REBOA-Learn · Read this first

Managing & Balancing the Aortic Balloon

The one thing that confuses everyone: a REBOA balloon splits the body into two blood compartments, so suddenly you have two sets of numbers — above the balloon and below it — and they tell you different things. This guide teaches you to read both, act on the gap between them, and run the inflate→partial→wean balancing act without crashing the patient.

When you're ready → Test yourself in the Simulator ↗

Every key rule below links to the exact page of the JTS CPG or a corpus textbook (📄) so you can verify it in one click. Links resolve when this page is opened from the FRSD SIM, or with the sim server running.

① The balloon makes two compartments

Inflate a balloon in the aorta and you've built a dam. Everything above it gets more pressure and flow; everything below it is cut off (complete) or rationed (partial). That's the whole point — and the whole problem.

ABOVE ▲

BALLOON

BELOW ▼

ABOVE the balloon — heart, brain, lungs. Gets the pressure boost. This is what a radial arterial line measures. It's the compartment you keep alive minute-to-minute.

BELOW the balloon — gut, kidneys, spinal cord, legs. On the ischemic clock. This is what a femoral (sheath side-arm) line measures. It's where the metabolic debt (acid, potassium, CO₂) silently piles up.

Two compartments → two arterial lines → two sets of labs. The radial keeps you driving the resuscitation; the femoral warns you what's coming when you let go.

The core idea in one sentence

The balloon controls bleeding below it and raises pressure above it — so the above numbers look reassuringly normal while the below compartment is quietly drowning in a debt that will hit the heart the moment you deflate.

② Why you draw BOTH — and what each one is for

You recommended drawing both. Here's the actual job of each, so the second sample stops feeling pointless:

Sample	What it represents	What you use it for
Proximal (radial, ABOVE)	What the heart, brain, and lungs are bathed in. Your "central" milieu.	Your primary resuscitation trend. Titrate the MTP, calcium, pH, and Hgb to this. It's the clean, minute-to-minute number.
Distal (femoral, BELOW)	The effluent of the ischemic compartment — gut/kidney/cord/legs behind the dam.	Your early-warning of the reperfusion hit. This is the K⁺/acid/CO₂ that will wash centrally the moment you open the balloon. It tells you what's coming.

The radial lies to you (optimistically) while the balloon is up

During occlusion the bad blood below is dammed — it isn't reaching your radial sample. So a radial gas that looks "manageable" is under-reading the true whole-body debt. That debt comes due 30–50 minutes after you reperfuse (lactate peak, pH nadir, K⁺ and CO₂ surge). Partial occlusion shrinks this blind spot, because a trickle of distal flow keeps washing the compartment out in real time.

📄 Abid 2020, Reperfusion Repercussions (PMID 32332257) · Forte 2020 partial-vs-complete (swine) outside CPG ID38 — journal source, not blind-verified

③ Acting on the discrepancy — the part you asked about

You don't treat the two numbers separately. You read the gradient — how much worse below is than above — and that gradient tells you how big the hidden debt is and how cautiously to reperfuse. Here are the four patterns and exactly what to do:

▼ Below MUCH worse than above

e.g. prox lactate 8 · K 5.0 · pH 7.18 distal lactate 14 · K 6.8 · pH 7.02

Means: a big sequestered ischemic debt — the balloon's been tight/up a while. This is the load that will slam the heart on deflation.

Do: PRE-STAGE the deflation kit (calcium, bicarb, D50, pressor). SLOW any planned deflation — small steps, treat between them. If hemodynamics allow, start opening the balloon a little now to wash it out gently rather than all at once later. Treat the K⁺ before you reperfuse it.

≈ Gradient is narrow (above ≈ below)

e.g. prox lactate 5 · K 4.6 distal lactate 6 · K 4.8

Means: either you're at a good partial state (distal washout keeping pace) or you've already reperfused. Little hidden debt.

Do: REASSURING — continue your graded wean. This is the state you're steering toward: low gradient = the balloon isn't hiding a storm.

▲ ABOVE worsening too — & source NOT controlled

radial lactate climbing, MAP soft, surgeon still working

Means: ongoing hemorrhage / under-resuscitation is now overwhelming even the central compartment.

