Shock is a life-threatening state of inadequate tissue perfusion: oxygen delivery to cells does not meet their demand. Cells switch to anaerobic metabolism, producing lactate and metabolic acidosis. If perfusion is not restored, cell injury progresses to organ failure and death. Low blood pressure is a late sign; shock can be present while systolic pressure is still normal.
Perfusion depends on cardiac output (heart rate × stroke volume) and systemic vascular resistance (SVR). Each type of shock fails at a different point.
| Type | Main problem | Common causes |
|---|
| Hypovolemic | Loss of circulating volume | Hemorrhage (trauma, GI bleeding), vomiting and diarrhea, burns, diuresis, third spacing |
| Cardiogenic | Pump failure | Large myocardial infarction (most common), severe HF, dysrhythmias, acute valve failure |
| Distributive | Massive vasodilation and maldistribution of flow | Septic, anaphylactic, neurogenic (spinal cord injury at or above about T6) |
| Obstructive | Blockage of filling or outflow | Tension pneumothorax, cardiac tamponade, massive pulmonary embolism |
Stages of shock
- Initial — cellular changes and rising lactate; few clinical signs.
- Compensatory — sympathetic and renin–angiotensin activation: tachycardia, vasoconstriction (cool pale skin, except early sepsis and neurogenic shock), tachypnea, oliguria, thirst, restlessness. BP is maintained.
- Progressive — compensation fails: hypotension, worsening acidosis, confusion, mottling, organ dysfunction.
- Refractory (irreversible) — profound hypotension unresponsive to treatment, multiple organ dysfunction.
Multiple organ dysfunction syndrome (MODS) is progressive failure of two or more organ systems (lungs, kidneys, liver, coagulation, brain, gut) and is the main cause of death after the initial shock.
Sepsis definitions (Sepsis-3, Singer et al., 2016): sepsis means an infection has triggered an abnormal body-wide response that is damaging organs. Septic shock is the subset in which, even after adequate fluids, vasopressors are required to hold MAP ≥ 65 mmHg and lactate stays above 2 mmol/L. Organ dysfunction is defined as an acute rise in the SOFA score of 2 points or more. The bedside qSOFA (respiratory rate ≥ 22/min, altered mentation, systolic BP ≤ 100 mmHg) flags adults with suspected infection who are at risk of a poor outcome; it does not define sepsis.
SIRS (historical 1992 definition): the 1992 ACCP/SCCM consensus defined sepsis as infection plus 2 or more SIRS criteria: temperature > 38 °C (100.4 °F) or < 36 °C (96.8 °F); heart rate > 90/min; respiratory rate > 20/min or PaCO₂ < 32 mmHg; WBC > 12,000/µL or < 4,000/µL or > 10% immature bands. Sepsis-3 judged this approach unhelpful for identifying sepsis because SIRS findings are common in hospitalized clients who never develop infection, so SIRS now survives only as a screening aid.
Typical hemodynamic patterns
| Type | Cardiac output | Filling pressure (CVP / PAWP) | SVR | Skin |
|---|
| Hypovolemic | ↓ | ↓ | ↑ | Cool, clammy, pale |
| Cardiogenic | ↓ | ↑ (PAWP high) | ↑ | Cool, clammy; crackles, JVD |
| Septic (early) | Normal or ↑ | ↓ or normal | ↓ | Warm, flushed; later cool and mottled |
| Anaphylactic | ↓ | ↓ | ↓ | Urticaria, flushing, angioedema |
| Neurogenic | ↓ (bradycardia) | ↓ | ↓ | Warm, dry below the injury |
| Obstructive | ↓ | ↑ CVP (tamponade, tension pneumothorax, PE) | ↑ | Cool; JVD |
Key clues by type
- Hypovolemic: tachycardia, narrow pulse pressure, flat neck veins, capillary refill > 2–3 seconds, low urine output, orthostatic changes. In trauma, look for the bleeding source.
- Cardiogenic: chest pain, new murmur, pulmonary crackles, S₃, JVD, dysrhythmias, hypotension despite congestion.
- Septic: fever or hypothermia, tachycardia, tachypnea, altered mental status, source of infection; older adults may be afebrile and present only with confusion.
