Recognising & Managing Haemorrhagic Shock

Shock is a state of inadequate oxygen delivery to the body's tissues and organs. When that inadequacy results from blood loss — whether visible or internal — it is called haemorrhagic shock or hypovolaemic shock. It is the leading cause of preventable death in trauma, and the window for intervention is often measured in minutes.

Understanding the progression of haemorrhagic shock — and crucially, recognising it before the most obvious signs appear — is one of the most valuable skills a first responder or bystander can develop.

---

The Physiology of Haemorrhagic Shock

The human body's response to blood loss is a sophisticated cascade of compensatory mechanisms. The heart beats faster. Blood vessels constrict to maintain blood pressure. Blood is redirected from non-essential areas (skin, gut) to critical organs (brain, heart, lungs). These mechanisms are effective — up to a point.

The danger in haemorrhagic shock is that the body compensates extremely well until it cannot. Blood pressure can remain normal until approximately 30–40% of blood volume has been lost. By the time hypotension appears, the patient is in serious danger.

This means waiting for the classic "low blood pressure" to recognise shock is waiting too long. The earlier signs — elevated heart rate, pallor, cool extremities — appear well before blood pressure drops and are the warning window that saves lives.

---

Classes of Haemorrhage

The American College of Surgeons Advanced Trauma Life Support (ATLS) classification divides haemorrhagic shock into four stages based on blood loss volume and clinical findings. These stages represent a progression along a continuum, not sharply defined steps.

Class	Blood Loss	Volume Lost (70 kg adult)	Heart Rate	Blood Pressure	Mental Status	Clinical Signs
I	Up to 15%	< 750 mL	Normal or slight increase (< 100)	Normal	Normal, possibly slight anxiety	Minimal skin changes
II	15–30%	750–1,500 mL	100–120 bpm	Normal or slightly reduced	Anxiety, restlessness	Pale, cool, slightly sweaty skin; delayed capillary refill
III	30–40%	1,500–2,000 mL	120–140 bpm	Reduced systolic	Confused, agitated	Markedly pale and cold, significant sweating, weak rapid pulse
IV	> 40%	> 2,000 mL	> 140 bpm (or bradycardia — ominous)	Severely reduced	Lethargic, unconscious	Ashen, cold, barely palpable pulse; imminent cardiac arrest

⚠️ Hypotension (low blood pressure) does not appear until Class III haemorrhage — after 1,500 mL of blood has been lost. Do not use blood pressure as the primary indicator of haemorrhagic shock. Elevated heart rate and pallor are the early warning signs.

---

Early Signs of Haemorrhagic Shock (Class I–II)

These signs should trigger immediate haemorrhage control even if the patient appears relatively well:

Heart rate elevation (tachycardia)

• A resting heart rate above 100 beats per minute in a trauma patient should immediately raise suspicion
• Feel the radial pulse (wrist) — is it fast? Is it weak and thin ("thready")?
• Note: fit athletes may have lower baseline heart rates — a rate of 80 may still represent tachycardia for them

Skin changes

• Pallor — skin that is pale or greyish compared to the patient's normal colouring
• Cool extremities — press the back of your hand against the patient's forearm and hand; if they are noticeably cooler than the torso, peripheral vasoconstriction is occurring
• Clamminess — cold, damp, sweaty skin is a response to the sympathetic nervous system activation in early shock
• Capillary refill — press the nail bed for 2 seconds and release; in normal circulation, colour returns in under 2 seconds; delayed return (> 2 seconds) suggests reduced peripheral perfusion

Breathing rate

• A respiratory rate above 20 breaths per minute (tachypnoea) is an early sign of physiological stress

Behavioural changes

• Unusual anxiety or restlessness
• Saying "I feel strange" or "something is wrong" without being able to specify
• Asking repeatedly for water (thirst is a compensatory response to blood loss)

---

Late Signs of Haemorrhagic Shock (Class III–IV)

These are signs that the body's compensation has been overwhelmed. They indicate a large blood loss and a patient in immediate danger:

• Hypotension — systolic blood pressure below 90 mmHg in an adult (not reliably measurable in the field without a monitor)
• Altered or absent consciousness — confusion, combativeness, or unconsciousness
• Absent or barely palpable peripheral pulses — the radial pulse at the wrist disappears; only central pulses (carotid, femoral) may remain
• Ashen or mottled skin colour — beyond pale; grey, blue-tinted, or mottled (patchy colouring due to pooled venous blood)
• Cold peripheries extending to the core — not just hands and feet, but forearms and legs becoming cold

Late-stage shock is a critical emergency. Survival without immediate surgical intervention is unlikely.

