🩸 Combat Trauma Hemorrhage Control Decision Algorithm

Bleeding Source Identification & the TCCC Hierarchy

Tactical Combat Casualty Care (TCCC) inverts the civilian ABC (Airway-Breathing-Circulation) trauma sequence into MARCH: Massive hemorrhage, Airway, Respiration, Circulation, Hypothermia/Head injury. Hemorrhage comes first because in penetrating combat trauma, exsanguination from an extremity or junctional wound can cause death in under five minutes — faster than most airway compromise kills.

• ~90%: Potentially survivable combat deaths (die from hemorrhage, pre-hospital)
• <5 min: Time to death, major arterial bleed (untreated extremity hemorrhage)
• 4: TCCC hierarchy steps (pressure → dressing → TQ → junctional/evac)
• 1st: MARCH sequence position (hemorrhage control before airway)

Why hemorrhage control comes before airway

Civilian trauma protocols teach ABC — Airway first. TCCC, developed from analysis of combat mortality data (notably the "Death on the Battlefield" study of U.S. Special Operations casualties, 1980s–2000s), found that the leading cause of preventable death on the battlefield was uncontrolled extremity and junctional hemorrhage, not airway obstruction.

A femoral or axillary arterial injury can exsanguinate a casualty in 3–5 minutes. Airway compromise, by contrast, typically allows more time before it becomes lethal. TCCC therefore reorders the sequence to MARCH: Massive hemorrhage control first, then Airway, Respiration, Circulation, Hypothermia prevention/Head injury — reflecting what actually kills fastest on the modern battlefield.

This reordering, adopted from Special Operations medicine in the 1990s and formalized by the Committee on TCCC, is credited with substantially reducing preventable prehospital death rates in U.S. combat casualties compared to earlier conflicts.

Analysis of casualties from Iraq and Afghanistan found that roughly 90% of potentially survivable combat deaths were attributable to hemorrhage — the single largest cause of preventable battlefield mortality, more than airway and tension pneumothorax combined.

Classifying the wound: extremity vs. junctional vs. torso

The first decision point in the algorithm is not "how bad is the bleeding" but "where is it, and can it be compressed?" This single classification determines the entire intervention pathway:

• Extremity wounds (arms, legs): compressible against bone or soft tissue. Amenable to direct pressure, hemostatic packing, and — critically — limb tourniquets, which encircle the limb proximal to the wound and cut off all arterial inflow.

• Junctional wounds (groin/inguinal, axilla/shoulder, neck/cervical): located at the "junction" between torso and limb, or at the base of the neck. These vessels (femoral, axillary, carotid/subclavian) are large-caliber and high-flow, but there is no limb circumference to encircle with a standard tourniquet — the wound sits too close to the trunk.

• Torso wounds (thoracic, abdominal, pelvic cavity): bleeding into the chest, abdomen, or pelvis from injured solid organs or major vessels. These are non-compressible from the outside — no amount of surface pressure reaches the bleeding source deep inside the body cavity.

Each category funnels the casualty down a different branch of the TCCC hemorrhage-control algorithm.

Rapid field assessment under fire

In the "Care Under Fire" phase of TCCC — while still receiving effective enemy fire — assessment is deliberately minimal: identify life-threatening external hemorrhage and treat it, usually by self-aid or buddy-aid application of a tourniquet, without a full physical exam.

Only once the casualty is moved to cover ("Tactical Field Care") does a more systematic MARCH assessment proceed: exposing wounds, checking for multiple injury sites, distinguishing arterial (bright red, pulsatile) from venous (darker, steady) bleeding, and estimating severity from visible blood loss, soaked clothing, and hemodynamic signs (rising heart rate, falling consciousness, weak pulse).

The decision algorithm modeled here begins at this identification step: wound location and bleeding severity are established, then the casualty is routed down the branch — direct pressure, tourniquet, junctional tourniquet, or evacuation-priority for non-compressible hemorrhage — that TCCC doctrine prescribes for that specific combination.

Direct Pressure & Hemostatic Dressing

For any compressible wound, TCCC doctrine starts with the simplest, fastest intervention: firm, sustained direct pressure over the bleeding point. If that alone does not control the bleeding, the wound is packed with a hemostatic dressing — gauze impregnated with an agent that accelerates the body's own clotting cascade.

• Factor XII: Kaolin (Combat Gauze) mechanism (activates intrinsic clotting cascade)
• Direct: Wound packing depth target (contact with bleeding vessel)
• ~2–3 min: Time to hemostasis (hemostatic gauze) (with sustained pressure)
• 2008: Fielded since (Combat Gauze replaced older agents)

Direct pressure — the first and simplest step

Direct pressure is the immediate first response to any compressible bleeding wound: a gloved hand, dressing, or knee is used to apply firm, focused force directly onto the bleeding point, not just the general wound area. Pressure must be sustained continuously — checking too early interrupts clot formation and restarts the bleeding.