- Anaphylactic: sudden onset minutes to hours after exposure; hives, flushing, lip or tongue swelling, stridor, wheeze, hoarseness, vomiting, cramping, hypotension. Skin signs are absent in some cases.
- Neurogenic: hypotension with bradycardia (loss of sympathetic tone), warm dry skin, poikilothermia, after spinal cord injury.
- Obstructive: tension pneumothorax (absent breath sounds, tracheal deviation late, JVD); tamponade (Beck's triad — hypotension, JVD, muffled heart sounds; pulsus paradoxus); PE (sudden dyspnea, pleuritic pain, hypoxemia).
Ongoing assessment: mental status (often the earliest change), HR, BP, MAP (target ≥ 65 mmHg in most adults), respiratory rate, SpO₂, skin temperature and capillary refill, hourly urine output (goal ≥ 0.5 mL/kg/h), temperature.
| Test | Purpose / key finding |
|---|
| Serum lactate | > 2 mmol/L (18 mg/dL) indicates hypoperfusion; ≥ 4 mmol/L (36 mg/dL) signals high risk. Repeat to confirm clearance when elevated |
| ABG | Metabolic acidosis (low pH, low HCO₃⁻), base deficit, hypoxemia |
| Blood cultures (2 sets) | Draw before antimicrobials in suspected sepsis if this causes no meaningful delay |
| CBC, coagulation, type and crossmatch | Hemoglobin (may be normal early in hemorrhage), platelets, DIC screening |
| Electrolytes, BUN, creatinine, liver tests, glucose | Organ dysfunction; baseline before nephrotoxic drugs |
| ECG, troponin, echocardiogram | Myocardial infarction, dysrhythmia, tamponade, right ventricular strain |
| Point-of-care ultrasound | Rapidly separates shock types (volume, pump, tamponade, pneumothorax) |
| Chest X-ray, CT | Infection source, pneumothorax, PE (CT angiography) |
| Serum tryptase | May support anaphylaxis if drawn within a few hours; never delays epinephrine |
| Hemodynamic monitoring | Arterial line; CVP; pulmonary artery catheter in selected cardiogenic shock (PAWP reflects left-sided filling; cardiac index) |
Fluid responsiveness is better judged by dynamic tests (passive leg raise with cardiac output measurement, pulse pressure variation) than by a single CVP value. Head-down (Trendelenburg) positioning is not recommended; lying flat with legs raised is used in anaphylaxis, and a passive leg raise is used as a test of fluid responsiveness.
General principles: treat the cause, restore perfusion, support oxygenation, prevent organ failure.
Septic shock — current Surviving Sepsis Campaign guidance (2026 update of the 2021 adult guidelines)
- Antimicrobials immediately, ideally within 1 hour of recognizing septic shock or probable sepsis; for possible sepsis without shock, give antimicrobials within 3 hours if concern for infection persists
- Obtain cultures and lactate first when this does not delay antibiotics; remeasure lactate to guide resuscitation
- For sepsis-induced hypoperfusion: at least 30 mL/kg IV crystalloid within the first 3 hours, reassessing frequently for response and overload. Balanced crystalloids (e.g., lactated Ringer's) are preferred over 0.9% saline; starches are not used
- Norepinephrine is the first-line vasopressor; initial MAP target 65 mmHg (60–65 mmHg is suggested for adults aged 65 years or older — conditional). Vasopressin is added rather than escalating norepinephrine further; epinephrine is added if MAP remains inadequate
- Vasopressors may be started through a peripheral IV rather than delaying until central access is available
- IV corticosteroids are suggested for adults with septic shock (usually hydrocortisone 200 mg/day in divided doses, typically when vasopressors are still needed)
- Screening: use tools such as NEWS, MEWS, or SIRS rather than qSOFA alone
- Source control (drain abscess, remove infected device) as soon as practical
Hypovolemic / hemorrhagic shock
- Stop the bleeding (direct pressure, tourniquet, surgery, endoscopy, interventional radiology)
- Hemorrhage: blood products early in a balanced ratio (plasma : platelets : red cells about 1:1:1) through a massive transfusion protocol; limit crystalloid
- Permissive hypotension in bleeding trauma (penetrating or blunt) until hemorrhage is controlled — except with traumatic brain injury
- Tranexamic acid within 3 hours of injury in significant bleeding: 1 g IV over 10 minutes, then 1 g over 8 hours
- Non-hemorrhagic fluid loss: isotonic crystalloid boluses with reassessment
- Warm all fluids and blood to prevent the lethal triad: hypothermia, acidosis, coagulopathy
Cardiogenic shock: emergent revascularization (PCI) for MI; cautious or no fluids if congested; inotropes (dobutamine) and vasopressors (norepinephrine); mechanical circulatory support (intra-aortic balloon pump, percutaneous ventricular assist device, ECMO); treat dysrhythmias.
