I’ve been (and remain) critical of the use of CVP to determine ‘filling status’ or more accurately volume-responsiveness, even using CVP trends; I’m generally in agreement with Dr Marik’s bold statement that “CVP should not be used to make clinical decisions regarding fluid management”1. However there might now appear to be a way of using CVP for this purpose.
Increasing PEEP in patients undergoing positive pressure ventilation can increase the CVP. It has been demonstrated in a small study of cardiac surgical patients2 that the degree to which a 10cmH2O increase in PEEP changes the CVP correlates with fluid responsiveness. The fluid responsiveness was determined by the change in cardiac output measured by thermodilution after a passive leg raise.
There are a number of limitations to this study that should prevent us from immediately extrapolating this method of determining fluid responsiveness to our ED / critical care patients, but the concept is interesting. This can be added to the growing pile of dynamic measures of circulatory filling.
Background Changes in central venous pressure (CVP) rather than absolute values may be used to guide fluid therapy in critically ill patients undergoing mechanical ventilation. We conducted a study comparing the changes in the CVP produced by an increase in PEEP and stroke volume variation (SVV) as indicators of fluid responsiveness. Fluid responsiveness was assessed by the changes in cardiac output (CO) produced by passive leg raising (PLR).
Methods In 20 fully mechanically ventilated patients after cardiac surgery, PEEP was increased +10 cm H2O for 5 min followed by PLR. CVP, SVV, and thermodilution CO were measured before, during, and directly after the PEEP challenge and 30° PLR. The CO increase >7% upon PLR was used to define responders.
Results Twenty patients were included; of whom, 10 responded to PLR. The increase in CO by PLR directly related (r=0.77, P<0.001) to the increase in CVP by PEEP. PLR responsiveness was predicted by the PEEP-induced increase in CVP [area under receiver-operating characteristic (AUROC) curve 0.99, P<0.001] and by baseline SVV (AUROC 0.90, P=0.003). The AUROC's for dCVP and SVV did not differ significantly (P=0.299).
Conclusions Our data in mechanically ventilated, cardiac surgery patients suggest that the newly defined parameter, PEEP-induced CVP changes, like SVV, appears to be a good parameter to predict fluid responsiveness.
1. Does central venous pressure predict fluid responsiveness? A systematic review of the literature and the tale of seven mares.
Chest. 2008 Jul;134(1):172-8
Full Text Link
2. Predicting cardiac output responses to passive leg raising by a PEEP-induced increase in central venous pressure, in cardiac surgery patients.
Br J Anaesth. 2011 Aug;107(2):251-7