For many venous and lower-flow arterial wounds, 2–3 minutes of uninterrupted, well-placed direct pressure is sufficient to allow the body's own coagulation cascade to form a stable clot. Direct pressure requires no equipment, can be applied by the casualty or a buddy immediately under fire, and buys time while more advanced interventions are readied if needed.

When direct pressure alone fails to stop the bleeding — common with deep wounds, large-caliber vessel injury, or wounds where the bleeding point cannot be precisely localized — the algorithm escalates to hemostatic wound packing.

Hemostatic dressings: kaolin, chitosan, and wound packing technique

Hemostatic dressings are gauze or granules impregnated with agents that accelerate clot formation on contact with blood, rather than simply absorbing it:

• Combat Gauze (kaolin-impregnated): the current U.S. military standard. Kaolin is an inert aluminosilicate clay mineral that activates Factor XII (Hageman factor) of the intrinsic coagulation cascade purely by surface contact — it triggers the body's own clotting chemistry rather than adding an external clotting agent.

• QuikClot: an early hemostatic product line, originally zeolite-based (which generated exothermic heat and risked burns), later reformulated as kaolin-based gauze similar in mechanism to Combat Gauze.

• Celox (chitosan-based): derived from shellfish-derived chitosan, which works by a different, non-enzymatic mechanism — its positively charged polymer chains bind to negatively charged red blood cell membranes, forming a physical gel-like clot (mucoadhesion) independent of the patient's own clotting factors, which can be an advantage in coagulopathic casualties.

Correct technique is essential: the dressing must be packed directly into the wound cavity, in firm contact with the actual bleeding source (not just laid over the wound opening), followed by at least 3 minutes of firm direct pressure on top of the packed gauze.

Kaolin does not clot blood by itself — it is not a chemical coagulant. It works purely as a contact-activation catalyst: its microscopic negatively-charged clay surface dramatically accelerates activation of Factor XII, kicking off the patient's own intrinsic clotting cascade far faster than an unpacked wound would clot on its own.

When packing is not enough

Hemostatic wound packing has real limits. It is effective for most compressible extremity and junctional-adjacent wounds, but can fail when:

• The wound tract is too narrow or deep to pack effectively against the actual bleeding vessel • Bleeding is from a high-flow arterial source (e.g. a partially transected femoral or brachial artery) that overwhelms the dressing's contact-activation clotting speed • The casualty is hypothermic, acidotic, or coagulopathic ("the lethal triad"), impairing the intrinsic clotting cascade the dressing depends on

When direct pressure and hemostatic packing fail to control bleeding on an extremity, TCCC doctrine escalates immediately to tourniquet application — there is no expectation to keep re-attempting packing on a still-bleeding limb wound. Time lost re-packing a failed dressing is time the casualty cannot afford.

Tourniquet Application for Extremity Hemorrhage

When direct pressure and hemostatic packing fail to control bleeding from an arm or leg wound, the algorithm escalates without hesitation to a limb tourniquet — a device that circumferentially occludes all arterial inflow to the limb distal to its placement, stopping hemorrhage completely regardless of the exact bleeding point.

• <1 min: Application time target (from decision to occlusion)
• 2–3 in: Placement (proximal to wound, "high and tight" if unsure)
• ~2 hrs: Limb ischemia tolerance (before significant tissue risk)
• Major: Modern combat TQ survival benefit (vs. pre-2005 no-tourniquet doctrine)

Windlass tourniquet mechanism and technique

A combat application tourniquet (CAT) or similar windlass device consists of a wide strap that encircles the limb and a rigid rod ("windlass") that, when rotated, twists and shortens the strap, generating enough circumferential pressure to collapse the underlying artery against bone.

Application sequence: 1. Place the tourniquet 2–3 inches proximal to the wound (or "high and tight," near the groin or shoulder, if the exact wound location is unclear or time-critical) 2. Route the strap through the buckle and pull fully tight before locking 3. Twist the windlass rod until bleeding stops and the distal pulse is no longer palpable 4. Secure the windlass rod in its clip and note the application time on the tourniquet itself — the time-of-application record is critical for downstream surgical and evacuation decisions

A properly applied tourniquet stops bleeding completely and immediately — it does not rely on the wound's own clotting response, which is why it is definitive rather than assistive.

The history behind "tourniquets are now first-line, not last-resort"

For decades, military and civilian first-aid teaching treated tourniquets as a dangerous last resort, taught to cause limb loss if left on too long. Combat experience in Iraq and Afghanistan overturned this: retrospective mortality studies showed that pre-hospital tourniquet application, even when applied liberally by non-medical personnel, dramatically reduced death from extremity hemorrhage with a low rate of limb complications when applied and removed within accepted time windows.

