From the Guidelines
An IVC maximum diameter <2.1 cm that collapses >50% with or without a sniff is indeed inconsistent with intravascular volume overload and suggests normal right atrial pressure, typically 0-5 mmHg, as supported by the 2015 ESC/ERS guidelines for the diagnosis and treatment of pulmonary hypertension 1.
Key Points
- The IVC diameter and collapsibility serve as useful bedside ultrasonographic markers for assessing a patient's volume status.
- During inspiration, negative intrathoracic pressure normally causes the IVC to collapse; this collapse is exaggerated when right atrial pressures are low.
- Conversely, in volume overload states, the IVC becomes dilated and loses this collapsibility.
- This assessment is particularly valuable in clinical scenarios such as managing heart failure, guiding fluid resuscitation, or evaluating patients with hypotension.
Clinical Application
- The technique requires placing the ultrasound probe in the subxiphoid region to visualize the IVC as it enters the right atrium, then measuring its diameter during normal respiration and during a sniff or deep inspiration to calculate the percentage of collapse.
- According to the guidelines, an IVC diameter < 2.1 cm that collapses > 50% with a sniff suggests a normal RA pressure of 3 mmHg (range, 0–5 mmHg) 1.
- In scenarios where the IVC diameter and collapse do not fit this paradigm, an intermediate value of 8 mmHg (range, 5–10 mmHg) may be used, or other indices of RA pressure should be integrated to downgrade or upgrade to the normal or high values of RA pressure.
From the Research
IVC Diameter and Collapsibility
- The IVC maximum diameter <2.1 cm, that collapses >50% with or without a sniff is inconsistent with intravascular volume overload and suggests normal right atrial pressure (0-5 mmHg) 2
- IVC collapsibility index (IVC CI) < 20% with no sniff suggests increased right atrial pressure and is inconsistent with overt hypovolemia in spontaneously breathing or ventilated patients 2
Factors Influencing IVC Diameter and Collapsibility
- The presence of significant tricuspid regurgitation, a larger body surface area, and younger age are associated with the IVC maximum diameter, independently of right atrial pressure 3
- IVC collapsibility index (IVCCI) is influenced only by right atrial pressure 3
Clinical Applications of IVC Ultrasonography
- Preoperative ultrasound IVC measurements can predict hypotension after induction of anesthesia 4
- IVC ultrasonographic criteria for hemodynamic congestion appear inconsistent, and a sequential or simultaneous combination of clinical scores of congestion, IVC ultrasonographic indices, and circulating levels of natriuretic peptides may be warranted 5