Bedside POCUS / ICU / emergency — Reference values: Inferior vena cava — diameter and respiratory variation, Inferior vena cava — distensibility with positive pressure.
POCUS answers focused bedside questions and should be integrated with physical exam, vital signs, laboratory data, evolution and local protocol. Green = reassuring finding in completed fields; yellow = borderline, incomplete or context-dependent; red = critical finding, especially with instability, trauma or cardiac arrest.
| Measurement | Usual value | Note |
|---|---|---|
| Inferior vena cava — diameter and respiratory variation | ≤2,1 cm + >50% | Echocardiographic pattern for estimating right atrial pressure during spontaneous breathing; do not use alone to decide fluids, especially with mechanical ventilation, athletes, pulmonary hypertension or right ventricular dysfunction.low or normal right-sided pressure: ≤2,1 cm e colapso >50%intermediate or context-dependent: discordant diameter and collapseprobable congestion in the acute setting: >2,1 cm e colapso <50% + clínicaSource: ASE right-heart guideline / ASE POCUS nomenclature |
| Inferior vena cava — distensibility with positive pressure | ≥18 % | With positive-pressure ventilation, high variation may suggest fluid responsiveness in some studies, but depends on rhythm, tidal volume, pressure, lung compliance, abdominal pressure and right ventricular function.low variation: <18%possible responsiveness: ≥18%do not use alone in severe shock: integrate heart and lungSource: ICU IVC distensibility studies / critical-care POCUS reviews |
| FAST/eFAST — minimum windows | pericardium, right upper quadrant, left upper quadrant, pelvis, pleurae and lung sliding | The goal is to detect pericardial, pleural or intraperitoneal free fluid and pneumothorax. In unstable trauma, any positive finding changes resuscitation and team priorities.complete and negative: all windows assessed without fluid or pneumothoraxincomplete or serial: poor window, equivocal finding or repeatpositive with instability: free fluid, hemothorax, pneumothorax or pericardiumSource: ACEP Sonoguide FAST/eFAST / ATLS practice |
| Pericardial effusion — diastolic thickness | <1 / 1–2 / >2 cm | Teaching classification: small, moderate and large. Severity is not determined by thickness alone: right-chamber collapse, plethoric inferior vena cava, exaggerated respiratory variation and instability suggest tamponade.no effusion: pericardium without fluidsmall or moderate and stable: <2 cm sem colapsohigh risk: >2 cm, hemopericárdio ou sinais de tamponamentoSource: ACEP cardiac tamponade / ASE POCUS cardiac nomenclature |
| Lung — B-lines | ≥3 per intercostal space or zone | Fewer than three B-lines in one space is usually normal. Diffuse bilateral pattern favors edema; focal pattern favors pneumonia, contusion, infarction, atelectasis or pleural disease.aerated lung: 0–2interstitial syndrome: ≥3diffuse edema with respiratory failure: bilateral pattern + clinical contextSource: ACEP Lung Sonoguide / international lung ultrasound recommendations |
| Pneumothorax — main signs | absent sliding, absent B-lines, barcode sign and lung point | Present lung sliding excludes pneumothorax at that point. Lung point is highly specific in the correct context; absent sliding alone is not specific.sliding present: pneumothorax excluded at that pointisolated absent sliding: may be atelectasis, apnea, mainstem intubation or adhesionprobable pneumothorax: lung point or barcode sign + clinical contextSource: ACEP Lung Sonoguide / BLUE protocol |
| Abdominal free fluid in trauma | any free fluid is FAST positive | FAST is most useful in unstable patients. In stable patients, a negative FAST does not exclude abdominal injury; consider computed tomography, observation and serial exam according to protocol.no fluid in assessed windows: FAST negative in completed fieldstrace or limited window: repeat or complementfree fluid with instability: activate trauma/shock protocolSource: ACEP FAST Sonoguide / FAST reviews |
| Abdominal aorta in POCUS — largest outer diameter | <3,0 cm | Measure outer wall to outer wall, sweeping proximal, mid and distal aorta to the bifurcation. Aneurysm is defined from 3.0 cm; 2.5–2.9 cm remains ectatic/borderline.no aneurysm if complete exam: <2,5 cmectasia or comparison zone: 2,5–2,9 cmabdominal aneurysm: ≥3,0 cmSource: ACEP Aorta Sonoguide / vascular ultrasound reviews |