Do: MORE OCCLUSION (tighten a touch) + more blood + push the surgeon for faster control. Before control, a deteriorating lab means do more, not less.

▲ ABOVE worsening — but source IS controlled

radial lactate/K rising right after you started weaning

Means: that's the debt washing in — reperfusion, not failure.

Do: KEEP GOING gently — resuscitate, buffer, calcium, treat K⁺. Do NOT re-clamp a controlled patient just because the lactate blipped up. That blip is the point.

The master switch over the whole table: "Is the source controlled?"

The same rising lactate means opposite things on either side of hemorrhage control. Before control → it's ongoing bleeding → tighten / transfuse / cut faster. After control → it's the reperfusion debt → resuscitate and keep weaning. Always answer this question first.

📄 JTS CPG ID 38 v1.4 — controlled reperfusion (source controlled + MTP + plan) · Nguyen 2025 Shock Delphi (PMID 40341373) outside CPG ID38 — journal source, not blind-verified

Practical note: a femoral arterial sample below a partial balloon is blood that has already crossed the balloon mixed with distal runoff — so treat the gradient as a strong relative index, not a pure tissue measurement. The trend and the size of the gap are what matter, not the exact decimal.

④ The titration dial — keep MAP up on the LEAST occlusion

The balloon is a dial, not a switch (with a partial catheter like the pREBOA-PRO). The whole game:

The rule

Give the smallest occlusion that keeps proximal MAP ≥ 55–65, and open it as fast as the hemodynamics and labs allow. Every minute of occlusion is distal ischemic dose.

Wean in ~0.2 mL steps toward distal SBP 20–50 with pulsatility (a damped, flat distal trace is lying — you need a real pulse crossing). 📄 JTS CPG ID 38 v1.4 — distal target 20–50 mmHg, pulsatile (p.6) · ~10% flow change per 0.2 mL removed (p.12)
MAP drops < 55 after a step? → give blood / calcium, or re-inflate 0.2 mL and wait. Bidirectional.
A rising proximal MAP is the BALLOON, not light anesthesia. When MAP creeps to 80–90 as you slow transfusion, wean the balloon — don't deepen anesthetic (propofol/volatile drop SVR in a shock patient). Keep anesthetic minimal but keep an amnestic on board (a paralytic alone is awareness).
Never chase proximal SBP > 180 — supranormal pressure pops fresh clot and loads a stunned heart. Treat it by opening the balloon.

Complete → partial as soon as you can

A complete Zone 1 balloon past ~30 minutes drives severe ischemia and an all-or-none reperfusion crash. Convert to partial once proximal hemodynamics tolerate it — most of the MAP benefit at a fraction of the ischemic cost, and it earns the longer window (Z1 ~2 h, Z3 ~4 h).

📄 complete <60 min/optimally <30 (p.6) · partial Z1 ~2 h / Z3 ~4 h (p.11)

⑩ Which balloon is in your hand

Everything in §④ about the "dial" assumes a partial-capable catheter. Before you lean on the partial window, read the label on the device. What CPG ID38 v1.4 says, in its own words:

