Resuscitative endovascular balloon occlusion of the aorta

Even though REBOA is a technique currently limited to the largest most technologically advanced sandstone centres, the college had decided to allocate 10 marks to it in Question 17 from the first paper of 2020. It is something one might describe as a "heroic" measure in the management of severe trauma, a shadowy territory at the edges of death which it shares with such techniques as resuscitative thoracotomy,  SAAP and EPR. The value of exploring this in the end-of-training-pathway exam is questionable, as it is unlikely to be a part of the standard toolkit of the average intensivist. However,  the company site claims there are numerous centres using them, and so this may be something moving steadily towards the mainstream.

If one were inclined to navigate the treacherous waves of FOAM, one could do no better than Chris Nickson's REBOA page from LITFL, which bears the stamp of authenticity from being written by somebody who's actually used those things. In terms of published peer-reviewed material, Napolitano (2017) is an excellent free paper which probably contains everything you need to answer Question 17.

History of REBOA

This is not a new idea, as very little is. Lieutenant Colonel Carl W. Hughes published on this topic in 1954, reporting his team's experience with exsanguinating Korean War casualties. Enrolment criteria were fairly arbitrary; in fact the author admits so: “It was arbitrarily decided that the catheter would be used only in moribund cases with evidence of intra-abdominal bleeding in which blood pressure could not be obtained after administration of 10 units of blood.” Hughes' original device is depicted below:

The outcomes were terrible, as befits "moribund cases with evidence of intra-abdominal bleeding".  There was the barest glimmer of a silver lining:  "Although both patients expired, the catheter was effective in temporarily restoring the blood pressure in one case".

Without further wars to stimulate interest, further exploration of this technique was minimal until a paper by Ledgerwood et al (1976) which reported on aortic occlusion in forty patients from Detroit General. At that stage, the city was often reported as the murder and arson capital of America, which made it easy to collect the cases. The authors did not use an endovascular balloon - they opened the chest and used a thoracic aortic clamp. In the 1980s, small case series (Low et al, 1986; Gupta et al, 1989) also reported fairly depressing survival rates, but they weren't zero, which kept a low-grade level of smouldering interest in the technique.  Ultimately, it was probably the 2010 study by Martinelli et al which properly stimulated interest when 46% of their severe pelvic trauma patients had survived. 

The REBOA equipment

Though there is a small group of what appear to be start-up companies producing equipment for REBOA specifically, the original papers and most subsequent research have been performed using existing vascular surgical equipment. For example, the Cook Medical Coda balloon is a 14-Fr object one could easily insert into a major vessel (not smaller than 24mm in diameter), and inflate there to achieve haemostasis. It's 120cm long, which gives you plenty of slack if your patient happens to have unexpectedly generous dimensions. The catheter is inserted through an introducer sheath (similar to other angiography devices); such a sheath can be upsized from a standard arterial line.

There is a whole range of such devices, and there does not appear to be any specific advantage of choosing one over another. One exception to this statement may be the appearance of percutaneous insertion kits, which might become available as this technique gains in popularity. 

The technique of REBOA

Probably the best technical description of this technique can be found in Stannard et al (2011). In brief, the steps are:

1. Arterial access in the femoral artery is achieved, eg. by means of a standard 18G arterial line
2. This access is upsized by rewiring and serial dilation until an angiographic sheath with a port can be inserted.
3. The occlusion balloon is then selected from among a range of devices. One can imagine the scenario of trying to explain which exact catheter you want on the phone to the floor manager of the operating theatre, if you yourself have no idea. For future reference, you want the 14Fr Coda balloon from Cook, a 12Fr Reliant from Medtronic, or a 6Fr Berenstein from Boston Scientific (which only inflates to 11.5mm).
4. The balloon is inserted via the sheath. At this stage, you've got to decide where you want its tip to end up. The aorta has been divided into zones for the purpose of describing where the REBOA device ends up, which is based on the position of the renal arteries. To borrow an image from the original Stannard paper:
   
   The balloon is not inserted on its own: usually, one needs to introduce it over a guidewire. Stannard et al recommend a 260cm Amplatz Stiff Wire Guide (again, in case you need to yell that as an instruction over the phone. )
5. The balloon should then be advanced into position. This is done under fluoroscopy where possible. If fluoroscopy is impossible, one may be able to use external anatomical landmarks when sizing the catheter prior to insertion: sternal angle to umbilicus to the insertion site.
6. The catheter is then inserted to the desired depth. Position should be confirmed radiologically, with the balloon inflated with radiocontrast. The correct positions are:
   Zone I = T4 to L1;
   Zone II = L2 to L4
   One does not really know how much fluid to add; Stannard et al recommend "the balloon is inflated until the outer edges of the balloon change from convex to parallel as the balloon takes on the contour of the aortic wall", which again relies on fluoroscopy equipment. Feeling for the contralateral femoral pulse and inflating until it disappears may be a reasonable alternative.
7. Once its position is confirmed, the balloon is secured in position. 

