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From Scan to Action: Effective Use of POCUS in Shock Cases

Dr. Abdolghader Pakniyat

From Scan to Action: Effective Use of POCUS in Shock Cases

A bedside roadmap from the first scan to diagnosis and reassessment

Shock is physiology in free fall: tissue oxygen delivery or use is inadequate. The bedside challenge is that the blood pressure number rarely tells you why. Point-of-care ultrasound (POCUS) helps by compressing your differential in minutes and turning “undifferentiated hypotension” into a treatable pattern—then letting you re-check the physiology after every intervention.

In adult shock assessment, structured POCUS can improve diagnostic classification and guide management. A 2018 RUSH review and diagnostic meta-analysis reported ~87% sensitivity and ~98% specificity for shock-type classification in the studied populations. In selected hypotensive ED patients, the SHoC-ED randomized trial did not demonstrate a survival benefit. A broader 2024 review of 18 shock RCTs suggested outcome benefits, with certainty varying by endpoint. Populations, protocols and operator expertise differ; no individual scan guarantees better outcomes.

The mindset: ultrasound answers focused clinical questions

When the room is loud and the patient is crashing, your brain needs simple categories. First ask whether you obtained an adequate view. Then interpret the finding and decide whether it explains the patient’s physiology. Not visualized is not the same as normal. Save representative clips, document limitations, and obtain expert or definitive imaging when uncertainty would change treatment. A difficult scan must not delay resuscitation.

Pump – Tank – Pipes

  • Pump (heart): is it contracting? is it obstructed (tamponade)? is the right heart failing/strained?
  • Tank (preload & volume tolerance): is filling low, adequate, or high? is there fluid where it shouldn’t be (bleeding, effusion)?
  • Pipes (flow & distribution): is there an outflow obstruction (PE)? a leak (ruptured AAA)? a tension pneumothorax compressing venous return?

RUSH is commonly summarized as Pump–Tank–Pipes, and some use HI-MAP for the major targets: Heart, IVC, Morison’s pouch (FAST), Aorta, Pneumothorax.

The SHoC consensus organizes scanning into core views, supplementary cardiac views and additional views selected by the clinical question. This is a practical consensus framework, not a requirement to finish every view before treating shock.

Before you scan: don’t let POCUS become a pause button

POCUS should be done during resuscitation, not instead of it.

Resuscitation first (parallel process):

  • Airway/oxygenation, monitors, large-bore access, bloods, ECG, lactate, cultures if septic, early empiric antibiotics when indicated.
  • If a life-threatening diagnosis is clinically obvious (e.g., classic tension pneumothorax), treat first—confirm with ultrasound only if it won’t delay the fix.

Machine + probe shortcuts

  • If you have one probe: a phased array can do heart, lungs (anterior), and FAST reasonably well.
  • If you can swap: phased (heart) → curvilinear (FAST/IVC/aorta) → linear (lung sliding/DVT).

Step 1: The SHoC “core” scan (for undifferentiated hypotension)

The SHoC-hypotension core views are:

  1. Basic cardiac views
  2. Lung views
  3. IVC views

A 30–90-second initial pass can be a teaching aim when feasible, not a validated deadline. Do not sacrifice diagnostic views or interrupt time-critical treatment to meet it.

When shock is completely undifferentiated, the heart is a useful starting point. Let the clinical threat determine the order: suspected tension pneumothorax or major hemorrhage takes priority over completing a cardiac sequence.

Core View A — The Heart (Pump)

Your mission: identify cardiac and obstructive contributors to shock, integrate adequate views with the clinical picture, and recognize when further assessment is needed.

What you’re looking for (quick visual answers)

  1. Pericardial effusion + tamponade physiology
  • Tamponade is a clinical-hemodynamic diagnosis supported by ultrasound. Look for RA inversion during atrial diastole (often ventricular systole), RV free-wall collapse in early ventricular diastole, and other findings such as a plethoric IVC. No isolated sign is definitive.
  • If tamponade is driving shock: the “fix” is decompression, not liters of fluid.
  1. LV systolic function (gross)
  1. RV size/strain
  • A dilated or dysfunctional RV has several possible causes, including acute PE, pulmonary hypertension and RV infarction. Acute PE may cause obstructive shock; RV infarction may cause cardiogenic shock. Integrate ECG, history and further testing rather than assigning shock type from RV size alone. See the SHOCK registry report on RV infarction and ACEP RUSH guidance.

Pearl: The heart view is your fastest “fork in the road.” SHoC prioritizes it early for exactly that reason.