Topic	CPG ID38 v1.4 text
Partial vs complete, and the device it names	"Partial REBOA is conditionally preferred over complete REBOA. This requires training of all surgical and damage control resuscitation team personnel and acquisition of the partial occlusion device. The pREBOA-PRO™ catheter is currently the only FDA-approved catheter for partial aortic occlusion." 📄 JTS CPG ID 38 v1.4 — partial conditionally preferred; device named (p.6)
Pressure targets (partial)	"A target central aortic SBP of 90-110 mmHg above the balloon, and minimum pulsatile SBP of 20 mmHg below the balloon, while titrating distal pressure to a target systolic blood pressure of 20 - 50 mmHg is desirable in partial occlusion." Two arterial-line transducers are required; "the pREBOA-PRO™ catheter provides the ability to measure above and below the catheter without additional access." 📄 JTS CPG ID 38 v1.4 — SBP 90–110 above, pulsatile ≥20 (20–50) below (p.6) "Distal SBP => 20mmHg (20 - 50 mmHg) or MAP ~20 mmHg" … "If utilizing MAP instead of SBP it is recommended to maintain a MAP of 20 mmHg (below the balloon) since MAP and SBP are very close in this low-pressure range." 📄 JTS CPG ID 38 v1.4 — distal SBP ≥20 or MAP ~20 (p.11)
Time limits	Complete: "Zone 1 REBOA – 60 minutes maximum, optimally < 30 minutes. Zone 3 REBOA – 60 minutes." Zone 3 "historically has been considered acceptable for up to 4 - 6 hours", now revised to "no greater than 60 minutes". 📄 JTS CPG ID 38 v1.4 — complete: Z1 60 max / optimally <30; Z3 60 (p.10) Partial: "Partial aortic occlusion of Zone 1 should ideally be limited to 2 hours, and Zone 3 should be limited to 4 hours. This continues to be an active area of clinical and animal research at the time of publication of this CPG." 📄 JTS CPG ID 38 v1.4 — partial: Z1 2 h / Z3 4 h — active research (p.6)
What "partial" means	"Partial aortic occlusion is defined as having partial blood flow past the balloon to minimize the risk of ischemia with longer occlusion times. In the absence of measuring flow, the best clinical surrogate is blood pressure." … "Due to the semi compliant design of the pREBOA-PRO™ catheter, several investigators have documented that inflation of the balloon does not need to be adjusted after initial setting of below MAP." 📄 JTS CPG ID 38 v1.4 — partial defined; pREBOA-PRO semi-compliant design (p.11)

HOUSE POSITION — ours, not the CPG's

The partial window is written around the pressure-regulated device named in the CPG; whether other (compliant) balloons inherit it is not established in CPG ID38 v1.4. Source of the stricter reading: Russo & Joseph 2026, PMID 42222899 (opinion).

⑤ EtCO₂ and the PaCO₂–EtCO₂ gap — your continuous gauge

EtCO₂ is the most useful real-time number in the room — but under REBOA its meaning shifts.

EtCO₂ tracks distal aortic flow / degree of occlusion (not just cardiac output). Tighten the balloon → less distal perfusion → EtCO₂ falls. Open it → distal reperfuses → EtCO₂ rises. 📄 Sadeghi/Hurtsén 2021, Shock — EtCO₂ vs distal aortic flow (R≈0.84) outside CPG ID38 — journal source, not blind-verified
So a falling EtCO₂ is ambiguous — it can mean "balloon tighter" or "cardiac output dropping / re-bleeding." Read it against the pressures: if you didn't tighten and EtCO₂ falls, suspect a re-bleed.
At each deflation step, expect an EtCO₂ SURGE — the sequestered CO₂ washing back, exactly like a tourniquet or cross-clamp release. A big surge = a big debt just released → slow down and treat.
The gap (PaCO₂ − EtCO₂) widens in shock (dead space); it should narrow as you restore central perfusion. A persistently wide gap means you're not truly resuscitating the central compartment, even if the pressure looks fine. outside CPG ID38 — journal source, not blind-verified no inline citation

Ventilation at reperfusion — the nuance

Increase minute ventilation to clear the washout CO₂ and support pH — but target normocapnia, not hypocapnia, and back off if more ventilation drops the BP (higher airway pressure steals preload in a hypovolemic patient). And anchor your acid–base decisions to the PaCO₂ on the gas, not the EtCO₂ — in trauma the gap is wide and EtCO₂ underestimates PaCO₂.

📄 Campion 2019 (WTA) — EtCO₂ underestimates PaCO₂ in trauma laparotomy outside CPG ID38 — journal source, not blind-verified

⑥ The lab levers — which way each one sends you

Finding	Means	Move
Lactate rising · source NOT controlled	Ongoing bleed / under-resuscitated	Tighten occlusion + blood + faster surgery
Lactate rising · source CONTROLLED	Reperfusion debt washing in	Keep weaning gently; buffer, calcium
Lactate clearing >10–20%/hr	Winning	Continue wean outside CPG ID38 — journal source, not blind-verified no inline citation
K⁺ ≥ 6 / climbing	Ischemic + transfused load	STOP weaning; calcium (protect) + insulin/D50 + bicarb + albuterol + ↑MV outside CPG ID38 — journal source, not blind-verified no inline citation
Ionized Ca low (<1.1)	Citrate + ischemia	Calcium — liberally, and before every deflation step outside CPG ID38 — journal source, not blind-verified no inline citation
pH < 7.2	Acidemia	Buffer/ventilate before next deflation step outside CPG ID38 — journal source, not blind-verified no inline citation
Prox SBP > 180 / MAP climbing	Balloon over-pressurizing	Wean MORE (afterload + pop-clot) outside CPG ID38 — journal source, not blind-verified no inline citation
Glucose falling	Anaerobic consumption (post-reperfusion hypoglycemia)	D50, recheck q15 min
EtCO₂ falling (you didn't tighten)	Falling CO / re-bleed	Find the bleed, resuscitate outside CPG ID38 — journal source, not blind-verified no inline citation

