Determining Volume Status Using Point-of-Care Ultrasound

Primary Assessment: IVC Evaluation

The American College of Critical Care Medicine suggests measuring IVC diameter 2-3 cm from the right atrial junction during the respiratory cycle to assess volume status 1, 2
IVC collapse >50% during inspiration suggests normal right atrial pressure (<10 mmHg) in non-ventilated patients, according to the American College of Critical Care Medicine 1, 2
A collapsed IVC suggests hypovolemia, though this must be interpreted with caution, as stated by the American College of Critical Care Medicine 1, 2
The Society of Critical Care Medicine notes that IVC assessment has significant limitations in mechanically ventilated patients, especially with high mean airway pressure, where reliability for predicting fluid responsiveness is reduced 1, 2
Right heart failure and elevated intra-abdominal pressure confound IVC interpretation and must be considered, as per the American College of Critical Care Medicine 1, 2
In neonates, particularly with umbilical central venous catheters in place, no validated normative IVC data exist, according to the American Academy of Pediatrics 1, 2

The American Society of Echocardiography recommends performing "eyeballing" assessment of cardiac contractility in multiple views: apical 4-chamber (A4C), parasternal long-axis (PLAX), parasternal short-axis (PSAX), and subcostal views 1, 2, 3
Qualitatively assess cardiac filling in apical windows to evaluate preload, as suggested by the American College of Cardiology 1, 2
Measure velocity-time integral (VTI) at the left ventricular outflow tract (LVOT) using pulse wave Doppler in apical 5-chamber view, according to the American Society of Echocardiography 1, 2, 4
VTI variation >15% between inspiration and expiration predicts fluid responsiveness with >90% sensitivity and specificity, as stated by the American College of Critical Care Medicine 1, 2, 4, 5
Normal LVOT VTI is 18-22 cm in adults; VTI <15 cm indicates potential hemodynamic compromise, and VTI ≤2.5 cm indicates severe compromise from cardiac dysfunction or significant hypovolemia, according to the American Heart Association 5

The American Thoracic Society recommends assessing for B-lines (vertical artifacts indicating extravascular lung water) in multiple lung zones for semi-quantitative evaluation 5
B-lines indicate interstitial syndrome and extravascular lung fluid but cannot distinguish cardiogenic from non-cardiogenic edema, as stated by the American Thoracic Society 5
Use validated lung ultrasound aeration scores incorporating A-lines, alveolar-interstitial patterns, and consolidations rather than simple B-line counts, according to the American College of Chest Physicians 5

Document presence of mechanical ventilation, right heart failure, or elevated intra-abdominal pressure that may confound interpretation, as suggested by the Society of Critical Care Medicine 1, 2
Perform qualitative assessment of biventricular function, according to the American College of Cardiology 2
If advanced skills available: measure VTI variation to assess fluid responsiveness, as recommended by the American Society of Echocardiography 2
Ensure proper Doppler alignment to avoid measurement errors, as stated by the American Society of Echocardiography 5
Scan multiple lung zones for B-lines, according to the American Thoracic Society 5
Quantify using validated aeration scores, as recommended by the American College of Chest Physicians 5
Remember B-lines indicate fluid but not the etiology, as stated by the American Thoracic Society 5

Avoid improper Doppler alignment when measuring VTI, which leads to underestimation, as warned by the American Society of Echocardiography 5
Do not assume B-lines indicate cardiogenic pulmonary edema; they cannot distinguish etiology, as stated by the American Thoracic Society 5
In mechanically ventilated patients, recognize that IVC collapsibility has reduced reliability, according to the Society of Critical Care Medicine 1, 2
In neonates and young children, apply findings cautiously due to lack of validated normative data, as recommended by the American Academy of Pediatrics 1, 2