Overview
Shock and bleeding represent some of the most time-critical emergencies an EMT will encounter in the prehospital setting. This guide covers the classification of bleeding, hemorrhage control techniques, the pathophysiology of all major shock types, and the assessment and management priorities essential for the NREMT exam. Mastery of these concepts is foundational to recognizing life threats early and implementing the correct interventions before a patient decompensates.
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Types of Bleeding
Arterial vs. Venous vs. Capillary Bleeding
| Type | Color | Flow Pattern | Severity |
|------|-------|-------------|----------|
| Arterial | Bright red | Spurts with each heartbeat | Most serious |
| Venous | Dark red | Steady stream | Moderate–serious |
| Capillary | Dark red | Slow ooze | Least serious |
Key Concepts
• Arterial bleeding is the most dangerous because blood is under high pressure from the left ventricle; even a small arterial injury can produce rapid, massive hemorrhage
• Venous bleeding flows steadily due to lower pressure in the venous system; easier to control but still potentially life-threatening at large vessel sites
• Blood color difference reflects oxygen content: arterial blood is oxygenated (bright red), venous blood is deoxygenated (dark red)
Hemorrhage Classification
| Class | Blood Loss | Signs & Symptoms |
|-------|-----------|-----------------|
| Class I | Up to 15% (~750 mL) | Minimal symptoms, slight anxiety |
| Class II | 15–30% (750–1500 mL) | Tachycardia, anxiety, narrowed pulse pressure |
| Class III | 30–40% (1500–2000 mL) | Marked tachycardia, hypotension, altered mental status |
| Class IV | >40% (>2000 mL) | Life-threatening, severe hypotension, lethargy |
Key Terms
• Hemorrhage – Significant blood loss from vascular disruption
• Pulse pressure – The difference between systolic and diastolic blood pressure; narrows early in shock
• Compensatory mechanisms – Physiologic responses (tachycardia, vasoconstriction) that maintain perfusion in early shock
> Watch Out For: Class III hemorrhage is the threshold where compensatory mechanisms begin to fail. A patient can have normal blood pressure through Class II — do not dismiss tachycardia alone as insignificant.
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Bleeding Control
Priority Order for External Hemorrhage Control
1. Direct pressure (first and preferred method — always attempt first)
2. Wound packing with hemostatic gauze (junctional or cavity wounds)
3. Tourniquet (life-threatening extremity bleeding uncontrolled by direct pressure)
Direct Pressure
• Apply firm, continuous pressure directly over the wound
• Use a gloved hand with dressings; do not release pressure to reassess
• Never remove a blood-soaked dressing — add additional dressings on top to preserve the developing clot
• Removing the original dressing disrupts clot formation and can dramatically worsen hemorrhage
Tourniquet Application
• Indications:
- Direct pressure fails to control life-threatening extremity bleeding
- Direct pressure cannot be applied (amputation, multiple casualties, inaccessible wound)
• Placement: 2–3 inches proximal to the wound (never over a joint)
• Tighten until bleeding stops; secure and do not remove in the field
• Document the exact time of application — write it on the tourniquet or patient's skin
• Communicate time to receiving hospital staff (tourniquet time affects limb viability)
Wound Packing with Hemostatic Gauze
• Indicated for junctional wounds where a tourniquet cannot be applied: groin (inguinal), axilla (armpit), neck, perineum
• Pack gauze firmly and deeply into the wound cavity
• Hold direct pressure for a minimum of 3–5 minutes after packing
• Hemostatic gauze (e.g., Combat Gauze, ChitoGauze) accelerates clotting through chemical agents
Key Terms
• Direct pressure – Firm manual compression applied to a wound to control bleeding
• Tourniquet – A device applied circumferentially to an extremity to stop blood flow distal to a wound
• Junctional wound – A wound at the junction of the trunk and an extremity where a tourniquet cannot be placed
• Hemostatic gauze – Gauze impregnated with clotting agents (e.g., kaolin, chitosan)
• Proximal – Closer to the body/heart; tourniquet placement relative to wound
> Watch Out For: Removing the original dressing is a classic NREMT distractor answer. The correct answer is always to add dressings on top without disturbing the original.
> Watch Out For: Tourniquet time documentation is a required step — forgetting it is both a patient safety issue and a common exam question.
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Types & Pathophysiology of Shock
Definition of Shock
Shock is a state of inadequate tissue perfusion in which cells do not receive sufficient oxygen and nutrients to meet metabolic demands, leading to cellular dysfunction, organ failure, and potentially death.
> The key concept: shock is a perfusion problem, not simply a blood pressure problem.