---

Management Priorities

1. Stop the Bleeding — Everything Else Is Secondary

The most important intervention in haemorrhagic shock is source control. Supplemental oxygen, warm blankets, and reassurance will not save a patient who is continuing to bleed at a significant rate.

Apply:

• Tourniquet — for arterial limb bleeding (5–7.5 cm above wound)
• Wound packing with haemostatic gauze — for junctional or deep cavity wounds
• Direct pressure — sustained firm pressure for wounds amenable to it

2. Warmth — Prevent the Lethal Triad

Haemorrhagic shock triggers a cascade known as the "lethal triad" of trauma death: hypothermia + acidosis + coagulopathy. They are self-reinforcing — cold blood clots poorly; poor clotting worsens blood loss; worsening blood loss drives acidosis; acidosis further impairs clotting.

Breaking the triad starts with preventing further heat loss:

• Remove wet clothing
• Cover the patient with a blanket, space blanket, sleeping bag, or any insulating material
• Protect from wind, ground cold, and precipitation
• Do not let a shocked patient lie directly on cold ground

3. Positioning

• Lay the patient flat — this aids venous return from the legs to the heart
• Elevate the legs if no suspected spinal injury or lower-limb fractures — can temporarily increase cardiac preload
• Do not elevate if there are femur fractures (can worsen internal bleeding), suspected spinal injury, or signs of respiratory distress

4. Fluid Considerations — The Permissive Hypotension Concept

In hospital settings, fluid resuscitation replaces lost blood volume. In the pre-hospital setting, aggressive fluid administration (IV saline, Ringer's lactate) prior to haemorrhage control was once standard practice. Modern trauma research has revised this significantly.

The concept of permissive hypotension (or hypotensive resuscitation) holds that targeting a systolic blood pressure of approximately 80–90 mmHg (rather than normal 120 mmHg) in penetrating trauma until surgical haemorrhage control is achieved may reduce re-bleeding by avoiding disruption of early clot formation. This is a hospital and paramedic-level decision, but the principle informs pre-hospital management: do not assume that a conscious, communicating patient with low-normal blood pressure needs fluid — they may be appropriately compensated.

In the pre-hospital setting without IV access: focus on haemorrhage control and warmth.

5. Psychological Support

A bleeding patient who is conscious is frightened. Fear increases heart rate and adrenaline, worsening the physiological stress response. Talking calmly, explaining what you are doing, maintaining physical contact (holding a hand), and projecting confidence all reduce the psychological component of shock. This is not secondary — it is active treatment.

---

Internal Bleeding — The Invisible Haemorrhage

Not all haemorrhage is visible. Internal bleeding — into the abdomen, chest, pelvis, or thigh — can be massive without a single drop of visible blood. Suspect internal bleeding in:

• Any significant abdominal or chest trauma
• Pelvis fracture (can lose 2–4 litres internally)
• Femur fracture (can lose 1–2 litres into the thigh)
• Mechanism of injury suggesting significant force (high-speed collision, fall from height, blast)

Signs of internal bleeding mirror haemorrhagic shock signs without visible external bleeding. The abdomen may become rigid, distended, or tender. There may be bruising appearing hours after injury (Grey Turner's sign for retroperitoneal bleeding, Cullen's sign for abdominal).

Pre-hospital management of internal bleeding is limited to:

• Immobilising fractures (reduces bleeding from bone ends)
• Pelvic binder application (reduces pelvic ring bleeding — improvise with a sheet tightly bound around the pelvis if a commercial binder is unavailable)
• Rapid transport — internal bleeding requires surgery

---

Quick Reference

Sign	Stage	Significance
Heart rate > 100 bpm	Class II — 15–30% loss	Act now — early warning
Cool, pale, clammy skin	Class II	Compensation underway
Capillary refill > 2 seconds	Class II–III	Reduced peripheral perfusion
Confusion or agitation	Class III — 30–40% loss	Significant blood loss
Hypotension	Class III	1,500+ mL already lost
Unconscious, barely palpable pulse	Class IV	Imminent cardiac arrest
Any shocked patient	Any	Stop bleeding first — everything else second
Wet clothing	Any	Remove — hypothermia worsens coagulopathy
Pelvic/femur fracture	Suspect internal	Can lose 1–4 litres invisibly

---

The Takeaway

Haemorrhagic shock kills by stealth. The body masks its severity until the compensation fails. Recognising the early signs — tachycardia, pallor, cool extremities — before blood pressure falls is what creates the window for effective intervention. And in that window, the only intervention that matters is stopping the source of bleeding.