Determination of pulse pressure variation in mechanical ventilated isoflurane anesthetized horses undergoing fluid replacement

Abstract

Fluid responsiveness is a very important parameter since tissue perfusion and oxygenation depends on patient's volemic state. Pulse pressure variation (PP) has been proven effective in differentiate patients that will respond to volume expansion (VE). For safe and effective fluid administration the aim of this study is to determinate the relationship between fluid responsiveness and "PP in response to volume expansion (VE) in isoflurane anesthetized horses by associating this volemic indicator with cardiac output. Six adult horses, males and females, will be anesthetized with isoflurane and submitted to two experimental protocols: water restriction for 12 hours and abdominal distension with CO2. Animals presenting hypotension during anesthesia (PAM < 70 mmHg) will receive hydroxyethyl starch solution (130/0,4; 5 mL / kg over 15 minutes). Parameters will be recorded at baseline (TBasal), imediatelly before (T0) and after VE (Tev). Animals will be considered fluid responsive if CO increased over 15%. Non-responsive animals will receive another volume expansion with colloid (5ml/kg over 15 minutes) followed, if remains non responsible, by isotonic cristaloid (lactated Ringer's solution 10 mL/kg, IV, over 15 minutes). If it remains non-responsive or present hypotension, dobutamine (1mcg/kg/min) Will be administered, with 0,5 mcg/kg/min increments, if necessary, until MAP reach 70-90mmHg. After MAP estabilization, animals will receive a final volume expansion with isotonic cristalloid. Multiple comparisons between treatments will be performed by ANOVA followed by Tukey test. Comparison among treatment effect over time and baseline values will be performed by ANOVA followed by Student's t test (p < 0.05). The ROC curve (receiver operating characteristic) will be generated for "PP and PVC, to determine the threshold value for each parameter. (AU)