Lesson
Recognize Perfusion Failure
Shock is inadequate cellular oxygen delivery or use. Blood pressure is one signal, but mentation, skin, urine, lactate trajectory, capillary refill, acid-base state, and organ function reveal whether the circulation is actually supporting tissue.
- Perfusion
- Compensated shock
- Lactate
- Capillary refill
- Organ trajectory
Mentation, skin, capillary refill, pulse, and urine reveal immediate perfusion.
Lactate, pH, kidney, liver, and dose requirement show direction of travel.
Stabilize oxygen delivery while the definitive cause is treated.
Look beyond one pressure
A patient can have normotensive shock when vasoconstriction preserves pressure while flow and organ perfusion fall. Conversely, a low pressure does not prove shock when mentation, urine, skin, lactate, and organ function remain adequate. Diagnose a circulation, not a threshold alone.
Read the trajectory
Trend mental status, temperature gradient, capillary refill, pulse quality, urine output, lactate, pH, creatinine, liver tests, and vasoactive requirement. A rising dose needed to preserve the same pressure can represent worsening shock even before a new laboratory value returns.
Treat cause and circulation together
Resuscitation supports oxygen delivery while the team controls hemorrhage, infection, anaphylaxis, myocardial ischemia, tamponade, pulmonary embolism, tension pneumothorax, or another driver. A normal pressure created by vasoconstriction does not replace definitive treatment.
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Lesson
Map the Hemodynamic Phenotype
Shock categories describe dominant physiology rather than sealed boxes. Preload, pump function, vascular tone, obstruction, and oxygen content can fail together, so bedside classification must be revised as new data arrive.
- Preload
- Cardiac output
- SVR
- Congestion
- Mixed shock
Volume loss or impaired filling limits stroke volume.
Ventricular failure, rate, or rhythm reduces forward flow.
Vasodilation or excessive vasoconstriction changes pressure and distribution.
Separate the four patterns
Hypovolemic shock begins with inadequate circulating volume. Distributive shock features pathologic vasodilation and maldistributed flow. Cardiogenic shock centers on pump failure, often with congestion. Obstructive shock limits filling or ejection through a mechanical barrier.
Use relationships, not memorized boxes
MAP is related to cardiac output and systemic vascular resistance. Cardiac output equals heart rate multiplied by stroke volume. Oxygen delivery also depends on hemoglobin and arterial oxygen content. Raising SVR can increase MAP while reducing stroke volume or regional flow.
Expect mixed physiology
Sepsis can depress myocardium, myocardial infarction can trigger inflammation and vasodilation, and a bleeding patient can also have right-ventricular failure. Ultrasound, ECG, examination, response to passive leg raise, and invasive hemodynamics when indicated refine the working phenotype.
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Lesson
Give Fluid Only When It Can Help
Fluids are a time-limited hemodynamic intervention. The question is not whether a patient is hypotensive, but whether additional preload is likely to increase useful flow without causing harmful congestion.
- Crystalloid
- Passive leg raise
- Stroke volume
- Fluid tolerance
- Reassessment
Passive leg raise or a small challenge asks whether flow can rise.
Stroke volume or pulse-pressure response is more useful than static filling alone.
Lung, venous, renal, and right-heart findings define the cost of more volume.
Choose the initial fluid
The 2026 Surviving Sepsis Campaign recommends crystalloids first and suggests balanced crystalloids over saline for initial sepsis resuscitation, with saline favored when traumatic brain injury changes the risk balance. Starches should not be used for sepsis resuscitation.
Test responsiveness dynamically
A passive leg raise or small fluid challenge paired with stroke-volume or pulse-pressure response is more informative than static filling pressure alone. Fluid responsiveness does not equal fluid requirement because the patient must also tolerate the resulting volume.
Stop when the physiology changes
After initial resuscitation, use perfusion response, lung findings, venous congestion, urine, lactate trajectory, capillary refill, and cardiac reserve to decide whether to continue. Persistent lactate alone should not trigger endless fluid administration.
