Pulse pressure variation as a guide to volume reposition during abdominal surgery: correlation between cardiac index and central venous pressure

Abstract

Despite the important technological advances available nowadays in the various medical practice fields, volume reposition is still arbitrarily guided. Pulse pressure variation (PPV) has been shown to be effective in differentiating, in humans, patients responsive to volume expansion (VE) from the non responsive ones in different clinical situations. Studies regarding values of PPV that can predict a value of VE in dogs are, however, still scarce. The current project aims to determine the relation between PPV and the responsiveness to VE in dogs, through the combination of this volemic indicator with transesophageal echocardiogram Doppler, as well as other conventional static parameters and establishing a value o PPV than can safely guide fluidoterapy in dogs. In order to achieve that objective, 30 adult animals submitted to abdominal surgery will be utilized. Hypotensive individuals (mean arterial pressure MAP < 75mmHg) will be subjected to initial VE with Lactated Ringer's Solution (20ml/kg for 20 minutes). All of the hemodynamic, metabolic and oxygenation parameters will be measured before and after the conclusion of VE. A 15% raise on the cardiac index (CI) after the VE will classify an animal as responsive. Those who do not respond in that magnitude will be considered nonresponsive. Values of PPV, central venous pressure CVP, PAM, CI and SV (systolic volume) will be analyzed and correlated with each other in order to demonstrate which parameter best follows the increase in the cardiac index, facing the volemic reposition. In addition to that, regarding the specific case of the PPV, there will be fixed the exact value that determines responsiveness or non responsiveness of animals to fluid therapy with the increase of CI. A receiver operating characteristics (ROC) curve will be generated for each hemodynamic parameter. The area above the curve will be calculated and compared. Linear correlations will be provided by the Spearman test. A value of p < 0,05 will be considered statistically significant. (AU)