Comparison of peripheral and central venous pressures in critically Ill patients.

We conducted a prospective study to determine the relationship between central (CVP) and peripheral (PVP) venous pressures in critically ill patients. CVP and PVP were measured on five different occasions in 20 critically ill patients in the intensive care unit. Results showed that the mean difference between PVP and CVP was 4.4 mmHg (95% CI = 3.7 to 5.0). However, PVP might be 1.9 mmHg below (95% CI = 0.7 to 3.1) or 10.6 mmHg above (95% CI = 9.4 to 11.8) the CVP. The mean difference between changes in PVP and corresponding changes in CVP was 0.3 mmHg (95% CI = -0.1 to 0.7). The actual change in PVP could be 3.0 mmHg below (95% CI = 2.3 to 3.7) or 3.6 mmHg above (95% CI = 2.9 to 4.3) the change in CVP. Overall, the direction of change in PVP (rise or drop) predicted a same direction of change in CVP with an accuracy of 78%. Changes in PVP > or = 2 mmHg predicted a change in same direction of CVP with an accuracy of 90%. The direction of changes in CVP > or = 2 mmHg were predicted by the direction of change in PVP with an accuracy of 91%. We conclude that PVP measurement does not give an accurate estimate of the absolute value of CVP in individual patients. However, as changes in PVP parallel, in direction, changes in CVP, serial measurements of PVP may have a value in determining volume status and guiding fluid therapy in critically ill patients.