Comparison of Tetrastarch and Lactated Ringers as volume replacement fluids in dogs undergoing acute normovolemic hemodylution

Abstract

This study aimed to compare Tetrastarch and Lactated Ringer's in dogs undergoing acute normovolemic hemodilution (ANH) targeting to reduce the hematocrit to 30%. The main hypothesis of this study is that Tetrastarch would result in superior hemodynamics, higher colloid oncotic pressure, and less extravascular lung water accumulation, in comparison to Lactated Ringer's, without negatively interfering on in hemostasis, renal function and systemic inflammatory response. Eight adult dogs will be anesthetized with 1.3 times de minimum alveolar concentration of isoflurane under mechanical ventilation. Dogs will be anesthetized on 3 occasions with 60-day intervals between procedures. During each experiment, animals will receive 1 of 3 treatments in a randomized crossover design: Control (no intervention), Tetrastarch (ANH with Tetrastarch administered at a 1:1 ratio), Lactated Ringer's (ANH with Lactated Ringer's administered at a 5:1 ratio). The hematocrit will be monitored during the washout intervals between procedures to certify the normalization of hematological parameters before each experiment. Variables (hemodynamic parameters, colloic oncotic pressure, hemostasis, and renal function) will be monitored at baseline (before ANH) and during 4 hours after induction of ANH. Animals will be recovered from anesthesia 4 hours after ANH. Additional measurements of creatinine, and renal tubular damage markers / inflammatory mediators will be performed after 24 and 72 hours of the end of ANH to verify the possibility of late development of renal tubular lesions and/or systemic inflammation associated with Tetrastarch in comparison to Lactated Ringer's. There are still several controversies regarding the use of Tetrastarch during the perioperative period. Even though Tetrastarch is likely to be superior than Lactated Ringer's with regards to its effects on hemodynamic function, maintenance of colloid oncotic pressure and risk of pulmonary edema, its use may compromise renal function in septic patients. We expect to contribute to a better understanding of the potential use of Tetrastarch as a volume replacement fluid during ANH in non septic patients. (AU)