1.3 Point-of-Care Ultrasound (POCUS / TFAST / AFAST / VetBLUE) & Rapid Interventions

Point-of-Care Ultrasound (POCUS / TFAST / AFAST / VetBLUE) & Rapid Interventions

Point-of-Care Ultrasound (POCUS) has revolutionized veterinary emergency and critical care medicine. Unlike comprehensive diagnostic ultrasonography—which requires extensive patient clipping, sedation, full dorsal recumbency, and 30 to 45 minutes of detailed anatomical scanning—veterinary POCUS is a rapid, goal-directed, problem-focused bedside assessment completed in under 3 to 5 minutes. It is designed to answer specific binary (yes/no) clinical questions at the patient's side during initial resuscitation:

• Is there free fluid in the peritoneal, pleural, or pericardial cavities?
• Is there a pneumothorax?
• Is there alveolar-interstitial syndrome (pulmonary edema, contusions, ARDS)?
• What is the intravascular volume / volume responsiveness status of the patient?

Because critically dyspneic or hemodynamically fragile patients can experience fatal decompensation from the physical restraint required for thoracic radiographs, POCUS allows the veterinary critical care team to establish life-saving diagnoses with the patient maintained in gentle sternal recumbency, standing position, or lateral recumbency without shaving (using 70% isopropyl alcohol and acoustic coupling gel parting the fur).

Abdominal Point-of-Care Ultrasound (AFAST)

The Abdominal Focused Assessment with Sonography for Trauma, Triage, and Tracking (AFAST) protocol evaluates four standardized acoustic target sites to detect free peritoneal fluid (hemoperitoneum, uroabdomen, septic peritonitis, biloma, ascites):

The 4 AFAST Target Acoustic Views

1. Diaphragmatico-Hepatic (DH) View:
   • Transducer Placement: Subxiphoid, angled cranially along the midline.
   • Anatomical Structures: Diaphragm-liver interface, gallbladder, caudal vena cava (CVC), and pericardial diaphragmatic window.
   • Clinical Significance: Detects dependent fluid between liver lobes and diaphragm; simultaneously screens for pericardial effusion and pleural effusion across the diaphragm.
2. Spleno-Renal (SR) View:
   • Transducer Placement: Left lateral flank, caudal to the 13th rib.
   • Anatomical Structures: Left kidney, spleen, and left retroperitoneal space.
   • Clinical Significance: Highest sensitivity site for small-volume fluid accumulation in blunt abdominal trauma; evaluates left retroperitoneal disruption.
3. Cysto-Colic (CC) View:
   • Transducer Placement: Caudal ventral abdomen over the urinary bladder, angled caudally toward the pelvic inlet.
   • Anatomical Structures: Urinary bladder apex, descending colon, and uterine/prostatic regions.
   • Clinical Significance: Evaluates the pelvic peritoneal pouch for dependent free fluid, bladder integrity/wall thickness, and intraluminal uroliths or clots.
4. Hepato-Renal (HR) View (or Umbilical View):
   • Transducer Placement: Right lateral flank over the 11th–13th intercostal spaces/flank.
   • Anatomical Structures: Right kidney, renal fossa, and caudate liver lobe.
   • Clinical Significance: Screens the right gutter and retroperitoneum. In deep-chested dogs or cats, an alternative Umbilical View is often used with the patient in lateral recumbency where fluid pools in the mid-abdomen.

The Abdominal Fluid Score (AFS 0–4 Scale)

The Abdominal Fluid Scoring system provides a validated, semiquantitative measurement of hemoperitoneum volume and tracks ongoing active hemorrhage over time:

• AFS 0 (Negative): No free fluid detected at any of the 4 sites.
• AFS 1 (Weak Positive): Free fluid (anechoic fluid pocket) detected at 1 single site only.
• AFS 2 (Weak-to-Moderate Positive): Free fluid detected at any 2 sites.
• AFS 3 (Moderate-to-Severe Positive): Free fluid detected at any 3 sites.
• AFS 4 (Severe / Massive Positive): Free fluid detected at all 4 sites.

Clinical Management Guided by AFS

• Low Fluid Scores (AFS 1–2): Typically indicate small-volume, self-limiting bleeds, mild peritonitis, or early ascites. Patients rarely require blood transfusions (<15% transfusion rate). The technician performs serial AFAST scans every 2 to 4 hours to ensure the score is not escalating.
• High Fluid Scores (AFS 3–4): Indicate massive hemoperitoneum (>20–30 mL/kg of free blood). These patients have a high statistical probability of requiring whole blood or packed red blood cell (pRBC) transfusions (>65% transfusion rate), have an anticipated significant drop in PCV over subsequent hours, and require immediate preparation for emergency surgical exploration (celiotomy) if hemodynamically unstable.