Core View B — The Lungs (Tank + Pipes)

Lung ultrasound contributes to shock assessment by identifying pleural and lung findings that must be interpreted with the circulation:

  • Pneumothorax signs; tension is determined clinically by respiratory or circulatory compromise
  • Interstitial syndrome, which may reflect pulmonary edema and reduced fluid tolerance
  • Pleural effusion / consolidation (possible shock source)

1) Pneumothorax (especially in ventilated patients)

  • Absent lung sliding raises suspicion but is not perfectly specific.
  • The barcode/stratosphere pattern records absent motion; it is not independent confirmation of pneumothorax. Sliding or B-lines exclude pneumothorax only at the sampled location. A true lung point supports pneumothorax, but its absence does not exclude it. Do not search for one before treating clinically suspected tension pneumothorax.

2) B-lines = interstitial syndrome (often pulmonary edema, but interpret clinically)

  • Three or more B-lines can define a positive scanning zone. Assess distribution across both lungs, pleural appearance and clinical context; one zone does not diagnose cardiogenic pulmonary edema. See the ERS thoracic ultrasound statement.
  • New or increasing B-lines can prompt reassessment of pulmonary congestion and fluid tolerance. They are not, by themselves, an absolute stop rule for fluids; consider their cause, perfusion and the whole clinical picture.

Core View C — The IVC (Filling status… with caveats)

IVC ultrasound is tempting because it feels like a direct window into volume—but it’s a pressure/flow interplay, not a simple “full vs empty.”

A pragmatic interpretation

  • Small + collapsible can support low right-sided filling pressures (possible hypovolemia).
  • Plethoric + minimally variable suggests high right atrial pressure (RV failure, tamponade, fluid overload, high intrathoracic pressure, etc.).

  • Measure the IVC in a subcostal long-axis view, about 2 cm distal to the right atrial junction.
  • In a spontaneously breathing adult, IVC diameter ≤2.1 cm with ≥50% inspiratory collapse supports normal right atrial pressure. This ASE pressure estimate is not a fluid-responsiveness threshold and should not be transferred unchanged to positive-pressure ventilation.
  • Keep the vessel centered and confirm its course; off-axis imaging or respiratory translation can create a misleading diameter change.

The reality check

Systematic reviews show IVC respiratory variation has variable diagnostic accuracy for fluid responsiveness and is influenced by ventilation mode, effort, RV function, and intra-abdominal pressure—so use it as one piece of the puzzle, not the answer.

Best use: trend it serially alongside heart + lung findings.

Step 2: Turn the core scan into a shock pattern (diagnosis by physiology)

Heart, lung and IVC findings help form a working shock hypothesis. Mixed shock, limited views and unresolved diagnoses remain possible.

1) Hypovolemic shock (or hemorrhagic shock)

Typical pattern

  • Hyperdynamic heart, small LV cavity
  • IVC small/collapsible (often)
  • Lungs mostly A-lines (dry)
  • FAST may reveal free fluid if bleeding (next step)

Treatment direction

  • Stop the leak + replace volume (blood if hemorrhage), reassess frequently.

2) Cardiogenic shock

Typical pattern

  • Poor LV systolic function
  • IVC plethoric, limited variation (often)
  • Lungs with diffuse B-lines ± pleural effusions

Treatment direction

  • Consider fluid only when improved preload is likely to help perfusion and congestion risk is acceptable; a positive responsiveness test alone is insufficient. Consider early vasoactive support and definitive cardiac management.

3) Obstructive shock (tamponade, PE, tension pneumothorax)

Tamponade pattern

  • Pericardial effusion + collapse signs + plethoric IVC

Massive PE pattern (supportive, not definitive)

  • RV dilation/strain pattern + small LV, often plethoric IVC
  • Add DVT scan if it helps (see below)

Tension pneumothorax pattern

  • Shock + lung signs (absent sliding) ± acute ventilator/airway clue
  • Treat emergently; ultrasound can confirm quickly when time allows.

4) Distributive shock (sepsis/anaphylaxis/vasoplegia)

Typical pattern

  • LV function may be hyperdynamic, normal or depressed; septic myocardial dysfunction is not confined to a late phase
  • IVC can be variable and misleading
  • Lungs may be A-lines early; may show focal consolidation/effusion as a source

Treatment direction

  • Treat the cause: sepsis may require antibiotics, source control, vasopressors and a reassessed fluid strategy; anaphylaxis requires prompt IM epinephrine as first-line treatment. Use the relevant cause-specific resuscitation pathway.

