JC: Selective aortic arch perfusion. St Emlyn’s

We generally try and review studies that are close to use in practice. but occasionally we spot something that is just interesting and which might give us a clue as to what resuscitation might look like in the future. One such technology is Selective Aortic Arch Perfusion (SAAP) which has been around for quite a while in animal models, but is yet to develop to the point of human practice.

This month there is a paper in the Scandinavian Journal of Trauma, Resuscitation and Emergency Medicine that proves that the concept can work in human models, and if endovascular resuscitation is your thing, then this will certainly be of interest. Here in Virchester we are some way off getting endovascular resuscitation techniques into practice, but around the country, and around the world there are services that are delivering this highly advanced technology to patients.

You will no doubt be familiar with the concepts of REBOA and ECMO from past blogs and podcasts. SAAP is different, and in some ways is a combination of the two. A balloon is passed in to the descending aorta to occlude it. Fluid can then be infused into the proximal aorta/arch to selectively perfuse the upper body, and equally importantly can create a perfusing pressure and blood flow to the coronary arteries.

The abstract is below, but as always we suggest you read the full paper yourself.

What kind of paper is this?

This is a feasibility study and as such should not be used to diretly guide clinical practice. In essence the authors sought to test whether SAAP was achievable in a cadaver model.

What did they do?

The authors used 4 human cadaver models to test whether SAAP could be achieved and then whether it was possible to cannulate the coronarty arteries via the SAAP catheter. The catheter is a size 11F device that is passed through the femoral artery into the aorta and then a distal balloon is inflated in the descending aorta distal to the left subclavian. This effectively isolates perfusion to the upper body. The authors then injected contrast into the proximal aorta to demonstrate flow. It is important to note that in this study the catheter was placed with the help of fluoroscopy.

What did they find?

They were able to successfully achieve SAAP in three of the four cadavers. In the fourth cadaver the balloon failed (possibly due to the fact that it had been used several times before). They were able to cannulate a coronary artery via the SAAP catheter in one cadaver.

Why does this matter?

As a feasibility study this study is a long way from prime time, but there are some interesting concepts here that may speak to a future technique in resuscitation. There is reasonable data from animal models that SAAP can be used as a technique in haemorrhagic shock, but perhaps more interestingly is the idea that it could be a technique used in cardiac arrest/instability. Occluding the aorta improves coronary artery perfusion and thus may act as a bridge to other interventions such as PCI, or may in itself (by increasing coronary perfusion) increase the potential success of advanced life support. Beyond that there is the possibility of using these techniques to achieve rapid cooling to achieve Emergency Preservation and Resuscitation (EPR) where patients are cooled as a preservation technique to allow the repair of devastating injury. Whilst that may sound some time off, it is something that colleagues have talked about as a concept for many years.

Where do we go next?

The concept is certainly really interesting and offers the potential for trials in humans, and in particular those with critical illness or injury. The challenges will be significant though. I would expect that if this technique is to be of benefit then it would need to be delivered as close as possible to the time of injury/arrest and that is a real challenge. The UK REBOA trial showed us that delaying these endovascular resuscitation techniques to the hospital lead to significant delays, and probably a reduction in efficacy. In the UK it looks likely that this would need to be delivered pre-hospitally and that’s a huge challenge in terms of patient selection, training, maintaining technical currency, and despatch.

Looking to the future there are also questions of equity, and whether such technologies will be available to all populations at all times (unlikely), and on a wider scale the realisation that these technologies are unlikely to filter down to the majority of the world’s population. The very fact that we are able to consider such technologies in the UK is something to reflect on. It is also likely that such innovations will be led by air ambulance charities and outside of the publicly funded NHS (but we are some way away from widespread delivery of that anytime soon).

Another challenge will be in deciding how to evaluate endovascular technologies in practice as RCTs are arguably not the ideal approach here.

So, we are certainly some distance from this technology becoming routine, but that said, we are always interested in innovation and in learning from those pushing the boundaries of resuscitation research. The paper is well worth a read for more detail and for a review of the images (which we cannot reproduce here for copyright reasons).

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References

1. Marsden, M., Barratt, J., Donald-Simpson, H. et al. Selective aortic arch perfusion: a first-in-human observational cadaveric study. Scand J Trauma Resusc Emerg Med 31, 97 (2023). https://doi.org/10.1186/s13049-023-01148-z
2. Manning JE, Murphy CA Jr, Hertz CM, et al. Selective aortic arch perfusion during cardiac arrest: a new resuscitation technique. Ann Emerg Med. 1992;21(9):1058–65.
3. Barnard EBG, Manning JE, Smith JE, Rall JM, Cox JM, Ross JD. A comparison of Selective Aortic Arch Perfusion and Resuscitative Endovascular Balloon Occlusion of the Aorta for the management of hemorrhage-induced traumatic cardiac arrest: A translational model in large swine. PLoS Med. 2017 Jul 25;14(7):e1002349. doi: 10.1371/journal.pmed.1002349. PMID: 28742797; PMCID: PMC5526509.
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5. Manning JE, Murphy CA Jr, Hertz CM, et al. Selective aortic arch perfusion during cardiac arrest: a new resuscitation technique. Ann Emerg Med. 1992;21(9):1058–65.
6. Scott Weingart, MD FCCM. EMCrit 123 – Selective Aortic Arch Perfusion (SAAP) with Jim Manning. EMCrit Blog. Published on May 6, 2014. Accessed on December 30th 2023. Available at [https://emcrit.org/emcrit/selective-aortic-arch-perfusion/ ].
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