Adult undifferentiated shock. Recognize hypoperfusion, identify the cause, and resuscitate simultaneously. Pediatric assessment and treatment require a separate pathway.
The Algorithm...
01 True Shock?
Assess mental status, BP / pulse, skin perfusion, respiratory effort, and urine output; obtain lactate when shock is suspected.
Normal BP does not exclude shock. Interpret the examination, trends, and laboratory findings together. See Recognition.
02 Initial Resuscitation
ABCs, IV / IO access, monitoring, and oxygen / ventilation as needed.
Immediate threats: Control hemorrhage, relieve tension pneumothorax / tamponade, treat an unstable rhythm, and recognize anaphylaxis.
Select fluids, blood, and vasoactive support according to the likely physiology—not a fixed treatment ladder. See Resuscitation.
03 What Type Of Shock?
Hypovolemic: Hemorrhage or nonhemorrhagic volume loss.
Distributive: Vasodilation / maldistributed flow; consider sepsis, anaphylaxis, and other causes.
Cardiogenic: Pump, rhythm, or mechanical cardiac failure.
Obstructive: Impaired filling or outflow; tension pneumothorax, tamponade, or high-risk PE.
History / examination + POCUS + ECG direct further testing. More than one mechanism may be present. See Cause.
04 Cause-Specific Treatment
Volume loss: Crystalloid for nonhemorrhagic depletion; blood and hemorrhage control for significant bleeding.
Septic shock: Antibiotics / source control, appropriate fluid, and norepinephrine when needed.
Anaphylaxis: IM epinephrine; refractory compromise requires escalation.
Cardiogenic / obstructive shock: Support perfusion while arranging definitive treatment. See Treatment.
05 Reassess / Destination
Reassess perfusion, respiratory status, fluid response / tolerance, and vasoactive requirements after interventions.
OR / Cath Lab / IR: Definitive treatment when indicated.
ICU: Persistent shock, advanced respiratory support, or vasoactive infusions.
Heart rate ÷ systolic BP: A value around 0.9 or higher increases concern, particularly with suspected blood loss.
Interpret with the examination and trend. Rate-limiting medication, pacing, or dysrhythmia may make the ratio misleading; a reassuring value does not exclude shock. Shock Index Review.
Lactate / Acid–Base Status
Obtain lactate when shock is suspected; trend an elevated result alongside clinical response.
Elevated lactate may reflect hypoperfusion, adrenergic stimulation, seizures, impaired clearance, or medications / toxins. A normal result does not exclude early or regional hypoperfusion.
Blood gas / base deficit may help assess severe illness, especially hemorrhage or a mixed acid–base disorder.
Use mmol/L for lactate thresholds. Neither lactate >4 nor a particular base deficit is required to recognize shock.ESICM — Perfusion Markers.
02Initial Resuscitation
ABCs / Access / Monitoring
Assess airway protection, ventilation, circulation, and consciousness. Pulseless collapse requires the cardiac-arrest pathway.
Establish reliable vascular access; large-bore IVs for rapid volume / blood delivery, with IO access when urgent access cannot otherwise be obtained.
Cardiac monitoring, frequent BP, pulse oximetry, temperature, and bedside glucose. Correct hypoxemia and inadequate ventilation.
Obtain an early ECG and blood samples while resuscitation proceeds. Track urine output; consider a catheter when accurate measurement will guide ongoing care.
Call for appropriate resuscitation, procedural, and critical-care support early. RCUK — ABCDE.
Airway / Respiratory Support
Intubation for failed oxygenation / ventilation, inability to protect the airway, or anticipated deterioration requiring airway control.
Preoxygenate and support perfusion during preparation. Induction and positive-pressure ventilation may precipitate cardiovascular deterioration.
Necessary airway control should not wait for complete resuscitation; shock alone is not an automatic indication for paralysis.
Major hemorrhage: External control, early blood-based resuscitation, and definitive hemorrhage control.
Tension pneumothorax: Immediate decompression when clinically suspected in an unstable patient; imaging must not delay treatment.
Tamponade: Urgent drainage / operative assessment according to cause.
Unstable dysrhythmia: Rhythm-specific cardioversion, pacing, or pharmacologic treatment.
Anaphylaxis: IM epinephrine and airway / circulatory support.
High-risk PE / acute cardiac mechanical problem: Immediate specialist involvement and definitive-treatment planning. See Cause-Specific Treatment.
03What Type Of Shock?
Four Mechanisms
Hypovolemic: Inadequate circulating volume.
Distributive: Loss of vascular tone and maldistributed flow.
Cardiogenic: Inadequate cardiac output from pump, rhythm, or mechanical failure.
Obstructive: Restricted cardiac filling or outflow.
These are working mechanisms, not exclusive diagnoses. Sepsis with myocardial dysfunction or trauma with several injuries may produce mixed shock. Classic filling-pressure / cardiac-output patterns are guides—not diagnostic requirements. ESICM — Mechanisms.
