Maintenance Fluid Therapy: Isotonic Versus Hypotonic Solutions

2024 AAHA Fluid Therapy Guidelines for Dogs and Cats

Fluids are drugs used in veterinary patients capable of producing beneficial therapeutic or inadvertent harmful effects within the body's intravascular, interstitial, and intracellular fluid spaces. The individualized design of a fluid therapy plan requires careful patient assessment and targeted selection of proper fluid types, administration routes, and rates, along with adjustments during therapy tailored specifically as per the individual patient's fluid requirement and therapeutic response. Personalized fluid prescriptions and vigilant patient monitoring help avoid patient morbidity from body fluid deficiencies, fluid excess, and electrolyte derangements and support better patient outcomes. These guidelines provide an overview of fluid dynamics within the fluid spaces of the body, describe various types of fluids and their uses, and outline recommendations for fluid administration for resuscitation, rehydration, and maintenance purposes. The guidelines also outline approaches to fluid therapy for anesthetized patients and reiterate the recommendations of reduced fluid rates in this population of patients. Additionally, the guidelines include practical fluid therapy strategies for patients with various common disorders. The goal of these guidelines is to help veterinary professionals safely and effectively prescribe and administer fluid therapy for canine and feline patients.

Intraoperative fluid therapy for video-assisted ovariohysterectomy in dogs

Background

Intraoperative fluids are still poorly studied in veterinary medicine. In humans the dosage is associated with significant differences in postoperative outcomes.

Objectives

The aim of this study is to verify the influence of three different fluid therapy rates in dogs undergoing video-assisted ovariohysterectomy.

Methods

Twenty-four female dogs were distributed into three groups: G5, G10, and G20. Each group was given 5, 10, and 20 mL·kg⁻¹·h⁻¹ of Lactate Ringer, respectively. This study evaluated the following parameters: central venous pressure, arterial blood pressure, heart rate, respiratory rate, temperature, acid-base balance, and serum lactate levels. Additionally, this study evaluated the following urinary variables: urea, creatinine, protein to creatinine ratio, urine output, and urine specific gravity. The dogs were evaluated up to 26 h after the procedure.

Results

All animals presented respiratory acidosis during the intraoperative period. The G5 group evidenced intraoperative oliguria (0.80 ± 0.38 mL·kg⁻¹·h⁻¹), differing from the G20 group (2.17 ± 0.52 mL·kg⁻¹·h⁻¹) (p = 0.001). Serum lactate was different between groups during extubation (p = 0.036), with higher values being recorded in the G5 group (2.19 ± 1.65 mmol/L). Animals from the G20 group presented more severe hypothermia at the end of the procedure (35.93 ± 0.61°C) (p = 0.032). Only the members of the G20 group presented mean potassium values below the reference for the species. Anion gap values were lower in the G20 group when compared to the G5 and G10 groups (p = 0.017).

Conclusions

The use of lactated Ringer's solution at the rate of 10 mL·kg⁻¹·h⁻¹ seems to be beneficial in the elective laparoscopic procedures over the 5 or 20 mL·kg⁻¹·h⁻¹ rates of infusion.

Fluid Overload

Fluid overload (FO) is characterized by hypervolemia, edema, or both. In clinical practice it is usually suspected when a patient shows evidence of pulmonary edema, peripheral edema, or body cavity effusion. FO may be a consequence of spontaneous disease, or may be a complication of intravenous fluid therapy. Most clinical studies of the association of FO with fluid therapy and risk of harm define it in terms of an increase in body weight of at least 5–10%, or a positive fluid balance of the same magnitude when fluid intake and urine output are measured. Numerous observational clinical studies in humans have demonstrated an association between FO, adverse events, and mortality, as have two retrospective observational studies in dogs and cats. The risk of FO may be minimized by limiting resuscitation fluid to the smallest amount needed to optimize cardiac output and then limiting maintenance fluid to the amount needed to replace ongoing normal and pathological losses of water and sodium.

Crystalloid and Colloid Compositions and Their Impact

This manuscript will review crystalloid (hypo-, iso-, and hyper-tonic) and colloid (synthetic and natural) fluids that are available for intravenous administration with a focus on their electrolyte, acid-base, colligative, and rheological effects as they relate to each solution's efficacy and safety. The goal is for the reader to better understand the differences between each fluid and the influence on plasma composition, key organ systems, and their implications when used therapeutically in animals with critical illness.

Terms, Definitions, Nomenclature, and Routes of Fluid Administration

Fluid therapy is administered to veterinary patients in order to improve hemodynamics, replace deficits, and maintain hydration. The gradual expansion of medical knowledge and research in this field has led to a proliferation of terms related to fluid products, fluid delivery and body fluid distribution. Consistency in the use of terminology enables precise and effective communication in clinical and research settings. This article provides an alphabetical glossary of important terms and common definitions in the human and veterinary literature. It also summarizes the common routes of fluid administration in small and large animal species.

Acute Diarrhea in Dogs: Current Management and Potential Role of Dietary Polyphenols Supplementation

Acute diarrhea is one of the most common reasons why pet owners seek veterinary care for their canine companions. In many cases, signs resolve spontaneously or with symptomatic therapy without a specific cause being discovered. However, life-threatening cases can occur. The etiology is complex, including infectious diseases (endoparasites, virus, bacteria, protozoa, fungal agents) by both zoonotic and non-zoonotic pathogens, dietary indiscretion, endocrine diseases, and stress (e.g., travel or environmental changes). In the last years, the role played by oxidative stress in the pathogenesis of acute and chronic enteropathies, independently from the initial noxa, has been highlighted by many researches in both humans and animals. As a result, a series of dietary antioxidant compounds have been studied for their potential use in the treatment of intestinal inflammation. This review summarizes the traditional therapeutic and nutritional options to manage canine acute diarrhea, highlighting the need to explore the role of oxidative stress and potential antioxidant supplementation, especially polyphenols, during acute diarrheic episodes.

Effects of Hypotonic and Isotonic Enteral Electrolyte Solutions Administered in Continuous Flow in Weaned Foals

The effects of fluid therapy with maintenance enteral electrolytic solutions administered by nasogastric route in continuous flow have not previously been studied in weaned foals. This study primary goal was to compare the effects of two maintenance enteral electrolytic solutions administered by nasogastric route in continuous flow on the hydro electrolytic balance in weaned foals. This paper was a controlled trial in a cross-over design (6 × 2) performed in six foals with a mean age of 7.3 ± 1.4 months; each animal received two treatments, IsoES and HypoES, with an interval of 7 days between treatments. After 12 h of fasting, the animals were treated with enteral electrolyte solutions administered via nasogastric route in continuous flow in a volume of 15 mL/kg/h for 12 h. The evaluations were performed at T-12h (the beginning of the fasting), T0h (end of fasting and beginning of fluid therapy), T4h (4 h of fluid therapy), T8h (8 h of fluid therapy), T12h (end of fluid therapy), and T24h (12 h after the end of fluid therapy). Twelve hours of fasting resulted in a reduction (P < 0.05) in body weight, abdominal circumference, whereas serum sodium, SID and enophthalmos increased. Twelve hours of fluid therapy normalized these parameters and promoted increased urinary volume and decreased urinary density without causing electrolyte imbalances. Both enteral electrolytic solutions were effective in reestablishing clinical and laboratorial variables without causing electrolyte imbalances.