Thoracic Point-of-Care Ultrasound (TFAST)

The Thoracic Focused Assessment with Sonography for Trauma, Triage, and Tracking (TFAST) protocol rapidly evaluates the pleural space, pericardial space, thoracic wall, and cardiovascular structures across three primary bilateral acoustic sites:

1. Chest Tube Site (CTS View)

• Transducer Placement: Bilateral thorax at the 7th to 9th intercostal spaces in the dorsal third of the thoracic cavity.
• Normal Findings ("Dry Lung"):
  • Glide Sign (Lung Sliding): Dynamic shimmering, glistening movement created by the visceral pleura sliding against the parietal pleura with every respiration.
  • A-Lines: Horizontal, hyperechoic, static reverberation artifact lines running parallel to the pleural line at equidistant intervals (indicates normal air-filled lung).
• Pneumothorax Findings:
  • Absence of the Glide Sign: Air within the pleural space separates parietal and visceral pleura, arresting the dynamic shimmering motion.
  • Absence of B-lines: Air completely blocks ultrasound beam penetration, preventing vertical comet-tail artifacts.
  • Lung Point: The definitive sonographic boundary where collapsed lung intermittently contacts the chest wall during inspiration, marking the margin of pneumothorax.

2. Pericardial Site (PCS View)

• Transducer Placement: Bilateral thorax at the 5th to 6th intercostal spaces in the ventral third of the thoracic cavity (cardiac notch).
• Normal Findings: Heart in direct acoustic contact with parietal pericardium and chest wall without intervening fluid.
• Pericardial Effusion & Tamponade Findings:
  • Anechoic Fluid Band: A black, fluid-filled space separating the hyperechoic parietal pericardium from the myocardial epicardium.
  • Cardiac Tamponade: Intrapericardial pressure exceeds right ventricular and right atrial diastolic pressures, resulting in right atrial diastolic collapse / diastolic invagination and right ventricular free-wall compression during diastole. This produces acute cardiogenic obstructive shock (hypotension, pulsus paradoxus, elevated central venous pressure) requiring immediate pericardiocentesis.

3. Hepato-Diaphragmatic (HD View)

• Transducer Placement: Subxiphoid window (shared with AFAST DH view) angled cranially.
• Clinical Significance:
  • Rapidly confirms or excludes pleural effusion (anechoic fluid seen cranial to the hyperechoic curvilinear diaphragm line, with consolidated lung lobes floating in fluid).
  • Evaluates the Caudal Vena Cava (CVC):
    • Flat, collapsing CVC during inspiration: Indicates hypovolemia, dehydration, or low systemic vascular preload (fluid responsive).
    • Distended, non-collapsing ("fat") CVC: Indicates volume overload, congestive right heart failure, or cardiac tamponade (fluid non-responsive / fluid contraindicated).
  • Gallbladder Halo Sign: Double-rim hypoechoic edema within the gallbladder wall, highly associated with canine anaphylactic shock (hepatic venous congestion), acute volume overload, or severe right-sided heart failure.

VetBLUE: Veterinary Bedside Lung Ultrasound Examination

The VetBLUE protocol evaluates 8 standardized transthoracic lung regions — 4 bilaterally applied views per hemithorax, scanned in order as the Caudodorsal (Cd, upper third of the 8th–9th intercostal space), Perihilar (Ph, middle third of the 6th–7th ICS), Middle (Md, lower third of the 4th–5th ICS), and Cranial (Cr, lower third of the 2nd–3rd ICS) lung regions — using a regional pattern approach to differentiate non-cardiac from cardiac causes of acute respiratory distress. The AFAST/TFAST Diaphragmatico-Hepatic view is often counted alongside them as a ninth acoustic window:

