Background: Delta pulse pressure (DPP) and delta down (DD) are indicators of volaemia. The threshold value of DPP for discriminating between responders and non-responders to fluid loading (FL) is 13%. This study aimed at comparing DD with DPP during intracranial surgery.
Methods: Twenty-six adult patients undergoing scheduled intracranial surgery under general anaesthesia were enrolled. DD and DPP were simultaneously measured every 10 min. A DPP>13% on two consecutive occasions prompted a 250 ml FL. Pairs of data were analysed using regression analysis, receiver operating characteristics (ROC) curve, and prediction probability (Pk).
Results: We found a significant correlation between DD and DPP (R2=0.5431, P<0.001). ROC curve analysis revealed an excellent accuracy of DD in predicting a DPP value higher or lower than 13% (area under the curve: 0.967, se: 0.013). The DD threshold associated with the best sensitivity (0.90) and specificity (0.99) was 5 mm Hg. The Pk of DD to predict a DPP value higher or lower than 13% was 0.97 (se: 0.01). A total of 41 FL performed in 19 patients resulted in a decrease of DD and DPP below 5 mm Hg and 13%, respectively, in all but one occasion.
Conclusions: DD is as efficient as DPP to assess hypovolaemia and predict responsiveness to FL in patients undergoing intracranial surgery. A 5 mm Hg DD value can be considered as a valuable threshold for initiating FL. These results support its use during intracranial surgery.