in only 4% of cases, primarily minor vascular injury or malposition.
Why Subclavian Access Works Best
One of the key findings of the study was the dominance of the subclavian vein as the preferred access site, used in nearly 90% of successful insertions.
Unlike the jugular or femoral veins, the subclavian vein remains patent even in low- or no-flow states, making it particularly suitable in cases of hypovolaemia. It is also anatomically anchored, reducing the risk of vessel collapse and aiding landmark-based insertion in the chaotic, time-critical pre-hospital environment.
“The subclavian line remains patent even in low flow or no flow states,” Paolo explains. “It’s attached to the clavicle, and unlike peripheral veins, it doesn’t collapse.”
Speed vs. Safety: The Ultrasound Question
Despite ultrasound being the gold standard in hospital settings, only 6% of pre-hospital trauma line insertions used it in this study.
Paolo emphasises that in the field, speed and context are everything.
“By the time you’ve powered on and configured an ultrasound device, a skilled clinician could already have placed a landmark-guided subclavian line. In the right hands, that difference can mean life or death.”
That said, the research reinforces that clinical governance and training are essential. At London’s Air Ambulance, all clinicians performing trauma lines undergo extensive simulation, procedural oversight, and post-case review to maintain safety standards.
Reassessing the Golden Hour
One of the most compelling insights from the paper is its challenge to the traditional concept of the “golden hour.”
In London, the average time from emergency call to hospital arrival is around 40 minutes. Yet patients in the study who received trauma lines benefited from advanced intervention around the 20-minute mark, effectively moving life-saving treatment earlier into the chain of survival.
“We’re no longer just passively transporting patients,” Paolo says. “We’re resuscitating them 20 minutes earlier than before, and that changes outcomes.”
A Measured Risk
With a complication rate of only 4%, the authors concluded that trauma lines represent an acceptable and proportionate risk in the context of pre-hospital haemorrhagic shock, especially when other access routes have failed.
“Acceptable risk is never something we want for our patients,” Paolo notes, “but sometimes it becomes something we must weigh carefully in light of the potential benefit.”
What This Means for the Future of Trauma Resuscitation
While the study shows clear improvements in pre-hospital survival, it found no significant difference in survival to hospital discharge, a limitation Paolo acknowledges.
“Each patient receives multiple interventions across their journey,” he explains. “We can’t isolate trauma lines as the sole reason for survival. But we can say they help get more patients to definitive care alive, and that’s a meaningful start.”
The study sets a new benchmark for evaluating high-acuity interventions outside hospital walls. For services capable of delivering pre-hospital blood transfusions, trauma lines may now represent the next step in advanced resuscitative care.
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