The literature continued...
A more recent study in the EM literature by Lyon, et. al. examined the IVC diameter pre and post blood donation (450mls) in a sample of donors at an outpatient facility. Measurements of the maximal diameter of the IVC behind the liver were made at the end of inspiration (IVCi) and at the end of expiration (IVCe) with the probe in a subxiphoid position in the sagittal axis. Patients were supine for the study.
The mean diameter of the IVC at end expiration before donation was 17.4mm and after donation was 11.9mm while IVCi pre donation was 13.3mm and post donation was 8.1mm, showing that in a small sample population there is a real and detectable drop in IVC diameter after blood loss (of about 5mm for 450cc donation).
Similarly, Blank and collegues measured IVC differences (J of Trauma) in a sample of 35 patients transferred to their hospital in shock, and not in shock (control). They found a significant difference (expectedly) in the IVC diameter pre recussitation (day of transfer) and post recussitation (day 5) in the shock group. Moreover, (also expected), there was a significant difference between the shock group and the non-shock group on day 1. The IVC diameter seemed to correlate well with hypovolemia in this cohort.
Images
The following are examples of the IVC in various states of intravascular volume level.
IVC in hypovolemic patient (i.e. sepsis, hemorrhagic shock), Note diameter ~1cm, est. RA pressure 0-5 cmH20 :
IVC in normal patient, note "sniff maneuver" with good IVC collapse. Est. RA pressure 11-15 cmH20
IVC in patient with cardiogenic shock (note lack of normal respiratory "bobbing", and large diameter); Est. RA pressure 15-20 cm H20
Also note dilated hepatic veins...
Table correlating IVC size, Respiratory Change and RA pressure (From Ma and Mateer, Emergency Ultrasound, 2003.)
| IVC size |
Respiratory Change |
RA Pressure (cm) |
| <1.5 |
Total Collapse |
0-5 |
| 1.5-2.5 |
>50% collapse |
5-10 |
| 1.5-2.5 |
<50% collapse |
11-15 |
| >2.5 |
<50% collapse |
16-20 |
| >2.5 |
No change |
>20 |
How to measure/technique
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