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Lesson
Build the Septic Shock Sequence
Septic shock requires simultaneous diagnostic, antimicrobial, source-control, perfusion, and organ-support work. No vasopressor compensates for delayed source control, and no fluid target removes the need for repeated individual reassessment.
- Sepsis
- Source control
- MAP target
- Norepinephrine
- Corticosteroids
Cultures, immediate antimicrobials, and early source control run in parallel.
Crystalloid, MAP near 65, and dynamic reassessment support perfusion.
Norepinephrine, then vasopressin, then selected epinephrine or inotropy.
Act immediately and preserve diagnostic judgment
The 2026 guideline treats sepsis and septic shock as medical emergencies. Obtain blood cultures as soon as possible and ideally before antimicrobials, but do not delay immediate antimicrobial therapy for probable or definite septic shock. Seek an anatomic source that needs control, ideally within six hours when required.
Set the initial hemodynamic target
For septic shock, begin with an initial MAP target near 65 mm Hg, using a practical range rather than chasing a single digit. In adults age 65 or older, the guideline suggests an initial range of 60 to 65 mm Hg. Individual perfusion and chronic pressure context still require bedside interpretation.
Escalate in a defined order
Use norepinephrine first. Add vasopressin when norepinephrine is escalating, then consider epinephrine when MAP remains inadequate. If cardiac dysfunction causes persistent hypoperfusion despite adequate fluid status and pressure, add dobutamine to norepinephrine or use epinephrine alone. Current guidance suggests intravenous corticosteroids for septic shock and recommends against high-dose, short-duration regimens.
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Lesson
Catecholamines: Receptors Become Hemodynamics
Norepinephrine, epinephrine, dopamine, and phenylephrine differ in alpha, beta, and dopaminergic activity. Their bedside effects depend on dose, receptor state, rhythm, acidosis, endogenous tone, and the circulation they enter.
- Alpha-1
- Beta-1
- Beta-2
- Norepinephrine
- Phenylephrine
Constriction raises resistance but can increase afterload and ischemia.
Contractility can improve flow while tachyarrhythmia increases oxygen demand.
Bronchodilation and vasodilation coexist with potassium shift and lactate production.
Start with norepinephrine when vasodilation dominates
Norepinephrine provides strong alpha-1 vasoconstriction with useful beta-1 support and less tachycardia than dopamine or epinephrine in many patients. It is first line for septic shock and a reasonable initial vasopressor for most hypotensive cardiogenic-shock patients.
Use epinephrine for the right physiology
Epinephrine provides alpha-1, beta-1, and beta-2 activity. It is first-line intramuscular treatment for anaphylaxis and can support refractory septic shock or cardiac dysfunction, but tachyarrhythmia, hyperglycemia, hypokalemia, and beta-2-related lactate production complicate interpretation.
Avoid receptor myths
Dopamine has dose-dependent effects but does not protect the kidney at low doses and carries important tachyarrhythmia risk. Phenylephrine is a nearly pure alpha-1 agonist that can lower heart rate and stroke volume through afterload and reflex effects, so it is not a default first-line infusion in cardiogenic shock.
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Lesson
Add a Different Vasoconstrictor Pathway
Vasopressin and angiotensin II increase vascular tone without relying on adrenergic receptors. They can reduce catecholamine exposure in selected vasodilatory shock, but each adds a distinct ischemic, cardiac, endocrine, or thrombotic safety profile.
- V1 receptors
- AT1 receptors
- Vasopressin
- Angiotensin II
- Thrombosis
Vascular smooth-muscle signaling supports catecholamine-resistant vasodilation.
Vasoconstriction and aldosterone signaling can rapidly raise pressure.
Ischemia, thrombosis, cardiac function, and organ perfusion remain the outcome.