Step 3: Add targeted “supplementary” and “additional” views (only if they answer your next decision)

Use core views for undifferentiated shock, then add clinically indicated examinations such as further cardiac views, proximal leg veins, ETT placement confirmation, aortic assessment, FAST or pelvic/intrauterine pregnancy views.

FAST / abdominal free fluid (Tank leak)

  • Use free-fluid views in trauma, suspected hemoperitoneum or ruptured ectopic pregnancy, and other appropriate shock presentations. FAST does not diagnose intraluminal GI bleeding, and a negative study does not exclude hemorrhage.

Aorta (Pipes catastrophe)

  • If an older patient has back/abdominal pain and collapse, scan the aorta while arranging urgent definitive care. POCUS identifies an aneurysm; it does not reliably exclude rupture or dissection. A limited scan is nondiagnostic. Do not let a negative FAST reassure you about retroperitoneal bleeding. See ACEP aortic guidance.

DVT scan (PE support)

  • If RV strain and the clinical story suggest PE, a proximal DVT can strengthen the diagnosis. A negative leg study or unrevealing cardiac scan does not exclude PE. Use the definitive PE pathway when feasible; in an unstable patient, integrate bedside findings with urgent specialist assessment.

Source-seeking ultrasound in septic shock (smart time investment)

  • Lung consolidation/effusion, biliary pathology, hydronephrosis, soft-tissue abscess—only if it will change actions now.

The part most people skip: ultrasound-guided reassessment

Shock management is a loop:

Intervention → physiologic response → adjust plan → repeat

POCUS is repeatable, bedside and real-time. After treatment, ask whether perfusion improved as well as whether the images changed: reassess mentation, capillary refill, skin temperature, urine output and lactate trend. ESICM guidance supports serial assessment and flow monitoring when shock does not respond to initial therapy.

Advanced Hemodynamic Layer: Responsiveness and Tolerance

Fluid responsiveness (will stroke volume rise if I give preload?)

Fluid responsiveness is an increase in stroke volume or cardiac output after a preload challenge. The threshold depends on the test and measurement method; for PLR, a rise around 10% in measured cardiac output performed well in a diagnostic meta-analysis. Do not apply one cutoff to every challenge.

Use a dynamic test that is valid for this patient and that you can measure reliably:

  • PLR provides a reversible preload challenge of roughly 300 mL, mobilizing blood from the legs and splanchnic compartment when performed from a semirecumbent position. Assess the response with a timely flow measurement, not blood pressure alone, and check that it returns toward baseline afterward. See PLR technique.
  • LVOT VTI, ∆VmaxAo, SVC/IVC indices, mini-fluid challenge, etc.

Check the validity conditions of the specific test. Conventional pulse-pressure/stroke-volume respiratory variation performs best with controlled ventilation, adequate tidal volume (often around 8 mL/kg predicted body weight in validation settings), regular rhythm and no major confounders. Low compliance, spontaneous effort and RV dysfunction can mislead. Do not abandon lung-protective ventilation to satisfy a shortcut. PLR, an end-expiratory occlusion test in a suitable intubated patient, or a carefully measured mini-fluid challenge have different requirements.

Fluid tolerance (can the patient safely accept more fluid?)

Responsiveness is not permission to give fluid. The patient also needs a perfusion problem that additional preload can improve, with an acceptable risk of congestion. Ultrasound contributes to that risk assessment; it cannot certify that the next bolus will be safe.

  • Left-sided congestion clues: a multiparametric filling-pressure assessment and lung findings; E/e′ alone is insufficient
  • Right-sided congestion clues: IVC and venous Doppler patterns, interpreted with RV function and the clinical picture

Optional but powerful: “flow vs congestion” profiles

  • “Flow”: LVOT VTI is stroke distance; ~18 cm is a teaching reference, not a universal CO cutoff. Absolute stroke volume requires LVOT area, and cardiac output also requires heart rate. Use consistent, well-aligned pulsed-wave Doppler and clinical context.
  • Filling-pressure estimate: an average E/e′ ≥14 may support increased mean left atrial pressure in applicable patients. Specify septal/lateral acquisition and use the relevant multiparametric algorithm; rhythm, valve disease and loading conditions can limit interpretation.
  • “Congestion”: VExUS (low 0–1, high 2–3)

“Warm/cold” and “wet/dry” profiles are useful descriptions, not prescriptions. Combine forward flow, perfusion and congestion with the cause of shock. Do not start diuresis, give fluid or choose an inotrope from one VTI, E/e′ or VExUS value.

