STEP 1: Arterial Access and Positioning of the Sheath
Access to the arterial circulation for REBOA for trauma should be obtained through the common femoral artery using one of three techniques: percutaneous, open exposure (e.g., cut down), or exchange over a guide wire from an existing common femoral arterial line.
Ultrasound is used to identify the common femoral artery above the branch of the profunda and the needle visualized passing into the common femoral artery (linear array transducer preferred). Ultrasound guided access improves first pass access and decreases complications.1 Once identified, the artery should be entered at a 45-degree angle with the needle, using either a 5 Fr micropuncture kit or 18 gauge femoral arterial line kit. After the wire has been passed into the artery, the needle is removed and a small incision made at the interface of the wire and skin and the catheter is passed over the wire.
Using landmarks, the location of the inguinal ligament is identified between the Anterior Superior Iliac Spine and pubic symphysis (NOT the inguinal crease). The common femoral artery is then accessed 2 cm below the inguinal ligament.
Selection and Positioning of Initial Sheath:
If REBOA is indicated, the arterial access catheter must be upsized to a 7 Fr sheath. This maneuver is accomplished by placing a 0.035 guide wire greater than twice the length of the existing arterial catheter through its inner lumen allowing the catheter to be removed over the wire while maintaining arterial access. After a larger opening is created at the wire/skin interface, the 7 Fr working sheath with its internal dilator in position can be inserted over the wire. When urgently needed, a 7 Fr sheath may be placed as the initial step by placing the 7 Fr sheath over the 0.035 guide wire, though this can increase risk of access site damage.
The sheath’s internal dilator must be firmly held in place to allow a smooth reverse taper from the wire to the diameter of the sheath to avoid arterial intimal injury. Once the dilator and sheath have been advanced over the wire through the skin into the artery, the dilator and wire are removed, leaving the sheath in place. It is important that the operator assure that the stopcock is in the “off” position to reduce bleeding.
STEP 2: Selection and Positioning of the Balloon
The two products covered by this CPG are the ER REBOA-PLUS and the pREBOA-PRO™ (Prytime Medical, Boerne, TX) catheters. ER-REBOA-PLUS™ is a complete occlusion balloon and the pREBOA-PRO™ is a partial occlusion balloon. These are currently the products chosen by the DoD. These catheters are wire-free and fluoroscopy free and smaller caliber than previously used balloons, allowing fewer steps for insertion and a smaller introducer sheath (7 Fr). They also have above balloon arterial pressure monitoring capability.
Attach 30 ml syringe to the balloon port. The syringe will be filled with 30 ml of saline. Negative pressure should be applied to the balloon to remove any air, then locked in place with the plunger at the 30 ml mark on the syringe. Air should be evacuated from the syringe. If using the pREBOA-PRO™ device there is an over pressurization safety valve proximal to the white valve on the balloon port. With the white balloon port in the locked position the safety valve should be primed by pressurizing the 30 ml saline filled syringe until saline escapes the safety valve.
The a-line port of the catheter should be flushed with saline. The balloon will now pass easily into the peel-away sheath.
If using the pressure monitoring capabilities, the pressure sensor and tubing should be attached to the catheter’s arterial stopcock and flushed with saline using standard arterial line setup and transducer connected to a monitor. Once the catheter is inserted, continuous care must be taken to prevent inadvertent emboli (air, thrombus, etc.) as well as keeping the a-line patent.
For Zone 1 occlusion, the catheter should be inserted to Zone 1 markers (between 45 - 49 cm, or measured with the balloon from the midsternum, or the P-tip from the sternal notch to the femoral access catheter). For Zone 3 occlusion, the catheter should be inserted to Zone 3 markers (between 26 - 29 cm, or the balloon measured at the umbilicus or the P-tip measured from the xiphoid process to the femoral access catheter). Distances are noted on the catheter shaft.
The peel away sheath is advanced over the P-tip and balloon to protect these as they enter the 7 Fr sheath. The peel away sheath is advanced into the end of the 7 Fr sheath approximately 5mm or until it hits a “stop.” The REBOA catheter is then advanced 10cm into the sheath. The peel away sheath can then be slid back onto the catheter hub or removed, if full advancement is necessary. The catheter should be advanced to the predetermined depth. Plain film x-ray, ultrasound, or fluoroscopy can confirm correct positioning of the catheter and adjustments can be made, if necessary, prior to inflation. There are two radio-opaque markers on the catheter to designate the location of the balloon. In cases of arrest there is no role for position confirmation and this can be done at a later time when the patient is stable.