Shock Classification Overview
```
SHOCK
├── Hypovolemic (low volume)
│ ├── Hemorrhagic (blood loss)
│ └── Non-hemorrhagic (dehydration, burns)
├── Distributive (maldistribution of blood flow)
│ ├── Anaphylactic
│ ├── Neurogenic
│ └── Septic
├── Cardiogenic (pump failure)
└── Obstructive (physical blockage)
```
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Hypovolemic Shock
• Mechanism: Decreased circulating blood or fluid volume → reduced preload → decreased cardiac output → inadequate perfusion
• Most common cause in trauma: Hemorrhage (blood loss)
• Other causes: Severe dehydration, burns (plasma loss), vomiting, diarrhea
• Signs: Tachycardia, pale/cool/diaphoretic skin, narrowing pulse pressure, eventual hypotension
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Distributive Shock
Blood volume is normal but is abnormally distributed due to widespread vasodilation — the vascular container becomes too large for the available volume.
#### Anaphylactic Shock
• Trigger: Severe allergic reaction (bee stings, medications, foods)
• Mechanism: Massive histamine release → systemic vasodilation + increased capillary permeability → fluid leaks out of vessels, effectively reducing circulating volume
• Unique signs: Urticaria (hives), angioedema, bronchospasm, stridor
• Treatment: Epinephrine (1:1000 IM), oxygen, diphenhydramine
#### Neurogenic Shock
• Mechanism: High spinal cord injury disrupts sympathetic nervous system control → uncontrolled vasodilation below the injury level
• Classic presentation: Bradycardia (not tachycardia) + warm, dry, flushed skin below injury level
• Key distinction from hemorrhagic shock: No tachycardia, skin is warm — this is due to loss of sympathetic tone
#### Septic Shock
• Mechanism: Systemic infection → massive inflammatory response → widespread vasodilation
• Note: Less commonly tested at EMT-Basic level but part of distributive shock category
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Cardiogenic Shock
• Mechanism: Pump failure — the heart cannot generate sufficient cardiac output to meet tissue perfusion needs despite normal blood volume
• Most common cause: Large myocardial infarction (MI) destroying significant ventricular muscle mass
• Other causes: Severe dysrhythmias, myocarditis, end-stage heart failure
• Signs: Tachycardia, hypotension, pulmonary edema (wet lungs), JVD, cool/clammy skin
• Key distinction: Patient may have JVD and crackles (fluid backing up) despite being in shock
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Obstructive Shock
• Mechanism: A physical obstruction prevents adequate cardiac output despite normal heart muscle and normal blood volume
• Common prehospital causes:
- Tension pneumothorax — air trapped in the pleural space compresses the heart and great vessels, reducing venous return
- Cardiac tamponade — blood accumulates in the pericardial sac, compressing the heart and preventing filling
• Tension pneumothorax signs: Absent breath sounds on affected side, tracheal deviation (late), JVD, hypotension
• Cardiac tamponade signs (Beck's Triad): JVD, muffled heart sounds, hypotension
Key Terms
• Cardiac output – Heart rate × Stroke volume; the volume of blood pumped per minute
• Preload – The volume of blood in the ventricle before contraction; reduced in hypovolemia
• Vasodilation – Widening of blood vessels, reducing vascular resistance and blood pressure
• Sympathetic nervous system – The "fight or flight" system that causes vasoconstriction and tachycardia in shock
• Histamine – Chemical mediator released in allergic reactions causing vasodilation and increased capillary permeability
• Tension pneumothorax – Life-threatening air accumulation in the pleural space under pressure
• Cardiac tamponade – Compression of the heart by fluid in the pericardial sac
> Watch Out For: Neurogenic shock is the one type of shock with bradycardia. All other shock states typically present with tachycardia. This is a favorite NREMT exam distinction.
> Watch Out For: Cardiogenic shock patients may have crackles in the lungs and JVD — fluid is backing up. Do NOT give aggressive IV fluids.
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Assessment of Shock
Compensated vs. Decompensated Shock
| Feature | Compensated Shock | Decompensated Shock |
|---------|-----------------|-------------------|
| Blood pressure | Normal | Hypotension |
| Heart rate | Tachycardia | Severe tachycardia |
| Skin | Pale, cool, slightly diaphoretic | Cold, mottled, cyanotic |
| Mental status | Anxious, restless | Altered, confused, lethargic |
| Compensation | Body maintaining perfusion pressure | Mechanisms failing |
Earliest Signs of Shock
1. Tachycardia — the earliest and most reliable compensatory sign in adults
2. Anxiety and restlessness
3. Narrowing pulse pressure
4. Pale, cool, slightly diaphoretic skin
> A normal blood pressure does NOT rule out shock. The body can maintain BP well into Class II hemorrhage through tachycardia and vasoconstriction.