| Proximal venous compression for thrombosis | walls should touch | Common femoral, femoral/deep femoral junction and popliteal veins should fully collapse with perpendicular compression. A noncompressible proximal vein is abnormal; incomplete exam should be repeated or complemented according to risk.compressible: walls touch at assessed pointsindeterminate: pain, obesity, oblique compression or incomplete windownoncompressible: compatible with proximal deep venous thrombosisSource: ACEP DVT Sonoguide / emergency compression ultrasound literature |
| Semiquantitative lung ultrasound score | 0–36 | When the service uses 12 zones, each zone receives 0 to 3: A-lines or up to two B-lines, three or more B-lines, coalescent B-lines and consolidation. Severity cutoffs vary by population; use mainly for trend and loss of aeration.low in completed fields: 0–5intermediate / follow trend: 6–15high in respiratory context: >15 + clínicaSource: ACEP Lung Sonoguide / lung ultrasound score literature |
| Bedside guided procedures | safe window + depth + vessels | For vascular access, thoracentesis, paracentesis, pericardiocentesis and drainage, record target, depth, needle path, structures to avoid, Doppler when useful and immediate complications.Source: ACEP POCUS guidelines / ACEP procedural ultrasound guidance |
| Parameter | Normal | Dysfunction |
|---|---|---|
| Thickening fraction | ≥ 30% | < 20% |
| Expiratory thickness | ≥ 1,5 mm | < 1,5 mm (atrofia) |
| Excursion (quiet breathing) | ≥ 10–15 mm | < 10 mm |
TF% = (inspiratory − expiratory thickness)/expiratory. Useful in difficult weaning, unexplained dyspnea and suspected phrenic palsy. Low effort on mechanical ventilation reduces TF without disease.
Source: Boon (Muscle Nerve) / ATS diaphragm US reviews
| Item | Reading |
|---|---|
| Negative FAST | No free fluid in windows; does not exclude injury — repeat/serial if unstable. |
| Positive FAST + unstable | Free fluid → laparotomy; changes resuscitation priority. |
| AAST I–II (spleen/liver/kidney) | Superficial laceration/small hematoma; often non-operative management. |
| AAST IV–V | Deep laceration, devascularization or hilar injury; high surgical/embolization risk. |
US does not grade parenchymal injury well — AAST grading is CT/surgical. eFAST detects free fluid and pneumothorax; use CEUS/CT to characterize solid organs.
Source: AAST Organ Injury Scale (rev. 2018) / ACEP eFAST
| Output | Color | Reading |
|---|---|---|
| POCUS without critical finding in completed fields | Green | Lung sliding present, FAST negative in assessed windows, aorta below 3.0 cm if scanned, compressible veins if tested and no selected alert. |
| Borderline, incomplete or context-dependent POCUS | Yellow | Intermediate inferior vena cava, unassessed window, trace fluid, small/moderate stable pericardial effusion, focal B-lines, ectatic aorta, indeterminate venous compression or need for serial repeat. |
| POCUS with critical or relevant abnormal finding | Red | Free fluid in trauma/shock, hemothorax, probable pneumothorax, tamponade, markedly reduced cardiac function, absent cardiac activity, overloaded right ventricle, aorta >=3.0 cm or noncompressible proximal vein. |
The calculator organizes findings for rapid communication. In emergency care, the result must be confirmed on the monitor, in the patient and in the institutional protocol before any invasive decision.
Source: ACEP POCUS guidelines / ACEP Sonoguide / ASE POCUS nomenclature
| Method | How to measure | Formula / use |
|---|---|---|
| Balik — supine | Maximum pleural separation in millimeters, in the largest free pocket. | Estimated volume = 20 × separation in millimeters. Useful at bedside; meaningful average error, does not replace measured drainage. |
| Goecke 1 — sitting | Craniocaudal effusion height in centimeters. | Estimated volume = height × 90. Simple, but less complete than adding the subpulmonary distance. |
| Goecke 2 / Hassan — sitting | Lateral height + distance between lung base and diaphragm, in centimeters. | Estimated volume = (height + distance) × 70. Good correlation in drainage studies, still an estimate. |
| Do not use formula alone | Septations, internal echoes, pleural nodules, trauma, fever or marked dyspnea. | Color should be driven by complexity and clinical context; large volume does not define etiology. |
Document side, patient position, window used, measurement used by the formula, and whether the fluid is free or loculated.