STEP 3: Inflation of the Balloon, Securing of the Apparatus, and Monitoring
A 30 ml syringe should be used. Fill syringe to 24 ml with 1/3 iodinated contrast and 2/3 saline, or all saline if contrast not available. 2 If using the ER REBOA-PLUS the balloon should be inflated until the blood pressure is augmented and contralateral femoral pulse is stopped, approximately 8 ml for Zone 1 or 2 ml for Zone 3. If using the pREBOA-PRO™ catheter balloon inflation is titrated to the patient's physiologic response.
Do not over-inflate the ER REBOA-PLUS balloon—balloon capacity is 24 ml—over-inflation can rupture the balloon or damage the aorta. The pREBOA-PRO™ safety valve is designed to protect the balloon from overinflation or too rapid inflation. Balloon inflation can be guided by fluoroscopy, hemodynamic response, and/or loss of the contralateral pulse. When fluoroscopy is available, inflate the balloon until the outer edges of the balloon change from convex to parallel as the balloon takes on the contour of the aortic wall. When inflation appears adequate to gain aortic wall apposition and/or central blood pressure is augmented, the three-way stopcock on the shaft of the balloon should be locked to maintain inflation and occlusion while other maneuvers are undertaken. Confirmatory X-ray may be used for radiographic confirmation of location. If no imaging is available in the austere environment, definitive confirmation of the balloon positioning should be accomplished directly with “hands-on” at the time of laparotomy. If the balloon is found to be malpositioned (e.g., Zone 2) the balloon can be deflated and catheter positioned to Zone 1 or 3 and the balloon re-inflated.
Securing the Inflated Balloon and Sheath:
As the central aortic pressure improves, the catheter will move caudally. To prevent catheter migration, HOLD the catheter in place or secure the catheter to the sheath, and sheath to the patient with a central line attachment device. For added monitoring and security, assign an assistant the task of holding the apparatus until balloon deflation is desired.
A trained assistant should monitor and communicate the “big three” factors imperative to maintenance of successful REBOA: MAP, maintenance of catheter position, and maintenance of occlusion (balloon inflation).
Pressure monitoring: The blood pressure should be monitored through the REBOA a-line port (above balloon pressure) and through the arterial sheath side port (the below balloon pressure). Immediately upon balloon inflation and successful arterial occlusion, the MAP increases. In order to prevent negative effects of increased circulating volume leading to hypertension, the clinician should consider partial aortic occlusion if the SBP exceeds 100 - 110 mmHg (corresponding MAP 65 mmHg). The arterial waveform should be monitored for changes including over-dampening (flattened waveform) or under-dampening (hyper-dynamic waveform). Measures should be taken to ensure that the transducer, pressure tubing, and lines are problem-free. The pressure monitoring system should include dedicated pressure tubing, fully primed and air-free, not of excessive length, and with minimal use of stopcocks. Be sure all connections are tight, but not over-tightened.
For partial occlusion, the below balloon systolic pressure should be at least 20 mmHg (corresponding MAP of 20 mmHg) and may be higher if tolerated.
Catheter position: The clinician should frequently check the measured distance of the catheter at the sheath to ensure that the catheter is not migrating. Notify the physician if catheter migration has occurred.
Maintenance of occlusion: Distal pulses should be monitored frequently. If pulses are present, and partial-REBOA is not intended, then balloon occlusion is not achieved and must be corrected. Notify the physician to add 0.5mm saline to the balloon and recheck MAP and distal pulses for evidence of complete occlusion.
STEP 4: Operative/Procedural Control of Bleeding
Control of bleeding below the diaphragm must occur very quickly, with a goal to keep the total aortic occlusion time less than 30 minutes. It is therefore important to start with damage control maneuvers to control bleeding such as clamping of the splenic or renal hilum, Pringle maneuver, clamping of any injured blood vessel, packing, or obtaining proximal and distal control of an injured blood vessel. At times, definitive control of bleeding such as solid organ removal, ligation of clamped vessels, or vascular shunt placement, may be deferred until after the REBOA has been deflated.
When partial REBOA is used, aortic occlusion is safe up to 2 hours. With pREBOA-PRO™, transition to partial occlusion as soon as the patient’s blood pressure will tolerate. Confirm partial occlusion by monitoring the below balloon pressure.