Differentiating Shock Types on Assessment
| Finding | Hemorrhagic Shock | Neurogenic Shock | Cardiogenic Shock |
|---------|-----------------|-----------------|-----------------|
| Heart rate | Tachycardia | Bradycardia | Tachycardia |
| Skin | Cool, pale, diaphoretic | Warm, dry, flushed (below injury) | Cool, clammy |
| JVD | Absent | Absent | Present |
| Lung sounds | Clear | Clear | Crackles |
| Mechanism | Trauma, bleeding | Spinal cord injury | Chest pain, cardiac history |
Pediatric Shock Assessment
• Children compensate extremely well — they can maintain near-normal blood pressure despite significant volume loss through powerful tachycardia and vasoconstriction
• Hypotension in a child = decompensated shock — this is a late and ominous finding
• A child's BP drop signals that the patient is critically ill and deterioration can be rapid
• Rely on tachycardia, mental status changes, and skin signs as early indicators in pediatric patients
Key Terms
• Compensated shock – Early shock where compensatory mechanisms maintain blood pressure
• Decompensated shock – Advanced shock where compensatory mechanisms fail and hypotension develops
• Tachycardia – Heart rate >100 bpm; the earliest compensatory response to shock in adults
• Diaphoresis – Profuse sweating; caused by sympathetic nervous system activation
• Mottling – Blotchy, patchy skin discoloration indicating severely compromised perfusion
> Watch Out For: A normal blood pressure does not mean a stable patient. Tachycardia alone in a trauma patient should raise immediate concern for compensated shock.
> Watch Out For: Pediatric patients can "look okay" until they suddenly crash. Never be falsely reassured by near-normal vitals in an injured child — the trend matters.
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Treatment of Shock
General Shock Management Priorities
1. Control external hemorrhage — direct pressure, tourniquet, wound packing
2. Maintain airway and breathing — ensure adequate ventilation
3. Administer high-flow oxygen — nonrebreather mask at 15 L/min; target SpO₂ ≥ 94%
4. Position appropriately
5. Prevent heat loss — keep patient warm (blanket)
6. Initiate rapid transport — do not delay for on-scene interventions
Patient Positioning
• Standard shock position: Supine (flat) with legs elevated 8–12 inches (modified Trendelenburg) — assists venous return from lower extremities
• Exceptions — do NOT elevate legs if:
- Suspected spinal injury
- Respiratory distress or difficulty breathing
- Head injury (may increase ICP)
- Lower extremity fractures
- Cardiogenic shock (increases preload on a failing heart)
Oxygen Administration
• High-flow oxygen via nonrebreather mask at 15 L/min
• Goal: SpO₂ ≥ 94%
• Rationale: Maximizes oxygen delivery to hypoperfused, oxygen-starved tissues
• If patient cannot tolerate NRB or has inadequate respiratory effort, consider BVM-assisted ventilation
Load and Go Philosophy
• For trauma patients in hemorrhagic shock, scene time should be minimized
• Definitive treatment for internal hemorrhage is surgery or interventional radiology — only available at the hospital
• The "platinum 10 minutes" concept: minimize on-scene time to get patient to definitive care rapidly
• Perform only life-saving interventions on scene (airway, bleeding control, spinal precautions if indicated)
• Continue assessment and treatment en route to the hospital
Shock Type-Specific Considerations
| Shock Type | Key EMT Treatment |
|-----------|------------------|
| Hemorrhagic | Control bleeding, oxygen, rapid transport |
| Anaphylactic | Epinephrine 1:1000 IM (if authorized), oxygen, diphenhydramine |
| Neurogenic | Spinal precautions, oxygen, warm patient (unable to regulate temperature) |
| Cardiogenic | Oxygen, position of comfort (semi-Fowler's), rapid transport — avoid fluid overload |
| Obstructive (tension PTX) | Needle decompression (ALS), rapid transport |
Key Terms
• Nonrebreather mask (NRB) – High-flow oxygen delivery device capable of delivering ~90% FiO₂ at 15 L/min
• SpO₂ – Peripheral oxygen saturation measured by pulse oximetry; goal ≥94% in shock
• Load and go – Prehospital philosophy prioritizing rapid transport over extended scene care
• Modified Trendelenburg – Supine position with legs elevated 8–12 inches to promote venous return
• Definitive care – Interventions that treat the root cause of a condition (e.g., surgery for internal hemorrhage)
> Watch Out For: For cardiogenic shock, do NOT elevate the legs — this increases venous return (preload) to an already failing heart and can worsen pulmonary edema.
> Watch Out For: High-flow oxygen is appropriate for all shock patients regardless of type. Never withhold oxygen from a patient in shock due to concerns