Comparison of Mean Arterial Blood Pressure and Heart Rate Changes in Response to Three Different Randomized Isotonic Crystalloid Boluses in Hypotensive Anesthetized Dogs

Simple Summary Anecdotal reports of a paradoxical exacerbation of hypotension in response to a bolus of a balanced isotonic crystalloid solution containing acetate buffers in dogs under general anesthesia was studied in a prospective clinical trial. The response to three different balanced isotonic crystalloid solutions administered as an intravenous bolus to dogs experiencing hypotension while anesthetized for elective orthopedic or dental procedures was investigated. None of the subjects experienced a paradoxical hypotensive reaction or an increase in blood pressure in response to a fluid bolus. The aim of this prospective, randomized, nonblinded, controlled clinical trial was to compare mean arterial blood pressure (MAP) and heart rate (HR) during an intravenous bolus of three different balanced isotonic crystalloid solutions in euvolemic, anesthetized dogs with hypotension. Thirty healthy dogs (American Society of Anesthesiologists Physical Status I-II) weighing at least 15 kg that presented for elective orthopedic or dental surgical procedures at the Ryan Veterinary Hospital for Small Animals of the University of Pennsylvania were included in this study. Anesthetized hypotensive patients (defined as a MAP <= 65 mmHg), were administered an infusion of Lactated Ringer's solution (LRS), Plasma-Lyte (PLYTE) or Canadian Plasma-Lyte (PLYTECA), selected at random. The infusion was administered over 15 min via a volumetric fluid pump. Differences in oscillometric MAP and HR between time points and across treatments were evaluated by mANOVA. Intravenous isotonic crystalloid infusions over 15 min did not significantly change MAP or HR in hypotensive dogs under general anesthesia. Neither LRS, PLYTE nor PLYTECA exacerbated hypotension or caused tachycardia.