Add vasopressin deliberately
The 2026 sepsis guideline suggests adding vasopressin when norepinephrine is escalating. Current labeling covers adults with vasodilatory shock that persists despite fluids and catecholamines and lists 0.01 to 0.07 units per minute for septic shock. Use the lowest effective institutional strategy and monitor ischemia, cardiac function, sodium-water effects, and taper response.
Reserve angiotensin II for selected vasodilatory shock
Angiotensin II activates vascular AT1 receptors and aldosterone signaling. Current labeling starts at 20 ng/kg/min with rapid titration limits and requires concurrent VTE prophylaxis because thrombotic events were more frequent in the pivotal trial. The 2026 sepsis guideline still prefers norepinephrine first.
Measure more than pressure
A rapid MAP response can coexist with digital, mesenteric, or myocardial ischemia, declining output, or unresolved infection. Track perfusion, rhythm, extremities, abdominal findings, lactate, urine, and the ability to reduce other support.
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Lesson
Support Flow in Cardiogenic Shock
Cardiogenic shock is a dynamic low-flow syndrome. The first hours require cause treatment, ventricular and congestion phenotype, serial staging, pressure support when needed, and early escalation when pharmacology cannot restore durable perfusion.
- SCAI stage
- Norepinephrine
- Dobutamine
- Milrinone
- Temporary support
Etiology, SCAI stage, congestion, and LV, RV, or biventricular failure guide care.
Rate, pressure, beta exposure, and kidney function determine the tradeoff.
Refractory low flow requires early expert transfer and a defined exit strategy.
Recognize and stage early
Cardiogenic shock can be normotensive. The 2025 ACC guidance emphasizes serial SCAI staging, shock-team activation, ECG, imaging, laboratory markers, and invasive hemodynamics when they will clarify phenotype or guide escalation. Most important changes can occur within the first 24 hours.
Choose pharmacology by phenotype
Norepinephrine is a reasonable first choice for most hypotensive cardiogenic-shock patients. Dobutamine increases contractility through beta-1 signaling but can accelerate rate and lower SVR. Milrinone inhibits PDE3, providing inotropy and vasodilation with a longer renal-dependent half-life. Both can worsen hypotension and arrhythmia.
Know when medicine is not enough
Persistent hypoperfusion, rising lactate, worsening organ injury, escalating vasoactive doses, mechanical complication, or unfavorable ventricular phenotype should trigger expert escalation and possible transfer. Temporary mechanical support requires a selected patient, a defined physiologic target, complication prevention, and an exit strategy.
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Lesson
Treat the Shock That Pressors Cannot Fix
Anaphylactic, hemorrhagic, and obstructive shock expose the limit of pressure-focused treatment. Immediate epinephrine, blood and hemorrhage control, or relief of obstruction changes survival because each treats the causal failure.
- Anaphylaxis
- Hemorrhage
- Pulmonary embolism
- Tamponade
- Tension pneumothorax
Immediate intramuscular treatment addresses airway, bronchospasm, and collapse.
Stop the loss and restore oxygen-carrying capacity, coagulation, and temperature.
Decompress, drain, reperfuse, or correct ventilation to restore filling and ejection.
Treat anaphylaxis with intramuscular epinephrine
Give epinephrine promptly in the anterolateral thigh when anaphylaxis is suspected. Airway, oxygen, positioning, fluids, repeated dosing, and escalation follow response. Antihistamines and corticosteroids do not replace epinephrine, and refractory shock requires experienced intravenous vasoactive support.
Restore what was lost
In hemorrhagic shock, control bleeding and use blood-component resuscitation according to the clinical system rather than masking volume loss with vasoconstriction alone. Excess crystalloid can dilute coagulation factors, worsen hypothermia, and increase tissue edema.
Remove the obstruction
Massive pulmonary embolism, cardiac tamponade, tension pneumothorax, and dynamic hyperinflation impair filling or ejection. Vasopressors may temporarily support coronary and cerebral pressure, but reperfusion, drainage, decompression, or ventilator correction is definitive.