Calcium does NOT lower potassium

Calcium protects the heart's membrane at a given K⁺ — it buys you time but the number stays high. To actually lower K⁺ you need insulin+dextrose / albuterol / bicarb (and definitive renal clearance). Give calcium for protection (especially before a deflation step), and shift the K⁺ with the others.

📄 JTS Anesthesia for Trauma CPG (ID 40) — hyperkalemia & ionized calcium

⑦ Reperfusion — the planned, gated event

Deflation is not a single act; it's a briefed, graded, kitted event. Open the gate first:

The 3-part deflation gate (Delphi consensus)

① the source is being controlled · ② blood / MTP is in the room · ③ the team has spoken the reperfusion plan aloud. Miss one and you reperfuse into a hole.

📄 Nguyen 2025 Shock Delphi (PMID 40341373) outside CPG ID38 — journal source, not blind-verified · JTS CPG ID 38 v1.4 — reperfusion over 10–30 min (p.8)

Stage the deflation kit before you touch the balloon: calcium, bicarb, D50 (± insulin), push-dose pressor, the hyperkalemia bundle.
Pre-correct the acidosis (pH > 7.2) and have blood running — don't deflate into an uncorrected pH.
Wean in steps over 10–30 min, watching MAP, K⁺, and the EtCO₂ surge. One person deflates, one holds the catheter ready to re-inflate.
The debt peaks 30–50 min AFTER full reperfusion — recheck K⁺, pH, and glucose then, even when you feel done. Catch the late K⁺ rebound and the hypoglycemia. outside CPG ID38 — journal source, not blind-verified

⑧ A worked case — watch the two numbers drive the decisions

Zone 1 partial REBOA for a blunt abdominal bleed. Illustrative numbers — follow the logic.

T+0 · inflate to complete

Proximal MAP 38→76, field dries. EtCO₂ drops 30→18 (distal flow cut off — expected). Note the inflation time.

T+15 · MAP creeps to 90

You slowed transfusion and MAP climbed. Cue to convert to partial — the balloon is the pressor. Wean 0.2 mL → distal pulsatile, distal SBP 24. EtCO₂ ticks up to 28 (distal reperfusing).

T+30 · draw BOTH

ABOVE: lactate 8 · K 4.8 · pH 7.18 BELOW: lactate 14 · K 6.8 · pH 7.02

Wide gradient → big sequestered debt. Source not yet controlled. Action: hold the partial state, give calcium now, pre-stage the kit — that 6.8 below is what hits the heart on full deflation. Don't reflexively re-tighten (MAP is fine); push surgical control.

T+50 · "I have control."

Open the gate (control ✓ · blood in room ✓ · plan spoken ✓). Begin graded wean. Each 0.2 mL step → small EtCO₂ surge (washout). One step drops MAP to 52 → re-inflate 0.2 mL + blood + calcium → MAP 61.

T+75 · radial K⁺ now 5.8

The below-debt is washing into the above-compartment. K⁺ is the governor → pause the wean. Calcium (protect) + insulin/D50 + ↑ minute ventilation. Don't open more aorta into a rising K⁺.

T+105 · gradient closing

ABOVE: lactate 5 · K 5.0 · pH 7.25 BELOW: lactate 6 · K 5.2

Narrow gradient = the storm is spent. Resume gentle weaning to full reperfusion.

T+135 · feel done — but aren't

Recheck at ~T+150: catch a late glucose of 60 (replace) and confirm K⁺ stable. Then sheath/disposition by the transport & coagulation rules.