Anaphylactic shock
- Epinephrine IM immediately — first-line and time-critical. Dose: 0.01 mg/kg of 1 mg/mL solution, maximum 0.5 mg in adults and 0.3 mg in children, into the mid-outer thigh; repeat every 5–15 minutes if symptoms persist
- Remove the trigger (stop infusion), call for help, airway support, high-flow oxygen, large-volume IV crystalloid for hypotension
- Refractory: IV epinephrine infusion by experienced staff; glucagon for clients on beta blockers who do not respond
- Antihistamines and corticosteroids are adjuncts only — they do not treat airway obstruction or shock and must never delay epinephrine
- Inhaled bronchodilator for persistent wheeze after epinephrine
Neurogenic shock: spinal immobilization, fluids cautiously, vasopressors (norepinephrine) to MAP goals set by spinal cord injury protocol, atropine for symptomatic bradycardia, pacing if needed.
Obstructive shock: needle decompression then chest tube (tension pneumothorax); pericardiocentesis (tamponade); thrombolysis or embolectomy (massive PE).
Drug safety
| Drug | Key safety points |
|---|
| Norepinephrine, vasopressin, phenylephrine | Tissue ischemia; extravasation causes necrosis — use a large proximal vein, check site often, stop infusion; phentolamine per protocol for alpha-agonist extravasation (norepinephrine, epinephrine, phenylephrine, dopamine). Correct hypovolemia first. Dysrhythmias (norepinephrine), reflex bradycardia (phenylephrine), digit and gut ischemia (vasopressin). Never flush or bolus through the vasopressor line; titrate to MAP |
| Epinephrine | Tachycardia, dysrhythmias, hypertension, anxiety, hyperglycemia, raised lactate. No absolute contraindication in anaphylaxis — including pregnancy, older age, and heart disease |
| Dobutamine | Tachycardia, dysrhythmias, hypotension from vasodilation |
| Dopamine | Not first-line; more dysrhythmias than norepinephrine |
| Hydrocortisone | Hyperglycemia, hypernatremia, infection risk, muscle weakness |
| Broad-spectrum antimicrobials | Ask about allergies; monitor kidney function and drug levels (vancomycin, aminoglycosides); Clostridioides difficile diarrhea |
| Blood products | Transfusion reactions, TACO, TRALI; citrate causes hypocalcemia (monitor ionized calcium); hyperkalemia; hypothermia |
| Tranexamic acid | Thrombosis risk; seizures at high doses; avoid after 3 hours from injury |
| Thrombolytics (PE) | Bleeding; contraindicated with recent surgery, stroke, or active bleeding |
| Atropine | Tachycardia, urinary retention, dry mouth, confusion |
| Glucagon | Nausea and vomiting — protect the airway; hyperglycemia |
Listed in priority order.
