The influence of PEEP and positioning on central venous pressure and venous hepatic hemodynamics in patients undergoing liver resection.

PURPOSE

In order to assess the occurrence of blood congestion in the liver during liver resection, we aimed to evaluate the influence of a positive-end-expiratory-pressure (PEEP) and positioning of patients on central venous pressure (CVP) and venous hepatic blood flow parameters. We further analyzed correlations between CVP and venous hepatic blood flow parameters.

METHODS

In 20 patients scheduled for elective liver resection we measured CVP and quantified venous hepatic hemodynamics by ultrasound assessment of flow-velocity and diameter of the right hepatic vein and the portal vein after equilibration following these maneuvers: M1: 0° supine position, PEEP 0 cmHO; M2: 0° supine position, PEEP 10 cmHO; M3: 20° reverse-trendelenburg position; PEEP 10 cmHO; M4: 20° reverse-trendelenburg position, PEEP 0cmHO.

RESULTS

Changing from supine to reverse-trendelenburg position led to a significant decrease in CVP (M3 5.95 ± 2.06 vs. M1 7.35 ± 2.18 mmHg and M2 8.55 ± 1.79 mmHg). A PEEP of 10 cmHO and reverse-trendelenburg position led to significant reduction of systolic (Vs) and diastolic (Vd) flow-velocities of the right hepatic vein (Vs M3 19.96 ± 6.47 vs. M1 27.81 ± 11.03 cm s;Vd M3 14.94 ± 6.22 vs. M1 20.15 ± 10.34 cm s and M2 20.19 ± 13.19 cm s) whereas no significant changes of flow-velocity occurred in the portal vein. No correlations between CVP and diameters or flow-velocities of the right hepatic and the portal vein were found.

CONCLUSIONS

Changes of central venous pressure due to changes of PEEP and positioning were not correlated with changes of venous hepatic blood flow parameters as measured after equilibration. Strategies aiming for low central venous pressure cannot be supported by these results. However, before ruling out low-CVP-strategies during liver resections these results should be confirmed by further studies.