The reliability of the central venous pressure measured via catheter inserted in the abdominal vena cava inferior

Objective

In our study, we compared the central venous pressure (CVP) measured via catheters inserted in the abdominal vena cava inferior (aVCI) and vena cava superior (VCS) in intensive care patients. The effects of mechanical ventilation, sedation and intra-abdominal pressure (IAP) on CVP at both localisations were evaluated.

Methods

During a 1-year period, 49 critically ill patients in the ICU were included in the study. In the patients in whom it was decided to change the pre-existing catheter due to prolonged stay, recent catheters were inserted in other localisations from the pre-existing localisations (the recent CVC was inserted in the aVCI if the pre-existing CVC was at the VCS, or the opposite). The pre-existing CVC was kept in place for 24 hours and CVP measurements were performed simultaneously via both of the catheters. IAP was measured via urinary bladder and the sedation scores, ventilation status, sedative drug use, PEEP values, peak and mean airway pressures (PAP and MAP) were recorded during the CVP measurements.

Results

We performed 148 simultaneous measurements in 49 patients. The mean CVP values obtained from the aVCI and VCS were 7.3 ± 2.9 mmHg and 6.4 ± 3.1 mmHg, respectively (P < 0.01). CVP values obtained via the aVCI and VCI were similar in 32.7% of the 123 measurements performed in mechanically ventilated patients. Eight percent of the 25 CVP measurements performed in spontaneously breathing patients were similar (P < 0.05). In the CVP measurements performed during IAP < 8 mmHg (n = 72) and IAP ≥ 8 mmHg (n = 76), the mean differences between aVCI and VCS pressures were 1.04 ± 1.06 mmHg and 1.71 ± 1.4 mmHg, respectively (P < 0.01). Mean CVP values obtained from the aVCI were higher when PAP ≥ 25 mmHg or MAP ≥ 12 mmHg (P < 0.01). The CVP differences were ≥ 3 mmHg at 26 (17%) of 148 simultaneous measurements.

Conclusions

We found that mechanical ventilation, PEEP, PAP, MAP and IAP were effective on the difference between CVP values obtained simultaneously via two different routes. Although the mean difference between the pressures obtained via the catheters inserted in the aVCI and VCS (0.9 mmHg) were statistically significant, the clinical importance of this difference may not be important.