- Airway and breathing
- Anaphylaxis: give IM epinephrine immediately (with airway assessment) — before oxygen, IV access, or antihistamines
- High-flow oxygen; prepare for intubation, especially with stridor or angioedema in anaphylaxis
- Anaphylaxis: position supine with legs elevated; sitting up if breathing is difficult; do not suddenly stand the client up
- Circulation
- Two large-bore IV or intraosseous access; start fluids, blood, and drugs as ordered
- Apply direct pressure to external bleeding
- Draw cultures and lactate, then give the first antimicrobial dose without delay in suspected sepsis
- Monitor perfusion
- MAP, HR, rhythm, SpO₂, mental status, skin, capillary refill every 5–15 minutes during resuscitation
- Hourly urine output by indwelling catheter — the most practical sign that resuscitation is working; report < 0.5 mL/kg/h
- Watch for fluid overload: new crackles, rising RR, falling SpO₂
- Vasoactive infusions
- Infusion pump, dedicated line, frequent site checks; titrate per order to MAP; never stop abruptly
- Temperature and metabolic
- Warm fluids and blankets in hemorrhage; monitor glucose, potassium, calcium
- In sepsis, fever itself is not treated as a resuscitation target; antipyretics may be given for comfort per order but do not replace source control
- Prevent complications
- Central line bundle, oral care, turning, VTE prophylaxis as ordered, stress ulcer prophylaxis in selected clients
- Psychosocial — explain care briefly and calmly; keep family informed
- Anaphylaxis: carry two epinephrine auto-injectors (or an approved nasal epinephrine spray where available) at all times; inject into the outer thigh at the first sign of a serious reaction, even through clothing, then call emergency services
- Epinephrine first, antihistamine second; a second dose may be needed; symptoms can return hours later (biphasic reaction), so go to the hospital after every use
- Wear medical identification; learn to read food labels; tell prescribers about allergies
- Sepsis: know warning signs — fever or shivering, confusion, fast breathing, fast heart rate, extreme pain, clammy skin — and seek care urgently. Keep vaccinations current and treat wounds and infections early
- After sepsis or critical illness: fatigue, weakness, sleep problems, and anxiety are common; follow-up and rehabilitation help recovery
- Clients with heart disease: report chest pain, sudden dyspnea, or fainting immediately
| Complication | What to watch for |
|---|
| Acute kidney injury | Urine output < 0.5 mL/kg/h, rising creatinine |
| ARDS | Worsening hypoxemia despite oxygen, bilateral infiltrates |
| DIC | Bleeding from lines and gums, petechiae, low platelets and fibrinogen, prolonged clotting times |
| MODS | Two or more failing organs; high mortality |
| Lethal triad in massive transfusion | Hypothermia, acidosis, coagulopathy |
| Airway obstruction (anaphylaxis) | Stridor, hoarseness, drooling, inability to speak |
| Refractory shock | Rising vasopressor needs, lactate not clearing |
| Extravasation | Blanching, coolness, pain at infusion site |
- Earliest signs: tachycardia, restlessness or confusion, tachypnea; hypotension is late
- Hypovolemic: low filling pressures, high SVR, cool clammy skin
- Cardiogenic: high PAWP, low cardiac output, crackles and JVD — avoid aggressive fluids
- Neurogenic: hypotension + bradycardia + warm dry skin; low cardiac output and low SVR
- Anaphylaxis: IM epinephrine 0.01 mg/kg (max 0.5 mg adult, 0.3 mg child) in the thigh first; antihistamines never replace it
- Septic shock: antimicrobials within 1 hour, lactate, 30 mL/kg crystalloid in 3 hours for hypoperfusion, norepinephrine first-line, MAP ≥ 65 mmHg
- Balanced crystalloid preferred over saline; no starches
- Urine output ≥ 0.5 mL/kg/h is the bedside measure of resuscitation response
- Massive hemorrhage: stop bleeding, 1:1:1 blood products, warm fluids, prevent the lethal triad
- Beck's triad = tamponade; absent breath sounds + JVD = tension pneumothorax
- Alpha-agonist vasopressor extravasation → stop, notify, phentolamine per protocol
Country Notes
United States
- CMS tracks a sepsis bundle measure (SEP-1) for hospitals, and CDC has published Hospital Sepsis Program Core Elements; nurses often trigger sepsis screening and bundle start.
- Epinephrine auto-injectors and an FDA-approved intranasal epinephrine spray are available by prescription.
Philippines
- Dengue is endemic; dengue shock from plasma leakage is an important cause of hypovolemic-type shock, most often around the time fever subsides. Watch rising hematocrit with falling platelets and narrowing pulse pressure.
- Leptospirosis after floods can cause septic shock with kidney failure and pulmonary hemorrhage; ask about wading in floodwater.
- Use kilograms for weight-based doses and urine output targets.
- Epinephrine auto-injectors or nasal spray may not be readily available or affordable for every client. Where no device is available, clinicians give epinephrine from a 1 mg/mL ampule by syringe at 0.01 mg/kg IM; teach clients a clear written emergency plan.