By Rwo-Wen Huang, MD and Laleh Gharahbaghian, MD, FACEP
Central venous pressure (CVP) is crucial for evaluating the patient’s intravascular volume and hemodynamics, which has important indications on management for sepsis, congestive heart failure, pulmonary edema, trauma, and surgery.1-5 Over or under fluid resuscitation can both be detrimental to critically ill patients or those with cardiovascular diseases.1-3 The gold standard was invasive monitoring with a central venous catheter, but due to the procedure’s inherent risks and potential to delay resuscitation, there has been ongoing research for noninvasive methods.1,4,6,7 Sonographic measurement of the inferior vena cava (IVC) has been widely studied and accepted as a tool to assess intravascular volume status.2,8-10 Multiple studies have demonstrated that respiratory variations of IVC measurements at 2cm from the right atrial-caval junction reliably reflects the central venous pressure.2,8-10 However, this technique is limited by body habitus, bowel gas, ascites, surgical scars, and wound dressing, thus providers have been searching for alternatives.3,6,8
The internal jugular vein (IJ) static and dynamic measurements on ultrasound have been proposed to provide accurate and rapid bedside CVP assessment in both spontaneously breathing and mechanically ventilated patients.1,3-7,11,12 Various methods have been employed:
1. Aspect ratio (height/width, Figure 1)
2. Cross sectional area with Valsalva maneuver (Clip 1)
3. Change in diameter with respiration (Clip 2)
4. Point of collapse (Figure 2)1,3-7,11,12
Keller et al. evaluated the IJ aspect ratio with the patients lying flat and head rotated to the side, and showed that an aspect ratio of 0.83 corresponded to a CVP of 8mm Hg in spontaneously breathing critically ill patients.1 Simon et al. measured right IJ cross sectional area (CSA) in patients without significant heart or pulmonary diseases and concluded that when CSA was measured with the head rotated at a supine position, an increase of > 17% during Valsalva excluded elevated right atrial pressure.11 Guarracino, et al. and Kent, et al. both used IJ anterior-posterior (AP) respiratory diameter change for volume assessment.6,12 Guarracino, et al. showed that in mechanically ventilated patients with the head elevated and rotated at 30 degrees, those with an IJ distensibility greater than 18% had increased systolic pressure and decreased heart rate with volume repletion.12 Broilo, et al. compared the respiratory variation of IJ directly with that of IVC and found good correlation in ventilated patients.3 Donahue, et al. evaluated the IJ AP diameter and area with the patients supine and at 35 degrees, suggesting that the end expiration diameter at the supine position had the highest association with CVP.7 Siva, et al. demonstrated that the height of the IJ collapse point on ultrasound in the spontaneously breathing patient positioned at 45 degrees accurately predicted CVP.4 Deol, et al. also studied the IJ collapse and determined that while it correlated well with jugular venous pressure, it underestimated CVP.5
Here we will discuss our recommended method to acquire and optimize the IJ views for volume status evaluation.
Sonographic imaging of the IJ has become a valuable instrument to evaluate intravascular volume status. In addition to its comparative ease to obtain images compared to the IVC in certain patient populations, IJ also has the advantage of its juxtaposition to the internal carotid artery which offers information on the cardiac index and fluid responsiveness. The combined data from both the right and left sided cardiac parameters should provide physicians a more accurate hemodynamic picture and in turn lead to appropriate fluid management. Future directions will include stricter standardization of the ultrasound technique for improved consistency and quality of data. Furthermore, studies with larger sample sizes in diverse patient populations are warranted before the IJ method can be validated in various practice settings.