Source: Balik 2006 / Ibitoye 2018 / Hassan 2017 / EFSUMB / ERS
| Window | What to look for | Color reading |
|---|---|---|
| Pericardium | Fluid between heart and pericardium, mainly in subxiphoid or parasternal window. | Green if absent; red with penetrating trauma, instability or tamponade signs. |
| Right upper quadrant | Hepatorenal space, inferior liver tip and right subdiaphragmatic/pleural region. | Free fluid is positive; in shock/trauma it should be communicated immediately. |
| Left upper quadrant | Perisplenic, left subdiaphragmatic and left pleural regions. | More difficult window; fluid around the spleen or above the diaphragm is relevant. |
| Pelvis | Fluid posterior to bladder, cul-de-sac or rectovesical space. | May be the first positive window; empty bladder reduces sensitivity. |
| eFAST thorax | Hemothorax above the diaphragm and pneumothorax by absent sliding, barcode sign or lung point. | Lung point or hemothorax in unstable trauma is red. |
| Serial exam | Repeat after deterioration, intervention, repositioning or initially limited window. | Yellow when incomplete; green or red depends on repeat exam. |
Source: ACEP FAST Sonoguide / trauma POCUS reviews
| Finding | Color | How to use |
|---|---|---|
| ≤2,1 cm + colapso >50% | Green | Suggests low/normal right atrial pressure during spontaneous breathing if image and context are adequate. |
| Discordant or intermediate | Yellow | Do not decide fluids by the inferior vena cava alone; look for hyperdynamic/reduced heart, B-lines, perfusion, lactate and clinical response. |
| >2,1 cm + colapso <50% | Red if unstable | Suggests elevated right-sided pressure/congestion; in shock consider obstruction, tamponade, right failure, pulmonary embolism or fluid overload. |
| Distensibilidade ≥18% em pressão positiva | Yellow | May suggest fluid responsiveness in some conditions; loses reliability with low tidal volume, arrhythmia, abdominal hypertension or right-sided dysfunction. |
Source: ASE right-heart guideline / critical-care IVC studies
| Finding | Interpretation | Priority |
|---|---|---|
| No pericardial fluid | Reassuring for the question “is there effusion?” | Green if the window is adequate. |
| Small effusion | Less than 1 cm; measure and correlate symptoms, malignancy, uremia, postoperative state or inflammation. | Yellow unless penetrating trauma or deterioration. |
| Moderate effusion | Between 1 and 2 cm; look for right-chamber collapse and plethoric inferior vena cava. | Yellow or red depending on stability. |
| Large, complex or hemopericardium | Greater than 2 cm, clots or trauma increase risk. | Red in the acute setting. |
| Tamponade signs | Right ventricular diastolic collapse, right atrial systolic collapse, plethoric inferior vena cava or compatible instability. | Immediate communication. |
Source: ACEP cardiac tamponade / ASE POCUS nomenclature
| Profile | Findings | Practical reading |
|---|---|---|
| A-lines with sliding | Horizontal artifacts and sliding pleura. | Aerated lung at that point; may be normal or obstructive depending on context. |
| Diffuse bilateral B-lines | Three or more B-lines per space/zone in several zones. | Favors interstitial edema; red with severe respiratory failure. |
| Focal B-lines or consolidation | Asymmetric pattern, irregular pleura, dynamic air bronchogram or subpleural consolidation. | Consider pneumonia, contusion, atelectasis, infarction or pleural disease. |
| Probable pneumothorax | Absent sliding with absent B-lines, barcode sign and/or lung point. | Red with trauma, ventilation or instability. |
| Pleural effusion | Anechoic or complex fluid above the diaphragm. | Use volume calculator as an estimate; complexity and symptoms define urgency. |
Source: ACEP Lung Sonoguide / BLUE protocol / lung ultrasound recommendations
| Question | Green | Yellow | Red |
|---|---|---|---|
| Abdominal aorta | <2.5 cm and complete outer-wall-to-outer-wall sweep. | 2.5–2.9 cm: ectatic/borderline; compare and document technique. | >=3.0 cm: aneurysm. Pain, hypotension or syncope makes the finding critical. |
| Suspected dissection/rupture | No indirect signs and low clinical concern if exam is complete. | Exam limited by gas/pain: do not exclude vascular catastrophe. | Flap, hematoma, free fluid, severe pain or shock: vascular/emergency pathway. |
| Proximal venous thrombosis | Femoral and popliteal veins compressible at assessed points. | Incomplete compression, pain, obesity, duplicated vein or partial window. | Noncompressible proximal vein or visible thrombus: compatible with deep venous thrombosis. |
| Pulmonary embolism integration | No thrombosis and no right ventricular dilation lowers probability but does not exclude. | Dyspnea with discordant findings requires clinical protocol. | Proximal thrombosis + dilated right ventricle/shock increases concern for relevant pulmonary embolism. |
Vascular POCUS is excellent for focused questions, but a limited exam does not replace complete vascular Doppler or CT when suspicion remains high.