⑨ After the OR — what the ICU nurse hunts for

The complication clock runs for 24 hours past the procedure. The post-REBOA watch list:

Complication	How you catch it
Access-limb ischemia / thrombosis (the classic)	Hourly bilateral lower-extremity pulse checks ×24 h — a tracked CPG metric. A cool, pulseless REBOA-side foot → vascular + duplex now.📄 JTS CPG ID 38 v1.4 — hourly bilateral LE neurovascular checks, sheath in and 24 h after (p.30)
AKI / myoglobinuria	Tea-colored urine, rising Cr/CK, falling UOP. UOP only becomes a meaningful endpoint after deflation. IVF, monitor K⁺, consider urine alkalinization.
Spinal cord ischemia (Zone 1)	Serial neuro exam — new lower-extremity weakness/paraplegia.
Bowel ischemia	Lactate that plateaus/re-rises, worsening abdominal exam/acidosis → surgical re-look.
Compartment syndrome (leg)	Tense calf, pain on passive stretch → fasciotomy.
Access site	Expanding hematoma, bruit/thrill → pseudoaneurysm; duplex.
Delayed metabolic debt	K⁺ rebound + acidosis 30–50 min post-deflation — recheck even when stable. outside CPG ID38 — journal source, not blind-verified
Sheath	Pull only after coagulopathy corrected → 30 min direct pressure → then the hourly pulse checks. Never to a host-nation facility.📄 JTS CPG ID 38 v1.4 — sheath vs transport time (p.30)

⑪ Transport and the sheath

Role 2 evacuees "should have hemorrhage control addressed, and balloon deflated prior to transfer." 📄 JTS CPG ID 38 v1.4 — deflate before transfer (p.14)

Complete occlusion: "Under no circumstance should a Zone 1 complete occlusion REBOA remain inflated during transport." A Zone 3 balloon "may remain inflated" only for a rare short rotary-wing leg, and that "requires exceptional communication and planning." 📄 JTS CPG ID 38 v1.4 — complete occlusion in transport (p.14)
Partial occlusion: transport "with a provider trained in partial REBOA" is "considered feasible" when arrival for definitive control is expected "within these time recommendations" (2 h Zone 1, 4 h Zone 3). "A medical provider trained in hemodynamic monitoring and manipulation of the occlusion balloon should always accompany the casualty." 📄 JTS CPG ID 38 v1.4 — partial occlusion in transport; attendant (p.14) Re-inflation en route "is an option for trained providers in the event of sudden profound hypotension"; anticipate simultaneous transfusion. 📄 JTS CPG ID 38 v1.4 — re-inflation en route (p.15)
Sheath by transport time: "The sheath should not be removed immediately prior to transport." Transport under 4 h → the sheath "may remain in place in patients with a high risk of rebleeding/continued bleeding." Transport over 4 h → remove it "at least 30 minutes prior to transport to allow for sufficient hemostasis." "The sheath must NEVER be left in place for transfer to a host nation hospital." 📄 JTS CPG ID 38 v1.4 — sheath vs transport time (p.30)
Checks: "While the sheath is in place and up to 24hrs after removal, the patient should undergo bilateral lower extremity neurovascular checks every 1 hour." 📄 JTS CPG ID 38 v1.4 — hourly NV checks (p.30) After removal, "most access-related complications occur within the first 1–6 hours after sheath removal, with the highest rate in the first 2 hours" — watch closely for six hours. 📄 JTS CPG ID 38 v1.4 — post-removal window (p.13)

Practice all of this — the titration, the two-compartment sampling, the reperfusion storm, and these ICU complications — in the dynamic trainer:

Open the Simulator → put it into your hands ↗

Training tool — not a substitute for clinical judgment, the JTS CPG, or local protocol.
Primary doctrine: JTS CPG ID 38 v1.4 (REBOA for Hemorrhagic Shock). Physiology anchors: Nguyen 2025 Shock Delphi consensus (PMID 40341373) · Abid 2020 reperfusion repercussions (PMID 32332257) · Sadeghi/Hurtsén 2021 Shock (EtCO₂) · Forte 2019/2020 · Davidson 2017 · Campion 2019 WTA · Marble 2022. Source links open the exact page of the CPG or corpus textbook when launched from the FRSD SIM.