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Lesson
Reduce Afterload Without Losing Perfusion
Nitroglycerin and sodium nitroprusside can rapidly reduce filling pressure or afterload when pressure and monitoring allow. They are not treatments for undifferentiated shock and can convert marginal perfusion into collapse.
- Nitroglycerin
- Nitroprusside
- Afterload
- Cyanide
- Continuous pressure
Reduce filling pressure and ischemic burden while screening major interactions.
Rapid afterload reduction requires continuous pressure and toxicity monitoring.
A lower pressure is useful only when organ perfusion and output improve.
Use nitroglycerin for venous and coronary goals
Nitroglycerin is predominantly venodilating at lower doses and adds arterial dilation at higher exposure. It can help selected acute pulmonary edema or myocardial ischemia when pressure is adequate. PDE5 inhibitors and riociguat create dangerous hypotensive interactions, and tolerance can develop during continuous use.
Use nitroprusside only with intensive monitoring
Nitroprusside dilates arterial and venous beds and can sharply lower afterload. Current labeling requires continuous blood-pressure monitoring and warns that cyanide production becomes dangerous at high infusion rates, with greater vulnerability in hepatic dysfunction and thiocyanate accumulation in renal dysfunction.
Titrate to perfusion, not a cosmetic pressure
Track mentation, urine, lactate, ischemia, filling pressure, and forward flow while lowering pressure or afterload. A lower SVR is useful only when the ventricle can translate it into improved output without coronary or cerebral hypoperfusion.
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Lesson
Run Vasoactive Therapy as a Closed Loop
High-alert infusions demand correct concentration, weight, units, pump programming, access surveillance, compatible delivery, meaningful monitoring, and a deliberate taper. The safest order is one that another clinician can independently reconstruct.
- Dose-rate calculation
- Peripheral access
- Extravasation
- Taper
- Handoff
Keep weight, time, concentration, and pump units visible through the equation.
Inspect access continuously and treat extravasation as a medication emergency.
Reduce support deliberately while pressure, perfusion, and cause remain controlled.
Calculate from dimensional analysis
For a weight-based infusion, multiply the ordered mcg/kg/min by dosing weight, convert minutes to hours, then divide by concentration in mcg/mL. Keep units visible through every step, use standardized concentrations, and perform an independent double check according to policy.
Do not delay life-saving pressure support solely for a central line
The 2026 sepsis guideline supports starting vasopressors peripherally rather than delaying MAP restoration. Use a well-functioning appropriate vein, inspect frequently, minimize duration and concentration burden according to local policy, and transition access when ongoing therapy requires it.
Respond to extravasation and de-escalate safely
Stop the infusion but keep access available for aspiration and local treatment according to the specific drug and protocol. Current norepinephrine labeling directs prompt phentolamine infiltration for ischemic extravasation. Once the cause improves, taper support with close pressure and perfusion monitoring because abrupt discontinuation can cause severe hypotension.
Quick check
Module test
Check the connections.
Each attempt draws 10 questions from the complete 124 question bank.
Each attempt draws a fresh set and rearranges the answer choices.
References
Current clinical foundation.
Lecture material was synthesized with the following contemporary guidance. Verify local policy and current guidance before applying clinical information.
- Society of Critical Care Medicine: 2026 Surviving Sepsis Campaign Adult Guidelines
- American College of Cardiology: 2025 Cardiogenic Shock Concise Clinical Guidance
- AAAAI and ACAAI: 2023 Anaphylaxis Practice Parameter Update
- DailyMed: Norepinephrine Bitartrate Injection
- DailyMed: Vasopressin Injection
- DailyMed: GIAPREZA Angiotensin II Injection
- DailyMed: Milrinone Lactate Injection
- DailyMed: Sodium Nitroprusside Injection