Source: ACEP Aorta Sonoguide / ACEP DVT Sonoguide / ACEP POCUS guidelines
| Zone score | Ultrasound finding | Reading |
|---|---|---|
| 0 | A-lines or up to two B-lines with sliding. | Preserved aeration at that point. |
| 1 | Three or more well-spaced B-lines. | Mild aeration loss / early interstitial syndrome. |
| 2 | Coalescent B-lines or partial white lung. | Moderate to marked loss; follow trend and distribution. |
| 3 | Tissue-like pattern/subpleural consolidation. | Severe aeration loss; correlate pneumonia, atelectasis, contusion, infarction or severe edema. |
The 0–36 sum assumes 12 zones. Absolute cutoffs vary by population; in emergency/ICU care, serial trend is often more useful than a single measure.
Source: ACEP Lung Sonoguide / lung ultrasound score literature
| Procedure | Before puncture | During/after |
|---|---|---|
| Vascular access | Identify vein and artery, compressibility, thrombus, depth and free path. | Prefer needle-tip visualization; confirm flow/position according to protocol. |
| Thoracentesis | Confirm free fluid, diaphragm, lung, depth and intercostal vessels when possible. | Reassess lung sliding and complications after the procedure. |
| Paracentesis | Map ascites, bowel loops, bladder, epigastric vessels and wall thickness. | Record site, depth, free/loculated fluid and tolerance. |
| Pericardiocentesis | Define largest pocket, relationship with liver/lung/coronaries and safest window. | In tamponade, communication and trained team are priority; POCUS guides but does not replace institutional protocol. |
| Abscess or collection drainage | Confirm fluid, septations, gas, vessels and deep structures. | Document path, aspirated content and whether immediate complication occurred. |
Source: ACEP POCUS guidelines / ACEP procedural ultrasound guidance
| Question | POCUS finding | Interpretation |
|---|---|---|
| Pump | Markedly reduced ventricular function, absent activity or effusion with tamponade. | Consider cardiogenic shock, arrest without effective activity or obstructive shock. |
| Tank | Very small/collapsible inferior vena cava, free fluid, aortic aneurysm or pulmonary congestion. | Separate hypovolemia, hemorrhage, congestion and vascular causes. |
| Pipes | Deep venous thrombosis, dilated right ventricle, pneumothorax or aortic aneurysm. | Raises suspicion for pulmonary embolism, obstruction or vascular catastrophe. |
| Lung | Diffuse B-lines, consolidation, effusion or absent sliding. | Helps choose between fluids, vasopressor, ventilation and drainage according to protocol. |
Source: ACEP POCUS guidelines / RUSH literature / BLUE protocol
| Item | What to document |
|---|---|
| Clinical question | Shock, trauma, dyspnea, arrest, sepsis, procedure or serial reassessment. |
| Technique | Probe, obtained windows, patient position, ventilation and limitations. |
| Positive and negative findings | Mention free fluid, pericardium, lung sliding, B-lines, cardiac function, inferior vena cava, aorta and venous compression when assessed. |
| Measurements and calculations | Inferior vena cava diameters, collapsibility/distensibility index, effusion thickness, mitral variation, aorta, lung score and pleural effusion estimate when useful. |
| Clinical integration | State whether the finding changes immediate management, requires complementary imaging, serial repeat or urgent communication. |
Source: ACEP POCUS guidelines / ASE POCUS nomenclature