Mechanism of action

Question 17 from the first paper of 2020 asked specifically for the mechanism of action of REBOA. This seems like a fairly straightforward thing to answer. Basically, you block the blood flow to the lower body, and stop the blood loss thereby, buying some time for damage control surgery. At the same time, cardiac output is redirected to the upper body, hopefully preserving the brain.  

Advantages of REBOA

Advantages and expected benefits, in general, might include:

• Rapid deployment of the device
• Technically, uncomplicated
• Uses existing equipment which should be available in a trauma centre
• Potentially lifesaving
• Decreases the risk of cardiac arrest by maximising coronary perfusion
• Improves cerebral perfusion 
• Potentially, decreases transfusion requirements 

Advantages over other sorts of aortic occlusion:

• Less invasive than thoracic aortic crossclamp
• Less damaging to the aorta and other structures than "proper" crossclamp

Indications for REBOA

This is actually such an unclear area that the CICM Question 17 from the first paper of 2020 asked only for "potential indications", perhaps acknowledging that all of them are completely arbitrary. For instance, the Fitzgerald paper used the following enrolment criteria:

• Blunt or penetrating trauma patient aged 18–60 years transported directly from scene with:
  • Potential exsanguinating subdiaphragmatic haemorrhage,
  • Hypovolaemic shock with an SBP <70 mmHg or agonal state/ pulseless cardiac arrest with electrical activity of <10 min and
  • Non/partial responder to volume resuscitation as determined by the Trauma Team Leader.

Contraindications to REBOA

Given that this is a relatively recent development and data in support of it are so far lacking, whatever contraindications you invent are also going to be fairly arbitrary. For instance, one might argue that this is a device which should not be used on the extremely elderly. Then, the question arises, what age cut-off do you choose? 80 is the new 70, they say. And what if they're a "good" 85, with minimal comorbidities?

Absolute contraindications are:

• Blunt cardiac injury
• Aortic injury, eg. dissection
• Penetrating neck or chest trauma
• Untreated causes of obstructive shock
  (eg. cardiac tamponade or tension pneumothorax)
• Inaccessible femoral vessels(if the pelvis is severely distorted or if pelvic trauma somehow otherwise decreases access to the femoral vessels).

Relative contraindications include:

• Prolonged cardiac arrest due to exsanguination (arbitrarily, 10 minutes)
• Significant comorbidities

Contraindications to REBOA include blunt cardiac or aortic injury, and penetrating neck or chest trauma where resuscitative thoracotomy may have an advantage in the provision of definitive hemorrhage control

Disadvantages and complications of using REBOA

Disadvantages

• The procedure, though relatively quick, may delay transport to the operating theatre where definitive management may take place. Of the ACE trial population, two patients arrested while ballon positioning was being attempted.
• The equipment and expertise is mainly available in large centres, but the technique probably has greatest merit in small peripheral hospitals, where it might be used to facilitate transfer to the larger hospital.
• Of the devices used, pretty much all will require primary repair of the artery upon removal.
• The Australian trauma scene may be insufficiently vibrant. The ACE trial (2019) found only 13 eligible patients, and only attempted REBOA in two because they really could not find any aortas to usefully occlude. That's in Man's Best Hospital, a high-volume trauma centre where ECMO cannulation teams roam listlessly through the grounds, looking for things to do now that the CHEER trial had ended.  "Despite considerable training and resource allocation to ensure 24-h availability, the introduction of REBOA failed to effectively demonstrate any impact on patient outcome" the authors concluded somberly. 

Complications:

• Aortic injury and femoral vessel injury
• Haematoma at the insertion site
• Thrombotic and ischaemic complications of the ipsilateral distal limb
• Ischaemia with prolonged inflation time
• Reperfusion injury: with the balloon deflated, horrible inflammatory material is flushed into the systemic circulation out of the lifeless lower body (the reader is reminded that half of the patient is effectively dead during REBOA)

Evidence in support of REBOA

• Nunez et al (2017): meta-analysis of 3 RCTs, 1276 patients in total.  No mortality benefit was seen when compared to resuscitative thoracotomy, until they massaged the data with a sensitivity analysis (adjusting for bias), and then REBOA started looking better.
• Borger van den Burg (2018): meta-analysis of 89 studies (mainly observational), 1436 patients, 49% mortality. "Promising", they said. 
• Yamamoto et al (2019): Japan, propensity score matching analysis, 385 patients; survival to discharge was higher in the REBOA group (45% vs 33%). 
• Chung et al (2020): Korea, 23 patients, 76% mortality. Authors conclusions: "it is better to perform REBOA before an arrest occurs".

In short:

• No mortality benefit has ever been convincingly demonstrated