In patients with pelvic fractures, interventional radiology embolization may be considered when available, after intra-abdominal hemorrhage has been ruled out or controlled and the REBOA has been positioned in Zone 3.
STEP 5: DEFLATION OF THE BALLOON
The balloon should be deflated once hemorrhage control has been obtained. Communicating with the assistant securing the catheter and the anesthesia team is critical before deflating the balloon. When deflating the balloon turn the three-way stopcock and withdraw saline slowly as this step can be anticipated to result in significant hypotension and may result in cardiac collapse. Further resuscitation may be necessary while deflating the balloon. While one person focuses on slowly deflating the balloon, another should hold the catheter and sheath in the position to avoid unintentional migration should the need to rapidly re-inflate the balloon arise.
Complete Occlusion:
If using complete occlusion catheters (ER-REBOA-PLUS™, COBRA-OS® etc.) this step can be anticipated to result in a significant decrease in afterload and hypotension and may result in cardiac collapse. Additional resuscitation may be needed even with slow balloon deflation. The user can anticipate approximately a 10% change in flow past the balloon during deflation with as little as 0.2 ml of fluid removal. Intermittent balloon inflation and deflation may be necessary during ongoing resuscitation until hemodynamic stability is restored.
Partial Occlusion:
If using pREBOA-PRO™ (partial occlusion catheter) the user is advised to gradually remove fluid from the balloon every 10 minutes to increase the distal SBP by 20 mmHg. These small adjustments in flow over time should mitigate the ischemic reperfusion changes often encountered with removing an aortic clamp or deflating a complete occlusion aortic balloon. This slow deliberate deflation method will minimize the need for reinflation unless further hemorrhage is encountered.
STEP 6: Removal of the Balloon and Sheath
Once definitive hemorrhage control has been obtained and coagulopathy corrected, the REBOA sheath should be removed and 30 minutes of direct pressure applied to the CFA access site.
An angiogram through the sheath to document distal limb perfusion is best practice, though not always available. An aortogram may be best accomplished in the Role 3 environment with access to specialists and/or surgical backup.
The sheath should not be removed immediately prior to transport and is best removed where vascular complications can be treated and managed. If the anticipated patient transport time is less than 4 hours, the sheath may remain in place in patients with a high risk of rebleeding/continued bleeding. If patient transport time exceeds 4 hours the sheath should be removed at least 30 minutes prior to transport to allow for sufficient hemostasis at the CFA puncture site. These patients should be monitored closely en route for signs of access site complications. While the sheath is in place and up to 24hrs after removal, the patient should undergo bilateral lower extremity neurovascular checks every 1 hour. Providers should have a low threshold to involve vascular surgery or obtain a lower extremity arteriogram if any vascular change occurs.
The sheath must NEVER be left in place for transfer to a host nation hospital.
Open vascular repair may be needed if a large sheath size is used, the patient is coagulopathic, if there is technical difficulty in sheath removal, or if open femoral cutdown was used for catheter placement. If open surgical repair of the arterial access site is necessary, the femoral artery proximal and distal to the sheath entry site should be exposed to allow control. Proximally, this may require dissection for 2 cm to 3 cm underneath the inguinal ligament as an assistant uses a narrow handheld retractor (e.g., short Wylie renal vein retractor) to lift the inguinal ligament off of the femoral sheath. Exposure distal to the sheath entry site often requires identification and control of both the superficial and profunda femoris arteries.
Once proximal and distal exposure and control with vessel loops or vascular clamps have been accomplished, the sheath may be removed. Consideration should be made for passage of embolectomy catheters distally to remove any potential clot and assure back bleeding. The resulting arteriotomy, especially the intima, should be closely examined and tailored with Potts scissors if necessary to allow primary transverse closure. Closure of the arteriotomy should be performed transversely using 5-0 or 6-0 permanent monofilament suture in either an interrupted or running fashion with care to capture all layers of the arterial wall with passage of the needle. Before closing the last suture, forward bleeding and back bleeding of the arterial segments should be allowed, followed by flushing of the surface with heparinized saline. Restoration of flow through the arterial segment should be confirmed using manual palpation for pulses distally and use of continuous wave Doppler of both the artery and more distal extremity. If there is any question of flow, it is recommended to perform an angiogram and appropriate intervention if any abnormalities are noted. Closure of the soft tissues above the femoral artery is accomplished in layers using absorbable suture in the soft tissues.