**1. Introduction**

Perioperative hemorrhage is a major complication in surgical patients, resulting in increased morbidity and mortality [1–4]. Severe hemorrhage can lead to severe hypotension resulting in reduced vital organs perfusion and oxygenation [5]. Ischemia followed by reperfusion—also known as ischemia-reperfusion (I-R) injury—will induce formation of free radical oxygen species, inflammatory mediators, and toxic metabolites which can cause organ injury [6–8]. Indeed, I-R injury is one of the main causes of perioperative acute kidney injury (AKI) [9,10]. AKI is common in patients undergoing major surgery and can contribute to increased perioperative mortality [11–15]. As such, strategies capable of attenuating I-R injury due to severe hemorrhage are both clinically relevant and desirable.

**Citation:** Davis, J.; Raisis, A.L.; Sharp, C.R.; Cianciolo, R.E.; Wallis, S.C.; Ho, K.M. Improved Cardiovascular Tolerance to Hemorrhage after Oral Resveratrol Pretreatment in Dogs. *Vet. Sci.* **2021**, *8*, 129. https://doi.org/10.3390/ vetsci8070129

Academic Editors: Ana Faustino and Paula A. Oliveira

Received: 24 May 2021 Accepted: 10 July 2021 Published: 12 July 2021

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**Copyright:** © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

Resveratrol is a naturally occurring polyphenol and administrating resveratrol in large doses parenterally has been shown to preserve organ function and improve survival in hemorrhagic shock rat models [6]. Resveratrol can activate expression of the Silent Information Regulator (SIRT1) gene to produce situin-1 protein which can inhibit pro-inflammatory mediators, enhance anti-oxidant pathways, and improve mitochondrial function. In addition, it also has an agonist effect at estrogen receptors [6–8,16]. These effects may explain why administering intraperitoneal or parenteral resveratrol as a resuscitation agent could improve blood pressure in rats with decompensated hemorrhagic shock [6,8]. Although rodent models are appropriate to investigate the mechanistic benefits of resveratrol, confirmation of resveratrol's benefits in large-animal models is needed before it can be safely tested on humans in a clinical setting [17,18]. Previous experimental studies have primarily used a single large dose of resveratrol during or after hemorrhage [6,8]. Because sterile preparation of parenteral resveratrol is not commercially available, translating this treatment strategy to patients at risk of hemorrhage remains difficult.

It is possible that oral resveratrol, taken for a prolonged period of time prior to hemorrhage, may achieve a similar benefit as parenteral resveratrol in hemorrhage. If this is the case, this strategy would be more clinically applicable for patients who are at risk of massive blood loss in elective major surgery. Another concern about the use of resveratrol in perioperative patients is its potential antiplatelet action [19,20]. Currently no safety data exists to guide clinicians whether resveratrol should be ceased prior to major surgery to avoid increased risk of bleeding.

We hypothesized that seven days of oral resveratrol treatment would improve hemodynamic tolerance to induced bleeding. Using a canine model, we aimed to investigate whether resveratrol, administered orally for seven days prior to anesthesia, could improve blood pressure tolerance due to induced hemorrhage. Our secondary objective was to investigate whether resveratrol could protect against AKI without inducing adverse effect on the coagulation.

#### **2. Materials and Methods**

#### *2.1. Animals and Selection Criteria*

Twelve donated adult entire male dogs were included in the study. The dogs were retired racing greyhounds, surrendered by their owners to be used as terminal blood donors. Physical examination, renal ultrasonography, urinalysis, complete blood count, serum creatinine (SCr), blood urea nitrogen, serum albumin concentration, platelet closure time (PCT), and Rotational Thromboelastometry (ROTEM® delta, Tem International GmbH, Munich, Germany) for all dogs were within reference intervals for adult Greyhounds [21]. Ethics approval was granted by the Murdoch University Animal Ethics Committee (permit number R2726/15) and the dogs cared for in accordance with the Australian code for the care and use of animals for scientific purposes.