Reassess after every major action

After fluids

Re-check:

  • LV size and contractility
  • IVC trend (not a single number)
  • Lungs for new/worsening B-lines (early warning of fluid intolerance)

When further fluid is being considered, use a valid dynamic assessment such as PLR with a reproducible LVOT VTI measurement. Use the same operator and keep the sample position and Doppler alignment consistent; small changes within measurement variability are inconclusive.

After vasopressors/inotropes

Re-check:

  • LV function (are we improving forward flow?)
  • RV (did increased afterload or hypoxia tip them into RV failure?)
  • IVC + lungs (are we overfilling the tank while the pump is still weak?)

After procedures / ventilation changes

Re-check the “procedural complications that cause shock” list:

  • Post-intubation: pneumothorax, dynamic hyperinflation, worsening RV failure
  • After central line: pneumothorax/hemothorax
  • After thoracostomy/pericardiocentesis: confirm physiologic improvement

Common pitfalls (and how to avoid them)

  1. Anchoring on the IVC
  • Use it as a trend + context; it’s a right-atrial pressure clue, not a direct “volume meter.”
  1. Calling “cardiogenic shock” based on a single poor-looking LV
  • Sepsis can depress LV; tachycardia and loading conditions can fool the eye. Correlate with lungs/IVC and the clinical picture.
  1. Overcalling pneumothorax from absent sliding
  • Apnea, mainstem intubation, pleurodesis, adhesions can mimic. A barcode M-mode pattern does not resolve the uncertainty. Integrate other lung findings and the clinical context.
  1. Missing dynamic LVOT obstruction (LVOTO)
  • Dynamic LVOTO is an important alternative physiology: it may require fluids if hypovolemic, primarily vasoconstrictors, reducing inotropes, and sometimes beta-blockade—very different from typical “more inotrope” reflexes. Confirm the physiology and individualize treatment with expert echocardiographic and perfusion monitoring; beta-blockade is not routine treatment for undifferentiated shock. Evidence here includes observational data and case reports, not a universal shock protocol.

Advanced add-on: VExUS (Venous Excess Ultrasound Score)

VExUS combines the IVC with hepatic, portal and intrarenal venous Doppler to assess systemic venous congestion. It does not directly measure circulating blood volume.

VExUS C grading:

  • Grade 0: IVC <2 cm; this does not exclude all congestion
  • Grade 1: IVC ≥2 cm + normal/mild Doppler patterns
  • Grade 2: IVC ≥2 cm + one severely abnormal Doppler pattern
  • Grade 3: IVC ≥2 cm + two or more severely abnormal Doppler patterns

Acquisition and limits: use consistent IVC and Doppler technique, representative cycles and ECG timing when available. Tricuspid regurgitation can distort hepatic flow; cirrhosis and portal thrombosis limit interpretation. If waveforms are inadequate, do not assign a reassuring score.

Evidence nuance: In the original cardiac-surgery cohort, VExUS C grade 3 at ICU admission predicted subsequent AKI with ~96% specificity but ~27% sensitivity ( original study). Since then, feasibility and risk-stratification data have grown. A 140-patient randomized trial in cardiorenal syndrome type 1 found no significant improvement in kidney-function recovery or 90-day survival, but improved decongestion. Additional randomized reports exist: a 2025 single-center study of 112 patients with sepsis or septic shock describes random allocation and found no statistically significant mortality difference. These population- and protocol-specific studies do not establish a general survival or kidney-recovery benefit.

When someone says, “BP is 70 systolic,” you can respond with:

  1. Heart: tamponade? LV failing? RV strained?
  2. Lungs: pneumothorax? B-lines/edema? effusion/consolidation?
  3. IVC: low/normal/high filling trend (with caveats)?
  4. Targeted add-ons: FAST / aorta / DVT / airway confirmation / pelvis if indicated
  5. Reassess after each intervention using the same core views (+ VTI/VExUS if you’re going advanced)

That’s the whole game: pattern → action → repeat.

Author

  • Dr. Abdolghader Pakniyat, emergency medicine specialist and EM Mastery Academy founder

    Dr. Abdolghader Pakniyat is an Emergency Medicine Specialist, clinical educator, and founder of EM Mastery Academy. He holds European Board certification in Emergency Medicine and RDMS (Abdomen) certification. His work connects resuscitation, point-of-care ultrasound, and clinical reasoning through practical, case-based education for frontline clinicians.
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