A comparison of central venous pressure (CVP) in the superior vena cava and common iliac vein in critically ill patients

Introduction

The measurement of CVP via the femoral route using a long catheter placed, under electrocardiographic guidance, in the inferior vena cava, close to the right atrium has been shown to accurately reflect superior vena cava pressure (SVCP) in critically ill adults [1]. We assessed the possibility of using widely available and more easily placed short catheters (15-20 cm in length), placed via the femoral route, to measure CVP.

Objective

To compare common iliac venous pressure (CIVP) with SVCP in critically ill mechanically ventilated patients. To document the effect of PEEP, mean airway pressure (MAP) and intra-abdominal pressure (IAP) on the difference between CIVP and CSVP.

Design

Randomised, blinded comparison. Twenty consecutive ICU patients requiring femoral catheterisation.

Methods

Pressure recorded from the femoral catheter (CIVP) was compared with pressure from the internal jugular or subclavian central venous catheter (SVCP). Correct position was confirmed by radiograph. Random order, simultaneous measurements of CSVP and CIVP were made in a blind fashion at hourly intervals for 6 h. PEEP, MAP and IAP were measured at the same time intervals.

Results

One hundred and forty pairs of measurements in 20 patients were compared. Paired measurements of CSVP and CIVP were compared using the method of Bland and Altman (Fig). The bias was 0.1 mmHg (95% CI 0.1 mmHg). The differences were distributed around the mean with a standard deviation of 1.1 mmHg. The limits of agreement are therefore 2.2 mmHg above or below the mean value (95% CI 0.2 mmHg). The effect of PEEP, MAP and IAP was assessed by comparing each parameter with the difference between CSVP and CIVP. Regression analysis showed no difference between CSVP and CIVP with increasing PEEP, MAP or IAP.

Figure

Conclusion

For clinical purposes CVP measured in the common iliac vein can replace standard intrathoracic CVP measurements in mechanically ventilated patients.