Sonographic Lung Profiles & Signs

1. A-Line Profile (Normal / "Dry Lung"):
   • Presence of the glide sign and horizontal A-lines without B-lines.
   • Clinical Correlates: Normal lungs, upper airway obstruction, laryngeal paralysis, or non-parenchymal hypoxemia.
2. B-Lines / "Lung Rockets" (Alveolar-Interstitial Syndrome / "Wet Lung"):
   • Vertical, hyperechoic, laser-like comet-tail artifacts originating directly from the pleural line that extend to the bottom edge of the acoustic screen without fading, moving synchronously with lung sliding and erasing A-lines.
   • Significance: ≥3 B-lines per intercostal space indicates excessive extravascular lung water / alveolar-interstitial fluid accumulation.
   • Differential Diagnoses: Cardiogenic pulmonary edema (left CHF), non-cardiogenic pulmonary edema (ARDS, electrocution, near-drowning), pulmonary contusions (focal trauma), acute aspiration pneumonia, or diffuse interstitial fibrosis.
3. Shred Sign (Fractal Sign):
   • An irregular, jagged, hyperechoic border separating consolidated, non-aerated lung tissue from adjacent aerated lung parenchyma.
   • Significance: Subpleural alveolar consolidation typical of bacterial pneumonia, severe pulmonary contusions, lung lobe torsion, or localized pulmonary infarction.
4. Tissue Sign (Hepatization):
   • Dense, parenchymal consolidation of an entire lung lobe exhibiting the sonographic echotexture of liver tissue. Often contains bright hyperechoic linear branches representing dynamic air bronchograms (confirming pneumonia) or static fluid bronchograms.
5. Nodule Sign:
   • Discrete, round, well-demarcated subpleural hypoechoic or target lesions interrupting the pleural line, characteristic of pulmonary metastatic neoplasia, fungal granulomas, or lung abscesses.

POCUS-Guided Emergency Interventions

When POCUS identifies life-threatening cavitary fluid or air accumulation, the veterinary technician immediately prepares and assists with or performs ultrasound-guided emergency interventions:

1. Emergency Thoracocentesis

• Indications: Tension pneumothorax, large-volume pleural effusion causing respiratory distress (spO2 <90%, severe orthopnea, cyanosis).
• Supplies: 18–22G butterfly catheter or over-the-needle IV catheter, 3-way stopcock, extension tubing, 20–60 mL syringe, sterile collection bowls, EDTA and red top tubes for fluid cytology/analysis.
• Anatomical Site: 7th to 9th intercostal space (dorsal third for pneumothorax; ventral third / costochondral junction for pleural effusion).
• Technique:
  • Maintain patient in sternal recumbency with supplemental flow-by oxygen.
  • Clip and aseptically prepare the site (or perform alcohol wipe down if catastrophic).
  • Critical Landmark Rule: Always insert the needle/catheter over the cranial border of the rib to avoid the intercostal neurovascular bundle (artery, vein, and nerve) running along the caudal rib border.
  • Advance at a 45-degree angle bevel up until negative pressure yields air or fluid; aspirate until slight negative resistance is encountered.

2. Emergency Pericardiocentesis

• Indications: Cardiac tamponade with hemodynamic collapse (hypotension, muffled heart sounds, jugular venous distension, pulsus paradoxus).
• Supplies: 14–18G over-the-needle catheter (5.5-inch) or dedicated fenestrated pericardiocentesis catheter, extension set, 3-way stopcock, 20–35 mL syringe, ECG monitor, defibrillator on standby.
• Anatomical Site: Right hemithorax at the 4th to 6th intercostal space at the costochondral junction (the cardiac notch avoids the large left ventricular coronary vessels and major lung lobes).
• Technique:
  • Attach continuous ECG leads to detect ventricular contact arrhythmias (ventricular premature complexes [VPCs] / ventricular tachycardia).
  • Aseptically prep and infiltrate local lidocaine (2%) into intercostal musculature and pleura.
  • Advance the catheter under direct real-time ultrasound guidance toward the pericardial sac with continuous light negative pressure.
  • Upon penetrating the pericardium, flash of non-clotting hemorrhagic or serosanguineous fluid is aspirated. Advance catheter over needle, withdraw the stylet, attach extension tubing, and evacuate fluid.
  • Note: Pericardial hemorrhagic effusion generally does not clot (defibrinated by cardiac motion); if blood immediately forms a clot in a collection syringe, accidental intracardiac chamber penetration has occurred.

3. Diagnostic & Therapeutic Abdominocentesis

• Technique: Guided directly by AFAST at the site of maximal fluid pocket depth (often SR or CC view) using a 20–22G needle or over-the-needle catheter.
• Point-of-Care Fluid Analysis:
  • PCV / TS: Compare fluid PCV with peripheral blood PCV (fluid PCV ≥ peripheral PCV confirms active/recent hemoperitoneum).
  • Septic Peritonitis: Fluid lactate >2.0 mmol/L higher than peripheral blood lactate, OR fluid glucose >20 mg/dL lower than peripheral blood glucose confirms bacterial sepsis.
  • Uroabdomen: Fluid creatinine >2:1 ratio and fluid potassium >1.4:1 to 2:1 ratio relative to serum confirms uroabdomen.
  • Bile Peritonitis: Fluid total bilirubin >2:1 ratio relative to serum bilirubin.

Summary: POCUS Target Sites, Findings & Clinical Actions