History / Examination — What Moves The Needle?
Hypovolemic
Hemorrhage: Trauma, GI / vaginal bleeding, abdominal or back pain, recent procedure, or anticoagulation.
Other losses: Vomiting / diarrhea, poor intake, burns, or substantial third spacing.
Assess wounds, abdomen / pelvis, mucous membranes, peripheral perfusion, and evidence of concealed bleeding.
Distributive
Sepsis: Possible source, fever / hypothermia, immunocompromise, recent infection or procedure.
Anaphylaxis: Abrupt illness after a likely trigger; wheeze, swelling, hives, or GI symptoms. Skin findings may be absent.
Other causes: Spinal injury, adrenal insufficiency / steroid interruption, medication or toxic exposure.
Warm extremities or a low diastolic BP may support vasodilation but do not establish the cause.
Cardiogenic
Chest discomfort, dyspnea, palpitations, known heart failure / coronary disease, or acute deterioration after MI.
Assess rhythm, JVP, crackles, edema, and a new murmur. Consider both LV and RV failure.
Heart — Pump: LV / RV size and function, pericardial effusion, and major mechanical abnormalities.
Volume / Lungs — Tank: Venous filling, lung sliding, B-lines, pleural fluid, and abdominal free fluid when relevant.
Vessels — Pipes: Aorta and DVT assessment according to the suspected cause.
Pericardial fluid alone does not establish tamponade; RV enlargement alone does not establish acute PE. Interpret with physiology and history.
IVC size alone should not determine fluid treatment. Repeat focused imaging when the patient changes or treatment response is unexpected. RUSH 2012 · ESICM 2025.
CXR: Pulmonary edema, pneumonia, pneumothorax, or pleural blood / fluid when it will assist management.
Laboratory testing: Consider CBC, chemistry / renal function, glucose, lactate, blood gas, coagulation studies, and type and cross according to severity and differential.
Cause-directed tests: Troponin for cardiac concern; cultures / infection testing; pregnancy testing; selected toxicology studies. Cortisol / thyroid testing belongs to a supported endocrine differential.
Before further volume, assess the likely deficit, expected benefit, and risk of worsening congestion.
Responsiveness: Would additional preload increase stroke volume / cardiac output?
Tolerance: Can the patient accept additional fluid without worsening pulmonary edema or venous congestion?
Consider a passive leg raise with measured stroke-volume / cardiac-output response, or a monitored fluid challenge. A BP change alone is less informative.
Example challenge: 200–500 mL crystalloid over 5–10 minutes, with immediate reassessment; adjust volume and rate to the patient.
Reassess perfusion and lung / venous congestion. A transient response does not justify unlimited fluid; obvious hemorrhage requires blood and control rather than repeated crystalloid challenges. ESICM 2025 — Fluid Therapy.
Hypovolemic Shock
Nonhemorrhagic Volume Loss
Crystalloid replacement with reassessment; correct ongoing losses and electrolyte abnormalities.
Select fluid and volume for the cause and comorbidities. Avoid applying one weight-based bolus to every hypotensive patient.
Hemorrhagic Shock
Control bleeding and start blood-based resuscitation. Activate the massive-transfusion pathway when major ongoing blood loss is suspected.
Use whole blood or balanced components according to the institutional protocol; limit crystalloid that delays or dilutes effective resuscitation.
Whole blood is a reasonable option, not established as universally superior to balanced components. EAST's recommendation is conditional. EAST 2024 — Whole Blood.
Warm the patient / products; monitor ionized calcium, coagulation, and ongoing blood loss. Correct abnormalities during major transfusion.
Consider early TXA for qualifying traumatic hemorrhage; follow the trauma-specific timing / dosing pathway, not a generic shock indication.
An initially reassuring hemoglobin does not exclude acute major bleeding. Arrange surgery, IR, endoscopy, or obstetric intervention according to the source. European Trauma Guideline 2023.
Distributive Shock
Septic Shock
Obtain cultures without delaying treatment. Antibiotics immediately, ideally within one hour of recognition; select coverage for the source and resistance risk.
Balanced crystalloid is preferred in most septic resuscitation. Concurrent TBI changes fluid selection.
SSC 2026 suggests at least 30 mL/kg in the first three hours for sepsis-induced hypoperfusion / septic shock. This is conditional, low-certainty guidance: individualize and reassess frequently.
Persistent or profound hypotension warrants vasopressor support; unstable patients may require fluid and pressor treatment concurrently. See Vasoactive Support.
Infection-directed treatment belongs here; SIRS alone neither establishes shock nor identifies its cause. SSC 2026.
Anaphylaxis
IM epinephrine immediately, repeated for persistent compromise; airway support and crystalloid for shock.
Refractory respiratory / circulatory compromise requires a monitored IV epinephrine infusion and experienced resuscitation support.