Modern limbs can tolerate roughly two hours of complete tourniquet ischemia before significant risk of permanent tissue damage — well within typical prehospital-to-surgical-care evacuation timelines in most conflict environments. This evidence shifted tourniquets from "avoid unless dying" to "apply immediately when direct pressure fails" — now taught as a routine, first-line-adjacent step in the TCCC hemorrhage algorithm, not an emergency measure of last resort.

Data from U.S. combat operations found that early, aggressive prehospital tourniquet use was associated with survival benefit and no significant increase in amputation rate compared to casualties who did not receive one — driving the doctrine shift that made tourniquets a first-line extremity intervention rather than a feared last resort.

Limits of the standard limb tourniquet

A windlass tourniquet works only where there is a limb circumference to encircle proximal to the wound and distal to the torso. It cannot be effectively applied to:

• Wounds at or above the groin crease (proximal thigh, hip, pelvis) • Wounds at or above the axilla (shoulder, upper arm near the chest wall) • Neck wounds

In these junctional locations there simply is no cylindrical limb segment left between the wound and the torso to wrap a strap around — this is precisely the gap that junctional tourniquet devices were engineered to fill, covered in the next stage.

Hemorrhage control methods by wound type

Junctional Tourniquet Devices for Non-Extremity Wounds

Junctional hemorrhage occurs at the groin, axilla, or base of the neck — anatomic "junctions" between the limbs and torso where major vessels (femoral, axillary, carotid/subclavian) run close to the body wall but where no standard limb tourniquet can gain a proximal purchase point. Purpose-built junctional tourniquet devices fill exactly this gap.

• 3: Junctional zones (groin, axilla, neck)
• ~19%: Junctional hemorrhage of battlefield deaths (of hemorrhagic combat fatalities)
• CRoC, SAM-JT, AAJT: Devices fielded (FDA-cleared combat junctional TQs)
• ~30–60s: Application time (trained operator, junctional device)

Why standard tourniquets fail at junctional wounds

A windlass limb tourniquet works by encircling a cylindrical limb segment and cinching it down until the strap compresses the artery against underlying bone. This mechanism has a hard geometric requirement: there must be a limb circumference proximal to the wound and distal enough from the torso to wrap.

Junctional wounds violate that requirement by definition:

• Groin/inguinal wounds: the femoral artery injury may be at or above the point where the leg meets the pelvis — there is no more "leg" proximal to the wound to encircle • Axilla/shoulder wounds: an axillary or proximal brachial artery injury near the shoulder leaves no upper-arm segment proximal to the injury • Neck wounds: carotid or subclavian vessel injury at the base of the neck has no limb geometry at all — a standard strap simply has nothing appropriate to wrap around, and circumferential neck compression risks airway obstruction and stroke

These vessels are large-caliber, high-flow, and located close to the heart, making junctional hemorrhage extremely fast and lethal — yet until junctional tourniquet devices were developed and fielded, medics had only direct pressure and hemostatic packing to offer, with a much higher failure rate on these deep, high-flow wounds.

Real junctional tourniquet devices

Several purpose-built devices, developed and fielded in the 2010s, solve the junctional geometry problem by compressing the artery against a fixed bony landmark (the pelvis or clavicle) proximal to the wound, rather than encircling a limb:

• Combat Ready Clamp (CRoC): a rigid, adjustable C-shaped clamp frame that straddles the pelvis; a compression pad is screw-tightened directly onto the femoral or axillary vessel against the underlying bone, providing focused, sustained mechanical pressure at the junctional zone.

• SAM Junctional Tourniquet (SAM-JT): uses an inflatable compression bladder mounted on a belt-like frame worn around the pelvis; the bladder is manually pumped to apply targeted pressure over the femoral or axillary junctional point.

• Abdominal Aortic and Junctional Tourniquet (AAJT): compresses the abdominal aorta itself, above the pelvic inlet, using an inflatable bladder cinched around the lower abdomen — effective for bilateral groin or pelvic junctional hemorrhage where a single-sided device would not control bleeding from both femoral vessels.

All three require the casualty to be positioned appropriately and the device correctly seated against the target bony landmark — misplacement can render them ineffective, so they demand more training than a simple windlass tourniquet.

Retrospective battlefield injury analyses found junctional hemorrhage accounted for a disproportionate share of potentially survivable combat deaths relative to how rarely junctional wounds occur — precisely because, before dedicated junctional tourniquets existed, medics had no mechanical option once direct pressure and packing failed at the groin, axilla, or neck.

