ECMO IN TRAUMA

cardiohelpECMO in multitrauma patients sounds like asking for complexity and lots of oozing blood – but it seems to have potential for actually stabilising the patient’s systems and get better outcome. The short version: ECMO restores normal physiology and unloads the venous system.

ECMO in trauma
Mostly, ECMO’s role in trauma som far has been as VV ECMO in ARDS after trauma, and is quite well documented with case series and case controls. Also, some patients have gotten VA ECMO for circulatory failure after a day or two in the ICU. I was interested in ECMO in the emergency multitrauma patient, made possible by the modern heparin-coated lines and filters, so you’ll run it on your patient without systemic heparin. Also, the coagulopathy in the patient might help fend off clot building. So ECMO in emergency trauma is feasible – and could be good:

ECMO restores circulation
As long as you can deliver blood volume from the patient or from blood bags to the ECMO circuit, you’ll get good central circulation. Heart, brain and other visceral organs will get better blood flow.

lethal-triadECMO fixes coagulopathy and the leathal triad
Sick trauma patients can also have heart failure, as in a stunned phase or cardiodepressed due to acidosis. The patient could also just be deranged with a low pH and/or cold. So how can VA ECMO help? ECMO can help by restoring cardiac output. The restored circulation will help normalise pH and increase lactate clearance. Also, the ECMO system makes it easy to control the patient’s temperature. So, looking at the leathal triad, ECMO corrects 2 out of 3. And the third will then follow. So ECMO might actually improve coagulation in this setting!

ECMO offloads the venous side
Arterial bleeds are bad, but can often be easier to find and control than venous bleeds. The venous bleeds can be more characterised by oozing. Diffuse oozing can mean lots of lost blood, but the bleed can be difficult to control surgically. Pressure and packing helps – and with VA ECMO, you’ll suck the right atrium/SVC/IVC almost empty, lowering the venous side pressure, thus limiting the venous bleeds further. We had a severe lung bleed at our hospital, where ECMO helped stop the bleeding, and there are reports on how other patients with severe lung bleeds or liver bleeds get easier to control once put on VA ECMO. In patients as well as in animal studies.

Placement of the arterial and venous cannulas also mean you can do different kinds of clamping, like clamping the IVC to also isolate the venous side of the liver, but still have good circualtion to the rest of the body and to the abdominal organs while avoiding venous congestion.

ecmo-restores-physiology-2Looking at data from M Larsson’s experiments on rabbits: Hemorrhagic shock was initiated and let run for the first 90 mins. At 90 mins the rabbits were resuscitated by normal guidelines and with warmed blood, the other group had the addition of ECMO.

See how the temperature curve quickly corrects at 90 mins in the ECMO group, and then how pH and BE improves after about an hour later. In the standard group, all parameters continue to decline despite standard resus with warmed blood.

Other coagulation data shows normalisation in the ECMO group, compared to further decline in the standard resus group.

ECMO gives you big lines in
Once you have the ECMO cannulas in place, you have almost unlimited volume loading access. Blood could possibly be given straight to the ECMO machine, delivering it to the trauma patient’s central circulation. Of course, focus must be on controlling the bleed in the patient. Also, the risk of infusing air into the ECMO system and stopping it, might lead you to prefer traditional iv infusion routes.

ECMO is a connection hub
We already mentioned giving blood products directly on the ECMO circuit. We also hook up hemofiltration straight to the ECMO circuit, making access easier and avoiding more cannulations and catheters in the patient. Of course, hemofiltration is for later.

Limitations and bleeding risk on ECMO
There aren’t really any absolute contra-indications. As Bedeir et al notes:“The risk from bleeding-related mortality in trauma patients on ECLS seems to be over-estimated” Even intercranial bleeds where fine, in the sense that the bleeding didn’t seem to get worse on ECMO without heparin. And the enhanced flow could also benefit the injured brain. But as always, injury should be deemed reversible. “Even with intracranial bleeding, the risk of ECLS-related bleeding may be over-estimated”, but a patient with severe TBI might not be your best trauma ECMO case, as they’ll have a slim survival potential, ECMO or not.

Muellenbach et al even reported “3 patients with significant ICH undergoing heparin-free ECLS for up to 5 days and also received factor VII and prothrombin complex. All three survived with no problems related to clotting circuits or thromboembolism”, and more ICH patients are included in the reviews below.

With heparin-coated ECMO sets and avoiding systemic heparinisation, the published case series and experimental data are limited, but don’t seem to show any increased bleed nor increases in clotting in the patients – but rather an improvement of the coagulation system.

Of course, heparinisation isn’t an all or nothing thing. Any level in-between full heparinisation and none can be sought for a specific patient. As the Bedeir review notes: “There was a recent trend towards initially heparin free circuitry followed by a lower-than-standard activated clotting time target range”.

Summary
ECMO helps restore normal physiology. ECMO restores cardiac output, thus helps normalise pH and lactate. On ECMO, warming is easy, fighting hypothermia. Correcting acidosis and hypothermia helps correct coagulopathy. The lethal triad works both ways. Running ECMO without systemic heparinisation, using heparin-coated sets, makes this possible.

Heparin can be added later, at a point after you have bleeding control. Also, many trauma ECMO patients only need a quite short run on VA ECMO until they can manage on their own. Hours to a few days.

With appropriate patient selection, ECLS should be regarded as a readily viable rescue therapy for trauma patients.

Extracorporeal Life Support in Trauma: Worth the Risks? J Trauma Acute Care Surg, 2016.

Extracorporeal membrane oxygenation in severe trauma patients with bleeding shock, Resuscitation, 2010.

Prolonged heparin-free extracorporeal membrane oxygenation in multiple injured acute respiratory distress syndrome patients with traumatic brain injury, J Trauma Acute Care Surg, 2012.

These two following articles by Magnus Larsson forms part of his PhD on ECMO in Trauma Patients with Hypovolaemic Shock, and both articles and the full PhD are fascinating reads! First time I’ve truely enjoyed reading a full thesis back to back!

Extracorporeal membrane oxygenation improves coagulopathy in an experimental traumatic hemorrhagic model, Eur J Trauma Emerg Surg, 2016.

Experimental extracorporeal membrane oxygenation reduces central venous pressure: an adjunct to control of venous hemorrhage?,Perfusion, 2010.

And some frontier docs were using heparin coated VA ECMO in trauma pts already in 1995:
Extracorporeal cardiopulmonary life support with heparin-bonded circuitry in the resuscitation of massively injured trauma patients, Am J Surg, 1995.

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