Antihistamines do not treat shock. Isolated bradykinin-mediated angioedema requires a different treatment pathway. See Anaphylaxis / Angioedema. RCUK 2021.
Adrenal Crisis
Suspect with adrenal disease / steroid interruption, hypotension, volume depletion, or compatible electrolyte / glucose abnormalities.
Hydrocortisone 100 mg IV / IM immediately, then 200 mg over 24 hours; crystalloid and correction of hypoglycemia / electrolyte abnormalities.
Neurogenic: Spinal injury with impaired sympathetic tone; evaluate for concurrent hemorrhage and follow spinal-cord perfusion guidance.
Medication / toxin: Identify the exposure; arrange toxicology / poison-center input and cause-specific treatment.
Myxedema or other endocrine crisis: Consider when the history and examination support it. These may produce mixed circulatory failure rather than classic high-output vasodilation.
Cardiogenic Shock
Obtain ECG / echocardiographic assessment; identify ischemia, dysrhythmia, ventricular dysfunction, or an acute mechanical lesion.
ACS / mechanical disease: Urgent cardiology and definitive-treatment planning. Revascularization or repair may be more important than another vasoactive escalation.
Hypotensive shock: Norepinephrine is a reasonable initial vasopressor. Consider inotropic support for persistent low output with adequate pressure and volume assessment.
Fluids are selective; assess congestion and preload response. Generic afterload reduction is not treatment for an undifferentiated hypotensive patient.
Tension pneumothorax: Immediate decompression, then definitive chest drainage; do not wait for imaging in an unstable patient.
Tamponade: Urgent pericardial drainage / surgery according to cause. Traumatic tamponade generally requires operative management.
Fluids and pressors may temporarily support circulation, but the priority is relieving the obstruction. RUSH — Obstructive Shock.
High-risk PE: Urgent reperfusion assessment—systemic thrombolysis, catheter treatment, or surgery according to risk, contraindications, and resources. Involve the PE response team when available. AHA/ACC 2026 — Acute PE.
Vasoactive Support — Match The Physiology
Norepinephrine: First-line septic vasopressor; also reasonable for hypotensive cardiogenic shock.
Vasopressin: Adjunct for septic vasoplegia with escalating norepinephrine requirements.
Epinephrine: Refractory septic shock or selected cardiac dysfunction; disease-specific first-line treatment for anaphylaxis uses the IM route initially.
Dobutamine: Selected low-output states with adequate pressure / volume assessment—not a substitute for a needed vasopressor.
Peripheral initiation: A monitored peripheral infusion can avoid delay for central access. Follow a standardized concentration / pump protocol, assess the site, and arrange ongoing access as needed. SSC 2026 — Vasopressors · ACC — Vasoactive Guidance.
Trend lactate when elevated; interpret persistent elevation in context rather than treating the number with additional fluid.
Reassess cardiac function, congestion, and fluid responsiveness when the response is inadequate or unexpected.
Rising pressor requirement or persistent hypoperfusion: Reassess the diagnosis, ongoing losses, mixed physiology, and adequacy of source control.
Consider arterial pressure monitoring for persistent shock / vasoactive support; selected patients need advanced hemodynamic assessment. ESICM 2025 — Monitoring.
Blood Pressure Targets
Septic shock: Initial MAP approximately 65 mm Hg; individualize for age, baseline pressure, and perfusion response. SSC 2026 — MAP.
Cardiogenic shock: An initial MAP around 65 mm Hg is reasonable, then adjust to perfusion and hemodynamics. ESICM 2025.
Uncontrolled traumatic hemorrhage: Selected patients may tolerate SBP 80–90 mm Hg until bleeding control; significant brain / spinal injury requires different targets. This is not a general target for medical shock. European Trauma Guideline 2023.
Definitive Treatment — OR / Cath Lab / IR
Ongoing hemorrhage, a drainable / surgical source, coronary occlusion, or another correctable lesion requiring intervention.
Sustained response to initial treatment without ongoing vasoactive or advanced respiratory support, but continued evaluation / treatment remains necessary.
Persistent uncertainty, recurrent hypotension, or organ dysfunction requires a setting capable of prompt escalation.
ICU Admission
Persistent / recurrent shock, vasoactive infusion, invasive ventilation, worsening organ dysfunction, or intensive monitoring requirements.
Communicate the suspected mechanism, interventions, response, fluid / blood totals, current support, and unresolved source-control needs.
Clarify goals of care and any treatment limits while continuing indicated resuscitation. SSC 2026.
Discharge
A transiently improved BP is insufficient. Consider discharge only when ongoing shock has been excluded, the cause and sustained recovery support a safe outpatient pathway, and follow-up is appropriate.
Persistent or unexplained hypoperfusion requires continued monitored care.
In The Pit
Crashing: ABC support; control bleeding, relieve obstruction, and treat unstable rhythms / anaphylaxis immediately.
Hypoperfusion: Normal BP does not exclude shock; reassess mentation, skin, urine output, and lactate in context.