Positioning within the TCCC algorithm

Junctional tourniquets are indicated specifically when: (1) the wound is confirmed junctional — groin, axilla, or neck — and (2) direct pressure with hemostatic wound packing has failed or is judged unlikely to succeed given visible high-flow arterial bleeding.

Unlike a limb tourniquet, which can be applied almost immediately by any trained casualty or buddy, junctional tourniquet devices are bulkier, require more setup time, and are typically carried at the medic or unit level rather than by every individual soldier — so hemostatic wound packing remains the immediate bridging intervention while a junctional device is retrieved and applied.

For neck wounds specifically, circumferential compression is never appropriate (airway and contralateral carotid flow must be preserved) — control instead relies on directed manual pressure and hemostatic packing, with any device-based approach limited to unilateral, off-midline compression.

Non-Compressible Torso Hemorrhage & REBOA

Non-compressible torso hemorrhage (NCTH) — bleeding into the chest, abdomen, or pelvis from injured solid organs or great vessels — cannot be stopped by any external pressure, dressing, or tourniquet, because the bleeding source is inaccessible from the body surface. It is widely regarded as the hardest unsolved problem in combat and civilian trauma hemorrhage control.

• ~85%: NCTH share of potentially survivable deaths (of hemorrhagic non-junctional/extremity deaths)
• 0: External control options (no field method stops internal bleeding)
• Aortic: REBOA concept (balloon occlusion, endovascular)
• Time: Dominant lever on survival (to surgical hemorrhage control)

Why non-compressible torso hemorrhage is uniquely lethal

Every hemorrhage-control method covered so far — direct pressure, hemostatic packing, limb tourniquets, junctional tourniquets — works by applying mechanical force between the outside world and the bleeding vessel. NCTH breaks that entire model: a lacerated spleen, liver, major thoracic vessel, or pelvic fracture bleeds into a body cavity that no external device can reach or compress.

There is no field-deployable equivalent of a tourniquet for the abdomen or chest. The rib cage and pelvic ring physically prevent effective external compression of injured organs inside them. This makes NCTH the leading cause of potentially survivable death among casualties who reach a hemorrhage-control decision point but cannot be saved by any of the mechanical interventions covered in stages 2–4.

Because field providers cannot stop the bleeding itself, the entire clinical strategy for NCTH shifts from "control the source" to "buy time and move fast" — permissive hypotensive resuscitation (avoiding over-aggressive fluid that raises blood pressure and worsens bleeding) combined with the most direct possible evacuation to a surgical team capable of opening the abdomen or chest and controlling the vessel by hand.

Non-compressible torso hemorrhage is estimated to account for the large majority of potentially survivable combat deaths that are not attributable to extremity or junctional bleeding — precisely because it is the one hemorrhage category with no effective external field intervention, making evacuation speed the single dominant factor in survival.

REBOA — an emerging far-forward option

Resuscitative Endovascular Balloon Occlusion of the Aorta (REBOA) is an emerging intervention designed to partially bridge the NCTH gap. A catheter is threaded into the femoral artery and advanced into the aorta; a balloon at its tip is inflated to temporarily occlude aortic blood flow above the level of the bleeding injury.

By occluding the aorta, REBOA reduces blood flow to the bleeding site in the abdomen or pelvis, temporarily slowing hemorrhage and preserving blood pressure to the heart and brain — buying critical minutes while the casualty is moved toward definitive surgical control.

REBOA is not a cure: it is a bridge, not a fix. The occluded aorta also stops blood flow to everything below the balloon, so occlusion time is tightly limited before ischemic injury to the lower body and abdominal organs becomes a serious complication. It requires specialized training, equipment, and vascular access skill that is not yet standard at the most far-forward levels of care — its role today is mainly at higher-echelon surgical and forward resuscitation teams rather than the point of injury.

When field control is impossible: evacuation as the intervention

For NCTH, the TCCC algorithm's "intervention" is fundamentally different in character from the previous stages: it is a logistics and triage priority, not a hands-on procedure. Casualties with suspected non-compressible torso hemorrhage are assigned the highest evacuation priority ("urgent surgical") because every minute of delay directly increases mortality, in a way that a tourniquet or hemostatic dressing cannot mitigate.

Field providers can still influence outcomes at the margins: permissive hypotensive resuscitation (targeting a lower-than-normal blood pressure with limited IV fluids until surgical control is achieved) reduces the rate of ongoing hemorrhage compared to aggressive fluid resuscitation, and pelvic binders can reduce pelvic volume and venous bleeding in pelvic fracture cases even though they cannot control arterial NCTH.

But fundamentally, the doctrine converges on a single point: for non-compressible torso hemorrhage, survival is a race against the evacuation clock to reach a surgeon, more than it is a question of which field device to apply.