Shock types and management
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shock types classification pathophysiology hemodynamic parameters
Harrison's Principles of Internal Medicine, Twenty First Edition
Page 8234
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shock management treatment resuscitation vasopressors
Harrison's Principles of Internal Medicine, Twenty First Edition
Page 8273
GradeResponse
GradeResponse
Shock: Types and Management
Classification of Shock
Shock is defined as a state of inadequate oxygen delivery relative to tissue demand, resulting in cellular hypoxia. There are four major categories (Harrison's, p. 8234):
| Type | Mechanism | Classic Example |
|---|---|---|
| Distributive | Maldistribution of blood flow; vasodilation | Septic, anaphylactic, neurogenic |
| Cardiogenic | Pump failure → decreased CO | MI, severe HF, myocarditis |
| Hypovolemic | Reduced circulating volume | Hemorrhage, burns, dehydration |
| Obstructive | Mechanical obstruction to flow | PE, cardiac tamponade, tension pneumothorax |
Hemodynamic Profiles
| Parameter | Distributive | Cardiogenic | Hypovolemic | Obstructive |
|---|---|---|---|---|
| CO/CI | ↑ (early) | ↓ | ↓ | ↓ |
| SVR | ↓↓ | ↑ | ↑ | ↑ |
| CVP/Preload | ↓/normal | ↑ | ↓↓ | ↑ (tamponade/PE) |
| PCWP | ↓/normal | ↑↑ | ↓ | Variable |
| ScvO₂ | ↑ (shunting) | ↓ | ↓ | ↓ |
| Skin | Warm, flushed | Cool, clammy | Cool, clammy | Cool, clammy |
1. Distributive Shock
Septic Shock
The most common cause of distributive shock.
Diagnosis: Sepsis + vasopressors needed to maintain MAP ≥65 mmHg + lactate >2 mmol/L despite adequate fluids.
Management (Harrison's, p. 8273 / Surviving Sepsis Campaign):
- Fluids: IV crystalloid 30 mL/kg within first 3 hours (saline or balanced crystalloids)
- Vasopressors (target MAP ≥65 mmHg):
- Norepinephrine — first-line vasopressor
- Vasopressin — add to reduce norepinephrine dose
- Dopamine — avoid except in bradycardia or tachyarrhythmia risk
- Source control: Antibiotics within 1 hour, drain/debride source
- Steroids: Hydrocortisone 200 mg/day if refractory to fluids + vasopressors
- Lactate-guided resuscitation — normalize elevated lactate levels
Anaphylactic Shock
- Epinephrine IM (0.3–0.5 mg, 1:1000) — immediate, first-line
- Antihistamines (diphenhydramine, ranitidine) — adjunct only
- Corticosteroids — prevent biphasic reaction
- IV fluids for hypotension
- Airway management if angioedema
Neurogenic Shock
- IV fluids first
- Vasopressors (norepinephrine or phenylephrine) for refractory hypotension
- Bradycardia: atropine or transcutaneous pacing
2. Cardiogenic Shock
Definition: Sustained hypotension (SBP <90 mmHg) + signs of hypoperfusion due to cardiac dysfunction.
Management:
- Treat the underlying cause:
- STEMI → emergent PCI (door-to-balloon <90 min)
- Arrhythmia → cardioversion/pacing
- Hemodynamic support:
- Vasopressors: Norepinephrine (preferred over dopamine — less arrhythmia)
- Inotropes: Dobutamine for low CO with adequate BP
- Mechanical support:
- Intra-aortic balloon pump (IABP)
- Impella, VA-ECMO for refractory cases
- Diuretics if pulmonary edema present (cautiously)
- Avoid aggressive fluid resuscitation (worsens pulmonary edema)
3. Hypovolemic Shock
Classification by blood loss (Hemorrhagic Shock — ATLS):
| Class | Blood Loss | HR | BP | RR | Mental Status |
|---|---|---|---|---|---|
| I | <750 mL (<15%) | <100 | Normal | 14–20 | Normal |
| II | 750–1500 mL (15–30%) | 100–120 | Normal | 20–30 | Anxious |
| III | 1500–2000 mL (30–40%) | 120–140 | ↓ | 30–40 | Confused |
| IV | >2000 mL (>40%) | >140 | ↓↓ | >35 | Lethargic/unconscious |
Management:
- Hemorrhagic: Damage control resuscitation
- 1:1:1 ratio — packed RBCs : FFP : platelets
- Tranexamic acid (TXA) within 3 hours of injury
- Permissive hypotension (target SBP 80–90 mmHg) until surgical control
- Surgical/interventional source control
- Non-hemorrhagic (dehydration, GI losses):
- IV isotonic crystalloids (normal saline or lactated Ringer's)
- Replace ongoing losses
4. Obstructive Shock
Cardiac Tamponade
- Emergency pericardiocentesis (needle or surgical)
- Avoid vasodilators; maintain preload
Massive Pulmonary Embolism
- Systemic thrombolysis (alteplase 100 mg over 2 h) — if hemodynamically unstable
- Surgical embolectomy or catheter-directed therapy — if thrombolysis contraindicated
- Anticoagulation (heparin) immediately
- Vasopressors (norepinephrine) for hypotension; avoid aggressive fluids (RV strain)
Tension Pneumothorax
- Needle decompression (2nd intercostal space, midclavicular line) — immediate
- Followed by chest tube insertion
General Shock Management Principles
| Step | Action |
|---|---|
| Airway | Secure airway; intubate if necessary |
| Access | Large-bore IV x2 or central line; arterial line for monitoring |
| Fluids | Cautious resuscitation guided by hemodynamics (avoid over-resuscitation) |
| Vasopressors | Norepinephrine is the default first-line agent for most shock types |
| Monitor | MAP ≥65 mmHg, UO ≥0.5 mL/kg/hr, lactate clearance, ScvO₂ ≥70% |
| Cause | Identify and treat the underlying etiology immediately |
Key Differentiating Clues at Bedside
- Warm extremities + hypotension → Distributive
- JVD + muffled heart sounds + hypotension (Beck's triad) → Tamponade
- Absent breath sounds + tracheal deviation → Tension pneumothorax
- S3 gallop + pulmonary crackles → Cardiogenic
- Trauma/active bleeding → Hypovolemic (hemorrhagic)
Sources: Harrison's Principles of Internal Medicine, 21st Edition (pp. 8234, 8273); Surviving Sepsis Campaign Guidelines; ATLS Guidelines.
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